CA2043052A1 - Standby heating element for a water heater - Google Patents
Standby heating element for a water heaterInfo
- Publication number
- CA2043052A1 CA2043052A1 CA 2043052 CA2043052A CA2043052A1 CA 2043052 A1 CA2043052 A1 CA 2043052A1 CA 2043052 CA2043052 CA 2043052 CA 2043052 A CA2043052 A CA 2043052A CA 2043052 A1 CA2043052 A1 CA 2043052A1
- Authority
- CA
- Canada
- Prior art keywords
- fluid
- heating element
- temperature
- standby
- water
- 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
Links
Landscapes
- Control Of Resistance Heating (AREA)
Abstract
Abstract of the Disclosure A water heater has a standby heating element that eliminates or greatly reduces the cyclical energization and de-energization of the high capacity heating elements during standby periods. The standby heating element is constantly energized, and it is sized to compensate for the water heater heat losses during the standby periods. The service lives of the high capacity heating elements and their controls are thus greatly increased, and the possibility of withdrawing undesirably cool or hot water from the water heater is eliminated.
Description
2~0~
Patent Docket 13026/9Oæ
Back~nd of the Invention 1. Field of the invention. This invention pertains to temperature control, and more particnlarly to apparatus for contro31irlg the temperature of a fluid.
2. Description of the prior art. Yarious equipment hæ been developed to colltrol the temperature of a fluid inside a closed vessel. For example, domestic and commercial water heaters are well known.
Fig 1 illustrates in schematic ~orm a typic~l circuit 1 employed in aI~
electric water heater 2. The circuit 1 includes an upper heating e]ement 4 that is controlled by a thermostat and temperature limit control combination 3. Ihe upper heating element 4 typically has a power rating of between appro~matel~ 2500 and 5500 watts. A. similar lower heating element S and lower thermostat control 7 are also instaUed in the water heater 2 as part of the circuit 1.
During periods when no hot water is withdrawn from the water heater 2, the standby periods, the water heater undergoes heating-cooling cycles. The thermostat controls 3 and 7 energize thç heating elements 4 and 5, respectively, until the- temperature of the water in the heater 2 reaches the callbrated switch-off point of the thermostats.~ From that time, the water loses heat until the water reaches the callbrated switch-on point of the thermostats. At that point, the heating process starts again, and another cycle begins. The difference between the calibrated switch-off and switch-on temperatures of the thennostats is referred to in the industry as the difl~erential of the thermostat. The di~erential of the thermostat is an inherent characteristic of electro-mechanical thennostats because of the very l~igh electric currents they are required to switch. Typical ~ifferentials of the thermostat incornmercia31y availab3e water heaters range ~om approximately 8~ to 25~ F.
, ~30~2 A typical prior domestic 52 gal. electric water heater 2 undergoes a heating-cooling cycle on the average of six times during a 24 hour standby period.
Each cycle has a small but cumu]ative adverse effect on the lives of the theImostat controls 3 and 7 and on the heating elements 4 and 5.
Another disadvantage of the prior contro] circuits 1 is that a person may withdraw water at the end of the cooling portion of the heating-cooling cycle.
At that point, the water may be coo]er than the person desires. A solution to that problem is to raise the callbrated switch-off and switch-on settings of the thermostat controLs 3 and 5 to higher temperatures. However, that solution is unsatisfactory because of the increase risk of scalding if the person withdraws water at the end of the heating portion of the heating-cooling cycle. In fact, the water heater industry, in conjunction with certification agencies, has recently revised the temperature switch-off and switch-on temperatures of eleetric water heaters from 140 F. to 120 F. in order to reduse the potential Iisk of scalding accidents.
New temperature contro]s have been designed that reduce the differential of the thermostat from previous ranges to approximately 6 F. to 10 F.
Nevertheless, a need rernains for improvements in water heater heating circuits.
Surnmar of the Invenbon In accordance with the present invention, an electric water heater is ~0 provided that has greatly improved performance and safety characteristics compared with prior water heaters. This is accomplished by designing the water heater electric circuit with a standby heating element that compensates for heat losses during standby periods.
