CA1076826A - Heat pump with a two-speed compressor - Google Patents
Heat pump with a two-speed compressorInfo
- Publication number
- CA1076826A CA1076826A CA308,163A CA308163A CA1076826A CA 1076826 A CA1076826 A CA 1076826A CA 308163 A CA308163 A CA 308163A CA 1076826 A CA1076826 A CA 1076826A
- Authority
- CA
- Canada
- Prior art keywords
- compressor
- outdoor coil
- coil
- heat pump
- low speed
- 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.)
- Expired
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- Air Conditioning Control Device (AREA)
Abstract
ABSTRACT
A method of operating a heat pump including a multispeed compres-sor and a heat pump apparatus including a multispeed compressor, wherein the compressor is actuated at a relatively high speed during the normal heating mode of operation and at a relatively low speed during the heating mode of operation when frost accumulates on the outdoor coil so as to de-frost the outdoor coil without actuating the reversing means of the heat pump system. The lower end of the operating range of the heat pump can be extended by running a heat pump system including a two-speed compressor at low speed during ambient conditions of about 0°F. At low speed operation, the effective outdoor coil surface is twice that at full speed and the heat pulp system can continue to operate without resorting to more costly auxiliary electric strip heat.
A method of operating a heat pump including a multispeed compres-sor and a heat pump apparatus including a multispeed compressor, wherein the compressor is actuated at a relatively high speed during the normal heating mode of operation and at a relatively low speed during the heating mode of operation when frost accumulates on the outdoor coil so as to de-frost the outdoor coil without actuating the reversing means of the heat pump system. The lower end of the operating range of the heat pump can be extended by running a heat pump system including a two-speed compressor at low speed during ambient conditions of about 0°F. At low speed operation, the effective outdoor coil surface is twice that at full speed and the heat pulp system can continue to operate without resorting to more costly auxiliary electric strip heat.
Description
10~6826 BACKGROUND AND SUMMARY OF THE INVENTION
This invention relates to a novel heat pump and more particularly, to a heat pump utilizing a multispeed compressor so as to provide for more efficient overall operation and to an improved method for operating a heat ;;
pump utilizing a multispeed compressor.
Prior heat pumps have generally included a single speed compressor, reversing means, an indoor coil, expansion means and an outdoor coil interconnected in a refrigerant circuit. When the reversing means is posi-tioned for a cooling mode of operation, refrigerant is forwarded from the compressor to the outdoor coil. The vaporous refrigerant is condensed in the outdoor coil which functions at this $ime as a condenser. Liquid re-frigerant passes from the outdoor coil through the expansion means to the indoor coil. The refrigerant expands within the indoor coil, cooling the air passing thereover. The cooled air is transmitted to the area to be cooled.
With the reversing means positioned for a heating mode of operation, refrigerant is forwarded from the compressor to the indoor coil which now ~unctions as a condenser. The hot vaporous refrigerant is condensed and the heat given off from the refrigerant passes to the air moving over the indoor coil to the environment to be heated. Refrigerant is metered through the expansion means and flows to the outdoor coil where it expands. As the coil temperature approaches freezing, frost will form on the outdoor coil reducing the heating capacity of the system. Periodically, the outdoor coil must be defrosted to remove the frost. The frequency of frost removal or deicing depends upon the amount of moisture in the air at the time that icing occurs and thle operating temperature of the outdoor coil. The rate of icing is a function of numerous variables, but in general, it will increase as the ambient temperature around the outside coil decreases from 45 F to approximately 35F. The temperature of the outdoor coil will be about 30F.
As the ambient temperature decreases below 35F, the rate of icing also - 1 - ,~ ....
':
10768Z~;
decreases since the amount of free moisture in the air decreases. Icing is very slow at ambient temperatures below 15F to 20F to none existing.
One way of accomplishing defrost:ing of the outdoor coil during heating operation is to reverse the revers;ng means from the heating mode to the cooling mode. However, this is inefficientJ inasmuch as cool air may be discharged from the indoor coil into the area to be heated during the deicing process or defrost cycle. Strip heat or fossil fuel has been used to add heat to the area to be heated during this period of time, however, this is also inefficient and wasteful of energy.
