U.S. patent application number 11/624743 was filed with the patent office on 2008-07-24 for heat pump apparatus and method.
This patent application is currently assigned to HALLOWELL INTERNATIONAL, LLC. Invention is credited to David N. Shaw.
Application Number | 20080173034 11/624743 |
Document ID | / |
Family ID | 39627565 |
Filed Date | 2008-07-24 |
United States Patent
Application |
20080173034 |
Kind Code |
A1 |
Shaw; David N. |
July 24, 2008 |
HEAT PUMP APPARATUS AND METHOD
Abstract
A heat pump system and method is presented having a primary
compressor, a booster compressor, an economizer, a microprocessor,
an air temperature sensor, and a temperature sensor for sensing a
temperature commensurate with the boiling temperature of
refrigerant in the outside coil. The microprocessor effects
controlled operation of the primary compressor, the booster
compressor and the economizer when a thermostat calls for heat and
in accordance with predetermined ranges of air temperature. The
microprocessor calculates a defrost trigger temperature, and
defrost operation is initiated when the sensed refrigerant boiling
temperature is lower than the trigger temperature for a period of
time.
Inventors: |
Shaw; David N.; (East
Falmouth, MA) |
Correspondence
Address: |
CANTOR COLBURN, LLP
20 Church Street, 22nd Floor
Hartford
CT
06103
US
|
Assignee: |
HALLOWELL INTERNATIONAL,
LLC
Bangor
ME
|
Family ID: |
39627565 |
Appl. No.: |
11/624743 |
Filed: |
January 19, 2007 |
Current U.S.
Class: |
62/160 ;
62/510 |
Current CPC
Class: |
F25B 2400/01 20130101;
F25B 2313/0315 20130101; F25B 2400/0401 20130101; F25B 13/00
20130101; F25B 2700/2106 20130101; F25B 1/10 20130101; F25B 2400/13
20130101; F25B 2313/02741 20130101 |
Class at
Publication: |
62/160 ;
62/510 |
International
Class: |
F25B 13/00 20060101
F25B013/00 |
Claims
1. A heat pump system including: a primary compressor; a booster
compressor; at least said primary compressor being a variable
capacity compressor, a refrigerant conduit system, said primary
compressor and said booster compressor being in series in said
refrigerant conduit system, and said conduit system including a
first conduit segment connected to deliver refrigerant to the inlet
to said primary compressor when said booster compressor in
inoperative, and said conduit system including a second conduit
segment between the discharge from said booster compressor and the
inlet to said primary compressor to deliver refrigerant between
said booster compressor and said primary compressor when both of
said compressors are operating; a first temperature sensor for
sensing the temperature of outdoor ambient air; a controller, said
controller being connected between a thermostat and said primary
and booster compressors, said controller receiving signals from
said first temperature sensor and from the thermostat to operate
said primary compressor and said booster compressor in a
predetermined sequence as follows: (a) effect a first mode of
operation of partial capacity operation of said primary compressor
(M1) when the thermostat is calling for heat and the signal from
said first temperature sensor indicates an outdoor air temperature
in a first range of temperatures; (b) effect operation in M1 and
effect a second mode of operation of full capacity operation of
said primary compressor (M2) when the thermostat is calling for
heat and the signal from said first temperature sensor indicates an
outdoor air temperature in a second range of temperatures; (c)
effect operation in M2 and effect a third mode of operation of full
capacity operation of said primary compressor, and operation of
said booster compressor (M3) when the thermostat is calling for
heat and the signal from said first temperature sensor indicates an
outdoor air temperature in a third range of temperatures.
2. A heat pump system as in claim 1 including; an electrical
resistance backup heater in the heat pump system; said controller
operating to effect full capacity operation of said primary
compressor and said booster compressor, and operation of said
electrical resistance backup heater when the thermostat is calling
for heat and the signal from said first temperature sensor
indicates an outdoor air temperature in a fourth range of
temperatures.
3. A heat pump system as in claim 1 wherein: M3 operation is
effected on a cyclical basis.
4. A heat pump system as in claim 1 wherein: said thermostat is a
multi-stage thermostat; and said controller effects operation in M1
when a first stage of said thermostat calls for heat and the
outdoor ambient temperature sensed by said first temperature sensor
is in said first range of temperatures; and, said controller
effects operation in M2 when a second stage of said thermostat
calls for heat and the outdoor ambient temperature sensed by said
first temperature sensor is in said second range of temperatures;
and said controller effects operation in M2 when a first stage of
said thermostat calls for heat and the outdoor ambient temperature
sensed by said first temperature sensor is in said third range of
temperatures; and said controller effects operation in M3 when a
second stage of said thermostat calls for heat and the outdoor
ambient temperature sensed by said first temperature sensor is in
said third range of temperatures.
