CA2125070A1 - Hot water supply system - Google Patents
Hot water supply systemInfo
- Publication number
- CA2125070A1 CA2125070A1 CA 2125070 CA2125070A CA2125070A1 CA 2125070 A1 CA2125070 A1 CA 2125070A1 CA 2125070 CA2125070 CA 2125070 CA 2125070 A CA2125070 A CA 2125070A CA 2125070 A1 CA2125070 A1 CA 2125070A1
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- Canada
- Prior art keywords
- hot water
- water
- housing
- outlet
- heat exchanger
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Abstract
A hot water supply system includes a water heating unit and a water storage unit connected to a water supply and having a first outlet for hot water connectible to a hot water supply pipe and a second outlet for the flow of water to the heating unit. There is a bypass conduit connecting the heater outlet to the hot water supply pipe and a valve for controlling the flow of water through the bypass conduit. A
sensor senses the temperature of water exiting the storage tank through the first outlet and there is a valve operating mechanism to open or close the valve depending on the temperature of the water measured by the sensor. The heater unit includes a sensor for sensing the temperature of flue gases in a passageway above the heat exchanger of the unit.
There is an air valve mounted adjacent the passageway which, in an open position, permits incoming air to enter the passageway and to mix with the flue gases, thereby cooling same.
sensor senses the temperature of water exiting the storage tank through the first outlet and there is a valve operating mechanism to open or close the valve depending on the temperature of the water measured by the sensor. The heater unit includes a sensor for sensing the temperature of flue gases in a passageway above the heat exchanger of the unit.
There is an air valve mounted adjacent the passageway which, in an open position, permits incoming air to enter the passageway and to mix with the flue gases, thereby cooling same.
Description
21250~0 ~, - 2 This invention relates to hot water heaters and to hot water supply systems.
A variety of hot water heating systems are known both for domestic and industrial use. A common system used in North America includes a rather large hot water storage tank which has means for heating the water stored in a tank. The source of the heat in these units can be electrical heating coils, gas fire burners or oil fire burners. Although hot water heaters employing electricity as the source of heat are still common for domestic water heaters, such units have lost favour with many consumers because of the high cost of electrical power in many regions.
Systems are also known for rapidly heating cold water by passing it through a coiled copper pipe positioned in or adjacent to a heating device. Such systems are commonly used in Europe and they can be made quite efficient but they suffer from the inability to provide large amounts of hot water quickly, unlike those systems which employ a hot water storage tank.
Because of the large number of existing hot water heating units that have a large storage tank and that employ electrical heat at the present time, it is believed that a demand exists for a system which would permit such existing units to be converted to a system which employs gas as the source of heat or to a system which can use either gas or electricity with the actual source of heat depending upon such variables as the amount of hot water required and the time of day at which the heating is required. By at least employing the hot water storage tank of these existing units, there could be a considerable cost savings as compared to purchasing a completely new hot water heating system employing gas as the source of heat. References herein to a "gas" fuel include such common gas fuels as natural gas and propane.
United States patent No. 4,671,212 issued June 9, 1987 to the present inventor Robert Smith describes a gas fired water heater that includes a housing enclosing an internal chamber divided by a vertical partition into two compartments, the partition having a top edge spaced below the top of the chamber. One of the compartments has a gas burner in the lower portion with an adjacent combustion air intake vent. A
first heat exchanger is located in the same compartment above the gas burner but below the top of the partition and a second heat exchanger is located in the other compartment. A flue pipe ducts flue gases from the housing and a blower is provided to blow the flue gases through the flue pipe which is connected to the unit at the bottom of the~housing.
United States patent No. 4,977,885 issued December 18, 1990 to E.B. Herweyer et al., describes a hot water heating system designed to supply hot water to a facility having a demand for such water that varies widely. This system has a water heater having an output capable of supplying water heated to a desired temperature at the normal flow rate and a storage tank for storing additional water heated to the desired temperature. Under conditions of normal flow rate, unheated water is supplied directly to the water heater with no flow to the tank. When the flow increases above the normal flow rate, unheated water is supplied to the tank and heated water is withdrawn from the tank and cold water is simultaneously supplied to the water heater. The flow between the tank and the water heater is limited to the capacity of the heater to supply water at the desired temperature, and the excess demand is supplied by heated water within the tank. A
temperature sensor is provided in the tank where the cold water enters.
The present invention provides an improved hot water heater employing a heat exchanger mounted above a burner, a passageway above the heat exchanger for conducting the flue gases to an outlet, and an unique air valve arrangement which moves to an open position to permit incoming air to enter the passageway above the heat exchanger and to mix with the flue gases, thereby cooling same. The air valve is moved to the open position when the temperature of the flue gases in the passageway is at or above a predetermined level.
According to another aspect of the invention, there is provided an improved hot water heater having a heat exchanger located a distance above a burner in a housing and a water pipe arrangement that extends around a flue gas duct in the region between the burner and the heat exchanger. The flow of water passing through this water pipe acts to maintain the sidewalls of the housing below a desired maximum temperature.
According to one aspect of the invention, a hot water supply system comprises a water heating unit having a capacity for heating water to a desired temperature range and having an inlet and a heater outlet and water supply means for -connection to a source of unheated water. A water storage tank is connected to the water supply means and has a first outlet for hot water connectible to a hot water supply pipe and a second outlet for the flow of water from the storage tank to the inlet of the heating unit. There is also a bypass conduit connecting the heater outlet to the hot water supply pipe and a valve mechanism for controlling the flow of water through the bypass conduit. There are also means for sensing the temperature of the water exiting the storage tank through the first outlet and valve operating means for opening or closing the valve mechanism depending on the temperature of the water measured by the sensing means, the valve operating mechanism opening the valve to permit water flow through the bypass conduit if the temperature is below a selected control temperature and closing the valve to shut off water flow through the bypass conduit if the sensed temperature is at least as high as the selected control temperature. There is a further conduit for connecting the second outlet of the storage tank to the inlet of the heating unit and for connecting the heater outlet to the storage tank so that the heating unit can be used to heat water contained in the storage tank.
According to another aspect of the invention, a hot water heater comprises a housing having top, bottom and sidewalls, an air inlet and an outlet for flue gases, and a burner mounted in a lower section of the housing. A heat exchanger is mounted in the housing above the burner and extends generally horizontally. The heat exchanger includes a tubular conduit having an inlet connected to a water supply and a hot water outlet. A passageway above the heat exchanger conducts the flue gases to the outlet of the housing and there are means for sensing the temperature of the flue gases in this passageway. An air valve mechanism is mounted in the housing adjacent the passageway and, in an open position, permits incoming air to enter the passageway and to mix with the flue gases, thereby cooling same. The control system moves the air valve between its open and closed positions with the air valve being moved to;the open position when the temperature of the flue gases in the-passageway is above a predetermined level and being moved to a closed position when the temperature of the flue gases is below this predetermined level.
In a preferred embodiment the air inlet is located at or near the top of the housing and there is a partition for separating the aforementioned passageway from incoming air entering through the air inlet when the temperature of the flue gases is below the predetermined level.
According to another aspect of the invention, a hot water heater comprises a housing having sidewalls, an air inlet and a flue gas outlet, and a main heat exchanger unit mounted in the housing in an upper portion thereof, this unit extending horizontally and having a number of air passageways formed therein. The unit includes a conduit for passing water to be heated through the unit. A burner is mounted in the housing below the heat exchanger and is spaced a substantial distance therefrom. A flue gas duct is mounted in the housing between the burner and the heat exchanger unit. A water pipe extends generally horizontally at least twice around the flue gas duct and is positioned adjacent exterior surfaces of the duct. This water pipe is connected to the conduit for the flow of heated water between them. There is a passage above the heat exchanger for conducting flue gases that have passed through the air passageways to the outlet. Water passing through the water pipe helps keep the sidewalls of the housing below a desired maximum temperature.
Further features and advantages will become apparent from the following detailed description taken in conjunction with the accompanying- drawings which illustrate preferred embodiments of the invention.