At about 0F, outdoor ambient temperature, the COP of the conven-tional heat pump refrigeration system drops below one and the heat pump is cycled off. Auxiliary strip heat is turned on to heat the environment to be warmed. It is desirous to extend the lower range of operation to use heat from the more efficient heat pump system than from less efficient auxiliary strip heat.
An object of the present invention is to provide a heat pump wherein the disadvantages and deficiencies of prior heat pumps are obviated.
According to one aspect of this invention there is provided a heat pump including a multispeed compressor, reversing means, an indoor coil, an outdoor coil, and expansion means connected in a refrigerant circuit and control means for operating the compressor, said control means preventing frosting of the outdoor coil during the heating mode of operation without ~;
actuating the revers;ng means from the heating mode to the cooling mode by sensing a predetermined condition and changing the compressor operation from relatively high speed to relatively low speed.
According to another aspect of this invention there is provided a method of operating a heat pump including a multispeed compressor, reversing means, an indoor coil, an outdoor coil, and expansion means connected in a refrigerant circuit~ the method of operation preventing frosting of the out-door coil during the heating mode of operation without actuating the reversing ', ~ -1~7f~8Z6 means from the heating mode to the cooling mode, comprising the steps of operating the compressor at a relatively high speed in a heating mode so as to provide heat from the indoor coil to heat an environment, operating the compressor at a relatively low speed in response to a predetermined condition so as to reduce the indoor coil capacity and elevate the temperature of the outdoor coil so as to defrost the outdoor coil without actuating the reversing means.
According to yet another aspect of this invention there is provided a method of extending the lower operating range of a heat pump during heating operation comprising the steps of operating a two-speed compressor at rela-tively high speed during normal operation and at relatively low speed during ambient temperatures causing the outdoor coil to operate below 32F to there-by elevate the outdoor coil temperature to above freezing and make more heat available at the outdoor coil for system operation.
BRIEF DESCRIPTION OF THE DRAWING
There is illustra~ed in the attached drawing a presently preferred embodiment of the present invention wherein:
Figure 1 is a schematic illustration of a heat pump system embody-ing the present invention; and Figure 2 is a graph illustrating the operation of the novel heat pump of the present inventior DETAILED DESCRIPTION OF THE PRESENT INVENTION
With reference to Figure 1 there is shown a heat pump embodying the present invention. The heat pump 10 of this invention comprises basically a two-speed compressor 12 which is adapted to forward refrigerant through the line 14 to a reversing means 16 that is operated by control means 18 as will be more fully described hereinafter. The refrigeration system also includes an outdoor coil 22, expansion means 26, 28 and indoor coil 30. Associated with the expansion means 26, 28 are one-way check valve means 34, 36.
Consider first the cooling mode of operation. The reversing means ` .
` lB ' ':
,'' :
~7 16 is properly actuated by control 18. The compressor 12 is actuated by control 13 so as to pump refrigerant through the line 14 to the reversing means 16 to line 17 to the outdoor coil 22 where the hot vaporous refrigerant is condensed. As shown, the outdoor coil may be air-cooled by the fan means 24. The outdoor coil 22 can be water cooled if desired. The refrigerant condensed in the outdoor coil 22 passes through the line 25, the one-way check valve 34, line 27 and through the expansion means 28 which may comprise a thermal expansion valve. From the expansion means 28, the - 3a -:.
`` B :
.. . ;. ... .... ... - .. .. .. . ~ .
... ... ~ . . ................ ... ~. ... ... .
-~0768~6 refrigerant passes through the line 29 to the indoor coil 30 where the re-frigerant vaporizes. Air to be cooled may be passed over the indoor coil 30 by the fan means 31. During the cooling mode of operation, the cooled air may be ducted or otherwise communicated with the area to be cooled. The refrigerant passes through the line 32 from the indoor coil 30 (which acts as an evaporator) to the reversing valve 16 and then through line 33 to the compressor 12.
During the heating mode of operation, the refrigerant forwarded from the compressor 12 passes through the discharge line 14 to the reversing valve 16 and line 32 to the indoor coil which now functions as a condenser.
The fan means 31 passes air over the indoor coil which air is heated. The heated air is communicated to the area to be heated. The refrigerant passes from the indoor coil 30 through the line 29, one-way check valve 36 and line 27 to the expansion means 26. The refrigerant metered through the expansion means 26 passes through line 25 to the outdoor coil 22 which now functions as an evaporator. The refrigerant returns to the compressor via line 17, reversing means 16, and line 33.