5. A heat pump system as in claim 1 including: an electrical
resistance backup heater in the heat pump system; and wherein said
thermostat is a multistage thermostat; and wherein; said controller
allows operation in M3 when a first stage of said thermostat calls
for heat and the outdoor ambient temperature sensed by said first
temperature sensor is in a fourth range of temperatures; and said
controller allows operation in M3 and allows operation of said
backup heater when a second stage of said thermostat calls for heat
and the outdoor ambient temperature sensed by said first
temperature sensor is in a fourth range of temperatures
6. A heat pump system as in claim 1 including: an outdoor coil in
said conduit system; said controller calculating a defrost trigger
temperature T1 based on the outdoor ambient temperature sensed at
said first temperature sensor; a second temperature sensor, said
second temperature sensor being positioned to sense a temperature
commensurate with the temperature of refrigerant in said conduit
system in or adjacent to said outdoor coil; said second temperature
sensor delivering a second temperature signal T2 to said
controller; and said controller operating to effect a defrost
operation of said heat pump system when T2 is equal to or less than
T1 for a predetermined period of time.
7. A heat pump system as in claim 6 wherein: said controller
determines T1 in accordance with a first algorithm when the heat
pump system is operating in mode M2.
8. A heat pump system as in claim 7 wherein said first algorithm
is: T1=0.85.times.A.degree. F.-10.5 where A.degree. F. is the
temperature of outside air entering said outside coil.
9. A heat pump system as in claim 6 wherein: said controller
determines T1 in accordance with a second algorithm when the heat
pump system is operating in mode M3.
10. A heat pump system as in claim 9 wherein said second algorithm
is: T1=0.7075.times.A.degree. F.-19.625 where A.degree. F. is the
temperature of outside air entering said outside coil.
11. A heat pump system as in claim 1 including: an economizer in
said refrigerant conduit system; and a third conduit segment from
said economizer to said second conduit segment; and wherein said
mode M3 includes operation of said economizer.
12. A heat pump system as in claim 11 wherein: operation of said
economizer is cyclical.
13. A heat pump system including: a primary compressor; a booster
compressor; at least said primary compressor being a variable
capacity compressor, a refrigerant conduit system, said primary
compressor and said booster compressor being in series in said
refrigerant conduit system, and said conduit system including a
first conduit segment connected to deliver refrigerant to the inlet
to said primary compressor when said booster compressor in
inoperative, and said conduit system including a second conduit
segment between the discharge from said booster compressor and the
inlet to said primary compressor to deliver refrigerant between
said booster compressor and said primary compressor when both of
said compressors are operating; an economizer in said refrigerant
conduit system; a third conduit segment from said economizer to
said second conduit segment; a first temperature sensor for sensing
the temperature of outdoor ambient air; a controller, said
controller being connected between a two step thermostat and said
primary and booster compressors, said controller receiving signals
from said first temperature sensor and from the thermostat to
operate said primary compressor, said booster compressor and said
economizer in a predetermined sequence as follows: (a) effect a
first mode of operation of partial capacity operation of said
primary compressor (M1) when either stage of the thermostat is
calling for heat and the signal from said first temperature sensor
indicates an outdoor air temperature in a first range of
temperatures; (b) effect operation in M1 when the first stage of
the thermostat is calling for heat and the signal from said first
temperature sensor indicates an outdoor temperature in a second
range of temperatures; and effect a second mode of operation of
full capacity operation of said primary compressor (M2) when the
second stage of the thermostat is calling for heat and the signal
from said first temperature sensor indicates an outdoor air
temperature in the second range of temperatures; (c) effect
operation in M2 when either stage of the thermostat is calling for
heat and the signal from said first temperature sensor indicates an
outdoor temperature in a third range of temperatures; and (d)
effect operation in M2 when the first stage of the thermostat is
calling for heat and the signal from said first temperature sensor
indicates an outdoor air temperature in a fourth range of
temperatures; and effect a third mode of operation of full capacity
operation of said primary compressor, said booster, and said
economizer (M3) when the second stage of the thermostat is calling
for heat and the signal from said first temperature sensor
indicates an outdoor air temperature in the fourth range of
temperatures.