In the drawings, Figure 1 is a schematic illustration of a hot water supply system including a water storage tank but not the water heating unit, this figure illustrating the use of the system with a bypass valve in the open position and heated water flowing through a bypass conduit;
Figure 2 is a schematic illustration similar to Figure 1 but showing the bypass valve in the closed position and heated water flowing through the outlet in the top of the storage tank;
Figure 3 is a front view of a hot water heater constructed in accordance with the invention, which heater can be used with the system illustrated in Figures 1 and 2;
Figure 4 is a cross-sectional elevation taken along the line IV-IV of Figure 7, which view shows a preferred flue gas duct and heat exchanger combination;
Figure 5 is a front elevation of the flue gas duct and heat exchanger combination shown in Figure 4;
Figure 6 is front view of one embodiment of the water heater of Figure 3 but with the front panel removed to show the interior of the housing;
Figure 7 is a front elevation of a second embodiment of the heater unit, again with the front cover removed to show the interior of the housing;
Figure 8 is a plan view of a preferred gas burner used in the water heater; and Figure 9 is a schematic illustration of the preferred control system that can be used to operate the hot water supply system of the invention.
Figures 1 and 2 of the drawings illustrate a hot water supply system 10 constructed in accordance with the invention.
The actual water heater used with this system is not shown in these figures but this heating unit 12 is illustrated in Figures 3, 4, 6 and 7. It will be understood that the water heating unit 12 has the capacity for heating cold water to a desired temperature, which temperature would be selected by the user. In the illustrated embodiment there is a temperature control knob 14 mounted on the front of the heating unit. Shown in Figure 1 is a water storage tank 16 that in a known manner is insulated so as to maintain the temperature of the hot water in the tank. This tank is connected at its base to water supply means in the form of supply pipe 18 which is connected to a source of unheated water, typically a municipal water supply pipe or a well. At `_ 2125070 g the top of the tank there is a first outlet 20 for hot water, which outlet is connected to a hot water supply pipe 22. In the base of the tank there is also a second outlet 24 for the flow of water from the storage tank to an inlet 26 of the heating unit.
Also shown in Figure 1 is a bypass conduit means in the form of water pipe 28 which is connected at the top of the water tank by T-connector 30 to the hot water supply pipe 22.
The pipe 28 is also connected by a further T-connector 32 to a hot water outlet 34 of the water heater. Located in the pipe 28 and controlling the flow of water therethrough is a solenoid valve 36 which is open in Figure 1 and closed in Figure 2. The T-connector 32 is also connected to a water inlet pipe 38 which empties into the bottom of the tank 16.
In the illustrated preferred embodiment, a portion of this pipe extends centrally along the axis of larger pipe section 40 which is connected to a smaller drain pipe 42. Located in the pipe 42 is a manually operated valve 44 for draining the system.
Mounted near the outlet 20 on the adjacent section of the hot water supply pipe 22 is a sensor 46 which provides means for sensing the temperature of the water exiting the storage tank 16 through the first outlet 20. The sensor can be an adjustable thermodisc operated by 24 volt electrical current through the electrical lines indicated at 48. In one preferred form of the system, this sensor is set to a temperature 10F below the setting of the temperature sensor located in the storage tank 16 (not shown). In one preferred `~ 2I25070 embodiment the selected control temperature is 100F. In this way, the solenoid valve 36 will be opened by the control system if the temperature of the water exiting the tank is below the control setting for the tank. As illustrated in Figure 1, when the valve 36 is open, hot water will flow directly through the bypass conduit or pipe 28 from the heater and into the hot water supply pipe 22. Thus a constant supply of hot water is assured with this system even under reasonably high demand situations where the supply of hot water in the storage tank will or has been used up.
There are further conduit means for connecting the second outlet 24 of the storage tank to the water inlet of the heating unit and for connecting the heater outlet 34 to the storage tank. This further conduit means can take the form of water pipe 50 and the aforementioned pipe 38. In a preferred embodiment, the pipe 38 should include an internal section 52 that goes to the centre of the storage tank. In one embodiment, this section is about 12 inches long. Thus, with the use of pipes 50 and 38, the water heater can be used to heat the water in the storage tank when the solenoid valve 36 is closed as illustrated by the water flow arrows in Figure 2.
It should be noted that the water storage tank 16 can be constructed in the same manner as known electrical water heaters that include a storage tank. This will permit the user or owner to have a choice as to the heating means to be used at any particular time or under any given conditions.
For example, a system can be set up so that the electrical heater in the storage tank only operates during non-peak hours ~-- 2125070 of electrical use, particularly if this will help to reduce the cost of electricity for the user. During peak hours of electrical use, the gas fired water heater can then be used to heat the water supply in the tank.
Turning now to the construction of the separate gas fired water heater shown in Figures 3, 4, 6 and 7, this heater includes a housing 60 having a top 62, a bottom 64 and sidewalls that can include a front panel 66 and a rear wall 68. In the preferred illustrated embodiment, the housing has both an air inlet 70 and an outlet 72 for flue gases in its top 62. Preferably, at least the front panel 66 can be detached from the remainder of the housing to permit access to the interior of the housing. Connected to both the inlet 70 and the outlet 72 are plastic pipes 74 and 76 respectively.
The pipe 74 is used to conduct fresh outside air into the heater while the pipe 76 conducts the flue gases to the outside atmosphere. In one preferred embodiment, these two pipes measure 2 inches in diameter and they are made from a plastic such as PVC or ABS. The length of these plpes is preferably 30 inches or less and for this reason the water heater 12 is preferably mounted on an exterior or outside wall of the building. A suitable cover should be placed on the outer end of these pipes to prevent water and other undesirable foreign materials from entering same. The front cover of the unit can also be provided with an on-off switch 78 and a small window 80 through which the controls for the unit can be monitored by the user. Although plastic pipes are less expensive and easier to use for the pipes 74 and 76, it is also possible to use suitable metal pipes, such as steel pipes.
Turning now to Figures 6 and 7 of the drawings, there is shown a preferred interior arrangement for the heating unit, which arrangement includes a gas fired burner 80 mounted in a lower section of the housing and a heat exchanger 82 mounted above the burner and spaced therefrom. The heat exchanger 82 extends generally horizontally as shown both in the transverse direction of the housing and in the front to back direction and it includes a tubular conduit in the form of a bent copper pipe 84. The preferred construction for the heat exchanger and the adjacent duct is illustrated in Figures 4 and 5 and is described in more detail below.
Mounted immediately below the outlet 72 is a vent fan or blower 86 which, in a preferred embodiment, has a plastic wheel. The fan wheel is turned by fan motor 88. A suitable fan and motor for this heater is made by Torrin. The motor can be a 120 volt motor.
Also mounted on the right hand side in the housing is a standard water pump 90 having a pump motor 92 that is electrically operated. The pump 90 is connected to the water inlet 26 and its outlet 94 is connected to the conduit 84 that runs through the heat exchanger. Mounted above ~he pump is the electronic control unit 96 for the heater. Also mounted in the bottom of the housing is a standard gas valve for supplying a fuel such as natural gas to the burner. This gas valve 98 includes a standard regulator 100 and a manual shut-off 102. The valve is connected to the burner by means of bent pipe 104 located in an air chamber or plenum 106 below the burner. The top of this chamber is covered by slotted steel plate 108 which permits the combustion air to pass upwardly from chamber 106 to the burner.
The burner 80 which can be of standard construction is illustrated in Figure 8. The burner has a central inlet manifold 110 which feeds gas to a bank of ten small burner units indicated at 112 with a nominal input, in a preferred embodiment, of ten kW (34,000 BTU/hour). At one corner of the burner is an ignition assembly 114 which can include a hot surface pilot.
Figures 4, 6 and 7 illustrate how fresh outside air is fed to the burner 80. The air first enters through the inlet 70 into an upper air chamber 118. This chamber extends over a rectangular, horizontal, sheet metal panel 120. From this upper chamber the fresh air is drawn to the bottom end of the unit by means of a rear, vertical passageway 122 shown clearly in Figure 4. This passageway could have the.same width as the chamber 120 and thus it permits the unobstructed flow of air to the aforementioned bottom air chamber 106 located below the burner. The passageway 122 is bounded on one side by the rear wall 68 of the housing and on the opposite side by an internal vertical partition wall 124. This wall 124 has a bottom edge 126 spaced from the bottom of the housing.