A feature of the present invention is the provision of a two-speed compressor operable at a relatively high speed (nominal 3600 RPM at two-pole high speed) for normal heating operation and operable at a rela-tively low speed (nominal 1800 RPM at four-pole low speed) in response to a predetermined condition to reduce the indoor coil capacity and elevate the temperature of the outdoor coil so as to defrost the outdoor coil without actuating the reversing means which may be of a conventional type.
The control means 13 for operating the compressor 12 may be responsive to a predetermined outdoor temperature or may be responsive to a predetermined temperature differential of the outdoor coil or air pressure drop across the outdoor coil. In any event, the control 13 will operate the compressor during the heating mode of operation to reduce the speed from 1~768Z~;
high speed to low speed, so as to decrease the cooling capacity of outdoor coil, and thereby increase the temperature of the outdoor coil. At low speed operation, there is effectively twice the surface of outdoor coil as compared to high speed operation. The outdoor coil temperature will in-crease so as to defrost the outdoor coil without actuating the reversing `' means. Also, at low speed operation, the capacity of the compressor is about one half that at high speed. This too is a factor in elevating the temperature of the outdoor coil. Since there is no reverse cycle operation required for this defrost mode of operation, no cool air will be dumped into the area to be treated and there will be no necessity for utilization of strip heat or other auxiliary heat to offset a cooling effect during this mode of operation. This results in energy conservation and stress on the compressor is greatly reduced. The reduction in stress is not linear, but is reduced more sharply. The exact magnitude of the reduction is not known.
In the past, it has been kno~,vn to initiate the defrost cycle responsive to the ambient temperature, responsive to a temperature differential across the outdoor coil, responsive to an air pressure drop across the outdoor coil and by timing means. Similar sensors are required to terminate the defrost operation and return the system to normal heating operation.
Another aspect of this invention is to increase the range of operation of a heat pump system. At very low ambient temperature, on the order of 0F, the outdoor coil surface cannot pick up sufficient heat. The coefficient of performance (COP) of the heat pump will drop to or below 1. Under these circums tances, standard heat pump operation must be terminated. By use of the present invention, the speed of the compressor is reduced from full speed to half speed, so as to effectively double the cooling surface of the outdoor coil and thereby, enable the heat pump system to continue operating to a lower ambient temperature and maintain the COP above 1.
With reference to Figure 2, there is illustrated a graph of BTU per hour 1{17~ S
versus the outdoor coil temperature in degrees Fahrenheit. The lines sloping upwardly to the right have been marked with appropriate legends (compressor at high speed and compressor at low speed) and the lines A
and B are indicative of outdoor coil capacities at varying degrees of a~bient temperature. The line A assumes an ambient temperature of 40F and the line B assumes an ambient temperature of 0F. With reference to line A, it will be noted that the intersection of line A and the compressor at high speed operation line occurs at about 30F. At this condition, there would be frosting of the outdoor coil. When the compressor is switched to low speed, it will be noted that the intersection of line A with the compressor at -low speed line, increases to about 36F. The effective surface of the outdoor coil is doubled as compared to the effective surface at high speed operation, ~;
resulting in warming of the outdoor coil. This will be sufficient to defrost the outdoor coil.
":
A refinement would be to cycle the fan 31 for the indoor coil in con-junction with the operation of the compressor 12. ~uring high speed opera-tion, as the evaporating temperature approaches 32F, the indoor fan 31 is cycled. If the indoor fan 31 speed is substantially reduced or stopped, the -head pressure will be increased, thus the pumping capacity of the compressor will be decreased significantly and the outdoor coil temperature will be in-creased, thus helping to defrost the outdoor coil 2Z. At this time, the out-door coil fan 24 is kept running so as to maximi~e heat pick up by the out-door coil 22, thereby enhancing defrost of coil 22. If this does not defrost theoutdoor coil, then after a programmed time delay, the compressor 12 can be switched to half speed operation. Another aid to defrost if a few more degrees of heat were needed at the outdoor coil 22, would be to switch the operation of the outdoor fan 24 from low to high speed. If defrost of the outdoor coil is still not adequate, then the heat pump system reversing valve 16 could be ;;
operated in a conventional fashion.