14. A heat pump system as in claim 13 including; an electrical
resistance backup heater in the heat pump system; said controller
operating to effect operation in M3 when the first stage of the
thermostat is calling for heat and the signal from said first
temperature sensor indicates an outdoor air temperature in a fifth
range of temperatures; and said controller operating to effect
operation of said backup heater (M4) when the second stage of the
thermostat is calling for heat and the signal from said first
temperature sensor indicates an outdoor air temperature in the
fifth range of temperatures.
15. A heat pump system as in claim 13 wherein: said first range of
temperatures is from about 60.degree. F. and above.
16. A heat pump system as in claim 13 wherein: said second range of
temperatures is from about 38.degree. F. to about 59.degree. F.
17. A heat pump system as in claim 13 wherein: said third range of
temperatures is from about 31.degree. F. to about 37.degree.
18. A heat pump system as in claim 13 wherein: said fourth range of
temperatures is from about 19.degree. F. to about 30.degree. F.
19. A heat pump system as in claim 14 wherein: said fifth range of
temperatures is from about 18.degree. F. and below.
20. A heat pump system as in claim 13 including: an outdoor coil in
said conduit system; said controller calculating a defrost trigger
temperature T1 based on the outdoor ambient temperature sensed at
said first temperature sensor and in accordance with an algorithm;
a second temperature sensor, said second temperature sensor being
positioned to sense a temperature commensurate with the temperature
of refrigerant in said conduit system in or adjacent to said
outdoor coil; said second temperature sensor delivering a second
temperature signal T2 to said controller; and said controller
operating to effect a defrost operation of said heat pump system
when T2 is equal to or less than T1 for a predetermined period of
time.
21. A heat pump system as in claim 20 wherein: said controller
determines T1 in accordance with a first algorithm when the heat
pump system is operating in mode M2.
22. A heat pump system as in claim 21 wherein said first algorithm
is: T1=0.85.times.A.degree. F.-10.5 where A.degree. F. is the
temperature of outside air entering said outside coil.
23. A heat pump system as in claim 20 wherein: said controller
determines T1 in accordance with a second algorithm when the heat
pump system is operating in mode M3.
24. A heat pump system as in claim 23 wherein said second algorithm
is: T1=0.7075.times.A.degree. F.-19.625 where A.degree. F. is the
temperature of outside air entering said outside coil.
25. A heat pump system as in claim 13 including: a refrigerant
accumulator, said accumulator being connected to the discharge from
said booster compressor to receive from the booster compressor upon
operation thereof and to store excess refrigerant absorbed in the
oil of said booster compressor when said booster compressor is not
operating.
26. 1. A defrost system for a heat pump system including: at least
one compressor; an outdoor coil in said heat pump system; a
refrigerant conduit system, said compressor and said outdoor coil
being being in said refrigerant conduit system; a first temperature
sensor for sensing the temperature of outdoor ambient air and
generating a first signal commensurate with the outdoor ambient air
temperature; a second temperature sensor, said second temperature
sensor being positioned to sense a temperature commensurate with
the temperature of refrigerant in said conduit system in or
adjacent to said outside coil, said second temperature sensor
generating a second signal commensurate with the temperature of
refrigerant in or adjacent to said outdoor coil; a controller, said
controller receiving said first signal from said first temperature
sensor and calculating a defrost trigger temperature T1 based on
the outdoor ambient temperature sensed at said first temperature
sensor, and said controller receiving said second temperature
signal T2 from said second temperature sensor; said controller
operating to effect a defrost operation of said heat pump system
when T2 is equal to or less than T1 for a predetermined period of
time.
27. A defrost system for a heat pump system as in claim 26 wherein:
said controller determines T1 in accordance with an algorithm
linear with outdoor ambient air temperature.
28. A method of operating a heat pump system having a primary
compressor and a booster compressor, at least said primary
compressor being a variable capacity compressor, and said
compressors being operable in series, the method including the
steps of: (a) sensing the temperature of outdoor ambient air; (b)
effecting a first mode of operation of partial capacity operation
of said primary compressor (M1) when heat is called for and the
outdoor air temperature is in a first range of temperatures; (c)
effecting operation in M1 and effecting a second mode of operation
of fall capacity operation of said primary compressor (M2) when
heat is called for and the outdoor air temperature is in a second
range of temperatures; (d) effecting operation in M2 and effecting
a third mode of operation of full capacity operation of said
primary compressor, said booster, and said economizer (M3) when
heat is called for and the outdoor air temperature is in a third
range of temperatures.
29. A method of operating a heat pump system as in claim 28 wherein
the system includes an electrical resistance backup heater, the
method including the step of: effecting fall capacity operation of
said primary compressor and said booster, and effecting operation
of electrical resistance backup heat when heat is called for and
the outdoor air temperature is in a fourth range of
temperatures.