The standby heating elernent is installed in the water heater elec~ric circuit together with the conventional high capacity heating elements and their thermostat controls. The standby heating element is constantly energized, and it has a relatively low power output. It is sized to match the heat loss of the water in the heater during standby periods. A typical rating for a standby heating element used in a 52 gal. water heater is between approximately 50 and lS0 watls 2~3~
Patent Docket 13026/9Oæ
Back~nd of the Invention 1. Field of the invention. This invention pertains to temperature control, and more particnlarly to apparatus for contro31irlg the temperature of a fluid.
2. Description of the prior art. Yarious equipment hæ been developed to colltrol the temperature of a fluid inside a closed vessel. For example, domestic and commercial water heaters are well known.
Fig 1 illustrates in schematic ~orm a typic~l circuit 1 employed in aI~
electric water heater 2. The circuit 1 includes an upper heating e]ement 4 that is controlled by a thermostat and temperature limit control combination 3. Ihe upper heating element 4 typically has a power rating of between appro~matel~ 2500 and 5500 watts. A. similar lower heating element S and lower thermostat control 7 are also instaUed in the water heater 2 as part of the circuit 1.
During periods when no hot water is withdrawn from the water heater 2, the standby periods, the water heater undergoes heating-cooling cycles. The thermostat controls 3 and 7 energize thç heating elements 4 and 5, respectively, until the- temperature of the water in the heater 2 reaches the callbrated switch-off point of the thermostats.~ From that time, the water loses heat until the water reaches the callbrated switch-on point of the thermostats. At that point, the heating process starts again, and another cycle begins. The difference between the calibrated switch-off and switch-on temperatures of the thennostats is referred to in the industry as the difl~erential of the thermostat. The di~erential of the thermostat is an inherent characteristic of electro-mechanical thennostats because of the very l~igh electric currents they are required to switch. Typical ~ifferentials of the thermostat incornmercia31y availab3e water heaters range ~om approximately 8~ to 25~ F.
, ~30~2 A typical prior domestic 52 gal. electric water heater 2 undergoes a heating-cooling cycle on the average of six times during a 24 hour standby period.
Each cycle has a small but cumu]ative adverse effect on the lives of the theImostat controls 3 and 7 and on the heating elements 4 and 5.
Another disadvantage of the prior contro] circuits 1 is that a person may withdraw water at the end of the cooling portion of the heating-cooling cycle.
At that point, the water may be coo]er than the person desires. A solution to that problem is to raise the callbrated switch-off and switch-on settings of the thermostat controLs 3 and 5 to higher temperatures. However, that solution is unsatisfactory because of the increase risk of scalding if the person withdraws water at the end of the heating portion of the heating-cooling cycle. In fact, the water heater industry, in conjunction with certification agencies, has recently revised the temperature switch-off and switch-on temperatures of eleetric water heaters from 140 F. to 120 F. in order to reduse the potential Iisk of scalding accidents.
New temperature contro]s have been designed that reduce the differential of the thermostat from previous ranges to approximately 6 F. to 10 F.
Nevertheless, a need rernains for improvements in water heater heating circuits.
Surnmar of the Invenbon In accordance with the present invention, an electric water heater is ~0 provided that has greatly improved performance and safety characteristics compared with prior water heaters. This is accomplished by designing the water heater electric circuit with a standby heating element that compensates for heat losses during standby periods.
The standby heating elernent is installed in the water heater elec~ric circuit together with the conventional high capacity heating elements and their thermostat controls. The standby heating element is constantly energized, and it has a relatively low power output. It is sized to match the heat loss of the water in the heater during standby periods. A typical rating for a standby heating element used in a 52 gal. water heater is between approximately 50 and lS0 watls 2~3~
With the standby heating element, the number of heating-cooling cycles of the heating circuit during standby periods is ~eatly reduced and eYen e~i~ated.
Consequently, the service lives of the high capacity thermostat controls and heating elements are extended. Moreover, the elimination of the heating-cooli~g cycles S results in a supply of hot water at a constant tempera~ure. As a consequence, the iikelihood of a person withdrawing undesirably cool or hot water, as is coramon with prior water heaters, is eliminated.