, ~ .. . . :
107~;826 Considering next system operation at an outdoor ambient temperature of about 0F, it will be noted that the intersection of line B and the compressor at high speed line is at approximately -6F, evaporating temperature. At these conditions, there is insufficient heat in the air and the heat pump operates at a COP of less than 1. Normally, the operation of the compressor is terminated if the outdoor temperature drops below 0 F to prevent damage to the compressor and strip heat or auxiliary heat is used to provide heat in the area to be heated. If the compressor operation is reduced to low speed operationJ the intersection occurs of line B with the compressor at low speed at approximately 1F. In this example, therefore, the compressor which would otherwise have to be shut down may continue to be operated so as to increase the lower range of system operation.
Yet another means of extending the lower range of operation is contem-plated by the present invention. This is to provide a secondary coil in parallel with the outdoor coil of an equal capacity to that of the outdoor coil.
By utilization of both coils during low ambient conditions through suitable controls and in conjunction with the compressor at low speed operation, there is more outdoor coil surface and more heat can be picked for a given heat pump system. The lower range of operation can be extended several degrees in this manner.
There has been provided by the present invention an improved heat pump system provided with a two-speed compressor which is operable in a rela-tively low speed mode in response to a predetermined condition during heating so as to reduce the indoor coil capaci$y and elevate the temperature of the outdoor coil so as to defrost the outdoor coil without actuating the revarsing means. Another aspect of the invention is the utilization of a heat pump system having a two-speed compressor operable in such fashion as to extend the lower range of operation to very low ambient conditions, on the order of 0 to -6F.
While I have shown a presently preferred embodiment of the present -7- ~-invention, it will be understood that specific variations in construction and arrangement of the heat pump disclosed can be made by those skilled in the art without departing from the invention as defined in the appended claims.
..........
This invention relates to a novel heat pump and more particularly, to a heat pump utilizing a multispeed compressor so as to provide for more efficient overall operation and to an improved method for operating a heat ;;
pump utilizing a multispeed compressor.
Prior heat pumps have generally included a single speed compressor, reversing means, an indoor coil, expansion means and an outdoor coil interconnected in a refrigerant circuit. When the reversing means is posi-tioned for a cooling mode of operation, refrigerant is forwarded from the compressor to the outdoor coil. The vaporous refrigerant is condensed in the outdoor coil which functions at this $ime as a condenser. Liquid re-frigerant passes from the outdoor coil through the expansion means to the indoor coil. The refrigerant expands within the indoor coil, cooling the air passing thereover. The cooled air is transmitted to the area to be cooled.
With the reversing means positioned for a heating mode of operation, refrigerant is forwarded from the compressor to the indoor coil which now ~unctions as a condenser. The hot vaporous refrigerant is condensed and the heat given off from the refrigerant passes to the air moving over the indoor coil to the environment to be heated. Refrigerant is metered through the expansion means and flows to the outdoor coil where it expands. As the coil temperature approaches freezing, frost will form on the outdoor coil reducing the heating capacity of the system. Periodically, the outdoor coil must be defrosted to remove the frost. The frequency of frost removal or deicing depends upon the amount of moisture in the air at the time that icing occurs and thle operating temperature of the outdoor coil. The rate of icing is a function of numerous variables, but in general, it will increase as the ambient temperature around the outside coil decreases from 45 F to approximately 35F. The temperature of the outdoor coil will be about 30F.
As the ambient temperature decreases below 35F, the rate of icing also - 1 - ,~ ....
':
10768Z~;
decreases since the amount of free moisture in the air decreases. Icing is very slow at ambient temperatures below 15F to 20F to none existing.
One way of accomplishing defrost:ing of the outdoor coil during heating operation is to reverse the revers;ng means from the heating mode to the cooling mode. However, this is inefficientJ inasmuch as cool air may be discharged from the indoor coil into the area to be heated during the deicing process or defrost cycle. Strip heat or fossil fuel has been used to add heat to the area to be heated during this period of time, however, this is also inefficient and wasteful of energy.
At about 0F, outdoor ambient temperature, the COP of the conven-tional heat pump refrigeration system drops below one and the heat pump is cycled off. Auxiliary strip heat is turned on to heat the environment to be warmed. It is desirous to extend the lower range of operation to use heat from the more efficient heat pump system than from less efficient auxiliary strip heat.