30. A method of operating a heat pump system as in claim 28 wherein
the system includes a multi-stage thermostat; the method including
the steps of: effecting operation in M1 when a first stage of the
thermostat calls for heat and the outdoor ambient temperature is in
said first range of temperatures; and, effecting operation in M2
when a second stage of the thermostat calls for heat and the
outdoor ambient temperature is in said second range of
temperatures; and effecting operation in M2 when a first stage of
said thermostat calls for heat and the outdoor ambient temperature
is in said third range of temperatures; and effecting operation in
M3 when a second stage of said thermostat calls for heat and the
outdoor ambient temperature is in said third range of
temperatures.
31. A method of operating a heat pump system as in claim 28 wherein
the system includes an electrical resistance backup heater, and a
multistage thermostat, the method including the steps of: effecting
operation in M3 when a first stage of the thermostat calls for heat
and the outdoor ambient temperature is in a fourth range of
temperatures; and effecting operation in M3 and effecting operation
of the backup heater when a second stage of the thermostat calls
for heat and the outdoor ambient temperature is in a fourth range
of temperatures
32. A method of operating a heat pump system as in claim 28 wherein
the system includes a conduit system for the flow of refrigerant,
and an outdoor coil in said conduit system for extracting heat
energy from outside ambient air, the method including the steps of:
calculating a defrost trigger temperature T1 based on the outdoor
ambient temperature; sensing the temperature T2 of refrigerant in
the conduit system in or adjacent to the outdoor coil; and
effecting a defrost operation of said heat pump system when T2 is
equal to or less than T1 for a predetermined period of time.
33. A method of operating a heat pump system as in claim 32
wherein: the temperature T1 is determined in accordance with a
first algorithm when the heat pump system is operating in mode
M2.
34. A method of operating a heat pump system as in claim 33 wherein
said first algorithm is typically: T1=0.85.times.A.degree. F.-10.5
where A.degree. F. is the temperature of outside air entering said
outside coil.
35. A method of operating a heat pump system as in claim 34
wherein: the temperature T1 is determined in accordance with a
second algorithm when the heat pump system is operating in mode
M3.
36. A method of operating a heat pump system as in claim 35 wherein
said second algorithm is typically: T1=0.7075.times.A.degree.
F.-19.625 where A.degree. F. is the temperature of outside air
entering said outside coil.
37. A method of operating a heat pump system having a primary
compressor, a booster compressor, and an economizer, at least said
primary compressor being a variable capacity compressor, and said
compressors being operable in series, the method including the
steps of: (a) sensing the temperature of outdoor ambient air; (b)
effecting a first mode of operation of partial capacity operation
of said primary compressor (M1) when heat is called for and the
outdoor air temperature is in a first range of temperatures; (c)
effecting operation in M1 and effecting a second mode of operation
of full capacity operation of said primary compressor (M2) when
heat is called for and the outdoor air temperature is in a second
range of temperatures; (d) effecting operation in M2 when heat is
called for and the outdoor air temperature is in a third range of
temperatures; (e) effecting operation in M2 and effecting a third
mode of operation of full capacity operation of said primary
compressor, said booster, and said economizer (M3) when heat is
called for and the outdoor air temperature is in a fourth range of
temperatures.
38. A method of operating a heat pump system as in claim 37 wherein
the system includes an electrical resistance backup heater, the
method including the step of: effecting full capacity operation of
said primary compressor and said booster, and effecting operation
of electrical resistance backup heat when heat is called for and
the outdoor air temperature is in a fifth range of
temperatures.
39. A method of operating a heat pump system as in claim 37
wherein: said first range of temperatures is from about 60.degree.
F. and above.
40. A method of operating a heat pump system as in claim 37
wherein: said second range of temperatures is from about 38.degree.
F. to about 59.degree. F.
41. A method of operating a heat pump system as in claim 37
wherein: said third range of temperatures is from about 31.degree.
F. to about 37.degree. F.
42. A method of operating a heat pump system as in claim 37
wherein: said fourth range of temperatures is from about 30.degree.
F. and below.
43. A method of operating a heat pump system as in claim 38
wherein: said fifth range of temperatures is from about 18 and
below.