Other advantages, benefits, and features of the invention will become apparent to those sl~lled in the art upon reading the detailed description of the invention.
Brief Description of the Drawings Fig. 1 is a schematic view of a heating circuit of a typical prior art water heater.
Fig. 2 is a schematic view of the heating circuit of a water heater according to the present invention.
Detailed Description of the Invention Referring to Fig. 2, an electric circuit 11 is schematically illustrated that includes the present invention. The electric circuit 11 is particu]arly useful when used in conjunction with a closed vessel or tank 9 for supplying hot water for residential and commercial uses. However, it will be understood that the invention is not limited to liquid storage applications.
The tank 9 typically has inlet and outlet ports and a drain faucet, which are well known and thus are not shown. The water heater tank is typically wrapped with insulation, also not shown.
~5 To heat the water in the tank 9, the electric circuit 11 comprises an upper heating element 4' and a lower heating element 5'. The upper heating element 4' is controlled by a known upper therrnostat and limit control combination 3'. The 2V~30~2 upper heating element 4' typically has a power rating of between approximatelty 2500 and 5500 watts. The electric circmt 11 further comprises a lower thermostat control 7 that controls the lower heating element 5'. The lower heating element 5' is generally sized with a power rating of betwee~ approximately 2sno and 5500 watts.
The thermostat controls 3' arld T operate to maintain the water in the tank 9 within a predetermined range of temperatures. When the temperature falls to a callbrated rninimurn temperature, the controls actuate to energize the respective heating elements, and heat is transferred from the heating elements to the water.
When the water reaches a calibrated ma~mum temperature, the controls operate to de-energize the heating elements. From that temperature, the water eventually cools down to the calibrated mil~imum temperature. Water cooling occurs continuously, including during standby periods when no water is withdrawn, through conduction,convection and radiant losses. As a consequence, the controls 3' and 7' operate over relatively long heating-cooling cycles to repeatedly reheat the water through a differential of the thermostats between the call~rated ma~num and minimum temperatures.
In accordance with the present invention, the electric circuit 11 is designed with a standby heating element 13 that greatly reduces and even eliminates cyclical operation of the thermostat controls 3' and 5' during standby penods. The standby heating elernent 13 is irnmersed in the water in the tank 9 like the conventional heating element. 4' and S'. The standby heating elemPnt is preferably connected by wires 15 directly to the main switch from the power lines L1 and L2and in parallel with the heating elements 4' and 5'. In that manner, the standbyheating element is continuously energized to transfer heat therefrom to the water ~3 regardless of the state of ener~zation of the heating elements 4' and 5'.
The standby heating element 13 is sized to compensate as closely as possible for the various heat losses from the tank 9 during standby periods. Typical power ratings for the standby heating element are between appro~amately 50 and 150 watts. When the standby heating element is in operation, the therrnostat controls 3' and 7' need not energize the heating elements 4' and 5', respectively, in on-offfashion during standby periods. (:onsequently, the service lives of the thermostat .
2~3~2 controls and heating elements are greatly extçnded. In additio~, water withdrawnfrom the tank 9 is always at a temperature within a much narrower range than is the case with prior water heaters, in which the thermostat contro]s and hçating e]ements continuously cycle through the differential of the thermostats. As a resu]t, the5 posslbility of withdrawing undesirably cool water at the end of the cooling portion of a heating-cooling cycle and the potential danger of scalds from water withdrawn at the end of the heating portion of a heating-cooling cycle are eliminated.
Thus, it is apparent that there has been provided, in accordance with the invention, a standby heating element ~or a water heater that fully satis~;es the ~ims and advantages set forth above. Wh~e the invention has been descnbed in conjunction with specific embodiments thereof, it is evident that many altematives, modifications, a~d variations wil~ be apparent to those skilled in the art in light of the foregoing descIiption. Accordingly, it is intended to embrace all such a~ternatives, modifications, and var~ations as fall withiII the spirit and broad scope of the appended 15 claims.