After combustion occurs the flue gases pass up through a special duct and heat exchanger unit described hereinafter and then, in the embodiment of Figure 6, they pass into passageway means above the heat exchanger that conducts the flue gases to the fan and the outlet of the housing. In Figure 6 the passageway means comprises a box-like chamber 128, the top of which is formed by the aforementioned panel 120. The flue gases pass out of this chamber through a circular opening at 130, which opening is coaxial with the fan wheel.
Figure 7 illustrates a preferred passageway construction for the flue gases leaving the heat exchanger unit. In this version there is a sloping collector hood 132 which extends from internal partition 134 at a relatively small acute angle to the horizontal to an upper edge 136. The edge 136 is spaced more than two-thirds the width of the heat exchanger 82 from the circular opening 130 that leads to the fan wheel.
This hood acts to direct the flue gas flow from the heat exchanger initially away from the outlet for the flue gases as indicated by the arrows in Figure 7. The gases must pass around the edge 136 before flowing to the right and out the opening 130. The hood helps to ensure an even draw of the flue gases across the heat exchanger and thus a more efficient heat exchange. Thus, the hood helps to define and is part of the flue gas passageway 142.
Another preferred feature of the embodiment of Figure 7 is the use of air valve means mounted in the horizontal panel 120 and adjacent the passageway that conducts the flue gases to the fan. This air valve, indicated schematically at 140, normally prevents the incoming fresh air from passing into flue gas passageway 142, forcing all of said air to pass down through the rear passageway 122. However, when the air valve is moved to the open position shown in Figure 7, it permits incoming fresh air to enter the passageway 142 and to mix with the flue gases, thereby cooling same. Electrical control means described hereinafter move this air valve between the open and closed positions. The air valve is moved to the open position when the temperature of the flue gases in the passageway 142 is above a predetermined level. The air valve is moved to the closed position when the temperature of the flue gases is below this predetermined level. The provision of this air valve provides a safety feature that allows dilution air in to lower the temperature if the outgoing combustion air exceeds 200F. This helps to protect the plastic piping that can be used to conduct the flue gases away from the housing to atmosphere. The air valve feature is not required if metal pipe will be used instead of plastic pipe.
For example, it is possible that on hot days, when the incoming air itself is fairly warm, the outgoing flue gases could exceed 200F even though they have passed through the heat exchanger. The air valve itself is~ equipped with a thermostat or a separate thermostat is provided to measure the temperature of the flue gases or the combination of air and flue gases in the passageway 142. This thermostat is indicated schematically at 144 and in one preferred version, it is located directly below the opening that is opened or closed by the air valve 140. The combination air valve and thermostat can be of standard construction similar to the air valves used in many car heating systems. In one preferred embodiment, the air valve 140 will open at least partially when the incoming air has a temperature of 50F or more and the temperature of the flue gases reach 200F at the thermostat.
As illustrated in Figure 7, the sides of the vertical duct that conducts the flue gases to the heat exchanger 82 are preferably insulated, this insulation being indicated at 146 and 148. This insulation which should be of a suitable non-combustible type such as mineral wool, preferably extends along the inside of internal partition 134 and along the exterior sidewall 150 to which the insulation can be attached.
A thin layer of insulation is preferably provided along the inner surface of the panel 124 at the rear of the water heater in order to reduce sound from the unit. It is desirable to heat up the incoming fresh air in passageway 122 and this air flow helps to prevent the rear wall 68 from becoming too hot.
In a preferred unit the insulation at 149 is a 1/8th inch layer of mineral wool. Insulation can also be provided across the front of the duct carrying the flue gases, which insulation (not shown) can be mounted on the front panel 66.
Turning now to the construction of the combination duct and heat exchanger illustrated in Figures 4 and 5, the actual heat exchanger 82 is located at the top of this unit and comprises a number of thin copper fins indicated at 154 through which extend a number of passes of a tubular conduit in the form of copper pipe 84. 180 bends are formed in the pipe at the end of each pass as shown. The illustrated unit is designed for a 50,000 BTU system but by adding additional modules of 50,000 each, the capacity of the water heater can be increased to 100,000, 150,000 or more BTU. The heat 21251~710 exchanger is mounted preferably inside vertical panels indicated at 160 to 163 which are made of copper. In a preferred embodiment, these walls have a thickness of only 30/lOOOths of an inch. Because the walls are made of copper, they are excellent heat conductors, and they will expand and contract as the temperature of the duct changes. These copper walls are formed with upper and lower end flanges 164 and 165 which extend horizontally. On these flanges are arranged vertically extending connecting flanges 166 and 167 which provide a means for connecting the unit to the internal rear panel 124 and to an internal front panel 168.
As shown in Figures 5 and 6, the heat exchanger has an inlet 170 connected to the water supply via connecting pipe 94 and the water inlet 26. The heat exchanger also has a hot water outlet indicated at 174 which, in the preferred embodiment, connects up to a water pipe means indicated generally at 176 that extends around the exterior of duct walls 160 to 163 in a region extending from the top of the burner 80 to the bottom of the heat exchanger unit 82. The water pipe 176 floats freely, that is, it is not connected to the adjacent panels 160-163. Thus the water that has been heated in the heat exchanger passes into this water pipe and flows around the outside of the flue gas duct and then out a bottom outlet 178. Preferably, like the conduit 84, the water pipe means consists of a continuous length of copper piping that extends at least twice around the duct formed by the copper panels 160 to 163. The water pipe means provides at least two advantages. Firstly, the flow of water through this pipe helps to keep the inside of the housing and, in particular, the area around the duct, cooler than it would otherwise be. This helps to prevent the exterior panels of the housing and other components of the heater unit from becoming excessively hot. Secondly, because of the heat exchange that occurs between the hot flue gases and the water flowing through the pipe, the water is further heated as it descends through the pipe from the heat exchanger. Thus, the efficiency of the heating unit is improved.
10In the preferred illustrated embodiment, the water pipe 176 is bent to form several rectangular loops, these loops being arranged one above the other and spaced from one another. The illustrated embodiment has three of these loops.
Turning now to the control system for this hot water 15supply system, a preferred form of which is illustrated in Figure 9 schematically, 120 volt alternating current can be provided to the heating unit 12 by means of an input cord or connector and fuse indicated at 180. Optionally, this can be connected to a front service panel disconnect switch 182 which 20is a simple switch that disconnects the power once the front panel 66 has been removed. The panel line is then connected to the main on-off circuit breaker or switch 78 which is located on the front of the unit and this switch may be provided with an indicator light. This main switch is 25connected to a transformer 184 capable of providing both 24 volt alternating current and 9 volt alternating current on the output side. Both of the reduced current lines 185 and 186 are connected to a main electronic control unit 188 which is provided with the usual service reset. The unit 188 includes a suitable microprocessor such as one made by Honeywell (trade-mark).
The information that is fed to the control unit 188 includes an outlet temperature operational signal from the aforementioned sensor 46 located at the first outlet of the water tank, this signal being fed through line 190. In addition, an electrical signal indicating the temperature of the water near the bottom of the tank is fed through line 192 from electronic temperature sensor 194. If the water tank 16 is equipped with its own electric water heater, then there is preferably provided a further sensor at 196 which will send a suitable electric signal to the control unit when an electrical current in the electric water heater is sensed.
The gas fired water heater will not operate if the electric water heater is in operation.
Mounted in the heater unit 12 are three further electronic temperature sensors indicated at.198, 200 and 202.
Sensor 198 provides a burner high temperature lock-out signal to the control unit if the temperature of the flue gases at the outlet exceed 220F. This signal is fed through line 204.
The sensor 200 is optional and it is provided to send an electrical signal to the control unit if the temperature of the incoming water entering the unit is 140F or more. If this should occur, a light on the control panel goes on and indicates to the user that he should run a descaling solution through the heat exchanger because the temperatures of the incoming and outgoing water are too close to one another. The sensor 202 is a high temperature, internal operational limit signal which can be set to transmit a signal to the control unit at either 180 or 200F in one preferred embodiment. The heater unit will shut down if the temperature of the water exiting the heater exceeds the set temperature.