44. A method of operating a heat pump system having a primary
compressor, a booster compressor, and an economizer, and a
multi-stage thermostat, at least said primary compressor being a
variable capacity compressor, and said compressors being operable
in series, the method including the steps of: (a) sensing the
temperature of outdoor ambient air; (b) effecting a first mode of
operation of partial capacity operation of said primary compressor
(M1) when the outdoor air temperature is in a first range of
temperatures and either the first stage or the second stage of the
thermostat is calling for heat; (c) effecting operation in M1 when
the outdoor air temperature is in a second range of temperatures,
and the first stage of the thermostat is calling for heat; and
effecting a second mode of operation of full capacity operation of
said primary compressor (M2) when the outdoor air temperature is in
the second range of temperatures and the second stage of the
thermostat is calling for heat; (d) effecting operation in M2 when
the outdoor air temperature is in a third range of temperatures and
either the first stage or the second stage of the thermostat is
calling for heat; (e) effecting operation in M2 when the outdoor
air temperature is in a fourth range of temperatures and the first
stage of the thermostat is calling for heat, and effecting full
capacity operation of said primary compressor, said booster, and
said economizer (M3) when the outdoor air temperature is in a
fourth range of temperatures and the second stage of the thermostat
is calling for heat.
45. A method of operating a heat pump system as in claim 44 wherein
the system includes an electrical resistance backup heater, the
method including the step of: effecting full capacity operation of
said primary compressor, said booster, and said economizer when the
outdoor temperature is in a fifth range of temperatures and the
first stage of the thermostat is calling for heat, and effecting
operation of electrical resistance backup heat when the outdoor air
temperature is in a fifth range of temperatures and the second
stage of the thermostat is calling for heat.
46. A method of operating a heat pump system as in claim 44
wherein: said first range of temperatures is from about 60.degree.
F. and above.
47. A method of operating a heat pump system as in claim 44
wherein: said second range of temperatures is from about 38.degree.
F. to about 59.degree. F.
48. A method of operating a heat pump system as in claim 44
wherein: said third range of temperatures is from about 31.degree.
F. to about 37.degree. F.
49. A method of operating a heat pump system as in claim 44
wherein: said fourth range of temperatures is from about 30.degree.
F. and below.
50. A method of operating a heat pump system as in claim 45
wherein: said fifth range of temperatures is from about 18 and
below.
51. A method of operating a heat pump system as in claim 44 wherein
the system includes a conduit system for the flow of refrigerant,
and an outdoor coil in said conduit system for extracting heat
energy from outside ambient air, the method including the steps of:
calculating a defrost trigger temperature T1 based on the outdoor
ambient temperature; sensing the temperature T2 of refrigerant in
the conduit system in or adjacent to the outdoor coil; and
effecting a defrost operation of said heat pump system when T2 is
equal to or less than T1 for a predetermined period of time.
52. A method of operating a heat pump system as in claim 44
wherein: the temperature T1 is determined in accordance with a
first algorithm when the heat pump system is operating in mode
M2.
53. A method of operating a heat pump system as in claim 44 wherein
said first algorithm is typically: T1=0.85.times.A.degree. F.-10.5
where A.degree. F. is the temperature of outside air entering said
outside coil.
54. A method of operating a heat pump system as in claim 44
wherein: the temperature T1 is determined in accordance with a
second algorithm when the heat pump system is operating in mode
M3.
55. A method of operating a heat pump system as in claim 44 wherein
said second algorithm is typically: T1=0.7075.times.A.degree.
F.-19.625 where A.degree. F. is the temperature of outside air
entering said outside coil.
56. A heat pump system including: a primary compressor; a booster
compressor; at least said primary compressor being a variable
capacity compressor, a refrigerant conduit system, said primary
compressor and said booster compressor being in series in said
refrigerant conduit system, and said conduit system including a
first conduit segment connected to deliver refrigerant to the inlet
to said primary compressor when said booster compressor in
inoperative, and said conduit system including a second conduit
segment between the discharge from said booster compressor and the
inlet to said primary compressor to deliver refrigerant between
said booster compressor and said primary compressor when both of
said compressors are operating; a first temperature sensor for
sensing the temperature of outdoor ambient air; a controller, said
controller being connected between a two step thermostat and said
primary and booster compressors, said controller receiving signals
from said first temperature sensor and from the thermostat to
operate said primary compressor, said booster compressor and said
economizer in a predetermined sequence as follows: (a) effect a
first mode of operation of partial capacity operation of said
primary compressor (M1) when either stage of the thermostat is
calling for heat and the signal from said first temperature sensor
indicates an outdoor air temperature in a first range of
temperatures; (b) effect operation in M1 when the first stage of
the thermostat is calling for heat and the signal from said first
temperature sensor indicates an outdoor temperature in a second
range of temperatures; and effect a second mode of operation of
full capacity operation of said primary compressor (M2) when the
second stage of the thermostat is calling for heat and the signal
from said first temperature sensor indicates an outdoor air
temperature in the second range of temperatures; (c) effect
operation in M2 when the first stage of the thermostat is calling
for heat and the signal from said first temperature sensor
indicates an outdoor temperature in a third range of temperatures;
and effect operation in M2 and cyclical on-off operation of said
booster compressor (M3-C) when the second stage of the thermostat
is calling for heat and the signal from the first temperature
sensor indicates an outdoor temperature in a third range of
temperatures; (d) effect operation in M3-C when the first stage of
the thermostat is calling for heat and the signal from said first
temperature sensor indicates an outdoor air temperature in a fourth
range of temperatures; and effect full capacity operation of said
primary compressor and said booster (M3), when the second stage of
the thermostat is calling for heat and the signal from said first
temperature sensor indicates an outdoor air temperature in the
fourth range of temperatures.