. . ~
Consequently, the service lives of the high capacity thermostat controls and heating elements are extended. Moreover, the elimination of the heating-cooli~g cycles S results in a supply of hot water at a constant tempera~ure. As a consequence, the iikelihood of a person withdrawing undesirably cool or hot water, as is coramon with prior water heaters, is eliminated.
Other advantages, benefits, and features of the invention will become apparent to those sl~lled in the art upon reading the detailed description of the invention.
Brief Description of the Drawings Fig. 1 is a schematic view of a heating circuit of a typical prior art water heater.
Fig. 2 is a schematic view of the heating circuit of a water heater according to the present invention.
Detailed Description of the Invention Referring to Fig. 2, an electric circuit 11 is schematically illustrated that includes the present invention. The electric circuit 11 is particu]arly useful when used in conjunction with a closed vessel or tank 9 for supplying hot water for residential and commercial uses. However, it will be understood that the invention is not limited to liquid storage applications.
The tank 9 typically has inlet and outlet ports and a drain faucet, which are well known and thus are not shown. The water heater tank is typically wrapped with insulation, also not shown.
~5 To heat the water in the tank 9, the electric circuit 11 comprises an upper heating element 4' and a lower heating element 5'. The upper heating element 4' is controlled by a known upper therrnostat and limit control combination 3'. The 2V~30~2 upper heating element 4' typically has a power rating of between approximatelty 2500 and 5500 watts. The electric circmt 11 further comprises a lower thermostat control 7 that controls the lower heating element 5'. The lower heating element 5' is generally sized with a power rating of betwee~ approximately 2sno and 5500 watts.
The thermostat controls 3' arld T operate to maintain the water in the tank 9 within a predetermined range of temperatures. When the temperature falls to a callbrated rninimurn temperature, the controls actuate to energize the respective heating elements, and heat is transferred from the heating elements to the water.
When the water reaches a calibrated ma~mum temperature, the controls operate to de-energize the heating elements. From that temperature, the water eventually cools down to the calibrated mil~imum temperature. Water cooling occurs continuously, including during standby periods when no water is withdrawn, through conduction,convection and radiant losses. As a consequence, the controls 3' and 7' operate over relatively long heating-cooling cycles to repeatedly reheat the water through a differential of the thermostats between the call~rated ma~num and minimum temperatures.
In accordance with the present invention, the electric circuit 11 is designed with a standby heating element 13 that greatly reduces and even eliminates cyclical operation of the thermostat controls 3' and 5' during standby penods. The standby heating elernent 13 is irnmersed in the water in the tank 9 like the conventional heating element. 4' and S'. The standby heating elemPnt is preferably connected by wires 15 directly to the main switch from the power lines L1 and L2and in parallel with the heating elements 4' and 5'. In that manner, the standbyheating element is continuously energized to transfer heat therefrom to the water ~3 regardless of the state of ener~zation of the heating elements 4' and 5'.
The standby heating element 13 is sized to compensate as closely as possible for the various heat losses from the tank 9 during standby periods. Typical power ratings for the standby heating element are between appro~amately 50 and 150 watts. When the standby heating element is in operation, the therrnostat controls 3' and 7' need not energize the heating elements 4' and 5', respectively, in on-offfashion during standby periods. (:onsequently, the service lives of the thermostat .
2~3~2 controls and heating elements are greatly extçnded. In additio~, water withdrawnfrom the tank 9 is always at a temperature within a much narrower range than is the case with prior water heaters, in which the thermostat contro]s and hçating e]ements continuously cycle through the differential of the thermostats. As a resu]t, the5 posslbility of withdrawing undesirably cool water at the end of the cooling portion of a heating-cooling cycle and the potential danger of scalds from water withdrawn at the end of the heating portion of a heating-cooling cycle are eliminated.
Thus, it is apparent that there has been provided, in accordance with the invention, a standby heating element ~or a water heater that fully satis~;es the ~ims and advantages set forth above. Wh~e the invention has been descnbed in conjunction with specific embodiments thereof, it is evident that many altematives, modifications, a~d variations wil~ be apparent to those skilled in the art in light of the foregoing descIiption. Accordingly, it is intended to embrace all such a~ternatives, modifications, and var~ations as fall withiII the spirit and broad scope of the appended 15 claims.