The heating unit also includes two pressure switches indicated at P1 and P2. The switch P1 is a high sensitivity pressure switch that is able to sense when the fan 86 is operating. A 120 volt alternating current is fed to the fan motor 88 via line 206 from the control unit. The fan must be operational before and during the operation of the burner and switch P1 will not permit the burner to operate if operation of the fan is not sensed. Electronic pressure switch P2 is provided to sense water pressure in the heating unit so as to ensure that there is water flowing through the unit when the burner is operating. The switch P2 sends a water pressure signal to the control unit through line 208. If no water pressure or insufficient water pressure is indicated by this signal, the control unit will turn off or not start up the burner.
Also shown schematically in Figure 9 is the gas valve assembly 98 to which two electrical control lines 210 and 212 are connected. Through line 210 the control unit can provide power to open a pilot valve in the valve assembly. Through line 212 power is provided to open a main burner valve which preferably has a soft start capability. Preferably a further sensor 214 is provided to sense pilot and main burner operation, this sensor sending a signal through line 216 to the control unit. Also shown in Figure 9 is the manually operated temperature control 14 by which the user sets the temperature desired for the hot water. A temperature control signal is sent through line 218 to the control unit.
Power is provided to the solenoid valve 36 through line 220 from control unit 188.
In a preferred embodiment of the heat exchanger 82, the sections of copper pipe at one side of the copper support duct are mounted so that they can "float" or "slide" in the surrounding copper panel. Preferably, the copper pipe "floats" at the end 85 which is the end opposite the heat exchanger inlet 170. This permits the copper pipe to expand or contract at a different rate than the surrounding copper panels, which condition can occur if they are at different temperatures. This feature helps to prevent heat exchanger failure and also helps prevent scale buildup.
A desirable feature of the present invention is that the water heater can be easily connected to the storage tank 16 by the use of flexible potable water hoses which are relatively inexpensive. These hoses are connected to the inlet 26 and the outlet 34 of the heater unit. It should also be noted that the heater unit 12 of the invention can be located as much as 30 feet from the storage tank. Thus, with the hot water supply system of the invention, one can obtain optimum use of floor space.
In the preferred burner unit for the water heater, there is a set purge period after which pilot burner ignition is initiated by means of the hot surface igniter. Once pilot - 212~070 flame has been established, the gas valve opens for the main burner ignition. The sensor 202 shuts off the burner in the event of excessive water temperature and, in one embodiment, this high temperature is set at 195F.
5In a preferred embodiment of the heating unit, burner combustion is supported by outside air drawn in through a balanced flue, that is, the intake plastic pipe 74 and the outlet pipe 76 are of the same length. With this system, inside air is not affected by the operation of the water 10heater. Also, in a preferred form of the water heater, the unit including the burner, heat exchanger and control are so constructed and arranged that they produce a water temperature rise of about 35F. to 40F. in the water each time it passes through the heat exchanger. With such a system, the amount of 15lime scale deposits formed in the heat exchanger is reduced.
It may be desirable to flush any lime scale deposits from the water heater of the invention once in a while. The flushing process is speedy and simple. The taps at the bottom of the water tank are turned off and the fittings at these 20taps are detached. The ends of the two flexible pipes are then placed in descaling fluid and the heater unit of the invention is turned on. The pump in the unit will then pump the fluid through the whole system and it should be run for about 15 minutes. The unit is then flushed with clean water 25for a few minutes to remove any residue of the descaling fluid.
A preferred embodiment of the present invention has been tested and has been found to be very efficient with an - 2125~70 operating efficiency of 80% or more. Compared to currently used water heating systems, a water heater constructed in accordance with the invention can typically result in an average cost saving of about 25% for a family of four persons.
Various modifications and changes to the described water heating unit and water supply system of the invention can be made and will be readily apparent to those skilled in this art. Accordingly, all such modifications and changes as fall within the scope of the appended claims are intended to be part of this invention.
A variety of hot water heating systems are known both for domestic and industrial use. A common system used in North America includes a rather large hot water storage tank which has means for heating the water stored in a tank. The source of the heat in these units can be electrical heating coils, gas fire burners or oil fire burners. Although hot water heaters employing electricity as the source of heat are still common for domestic water heaters, such units have lost favour with many consumers because of the high cost of electrical power in many regions.
Systems are also known for rapidly heating cold water by passing it through a coiled copper pipe positioned in or adjacent to a heating device. Such systems are commonly used in Europe and they can be made quite efficient but they suffer from the inability to provide large amounts of hot water quickly, unlike those systems which employ a hot water storage tank.
Because of the large number of existing hot water heating units that have a large storage tank and that employ electrical heat at the present time, it is believed that a demand exists for a system which would permit such existing units to be converted to a system which employs gas as the source of heat or to a system which can use either gas or electricity with the actual source of heat depending upon such variables as the amount of hot water required and the time of day at which the heating is required. By at least employing the hot water storage tank of these existing units, there could be a considerable cost savings as compared to purchasing a completely new hot water heating system employing gas as the source of heat. References herein to a "gas" fuel include such common gas fuels as natural gas and propane.
United States patent No. 4,671,212 issued June 9, 1987 to the present inventor Robert Smith describes a gas fired water heater that includes a housing enclosing an internal chamber divided by a vertical partition into two compartments, the partition having a top edge spaced below the top of the chamber. One of the compartments has a gas burner in the lower portion with an adjacent combustion air intake vent. A
first heat exchanger is located in the same compartment above the gas burner but below the top of the partition and a second heat exchanger is located in the other compartment. A flue pipe ducts flue gases from the housing and a blower is provided to blow the flue gases through the flue pipe which is connected to the unit at the bottom of the~housing.
United States patent No. 4,977,885 issued December 18, 1990 to E.B. Herweyer et al., describes a hot water heating system designed to supply hot water to a facility having a demand for such water that varies widely. This system has a water heater having an output capable of supplying water heated to a desired temperature at the normal flow rate and a storage tank for storing additional water heated to the desired temperature. Under conditions of normal flow rate, unheated water is supplied directly to the water heater with no flow to the tank. When the flow increases above the normal flow rate, unheated water is supplied to the tank and heated water is withdrawn from the tank and cold water is simultaneously supplied to the water heater. The flow between the tank and the water heater is limited to the capacity of the heater to supply water at the desired temperature, and the excess demand is supplied by heated water within the tank. A
temperature sensor is provided in the tank where the cold water enters.
The present invention provides an improved hot water heater employing a heat exchanger mounted above a burner, a passageway above the heat exchanger for conducting the flue gases to an outlet, and an unique air valve arrangement which moves to an open position to permit incoming air to enter the passageway above the heat exchanger and to mix with the flue gases, thereby cooling same. The air valve is moved to the open position when the temperature of the flue gases in the passageway is at or above a predetermined level.
According to another aspect of the invention, there is provided an improved hot water heater having a heat exchanger located a distance above a burner in a housing and a water pipe arrangement that extends around a flue gas duct in the region between the burner and the heat exchanger. The flow of water passing through this water pipe acts to maintain the sidewalls of the housing below a desired maximum temperature.
According to one aspect of the invention, a hot water supply system comprises a water heating unit having a capacity for heating water to a desired temperature range and having an inlet and a heater outlet and water supply means for -connection to a source of unheated water. A water storage tank is connected to the water supply means and has a first outlet for hot water connectible to a hot water supply pipe and a second outlet for the flow of water from the storage tank to the inlet of the heating unit. There is also a bypass conduit connecting the heater outlet to the hot water supply pipe and a valve mechanism for controlling the flow of water through the bypass conduit. There are also means for sensing the temperature of the water exiting the storage tank through the first outlet and valve operating means for opening or closing the valve mechanism depending on the temperature of the water measured by the sensing means, the valve operating mechanism opening the valve to permit water flow through the bypass conduit if the temperature is below a selected control temperature and closing the valve to shut off water flow through the bypass conduit if the sensed temperature is at least as high as the selected control temperature. There is a further conduit for connecting the second outlet of the storage tank to the inlet of the heating unit and for connecting the heater outlet to the storage tank so that the heating unit can be used to heat water contained in the storage tank.