57. A heat pump system as in claim 56 including; an electrical
resistance backup heater in the heat pump system; said controller
operating to effect operation in M3 when the first stage of the
thermostat is calling for heat and the signal from said first
temperature sensor indicates an outdoor air temperature in a fifth
range of temperatures; and said controller operating to effect
operation of said backup heater (M4) when the second stage of the
thermostat is calling for heat and the signal from said first
temperature sensor indicates an outdoor air temperature in the
fifth range of temperatures.
58. A heat pump system as in claim 56 including: an economizer in
said refrigerant conduit system; a third conduit segment from said
economizer to said second conduit segment; and wherein each of
modes M3-C and M3 include cyclical on-off operation of said
economizer.
59. A heat pump system operating in a cooling mode, including: a
primary compressor; a booster compressor; at least said primary
compressor being a variable capacity compressor, a refrigerant
conduit system, said primary compressor and said booster compressor
being in series in said refrigerant conduit system, and said
conduit system including a first conduit segment connected to
deliver refrigerant to the inlet to said primary compressor when
said booster compressor in inoperative, and said conduit system
including a second conduit segment between the discharge from said
booster compressor and the inlet to said primary compressor to
deliver refrigerant between said booster compressor and said
primary compressor when both of said compressors are operating; a
first temperature sensor for sensing the temperature of outdoor
ambient air; a controller, said controller being connected between
a multi-stage thermostat and said primary and booster compressors,
said controller receiving signals from said first temperature
sensor and from the thermostat to operate said primary compressor
and said booster compressor in a predetermined sequence as follows:
(a) effect a first mode of operation of partial capacity operation
of said primary compressor (M1) when a first stage of the
thermostat calls for cooling, and without regard to the signal from
said first temperature sensor; (b) effect a second mode of
operation of full capacity operation of said primary compressor
(M2) when M1 is not sufficient to meet the need for cooling and a
second stage of the thermostat calls for more cooling.
60. A heat pump system operating in a cooling mode as in claim 59,
including: an economizer in said cooling system; the predetermined
operating sequence including to effect M1 and M2 when the signal
from said first temperature sensor indicates a an outdoor
temperature in a first range of temperatures; and effect a third
mode of operation of full capacity operation of said primary
compressor and operation of said booster compressor and operation
of said economizer, or cyclical on-off operation thereof, when the
thermostat is calling for cooling and the signal from said first
temperature sensor indicates an outdoor air temperature higher than
said first range of temperatures.
61. A method of operating a heat pump system in cooling, the system
having a primary compressor and a booster compressor, at least said
primary compressor being a variable capacity compressor, and said
compressors being operable in series, the method including the
steps of: (a) effecting a first mode of operation of partial
capacity operation of said primary compressor (M1) when a first
stage of a thermostat calls for cooling is called for and without
regard to the signal from said first temperature sensor; (b)
effecting a second mode of operation of full capacity operation of
said primary compressor (M2) when cooling is called for and the
outdoor air temperature is in a second range of temperatures; (c)
effecting operation in M2 and effecting a third mode of operation
of full capacity operation of said primary compressor, said
booster, and said economizer (M3) when M1 is not sufficient to meet
the need for cooling and a second stage of the thermostat calls for
more cooling.
62. A method of operating heat pump system in a cooling mode as in
claim 61, including: an economizer in said cooling system; and
including the steps of effecting operation in M1 and M2 when the
signal from said first temperature sensor indicates a an outdoor
temperature in a first range of temperatures; and effecting a third
mode of operation of full capacity operation of said primary
compressor and operation of said booster compressor and operation
of said economizer, or cyclical operation thereof, when the
thermostat is calling for cooling and the signal from said first
temperature sensor indicates an outdoor air temperature higher than
said first range of temperatures.