. . ~
Claims (8)
1. An electric circuit for maintaining a fluid in a tank at a substantially constant temperature between a first calibrated temperature and second calibrated temperature lower than the first calibrated temperature comprising:
a. a source of electric power;
b. at least one heating element connected to the source of electric power and immersed in the fluid;
c. control means for actuating the heating element between an energized state in which the heating element transfers heat to the fluid to raise the fluid temperature to the first calibrated temperature and a de-energized state in which no heat is transferred to the fluid by the heating element and the fluid loses heat such that the temperature thereof tends to fall to the second calibrated temperature; and d. a standby heating element connected to the source of electric power and immersed in the fluid, the standby heating element being continuously energized to transfer an amount of heat to the fluid substantially equal to the heat lost by the fluid while the heating element is de-energized and the fluid temperature tends to fall from the first to the second calibrated temperatures, so that the standby heating element can maintain the fluid at the constant temperature without the control means actuating the heating element.
a. a source of electric power;
b. at least one heating element connected to the source of electric power and immersed in the fluid;
c. control means for actuating the heating element between an energized state in which the heating element transfers heat to the fluid to raise the fluid temperature to the first calibrated temperature and a de-energized state in which no heat is transferred to the fluid by the heating element and the fluid loses heat such that the temperature thereof tends to fall to the second calibrated temperature; and d. a standby heating element connected to the source of electric power and immersed in the fluid, the standby heating element being continuously energized to transfer an amount of heat to the fluid substantially equal to the heat lost by the fluid while the heating element is de-energized and the fluid temperature tends to fall from the first to the second calibrated temperatures, so that the standby heating element can maintain the fluid at the constant temperature without the control means actuating the heating element.
2. In a water heater subject to heat losses during standby periods when no hot water is withdrawn from the water heater and having at least one heating element immersed in the water in the heater, and thermostat means for cyclically energizing and de-energizing the heating element to transfer heat therefrom to the water and thereby control the water temperature through a differential of the thermostat means between predetermined high and low temperatures, the improvement comprising a standby heating element immersed in the water and continuously energized to compensate for the heater heat losses and to maintain the water between the predetermined high and low temperatures during the standby periods and thereby substantially eliminate cyclical energizing and de-energizing of the heating element during standby periods.
3. The improvement of claim 2 wherein the standby heating element has a power rating of between approximately 50 and 150 watts.
4. Apparatus for heating a fluid comprising:
a. a tank for holding the fluid, the fluid losing heat during standby periods when no fluid is withdrawn from the tank;
b. at least one first heating element immersed in the fluid;
c. control means for cyclically energizing and de-energizing the first heating element to transfer heat to the fluid during a heating portion of the cycle when the first heating element is energized to raise the fluid temperature to a first calibrated temperature, the fluid temperature tending to fall to a second calibrated temperature lower than the first calibrated temperature during a cooling portion of the cycle when the first heating element is de-energized; and d. a standby heating element immersed in the fluid and continuously energized to transfer heat to the fluid in an amount substantially equal to the fluid heat losses during the cooling portion of the cycle, so that the fluid remains at a constant temperature during standby periods without cyclically energizing and de-energizing the first heating element by the control means.
a. a tank for holding the fluid, the fluid losing heat during standby periods when no fluid is withdrawn from the tank;
b. at least one first heating element immersed in the fluid;
c. control means for cyclically energizing and de-energizing the first heating element to transfer heat to the fluid during a heating portion of the cycle when the first heating element is energized to raise the fluid temperature to a first calibrated temperature, the fluid temperature tending to fall to a second calibrated temperature lower than the first calibrated temperature during a cooling portion of the cycle when the first heating element is de-energized; and d. a standby heating element immersed in the fluid and continuously energized to transfer heat to the fluid in an amount substantially equal to the fluid heat losses during the cooling portion of the cycle, so that the fluid remains at a constant temperature during standby periods without cyclically energizing and de-energizing the first heating element by the control means.