According to another aspect of the invention, a hot water heater comprises a housing having top, bottom and sidewalls, an air inlet and an outlet for flue gases, and a burner mounted in a lower section of the housing. A heat exchanger is mounted in the housing above the burner and extends generally horizontally. The heat exchanger includes a tubular conduit having an inlet connected to a water supply and a hot water outlet. A passageway above the heat exchanger conducts the flue gases to the outlet of the housing and there are means for sensing the temperature of the flue gases in this passageway. An air valve mechanism is mounted in the housing adjacent the passageway and, in an open position, permits incoming air to enter the passageway and to mix with the flue gases, thereby cooling same. The control system moves the air valve between its open and closed positions with the air valve being moved to;the open position when the temperature of the flue gases in the-passageway is above a predetermined level and being moved to a closed position when the temperature of the flue gases is below this predetermined level.
In a preferred embodiment the air inlet is located at or near the top of the housing and there is a partition for separating the aforementioned passageway from incoming air entering through the air inlet when the temperature of the flue gases is below the predetermined level.
According to another aspect of the invention, a hot water heater comprises a housing having sidewalls, an air inlet and a flue gas outlet, and a main heat exchanger unit mounted in the housing in an upper portion thereof, this unit extending horizontally and having a number of air passageways formed therein. The unit includes a conduit for passing water to be heated through the unit. A burner is mounted in the housing below the heat exchanger and is spaced a substantial distance therefrom. A flue gas duct is mounted in the housing between the burner and the heat exchanger unit. A water pipe extends generally horizontally at least twice around the flue gas duct and is positioned adjacent exterior surfaces of the duct. This water pipe is connected to the conduit for the flow of heated water between them. There is a passage above the heat exchanger for conducting flue gases that have passed through the air passageways to the outlet. Water passing through the water pipe helps keep the sidewalls of the housing below a desired maximum temperature.
Further features and advantages will become apparent from the following detailed description taken in conjunction with the accompanying- drawings which illustrate preferred embodiments of the invention.
In the drawings, Figure 1 is a schematic illustration of a hot water supply system including a water storage tank but not the water heating unit, this figure illustrating the use of the system with a bypass valve in the open position and heated water flowing through a bypass conduit;
Figure 2 is a schematic illustration similar to Figure 1 but showing the bypass valve in the closed position and heated water flowing through the outlet in the top of the storage tank;
Figure 3 is a front view of a hot water heater constructed in accordance with the invention, which heater can be used with the system illustrated in Figures 1 and 2;
Figure 4 is a cross-sectional elevation taken along the line IV-IV of Figure 7, which view shows a preferred flue gas duct and heat exchanger combination;
Figure 5 is a front elevation of the flue gas duct and heat exchanger combination shown in Figure 4;
Figure 6 is front view of one embodiment of the water heater of Figure 3 but with the front panel removed to show the interior of the housing;
Figure 7 is a front elevation of a second embodiment of the heater unit, again with the front cover removed to show the interior of the housing;
Figure 8 is a plan view of a preferred gas burner used in the water heater; and Figure 9 is a schematic illustration of the preferred control system that can be used to operate the hot water supply system of the invention.
Figures 1 and 2 of the drawings illustrate a hot water supply system 10 constructed in accordance with the invention.
The actual water heater used with this system is not shown in these figures but this heating unit 12 is illustrated in Figures 3, 4, 6 and 7. It will be understood that the water heating unit 12 has the capacity for heating cold water to a desired temperature, which temperature would be selected by the user. In the illustrated embodiment there is a temperature control knob 14 mounted on the front of the heating unit. Shown in Figure 1 is a water storage tank 16 that in a known manner is insulated so as to maintain the temperature of the hot water in the tank. This tank is connected at its base to water supply means in the form of supply pipe 18 which is connected to a source of unheated water, typically a municipal water supply pipe or a well. At `_ 2125070 g the top of the tank there is a first outlet 20 for hot water, which outlet is connected to a hot water supply pipe 22. In the base of the tank there is also a second outlet 24 for the flow of water from the storage tank to an inlet 26 of the heating unit.
Also shown in Figure 1 is a bypass conduit means in the form of water pipe 28 which is connected at the top of the water tank by T-connector 30 to the hot water supply pipe 22.
The pipe 28 is also connected by a further T-connector 32 to a hot water outlet 34 of the water heater. Located in the pipe 28 and controlling the flow of water therethrough is a solenoid valve 36 which is open in Figure 1 and closed in Figure 2. The T-connector 32 is also connected to a water inlet pipe 38 which empties into the bottom of the tank 16.
In the illustrated preferred embodiment, a portion of this pipe extends centrally along the axis of larger pipe section 40 which is connected to a smaller drain pipe 42. Located in the pipe 42 is a manually operated valve 44 for draining the system.
Mounted near the outlet 20 on the adjacent section of the hot water supply pipe 22 is a sensor 46 which provides means for sensing the temperature of the water exiting the storage tank 16 through the first outlet 20. The sensor can be an adjustable thermodisc operated by 24 volt electrical current through the electrical lines indicated at 48. In one preferred form of the system, this sensor is set to a temperature 10F below the setting of the temperature sensor located in the storage tank 16 (not shown). In one preferred `~ 2I25070 embodiment the selected control temperature is 100F. In this way, the solenoid valve 36 will be opened by the control system if the temperature of the water exiting the tank is below the control setting for the tank. As illustrated in Figure 1, when the valve 36 is open, hot water will flow directly through the bypass conduit or pipe 28 from the heater and into the hot water supply pipe 22. Thus a constant supply of hot water is assured with this system even under reasonably high demand situations where the supply of hot water in the storage tank will or has been used up.
There are further conduit means for connecting the second outlet 24 of the storage tank to the water inlet of the heating unit and for connecting the heater outlet 34 to the storage tank. This further conduit means can take the form of water pipe 50 and the aforementioned pipe 38. In a preferred embodiment, the pipe 38 should include an internal section 52 that goes to the centre of the storage tank. In one embodiment, this section is about 12 inches long. Thus, with the use of pipes 50 and 38, the water heater can be used to heat the water in the storage tank when the solenoid valve 36 is closed as illustrated by the water flow arrows in Figure 2.
It should be noted that the water storage tank 16 can be constructed in the same manner as known electrical water heaters that include a storage tank. This will permit the user or owner to have a choice as to the heating means to be used at any particular time or under any given conditions.
For example, a system can be set up so that the electrical heater in the storage tank only operates during non-peak hours ~-- 2125070 of electrical use, particularly if this will help to reduce the cost of electricity for the user. During peak hours of electrical use, the gas fired water heater can then be used to heat the water supply in the tank.
Turning now to the construction of the separate gas fired water heater shown in Figures 3, 4, 6 and 7, this heater includes a housing 60 having a top 62, a bottom 64 and sidewalls that can include a front panel 66 and a rear wall 68. In the preferred illustrated embodiment, the housing has both an air inlet 70 and an outlet 72 for flue gases in its top 62. Preferably, at least the front panel 66 can be detached from the remainder of the housing to permit access to the interior of the housing. Connected to both the inlet 70 and the outlet 72 are plastic pipes 74 and 76 respectively.
The pipe 74 is used to conduct fresh outside air into the heater while the pipe 76 conducts the flue gases to the outside atmosphere. In one preferred embodiment, these two pipes measure 2 inches in diameter and they are made from a plastic such as PVC or ABS. The length of these plpes is preferably 30 inches or less and for this reason the water heater 12 is preferably mounted on an exterior or outside wall of the building. A suitable cover should be placed on the outer end of these pipes to prevent water and other undesirable foreign materials from entering same. The front cover of the unit can also be provided with an on-off switch 78 and a small window 80 through which the controls for the unit can be monitored by the user. Although plastic pipes are less expensive and easier to use for the pipes 74 and 76, it is also possible to use suitable metal pipes, such as steel pipes.
Turning now to Figures 6 and 7 of the drawings, there is shown a preferred interior arrangement for the heating unit, which arrangement includes a gas fired burner 80 mounted in a lower section of the housing and a heat exchanger 82 mounted above the burner and spaced therefrom. The heat exchanger 82 extends generally horizontally as shown both in the transverse direction of the housing and in the front to back direction and it includes a tubular conduit in the form of a bent copper pipe 84. The preferred construction for the heat exchanger and the adjacent duct is illustrated in Figures 4 and 5 and is described in more detail below.