An object of the present invention is to provide a heat pump wherein the disadvantages and deficiencies of prior heat pumps are obviated.
According to one aspect of this invention there is provided a heat pump including a multispeed compressor, reversing means, an indoor coil, an outdoor coil, and expansion means connected in a refrigerant circuit and control means for operating the compressor, said control means preventing frosting of the outdoor coil during the heating mode of operation without ~;
actuating the revers;ng means from the heating mode to the cooling mode by sensing a predetermined condition and changing the compressor operation from relatively high speed to relatively low speed.
According to another aspect of this invention there is provided a method of operating a heat pump including a multispeed compressor, reversing means, an indoor coil, an outdoor coil, and expansion means connected in a refrigerant circuit~ the method of operation preventing frosting of the out-door coil during the heating mode of operation without actuating the reversing ', ~ -1~7f~8Z6 means from the heating mode to the cooling mode, comprising the steps of operating the compressor at a relatively high speed in a heating mode so as to provide heat from the indoor coil to heat an environment, operating the compressor at a relatively low speed in response to a predetermined condition so as to reduce the indoor coil capacity and elevate the temperature of the outdoor coil so as to defrost the outdoor coil without actuating the reversing means.
According to yet another aspect of this invention there is provided a method of extending the lower operating range of a heat pump during heating operation comprising the steps of operating a two-speed compressor at rela-tively high speed during normal operation and at relatively low speed during ambient temperatures causing the outdoor coil to operate below 32F to there-by elevate the outdoor coil temperature to above freezing and make more heat available at the outdoor coil for system operation.
BRIEF DESCRIPTION OF THE DRAWING
There is illustra~ed in the attached drawing a presently preferred embodiment of the present invention wherein:
Figure 1 is a schematic illustration of a heat pump system embody-ing the present invention; and Figure 2 is a graph illustrating the operation of the novel heat pump of the present inventior DETAILED DESCRIPTION OF THE PRESENT INVENTION
With reference to Figure 1 there is shown a heat pump embodying the present invention. The heat pump 10 of this invention comprises basically a two-speed compressor 12 which is adapted to forward refrigerant through the line 14 to a reversing means 16 that is operated by control means 18 as will be more fully described hereinafter. The refrigeration system also includes an outdoor coil 22, expansion means 26, 28 and indoor coil 30. Associated with the expansion means 26, 28 are one-way check valve means 34, 36.
Consider first the cooling mode of operation. The reversing means ` .
` lB ' ':
,'' :
~7 16 is properly actuated by control 18. The compressor 12 is actuated by control 13 so as to pump refrigerant through the line 14 to the reversing means 16 to line 17 to the outdoor coil 22 where the hot vaporous refrigerant is condensed. As shown, the outdoor coil may be air-cooled by the fan means 24. The outdoor coil 22 can be water cooled if desired. The refrigerant condensed in the outdoor coil 22 passes through the line 25, the one-way check valve 34, line 27 and through the expansion means 28 which may comprise a thermal expansion valve. From the expansion means 28, the - 3a -:.
`` B :
.. . ;. ... .... ... - .. .. .. . ~ .
... ... ~ . . ................ ... ~. ... ... .
-~0768~6 refrigerant passes through the line 29 to the indoor coil 30 where the re-frigerant vaporizes. Air to be cooled may be passed over the indoor coil 30 by the fan means 31. During the cooling mode of operation, the cooled air may be ducted or otherwise communicated with the area to be cooled. The refrigerant passes through the line 32 from the indoor coil 30 (which acts as an evaporator) to the reversing valve 16 and then through line 33 to the compressor 12.
During the heating mode of operation, the refrigerant forwarded from the compressor 12 passes through the discharge line 14 to the reversing valve 16 and line 32 to the indoor coil which now functions as a condenser.
The fan means 31 passes air over the indoor coil which air is heated. The heated air is communicated to the area to be heated. The refrigerant passes from the indoor coil 30 through the line 29, one-way check valve 36 and line 27 to the expansion means 26. The refrigerant metered through the expansion means 26 passes through line 25 to the outdoor coil 22 which now functions as an evaporator. The refrigerant returns to the compressor via line 17, reversing means 16, and line 33.