5. In combination with a tank for supplying a heated fluid, and first heating means for cyclically raising the temperature of the fluid during a standby period when no fluid is supplied by the tank from a second calibrated temperature to a first calibrated temperature higher than the second calibrated temperature during a heating portion of the cycle and for allowing heat losses of the fluid during the standby period to lower the fluid temperature from the first to the second calibrated temperatures during a cooling portion of the cycle, a standby heating element immersed in the fluid, the standby heating element continuously transferring heat therefrom to the fluid to compensate for the heat losses of the fluid during the cooling portion of the first heating means cycle during the standby period and thereby eliminating the cyclical raising of the fluid temperature by the first heating means.
6. A water heater comprising:
a. a tank for holding water and having inlet and outlet ports, the tank and water being subject heat losses during standby periods when no water enters and leaves the tank through the inlet and outlet ports; and b. a standby heating element immersed in the water in the tank, the standby heating element being continuously energized and having a rating that substantially equals the tank and water heat losses during standby periods to thereby maintain the water temperature at a constant temperature during the standby periods.
a. a tank for holding water and having inlet and outlet ports, the tank and water being subject heat losses during standby periods when no water enters and leaves the tank through the inlet and outlet ports; and b. a standby heating element immersed in the water in the tank, the standby heating element being continuously energized and having a rating that substantially equals the tank and water heat losses during standby periods to thereby maintain the water temperature at a constant temperature during the standby periods.
7. A method of heating a fluid in a tank comprising the steps of:
a. immersing at least one heating element in the fluid;
b. energizing the heating element to raise the fluid tempera-ture from a second calibrated temperature to a first calibrated temperature higher than the second calibrated temperature in response to the fluid temperature falling to the second calibrated temperature because of withdrawal of fluid from the tank;
c. de-energizing the heating element when the fluid temperature reaches the first calibrated temperature;
d. immersing a standby heating element in the fluid; and e. continuously energizing the standby heating element to maintain the fluid at a constant temperature between the first and second calibrated temperatures during standby periods when no fluid is withdrawn from the tank.
a. immersing at least one heating element in the fluid;
b. energizing the heating element to raise the fluid tempera-ture from a second calibrated temperature to a first calibrated temperature higher than the second calibrated temperature in response to the fluid temperature falling to the second calibrated temperature because of withdrawal of fluid from the tank;
c. de-energizing the heating element when the fluid temperature reaches the first calibrated temperature;
d. immersing a standby heating element in the fluid; and e. continuously energizing the standby heating element to maintain the fluid at a constant temperature between the first and second calibrated temperatures during standby periods when no fluid is withdrawn from the tank.
8. A method of supplying a fluid at a predetermined temperature comprising the steps of:
a. providing a tank filled with the fluid at the predetermined temperature;
b. determining the heat losses of the fluid during standby periods when no fluid is supplied by the tank; and c. continuously heating the fluid with an amount of heat equal to the fluid heat losses, so that the fluid remains at the predetermined temperature.
a. providing a tank filled with the fluid at the predetermined temperature;
b. determining the heat losses of the fluid during standby periods when no fluid is supplied by the tank; and c. continuously heating the fluid with an amount of heat equal to the fluid heat losses, so that the fluid remains at the predetermined temperature.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US60398990A | 1990-10-26 | 1990-10-26 | |
| US603,989 | 1990-10-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2043052A1 true CA2043052A1 (en) | 1992-04-27 |
Family
ID=24417726
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2043052 Abandoned CA2043052A1 (en) | 1990-10-26 | 1991-05-22 | Standby heating element for a water heater |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2043052A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6058245A (en) * | 1998-08-05 | 2000-05-02 | Afc Enterprises, Inc. | Electric boost heater for deep fryer |
-
1991
- 1991-05-22 CA CA 2043052 patent/CA2043052A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6058245A (en) * | 1998-08-05 | 2000-05-02 | Afc Enterprises, Inc. | Electric boost heater for deep fryer |
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