Mounted immediately below the outlet 72 is a vent fan or blower 86 which, in a preferred embodiment, has a plastic wheel. The fan wheel is turned by fan motor 88. A suitable fan and motor for this heater is made by Torrin. The motor can be a 120 volt motor.
Also mounted on the right hand side in the housing is a standard water pump 90 having a pump motor 92 that is electrically operated. The pump 90 is connected to the water inlet 26 and its outlet 94 is connected to the conduit 84 that runs through the heat exchanger. Mounted above ~he pump is the electronic control unit 96 for the heater. Also mounted in the bottom of the housing is a standard gas valve for supplying a fuel such as natural gas to the burner. This gas valve 98 includes a standard regulator 100 and a manual shut-off 102. The valve is connected to the burner by means of bent pipe 104 located in an air chamber or plenum 106 below the burner. The top of this chamber is covered by slotted steel plate 108 which permits the combustion air to pass upwardly from chamber 106 to the burner.
The burner 80 which can be of standard construction is illustrated in Figure 8. The burner has a central inlet manifold 110 which feeds gas to a bank of ten small burner units indicated at 112 with a nominal input, in a preferred embodiment, of ten kW (34,000 BTU/hour). At one corner of the burner is an ignition assembly 114 which can include a hot surface pilot.
Figures 4, 6 and 7 illustrate how fresh outside air is fed to the burner 80. The air first enters through the inlet 70 into an upper air chamber 118. This chamber extends over a rectangular, horizontal, sheet metal panel 120. From this upper chamber the fresh air is drawn to the bottom end of the unit by means of a rear, vertical passageway 122 shown clearly in Figure 4. This passageway could have the.same width as the chamber 120 and thus it permits the unobstructed flow of air to the aforementioned bottom air chamber 106 located below the burner. The passageway 122 is bounded on one side by the rear wall 68 of the housing and on the opposite side by an internal vertical partition wall 124. This wall 124 has a bottom edge 126 spaced from the bottom of the housing.
After combustion occurs the flue gases pass up through a special duct and heat exchanger unit described hereinafter and then, in the embodiment of Figure 6, they pass into passageway means above the heat exchanger that conducts the flue gases to the fan and the outlet of the housing. In Figure 6 the passageway means comprises a box-like chamber 128, the top of which is formed by the aforementioned panel 120. The flue gases pass out of this chamber through a circular opening at 130, which opening is coaxial with the fan wheel.
Figure 7 illustrates a preferred passageway construction for the flue gases leaving the heat exchanger unit. In this version there is a sloping collector hood 132 which extends from internal partition 134 at a relatively small acute angle to the horizontal to an upper edge 136. The edge 136 is spaced more than two-thirds the width of the heat exchanger 82 from the circular opening 130 that leads to the fan wheel.
This hood acts to direct the flue gas flow from the heat exchanger initially away from the outlet for the flue gases as indicated by the arrows in Figure 7. The gases must pass around the edge 136 before flowing to the right and out the opening 130. The hood helps to ensure an even draw of the flue gases across the heat exchanger and thus a more efficient heat exchange. Thus, the hood helps to define and is part of the flue gas passageway 142.
Another preferred feature of the embodiment of Figure 7 is the use of air valve means mounted in the horizontal panel 120 and adjacent the passageway that conducts the flue gases to the fan. This air valve, indicated schematically at 140, normally prevents the incoming fresh air from passing into flue gas passageway 142, forcing all of said air to pass down through the rear passageway 122. However, when the air valve is moved to the open position shown in Figure 7, it permits incoming fresh air to enter the passageway 142 and to mix with the flue gases, thereby cooling same. Electrical control means described hereinafter move this air valve between the open and closed positions. The air valve is moved to the open position when the temperature of the flue gases in the passageway 142 is above a predetermined level. The air valve is moved to the closed position when the temperature of the flue gases is below this predetermined level. The provision of this air valve provides a safety feature that allows dilution air in to lower the temperature if the outgoing combustion air exceeds 200F. This helps to protect the plastic piping that can be used to conduct the flue gases away from the housing to atmosphere. The air valve feature is not required if metal pipe will be used instead of plastic pipe.
For example, it is possible that on hot days, when the incoming air itself is fairly warm, the outgoing flue gases could exceed 200F even though they have passed through the heat exchanger. The air valve itself is~ equipped with a thermostat or a separate thermostat is provided to measure the temperature of the flue gases or the combination of air and flue gases in the passageway 142. This thermostat is indicated schematically at 144 and in one preferred version, it is located directly below the opening that is opened or closed by the air valve 140. The combination air valve and thermostat can be of standard construction similar to the air valves used in many car heating systems. In one preferred embodiment, the air valve 140 will open at least partially when the incoming air has a temperature of 50F or more and the temperature of the flue gases reach 200F at the thermostat.
As illustrated in Figure 7, the sides of the vertical duct that conducts the flue gases to the heat exchanger 82 are preferably insulated, this insulation being indicated at 146 and 148. This insulation which should be of a suitable non-combustible type such as mineral wool, preferably extends along the inside of internal partition 134 and along the exterior sidewall 150 to which the insulation can be attached.
A thin layer of insulation is preferably provided along the inner surface of the panel 124 at the rear of the water heater in order to reduce sound from the unit. It is desirable to heat up the incoming fresh air in passageway 122 and this air flow helps to prevent the rear wall 68 from becoming too hot.
In a preferred unit the insulation at 149 is a 1/8th inch layer of mineral wool. Insulation can also be provided across the front of the duct carrying the flue gases, which insulation (not shown) can be mounted on the front panel 66.
Turning now to the construction of the combination duct and heat exchanger illustrated in Figures 4 and 5, the actual heat exchanger 82 is located at the top of this unit and comprises a number of thin copper fins indicated at 154 through which extend a number of passes of a tubular conduit in the form of copper pipe 84. 180 bends are formed in the pipe at the end of each pass as shown. The illustrated unit is designed for a 50,000 BTU system but by adding additional modules of 50,000 each, the capacity of the water heater can be increased to 100,000, 150,000 or more BTU. The heat 21251~710 exchanger is mounted preferably inside vertical panels indicated at 160 to 163 which are made of copper. In a preferred embodiment, these walls have a thickness of only 30/lOOOths of an inch. Because the walls are made of copper, they are excellent heat conductors, and they will expand and contract as the temperature of the duct changes. These copper walls are formed with upper and lower end flanges 164 and 165 which extend horizontally. On these flanges are arranged vertically extending connecting flanges 166 and 167 which provide a means for connecting the unit to the internal rear panel 124 and to an internal front panel 168.
As shown in Figures 5 and 6, the heat exchanger has an inlet 170 connected to the water supply via connecting pipe 94 and the water inlet 26. The heat exchanger also has a hot water outlet indicated at 174 which, in the preferred embodiment, connects up to a water pipe means indicated generally at 176 that extends around the exterior of duct walls 160 to 163 in a region extending from the top of the burner 80 to the bottom of the heat exchanger unit 82. The water pipe 176 floats freely, that is, it is not connected to the adjacent panels 160-163. Thus the water that has been heated in the heat exchanger passes into this water pipe and flows around the outside of the flue gas duct and then out a bottom outlet 178. Preferably, like the conduit 84, the water pipe means consists of a continuous length of copper piping that extends at least twice around the duct formed by the copper panels 160 to 163. The water pipe means provides at least two advantages. Firstly, the flow of water through this pipe helps to keep the inside of the housing and, in particular, the area around the duct, cooler than it would otherwise be. This helps to prevent the exterior panels of the housing and other components of the heater unit from becoming excessively hot. Secondly, because of the heat exchange that occurs between the hot flue gases and the water flowing through the pipe, the water is further heated as it descends through the pipe from the heat exchanger. Thus, the efficiency of the heating unit is improved.
10In the preferred illustrated embodiment, the water pipe 176 is bent to form several rectangular loops, these loops being arranged one above the other and spaced from one another. The illustrated embodiment has three of these loops.