Description
RELATIONSHIP TO OTHER APPLICATIONS
[0001] This application relates to heat pumps of the type disclosed
and claimed in my previously issued U.S. Pat. Nos. 6,931,871,
6,276,148, 5,927,088, and 5,839,886 and my pending U.S. patent
applications Ser. Nos. PCT/US05/34651 and 10/959,254. The entire
contents of my said United States patents and patent applications
are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] This invention relates to the field of heat pumps. More
particularly, this invention relates to the field of air source
heat pumps having a primary compressor and a booster compressor
connected in series, the heat pumps being suitable for heating
operation at temperatures down to zero degrees Fahrenheit and
lower.
SUMMARY OF THE INVENTION
[0003] In accordance with the present invention, a primary
compressor and a booster compressor are connected to operate in
series in a heat pump system. The primary compressor is a variable
capacity or partially unloadable compressor, and the booster is
preferably a single speed compressor. The system also incorporates
a temperature sensor for sensing the temperature of outdoor ambient
air, a two stage indoor thermostat and a microprocessor. For
heating operation, the system is capable of operation in any one of
three modes, M1, M2, M3, depending on outdoor air temperature and
the heating load on the system. M1 is partial capacity operation of
the primary compressor; M2 is full capacity operation of the
primary compressor; and M3 is full capacity operation of each of
the primary compressor, the booster compressor, and an economizer.
For outdoor temperatures in a first range between about 60.degree.
F. and up (i.e., up to where heating operation is no longer
allowed), only operation in M1 is allowed. For outdoor air
temperatures in a second range of from about 38.degree. F. to about
59.degree. F., operation in M1 is allowed, and, if M1 operation
does not provide enough heat, operation in M2 is also allowed. For
outdoor air temperatures in a third range of from about 31.degree.
F. to about 37.degree. F., operation in only M2 is allowed. For
outdoor air temperatures in a fourth range of from about 19.degree.
F. to about 37.degree. F., operation in M2 is allowed, and, if M2
operation does not provide enough heat, operation in M3 is allowed.
For outdoor air temperatures in a fifth range of from about
18.degree. F. and below, operation in M3 is allowed, and, if M3
operation does not provide enough heat, the system may also include
an M4 mode in which electrical resistance heat is added to the
system.
[0004] The temperature sensor delivers signals to the
microprocessor, and the microprocessor enables or allows operation
in M1, M2 and M3 (and M4), i.e., conditions are created wherein
operation in those modes will occur if the thermostat calls for
heat. When the thermostat calls for heat, the microprocessor will
generate signals to cause operation in M1, M2, M3 or M4 depending
on the outdoor air temperature.
[0005] For cooling operation, only the primary compressor operates
in either Mode 1 or 2 depending only on which indoor thermostat
stage is calling for cooling operation.
[0006] The heat pump system also incorporates a demand defrost
cycle in modes M2, M3 and M4 (if M4 is present). Outdoor air
temperature is sensed by a temperature sensor external to the
outdoor (evaporator) coil, and a signal representing that
temperature is delivered to a system microprocessor. Based on the
sensed outdoor air temperature, the microprocessor calculates a
defrost trigger temperature T1 for each of modes M2 and M3 (M4 is
identical to M3 for demand defrost purposes). A temperature T2 is
also sensed that is commensurate with the temperature of the
refrigerant boiling in the outdoor coil.
[0007] T2 is sensed by a sensor mounted on one of the tubes feeding
an evaporator circuit directly downstream of the normal pressure
reduction/flashing process. Whenever T2 then drops to a value equal
to or less than the calculated T1 continuously for 10 minutes, a
defrost cycle is triggered to defrost the outdoor coil. The defrost
cycle continues until T2 rises to a predetermined defrost
terminating value.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Referring to the drawings, where like elements are numbered
alike in some of the figures:
[0009] FIG. 1 is a schematic drawing of the heat pump system of the
present invention for heating modes M1 and M2;
[0010] FIG. 2 is a schematic drawing of the heat pump system of the
present invention for heating mode M3, and M4 if present.
[0011] FIG. 3 is a schematic drawing of the heat pump system of the
present invention for cooling modes M1 and M2.
[0012] FIG. 3A is a schematic drawing of the heat pump system of
the present invention for cooling modes M3 or M3-C.
[0013] FIG. 4 is a table showing the temperature ranges of
operation for heating modes M1, M2, M3, and M4, if present.
[0014] FIG. 4A is a modified version of the table of FIG. 4.
