GB2130347A - Heating installation - Google Patents

Abstract

Heating installation comprising a water tank 16, a cold water inlet 17 to the tank, a hot water outlet from the tank, a water heater for heating water in the tank, a hot pipe 23 connected to the outlet, a cold pipe 24 for supplying cold water direct to the hot pipe, a valve 26 and a thermostat 27 for controlling the rate of supply from the cold pipe to the hot pipe according to the temperature of the hot water passing through the outlet, and at least one baffle plate within the tank and partially separating a supply portion of the tank from heat exchange portion of the tank so that when water is heated in heat exchange portion of the tank a thermosyphonic flow is created in a circuit including down the supply portion and up the heat exchange portion. <IMAGE>

Description

SPECIFICATION Heating installation The present invention relates to a heating installation, and more particularly, a domestic hot water and central heating boiler.

In most domesticwater heating systems water is heated in a boiler and is fed off through radiators and through a hot water storage tank. The water in the hot water storage tank is heated by heat exchange and is then used for domestic purposes. The domestic hot water is not directly heated by the boiler and none of the water which is heated by the boiler is used as domestic hot water.

According to the present invention there is provided a heating installation comprising a watertank, a cold water inletto the tank, a hotwater outletfrom the tank, a water heatetfor heating water in the tank, a hot pipe connected to the outlet, a cold pipe for supplying cold water directto the hot pipe, a valve and a thermostat for controlling the rate ofsupplyfrom the cold pipe to the hot pipe according to the temperature ofthe hot water passing through the outlet, and at least one baffle plate within the tank and partially separating a supply portion ofthetankfrom heat exchange portion of the tank so that when water is heated in heat exchange portion ofthetankathermosyphonic flow is created in a circuit including down the supply portion and up the heat exchange portion.

Preferablythe cold water inlettothetank is arranged adjacentthetop of supply portion ofthetank so that cold water passing from the inlet into the supply portion will be concurrentwith the thermosyphonicflow.

A constructional embodiment ofthe present inventin will now be described by way of example with reference to the accompanying drawings wherein: FIGURE 1 shows a schematicviewofa heating installation according tothe present invention; FIGURE 2 shows a front elevation of a water heater and heater exchanger of The installation; FIGURE 3 shows a plan view of the water heater and heat exchanger; and FIGURE 4 shows a sectional view of an air inletto the water heater.

There is provided a boiler comprising a burnerfor heat exchanger 5, an air inlet 6 and an air outlet. The air inlet 6 and air outlet comprise a so-called "balanced flue". Air passing through the inlet 6 passes over a water tank 16 and down through a passage 9 in heat exchange relationship with a front wall 8 of the tank 16. In most boilers the air inlet passage is separate and remote from the heat exchanger and therefore even when the burner is inoperative warm airwill rise in the heat exchanger and cold air will fall in the air inlet passage thus creating a current and a consequent loss of heat through the outlet.It has been thought desirable to have a thermostically control led closure member in the outlet but this is not possible since upon failure of the closure member in the closed position dangerous fumes would build up in the heat exchanger or would exude through other orifices. In the present invention the air in the passage 9 is heated by the surface of the wall 8 and will thus tend not to fall so that a partial balance is created between the air in the passage 9 and the air in the heat exchanger 5, thereby minimising current and loss of heat through the outlet.

The water tank 16 is thermally insulated and the boiler is provided with casing containing a gas valve 11, a central heating water pump 12 and a scale reducer 13. The heat exchangers includes a plurality of heating tubes 14through which pass the flames or combustion gases from the burner4. Acoil 15 surrounds the heating tubes 14 and lies in watertank 16.

Waterisfedtothetank 16via cold water inlet17 which has a first branch 18 adjacent one side of the tank and a second branch 19 adjacent the other side of the tank. The water in the tank is heated by the tubes 14 and the water in the coil 15, which is finned for heat exchange purposes, is heated by the water in the tank 16. The water in the coil 15 is circulated by the pump 12 and passesoutthrough radiatorfeed 20 and back through radiator return 21. Hot water for domestic use is drawn offfrom the tank 16via hotwater outlet 22.

The tank 16may contain approximately 15 litres of water which can be heated to a temperature of approximately 90"C. As hot water is drawn off through the outlet 22 and down through pipe 23 it is mixed with coldwaterfrom branch 24 off cold feed pipe 25 which suppliesthe cold inlet 17 through scale reducer 13. In the branch 24there is a valve 26 which is connected to and controlled by a thermostat 27. When the water drawn offthrough pipe 23 is at its hottestthe thermostat 27 will open the valve 26 to allow a greater amount of cold water to be supplied through branch 24. As the initial quantity of water in the tank 16 is used the tank 1 will be topped up with cold waterfrom the inlet 17.An orifice in the branch 18 discharges water vertically downwards in such a way thatthere will be no possibility of water issuing from the branch 18 passing directto outlet 22. An orifice in the branch 19 also discharges water vertically downwardly. The orifices are fitted with restrictors so that there will be greater resistance in the branch 18 and the flows from the branches 18 and 19will thereby be substantially the same. Baffle plates 28 and 29 are provided to ensure thatthe cold waterfrom branches 18 and 19 passes down the outer extremities ofthe tank 16 before flowing into the middle and up through the tank in the heat exchange relationship with the tubes 14.

As hot water is used through the pipe 23 cold water enters the tank 16 through branches 18 and 19. In a pocket integral with branch 19 is a thermostat 30 and when cold water passes over the thermostat 30 from the branch 19the pump 12will be switched offwhich thenpermitsthewholeburneroutputto beusedfor heating waterforthetaps.