Turning now to the control system for this hot water 15supply system, a preferred form of which is illustrated in Figure 9 schematically, 120 volt alternating current can be provided to the heating unit 12 by means of an input cord or connector and fuse indicated at 180. Optionally, this can be connected to a front service panel disconnect switch 182 which 20is a simple switch that disconnects the power once the front panel 66 has been removed. The panel line is then connected to the main on-off circuit breaker or switch 78 which is located on the front of the unit and this switch may be provided with an indicator light. This main switch is 25connected to a transformer 184 capable of providing both 24 volt alternating current and 9 volt alternating current on the output side. Both of the reduced current lines 185 and 186 are connected to a main electronic control unit 188 which is provided with the usual service reset. The unit 188 includes a suitable microprocessor such as one made by Honeywell (trade-mark).
The information that is fed to the control unit 188 includes an outlet temperature operational signal from the aforementioned sensor 46 located at the first outlet of the water tank, this signal being fed through line 190. In addition, an electrical signal indicating the temperature of the water near the bottom of the tank is fed through line 192 from electronic temperature sensor 194. If the water tank 16 is equipped with its own electric water heater, then there is preferably provided a further sensor at 196 which will send a suitable electric signal to the control unit when an electrical current in the electric water heater is sensed.
The gas fired water heater will not operate if the electric water heater is in operation.
Mounted in the heater unit 12 are three further electronic temperature sensors indicated at.198, 200 and 202.
Sensor 198 provides a burner high temperature lock-out signal to the control unit if the temperature of the flue gases at the outlet exceed 220F. This signal is fed through line 204.
The sensor 200 is optional and it is provided to send an electrical signal to the control unit if the temperature of the incoming water entering the unit is 140F or more. If this should occur, a light on the control panel goes on and indicates to the user that he should run a descaling solution through the heat exchanger because the temperatures of the incoming and outgoing water are too close to one another. The sensor 202 is a high temperature, internal operational limit signal which can be set to transmit a signal to the control unit at either 180 or 200F in one preferred embodiment. The heater unit will shut down if the temperature of the water exiting the heater exceeds the set temperature.
The heating unit also includes two pressure switches indicated at P1 and P2. The switch P1 is a high sensitivity pressure switch that is able to sense when the fan 86 is operating. A 120 volt alternating current is fed to the fan motor 88 via line 206 from the control unit. The fan must be operational before and during the operation of the burner and switch P1 will not permit the burner to operate if operation of the fan is not sensed. Electronic pressure switch P2 is provided to sense water pressure in the heating unit so as to ensure that there is water flowing through the unit when the burner is operating. The switch P2 sends a water pressure signal to the control unit through line 208. If no water pressure or insufficient water pressure is indicated by this signal, the control unit will turn off or not start up the burner.
Also shown schematically in Figure 9 is the gas valve assembly 98 to which two electrical control lines 210 and 212 are connected. Through line 210 the control unit can provide power to open a pilot valve in the valve assembly. Through line 212 power is provided to open a main burner valve which preferably has a soft start capability. Preferably a further sensor 214 is provided to sense pilot and main burner operation, this sensor sending a signal through line 216 to the control unit. Also shown in Figure 9 is the manually operated temperature control 14 by which the user sets the temperature desired for the hot water. A temperature control signal is sent through line 218 to the control unit.
Power is provided to the solenoid valve 36 through line 220 from control unit 188.
In a preferred embodiment of the heat exchanger 82, the sections of copper pipe at one side of the copper support duct are mounted so that they can "float" or "slide" in the surrounding copper panel. Preferably, the copper pipe "floats" at the end 85 which is the end opposite the heat exchanger inlet 170. This permits the copper pipe to expand or contract at a different rate than the surrounding copper panels, which condition can occur if they are at different temperatures. This feature helps to prevent heat exchanger failure and also helps prevent scale buildup.
A desirable feature of the present invention is that the water heater can be easily connected to the storage tank 16 by the use of flexible potable water hoses which are relatively inexpensive. These hoses are connected to the inlet 26 and the outlet 34 of the heater unit. It should also be noted that the heater unit 12 of the invention can be located as much as 30 feet from the storage tank. Thus, with the hot water supply system of the invention, one can obtain optimum use of floor space.
In the preferred burner unit for the water heater, there is a set purge period after which pilot burner ignition is initiated by means of the hot surface igniter. Once pilot - 212~070 flame has been established, the gas valve opens for the main burner ignition. The sensor 202 shuts off the burner in the event of excessive water temperature and, in one embodiment, this high temperature is set at 195F.
5In a preferred embodiment of the heating unit, burner combustion is supported by outside air drawn in through a balanced flue, that is, the intake plastic pipe 74 and the outlet pipe 76 are of the same length. With this system, inside air is not affected by the operation of the water 10heater. Also, in a preferred form of the water heater, the unit including the burner, heat exchanger and control are so constructed and arranged that they produce a water temperature rise of about 35F. to 40F. in the water each time it passes through the heat exchanger. With such a system, the amount of 15lime scale deposits formed in the heat exchanger is reduced.
It may be desirable to flush any lime scale deposits from the water heater of the invention once in a while. The flushing process is speedy and simple. The taps at the bottom of the water tank are turned off and the fittings at these 20taps are detached. The ends of the two flexible pipes are then placed in descaling fluid and the heater unit of the invention is turned on. The pump in the unit will then pump the fluid through the whole system and it should be run for about 15 minutes. The unit is then flushed with clean water 25for a few minutes to remove any residue of the descaling fluid.
A preferred embodiment of the present invention has been tested and has been found to be very efficient with an - 2125~70 operating efficiency of 80% or more. Compared to currently used water heating systems, a water heater constructed in accordance with the invention can typically result in an average cost saving of about 25% for a family of four persons.
Various modifications and changes to the described water heating unit and water supply system of the invention can be made and will be readily apparent to those skilled in this art. Accordingly, all such modifications and changes as fall within the scope of the appended claims are intended to be part of this invention.
Claims (25)
1. A hot water supply system comprising:
(a) a water heating unit having a capacity for heating water to a desired temperature range, and having a water inlet and a heater outlet for heated water;
(b) water supply means for connection to a source of unheated water;
(c) a water storage tank connected to said water supply means and having a first outlet for hot water connectible to a hot water supply pipe and a second outlet for the flow of water from said storage tank to the inlet of said heating unit;
(d) bypass conduit means connecting said heater outlet to said hot water supply pipe;
(e) a valve means for controlling flow of water through said bypass conduit means;
(f) means for sensing the temperature of water exiting said storage tank through said first outlet;
(g) valve operating means for opening and closing said valve means depending on the temperature of the water measured by said sensing means, said valve operating means opening said valve means to permit water flow through said bypass conduit means if the sensed temperature is below a selected control temperature and closing said valve means to shut off water flow through said bypass conduit means if said sensed temperature is at least as high as said selected control temperature; and (h) further conduit means for connecting said second outlet of said storage tank to said inlet of the heating unit and for connecting said heater outlet to said storage tank, wherein said heating unit can be used to heat water contained in said storage tank.
(a) a water heating unit having a capacity for heating water to a desired temperature range, and having a water inlet and a heater outlet for heated water;
(b) water supply means for connection to a source of unheated water;
(c) a water storage tank connected to said water supply means and having a first outlet for hot water connectible to a hot water supply pipe and a second outlet for the flow of water from said storage tank to the inlet of said heating unit;
(d) bypass conduit means connecting said heater outlet to said hot water supply pipe;
(e) a valve means for controlling flow of water through said bypass conduit means;
(f) means for sensing the temperature of water exiting said storage tank through said first outlet;
(g) valve operating means for opening and closing said valve means depending on the temperature of the water measured by said sensing means, said valve operating means opening said valve means to permit water flow through said bypass conduit means if the sensed temperature is below a selected control temperature and closing said valve means to shut off water flow through said bypass conduit means if said sensed temperature is at least as high as said selected control temperature; and (h) further conduit means for connecting said second outlet of said storage tank to said inlet of the heating unit and for connecting said heater outlet to said storage tank, wherein said heating unit can be used to heat water contained in said storage tank.