A feature of the present invention is the provision of a two-speed compressor operable at a relatively high speed (nominal 3600 RPM at two-pole high speed) for normal heating operation and operable at a rela-tively low speed (nominal 1800 RPM at four-pole low speed) in response to a predetermined condition to reduce the indoor coil capacity and elevate the temperature of the outdoor coil so as to defrost the outdoor coil without actuating the reversing means which may be of a conventional type.
The control means 13 for operating the compressor 12 may be responsive to a predetermined outdoor temperature or may be responsive to a predetermined temperature differential of the outdoor coil or air pressure drop across the outdoor coil. In any event, the control 13 will operate the compressor during the heating mode of operation to reduce the speed from 1~768Z~;
high speed to low speed, so as to decrease the cooling capacity of outdoor coil, and thereby increase the temperature of the outdoor coil. At low speed operation, there is effectively twice the surface of outdoor coil as compared to high speed operation. The outdoor coil temperature will in-crease so as to defrost the outdoor coil without actuating the reversing `' means. Also, at low speed operation, the capacity of the compressor is about one half that at high speed. This too is a factor in elevating the temperature of the outdoor coil. Since there is no reverse cycle operation required for this defrost mode of operation, no cool air will be dumped into the area to be treated and there will be no necessity for utilization of strip heat or other auxiliary heat to offset a cooling effect during this mode of operation. This results in energy conservation and stress on the compressor is greatly reduced. The reduction in stress is not linear, but is reduced more sharply. The exact magnitude of the reduction is not known.
In the past, it has been kno~,vn to initiate the defrost cycle responsive to the ambient temperature, responsive to a temperature differential across the outdoor coil, responsive to an air pressure drop across the outdoor coil and by timing means. Similar sensors are required to terminate the defrost operation and return the system to normal heating operation.
Another aspect of this invention is to increase the range of operation of a heat pump system. At very low ambient temperature, on the order of 0F, the outdoor coil surface cannot pick up sufficient heat. The coefficient of performance (COP) of the heat pump will drop to or below 1. Under these circums tances, standard heat pump operation must be terminated. By use of the present invention, the speed of the compressor is reduced from full speed to half speed, so as to effectively double the cooling surface of the outdoor coil and thereby, enable the heat pump system to continue operating to a lower ambient temperature and maintain the COP above 1.
With reference to Figure 2, there is illustrated a graph of BTU per hour 1{17~ S
versus the outdoor coil temperature in degrees Fahrenheit. The lines sloping upwardly to the right have been marked with appropriate legends (compressor at high speed and compressor at low speed) and the lines A
and B are indicative of outdoor coil capacities at varying degrees of a~bient temperature. The line A assumes an ambient temperature of 40F and the line B assumes an ambient temperature of 0F. With reference to line A, it will be noted that the intersection of line A and the compressor at high speed operation line occurs at about 30F. At this condition, there would be frosting of the outdoor coil. When the compressor is switched to low speed, it will be noted that the intersection of line A with the compressor at -low speed line, increases to about 36F. The effective surface of the outdoor coil is doubled as compared to the effective surface at high speed operation, ~;
resulting in warming of the outdoor coil. This will be sufficient to defrost the outdoor coil.
":
A refinement would be to cycle the fan 31 for the indoor coil in con-junction with the operation of the compressor 12. ~uring high speed opera-tion, as the evaporating temperature approaches 32F, the indoor fan 31 is cycled. If the indoor fan 31 speed is substantially reduced or stopped, the -head pressure will be increased, thus the pumping capacity of the compressor will be decreased significantly and the outdoor coil temperature will be in-creased, thus helping to defrost the outdoor coil 2Z. At this time, the out-door coil fan 24 is kept running so as to maximi~e heat pick up by the out-door coil 22, thereby enhancing defrost of coil 22. If this does not defrost theoutdoor coil, then after a programmed time delay, the compressor 12 can be switched to half speed operation. Another aid to defrost if a few more degrees of heat were needed at the outdoor coil 22, would be to switch the operation of the outdoor fan 24 from low to high speed. If defrost of the outdoor coil is still not adequate, then the heat pump system reversing valve 16 could be ;;
operated in a conventional fashion.