When hotwater is first taken through pipe 23 it is at its highest temperature and the thermostat 27 allows the greatest amount of cold waterthrough mixer valve 26 that the desired temperature of water is achieveXt forthe hottap supply. As the hot water is used up the waterfrom the lower region ofthetankwill be fed through pipe 23. The thermostat will sense a drop in temperature ofthe mixer and operate to control valve 26 and thereby allow a lesser amount of cold waterto be mixed with the hot.

When the boiler is heating and has heated the water in thetankthe baffle plates 28 and 29 create a thermosyphon flow down the outside ofthe plates and up through the space between the plates in a continuous circuit. When hotwateris used, the flow from the pipes 18 and 19 assists the thermosyphon flow and greater flow is created when most needed.

The increased flow creates a greater heat exchange effect up and around heating tubes 14.

As the hot water is used up, the cold water replenishing the tank passes over thermostat 30 which will cause the gas burnerto be ignited. Since at very lowwaterflow rates the heat input from the burner would exceed the heat drawn with water at high temperature, the connected between branches 18 and 19 comprises a finned tube which allows pre-heating of the water before it impinges upon thermostat 30 and thereby prevents operation of thermostat 30. As soon as the flow rate exceeds the minimum necessary to achieve heat balance between the burner and water flow, the pre-heating ofthe cold feed to branch 19 is reduced so that cold feed water remains at a temperature low enough to trip the thermostat and activatethe burner.

As shown in Figure 4 an electricfan 41 is provided to create airflowfrom passage 9 and into the boiler. A sensor switch 42 operates on the difference in air pressure in passage 9 and above the fan 41 and ensures that ignition ofthegas burner4cannottake place unlessthe fan 41 is working.

The burner 4 has a pilot light for ignition purposes and when the burner is not ignited the pilot light maintains approximately 3 gallons of water in the tank, at a temperature of approximately 70"C which is warm enough for many domestic hot water purpose.

This is different from the normal usage of a pilot light in other appliances, where the gas consumed bathe pilot light is substantially wasted to atmosphere and where the main burner must be ignited two raise the temperature of the water to a usable level.

It is necessaryto ensure a minimal supply ofairfor combustion ofthe pilot flame, particularly in flues so longthatnoairflowreachesthe pilot light. This is achieved on an intermitfbnt basis by use of a delay switch and series resistance which operatesthefan briefly at regular intervals at low speed to provide adequateairforthepilotflame but without cooling the water unduly nor consuming too much current.

Thermostat40 is set at approximately 91"C and overrides the thermostat 30 when necessaryto hold the burner on until the whole heat exchanger has heated upto 90"C.

Claims (12)

1. Heating installation comprising a water tank, a cold water inletto thetank, a hot water outletfrom the tank, a water heater for heating water in the tank, a hot pipeconnectedtothe outlet, a cold pipeforsupplying cold water directto the hot pipe, a valve and a thermostat for controlling the rate of supply from a cold pipe to the hot pipe according to the temperature ofthe hotwaterpassing through the outlet, and at least one baffle plate within the tank and partially separating a supply portion ofthefankfrom heat exchange portion of the tank so that when water is heated in heat exchange portion ofthetank a thermosyphonicflow is created in a circuit including downthe supply portion anduptheheatexchange portion.

2. An installation as claimed in claim 1,wherein the cold water inlet to the tank is arranged adjacent the top ofthe supply portion ofthe tank so thatcold watèr passing from the inlet into the supply portionwill be concurrent with thethermosyphonicfiow.

3. An installation as claimed in claim 1 ort wherein the water heater comprises a heat exchanger and a burner beneath the heat exchanger.

4. An installation as claimed in claim 3, wherein the heat exchanger is arranged substantially centrally withinthetankand a baffle plate is arranged on each side ofthe heat exchanger.

5. An installation as claimed in claim 4, wherein a central heating coil is arranged within the tank and surrounding the heat exchanger, the central heating coil having radiatorfeed and return connections.

6. An installation as claimed in claim 4 or 5, wherein the cold water inlet comprises first and second branches having orifices for discharging water vertically downwards into the supply portions ofthe tank, the orifices having restrictors so that the branches will supply at substantiallythe same rate.

7. An installation as claimed in claim 6, when claim 6isappendedtoclaim 5,whereinthe branch on one side ofthetank is connected to the branch on the other side ofthetank by a tube, a central heating pump is connected to the central heating coil and a second thermostat is arranged in a pocket ofthe branch on said other side of the tank, the thermostat having a first presetting so that when cold waterflows over it the central heating pump is switched off.

8. An installation as claimed in claim 7, wherein the tube isfinned to allow pre-heating of cold water before it impinges upon the second thermostat and the second thermostat has a second pre-setting so that it is activated only when water flow conditions are such that the pre-heating is reduced and.tfiscatd.

feedwater remains atthe second pre-set tempera ture.

9. An installation as claimed in any one of claims 1 to 8, wherein air inlet and outlets are provided and between the inlet and outlets there is a passage in heat exchange relationship with awall ofthewatertank.

10. An installation as claimed in claim 9, wherein an electricfan is provided to createAlow-in the passage and a sensor switch is provided to ensure that ignition ofthe water heater cannot take place unlessthefan is working.

11. An installation as claimed in claim 10, wherein a delay switch is provided scthatthe fan is operated briefly at regular intervalsto provide adequate air for a pilot light.

12. A heating installation substantially as described herein with reference to and as illustrated by the accompanying drawings.