2. A hot water supply system according to claim 1 wherein said heating unit is a gas fired unit having a coil-type heat exchanger for heating water passing through the unit.
3. A hot water supply system according to claim 2 wherein said further conduit means are connected to said storage tank in the vicinity of the bottom thereof;
4. A hot water supply system according to any one of claims 1 to 3 wherein said selected control temperature is about 100°F.
5. A hot water supply system according to any one of claims 1 to 3 wherein said valve operating means includes an electrically operated solenoid.
6. A hot water supply system according to any one of claims 1 to 3 wherein said bypass conduit means is a water conduit extending between said further conduit means that connects said heater outlet to said storage tank and said hot water supply pipe which leads to a facility having a demand for heated water.
7. A hot water supply system according to any one of claims 1 to 3 wherein said water storage tank has electrical heating means contained therein for heating water in said tank, said gas fired unit being used as an alternative to said electrical heating means.
8. A hot water heater comprising:
a housing having top, bottom and sidewalls, an air inlet and an outlet for flue gases;
a burner mounted in a lower section of said housing;
a heat exchanger mounted in said housing above said burner and extending generally horizontally, said heat exchanger including a tubular conduit having an inlet connected to a water supply and a hot water outlet;
passageway means above said heat exchanger for conducting said flue gases to said outlet of said housing;
means for sensing the temperature of said flue gases in said passageway means;
air valve means mounted in said housing adjacent said passageway means and, in an open position, permitting incoming air to enter said passageway means and to mix with said flue gases, thereby cooling same; and control means for moving said air valve means between open and closed positions, said air valve means being moved to said open position when the temperature of said flue gases in said passageway means is above a predetermined level and being moved to a closed position when the temperature of said flue gases is below said predetermined level.
a housing having top, bottom and sidewalls, an air inlet and an outlet for flue gases;
a burner mounted in a lower section of said housing;
a heat exchanger mounted in said housing above said burner and extending generally horizontally, said heat exchanger including a tubular conduit having an inlet connected to a water supply and a hot water outlet;
passageway means above said heat exchanger for conducting said flue gases to said outlet of said housing;
means for sensing the temperature of said flue gases in said passageway means;
air valve means mounted in said housing adjacent said passageway means and, in an open position, permitting incoming air to enter said passageway means and to mix with said flue gases, thereby cooling same; and control means for moving said air valve means between open and closed positions, said air valve means being moved to said open position when the temperature of said flue gases in said passageway means is above a predetermined level and being moved to a closed position when the temperature of said flue gases is below said predetermined level.
9. A hot water heater according to claim 8 wherein said air inlet is located at or near the top of said housing and there are partition means for separating said passageway means from incoming air entering through said air inlet when the temperature of the flue gases is below said predetermined level.
10. A hot water heater according to claim 9 including an air passageway for conducting incoming air from said air inlet to said lower section of said housing.
11. A hot water heater according to claim 10 wherein said air passageway for conducting incoming air has a width substantially the same as said heat exchanger taken in the transverse direction of said housing and is located between a back sidewall of the housing and an internal, vertical partition wall.
12. A hot water heater according to any one of claims 8 to 11 including fan means for blowing flue gases through a flue pipe or conduit.
13. A hot water heater according to any one of claims 9 to 11 wherein said air valve means includes a movable valve member capable of opening or closing an opening formed in said partition means.
14. A hot water heater according to any one of claims 8 to 11 including a collector hood mounted in said housing above said heat exchanger, said hood acting to direct flue gas flow from said heat exchanger initially away from said outlet for the flue gases, said hood at least partially defining said passageway means.
15. A hot water heater according to any one of claims 8 to 11 wherein said heat exchanger is a coil type heat exchanger and said tubular conduit is copper tubing having a number of fins arranged thereon.
16. A hot water heater according to any one of claims 8 to 11 wherein said predetermined temperature level is about 160°F.
17. A hot water heater according to any one of claims 8 to 11 wherein said outlet of said housing is connected to a flue pipe made of plastics material.
18. A hot water heater comprising:
a housing having sidewalls, an air inlet and a flue gas outlet;
a main heat exchanger unit mounted in said housing in an upper portion thereof, said unit extending horizontally and having a number of air passageways formed therein, said unit including conduit means for passing water to be heated through said unit;
a burner mounted in said housing below said heat exchanger unit and spaced a substantial distance therefrom;
a flue gas duct mounted in said housing between said burner and said heat exchanger unit;
water pipe means extending generally horizontally at least twice around said flue gas duct and positioned adjacent exterior surfaces of said duct, said water pipe means being connected to said conduit means for the flow of heated water between them; and passage means above said heat exchanger for conducting flue gases that have passed through said air passageways to said outlet;
wherein water passing through said water pipe means helps to maintain said sidewalls of the housing below a desired maximum temperature.
a housing having sidewalls, an air inlet and a flue gas outlet;
a main heat exchanger unit mounted in said housing in an upper portion thereof, said unit extending horizontally and having a number of air passageways formed therein, said unit including conduit means for passing water to be heated through said unit;
a burner mounted in said housing below said heat exchanger unit and spaced a substantial distance therefrom;
a flue gas duct mounted in said housing between said burner and said heat exchanger unit;
water pipe means extending generally horizontally at least twice around said flue gas duct and positioned adjacent exterior surfaces of said duct, said water pipe means being connected to said conduit means for the flow of heated water between them; and passage means above said heat exchanger for conducting flue gases that have passed through said air passageways to said outlet;
wherein water passing through said water pipe means helps to maintain said sidewalls of the housing below a desired maximum temperature.
19. A hot water heater according to claim 18 wherein said flue gas duct is generally rectangular in horizontal cross-section, is made of copper and has vertically extending sides spaced from the sidewalls of said housing.
20. A hot water duct according to claim 18 wherein at least some of said sidewalls of said housing are insulated to reduce the passage of heat therethrough.
21. A hot water heater according to claim 19 including a blower unit for drawing flue gases through said heat exchanger unit and out of said flue gas outlet.
22. A hot water heater according to any one of claims 18 to 21 including an air passageway for conducting incoming air from said air inlet, which is located at or near the top of said housing, to a lower section of the housing positioned below said burner, said air passageway having a width substantially the same as the heat exchanger unit taken in the transverse direction of the housing.
23. A hot water heater according to any one of claims 18 to 21 wherein said conduit means forms a number of horizontal passes across the heat exchanger unit and is connected at one end to a water inlet and at an opposite end to said water pipe means which extends to a hot water outlet for the water heater.
24. A hot water heater according to any one of claims 18, 19 and 21 wherein said water pipe means is a continuous copper pipe that is bent to form several loops extending around said flue gas duct, said loops being arranged one above another and spaced from one another.
25. A hot water duct according to claim 24 wherein at least two sidewalls of said housing are insulated to reduce the passage of heat therethrough.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US25179194A | 1994-05-31 | 1994-05-31 | |
| US08/251,791 | 1994-05-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2125070A1 true CA2125070A1 (en) | 1995-12-01 |
Family
ID=22953422
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2125070 Abandoned CA2125070A1 (en) | 1994-05-31 | 1994-06-03 | Hot water supply system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2125070A1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6345769B2 (en) | 2000-04-17 | 2002-02-12 | Canadian Gas Research Institute | Water heating apparatus with sensible and latent heat recovery |
| WO2013150536A3 (en) * | 2012-04-05 | 2013-11-28 | Golan-Plastic Products Ltd. | Hot water supply system |
| CN109812797A (en) * | 2019-03-11 | 2019-05-28 | 大唐桂冠合山发电有限公司 | Low-pressure heater draining system |
-
1994
- 1994-06-03 CA CA 2125070 patent/CA2125070A1/en not_active Abandoned
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6345769B2 (en) | 2000-04-17 | 2002-02-12 | Canadian Gas Research Institute | Water heating apparatus with sensible and latent heat recovery |
| WO2013150536A3 (en) * | 2012-04-05 | 2013-11-28 | Golan-Plastic Products Ltd. | Hot water supply system |
| CN109812797A (en) * | 2019-03-11 | 2019-05-28 | 大唐桂冠合山发电有限公司 | Low-pressure heater draining system |
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| Date | Code | Title | Description |
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| FZDE | Dead |