, ~ .. . . :
107~;826 Considering next system operation at an outdoor ambient temperature of about 0F, it will be noted that the intersection of line B and the compressor at high speed line is at approximately -6F, evaporating temperature. At these conditions, there is insufficient heat in the air and the heat pump operates at a COP of less than 1. Normally, the operation of the compressor is terminated if the outdoor temperature drops below 0 F to prevent damage to the compressor and strip heat or auxiliary heat is used to provide heat in the area to be heated. If the compressor operation is reduced to low speed operationJ the intersection occurs of line B with the compressor at low speed at approximately 1F. In this example, therefore, the compressor which would otherwise have to be shut down may continue to be operated so as to increase the lower range of system operation.
Yet another means of extending the lower range of operation is contem-plated by the present invention. This is to provide a secondary coil in parallel with the outdoor coil of an equal capacity to that of the outdoor coil.
By utilization of both coils during low ambient conditions through suitable controls and in conjunction with the compressor at low speed operation, there is more outdoor coil surface and more heat can be picked for a given heat pump system. The lower range of operation can be extended several degrees in this manner.
There has been provided by the present invention an improved heat pump system provided with a two-speed compressor which is operable in a rela-tively low speed mode in response to a predetermined condition during heating so as to reduce the indoor coil capaci$y and elevate the temperature of the outdoor coil so as to defrost the outdoor coil without actuating the revarsing means. Another aspect of the invention is the utilization of a heat pump system having a two-speed compressor operable in such fashion as to extend the lower range of operation to very low ambient conditions, on the order of 0 to -6F.
While I have shown a presently preferred embodiment of the present -7- ~-invention, it will be understood that specific variations in construction and arrangement of the heat pump disclosed can be made by those skilled in the art without departing from the invention as defined in the appended claims.
..........
Claims (8)
1. A method of operating a heat pump including a multispeed com-pressor, reversing means, an indoor coil, an outdoor coil, and expansion means connected in a refrigerant circuit, the method of operation preventing frosting of the outdoor coil during the heating mode of operation without actuating the reversing means from the heating mode to the cooling mode, comprising the steps of operating the compressor at a relatively high speed in a heating mode so as to provide heat from the indoor coil to heat an environment, operating the compressor at a relatively low speed in response to a predetermined condition so as to reduce the indoor coil capacity and elevate the temperature of the outdoor coil so as to defrost the outdoor coil without actuating the reversing means.
2. A method as in Claim 1 including the step of detecting the build-up of frost on the outdoor coil during the heating mode of operation and changing the compressor from high speed operation to low speed opera-tion in response to a predetermined frost build-up on the outdoor coil.
3. A method as in Claim 1 including the step of changing the com-pressor from high speed operation to low speed operation when the outdoor temperature drops below a predetermined value.
4. A method as in Claim 1 including the step of changing the com-pressor from high speed operation to low speed operation in response to temperature conditions of the outdoor coil.
5. A heat pump including a multispeed compressor, reversing means, an indoor coil, an outdoor coil, and expansion means connected in a refrig-erant circuit and control means for operating the compressor, said control means preventing frosting of the outdoor coil during the heating mode of operation without actuating the reversing means from the heating mode to the cooling mode by sensing a predetermined condition and changing the compressor operation from relatively high speed to relatively low speed.
6. A heat pump as in Claim 5 wherein the outdoor coil has two circuits, only one of which is operable during normal operation, the second circuit being operable when the compressor is switched from high speed operation to low speed operation.
7. A method of extending the lower operating range of a heat pump during heating operation comprising the steps of operating a two-speed compressor at relatively high speed during normal operation and at rela-tively low speed during ambient temperatures causing the outdoor coil to operate below 32°F to thereby elevate the outdoor coil temperature to above freezing and make more heat available at the outdoor coil for system operation.
8. The method of Claim 7 wherein the outdoor coil includes two separate circuits, only one of which is operable during normal operation, comp rising the steps of passing refrigerant through the second circuit when the compressor is switched from high speed operation to low speed operation.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US87907578A | 1978-02-21 | 1978-02-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1076826A true CA1076826A (en) | 1980-05-06 |
Family
ID=25373388
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA308,163A Expired CA1076826A (en) | 1978-02-21 | 1978-07-26 | Heat pump with a two-speed compressor |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1076826A (en) |
-
1978
- 1978-07-26 CA CA308,163A patent/CA1076826A/en not_active Expired
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