[0015] FIG. 5 is a chart illustrating the determination of trigger
temperatures for defrost operation.
[0016] FIG. 6 is a schematic showing incorporation of a refrigerant
compensator for modes M3 and M4.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0017] Referring to FIGS. 1 and 2, a closed loop heat pump system
for heating operation is shown. The system includes a first or
booster compressor 22, a second or high stage primary compressor
24, an indoor coil or condenser 26 that delivers heated air to a
space to be heated, an outdoor coil or evaporator 28 which receives
outdoor air from which heat energy is to be extracted, an
economizer 30 which has a solenoid operated control valve 31, a
four way flow control valve 32, and a conduit system 34 for
connecting the foregoing components in a closed loop system for the
flow of refrigerant. Flow control valve 32 operates to reverse the
flow of refrigerant to effect cooling operation and for defrost
operation. The system also has a microprocessor 36 and a two stage
thermostat 38, such as is available from White Rogers. The system
also has thermal expansion valves 40 and 42 in conduit 34
associated, respectively, with indoor coil 26 and outdoor coil 28,
and check valves 44 and 46 for bypassing refrigerant flow around
expansion valves 40 and 42, respectively, depending on the
direction of refrigerant flow in the system. The check valves 44
and 46 may actually be internal parts of their respective expansion
valves, but they are shown separately to facilitate the description
of operation. The system also includes a first temperature sensor
48 positioned near outdoor coil 28 for sensing the temperature of
outdoor air flowing over outdoor coil 28, and a second temperature
sensor 50 on or just adjacent to conduit 34 where it enters outdoor
coil 28 to sense temperature commensurate with the boiling
refrigerant in outdoor coil 28. Air handlers and/or fans for coils
26 and 28 are not shown, but the flow or air over these coils is
indicated by arrows.
[0018] Primary compressor 22 is preferably a Bristol twin single
(TS) compressor having two reciprocating pistons and cylinders.
However, it can also be any multi-capacity or unloadable positive
displacement or multi-speed compressor. Booster compressor 22 is
any type of a positive displacement single speed compressor. The
flow capacity of the primary compressor is preferably split
50%/100%, i.e., where 100% is the flow capacity when both cylinders
are operating, and 50% is the percentage of total flow capacity
when only one piston is reciprocating. In addition, the flow
capacity of booster compressor is larger than the flow capacity of
primary compressor, preferably by a ratio of from about 1.3/1 to
about 1.7/1, depending on the climate where the system is to be
used.
[0019] In initial operation of the system in the heating mode, a
signal representing the ambient air temperature sensed by
temperature sensor 48 is delivered to microprocessor 36, and the
microprocessor will enable or allow partial capacity operation of
primary compressor 24 upon receipt of a signal from thermostat 38
calling for heat if the outdoor ambient temperature is in a first
range between about 60.degree. F. and above. A signal calling for
heat is delivered to microprocessor 36 from stage 1 of thermostat
38 when the temperature of the space to be heated falls below the
set point of the thermostat by, e.g., 0.6.degree. F.-1.2.degree. F.
If the temperature sensed at sensor 48 is in the first range of at
or between about 60.degree. F. and above, the microprocessor causes
operation of one cylinder of primary compressor 24. That is,
partial capacity operation of primary compressor 24 is effected.
When that happens, compressed hot refrigerant vapor is circulated
in conduit system 34 by delivery from primary compressor 24 through
4 way valve 32 and then to indoor condenser coil 26 where heat is
extracted by air from an air handler passing over indoor coil 26 to
be delivered to the space to be heated. On leaving the indoor
condenser coil 26, the refrigerant is in the form of a warm liquid,
and it flows through check valve 44, which is open, bypassing
expansion valve 40. The warm refrigerant liquid then flows directly
through the liquid side of economizer 30 and is delivered toward
thermal expansion valve 42. Since direction of flow and pressure of
the refrigerant close check valve 46, the warm liquid refrigerant
is delivered to and flows through thermal expansion valve 42 where
part of the refrigerant is flashed or boiled to vapor. The two
phase refrigerant mixture then flows to outdoor coil 28 where the
remaining liquid refrigerant is vaporized due to extraction of heat
from the outside air. The resulting cool vapor is then delivered
through 4 way valve 32 and through check valve 52 and conduit
section 54 to the inlet to primary compressor 24. The refrigerant
then goes through repeat cycles of compression; subsequent vapor
cooling and condensation into liquid; then liquid flashing or
expansion; subsequent boiling or evaporation while it is
concurrently transferring heat energy into indoor air while cooling
and condensing and extracting heat energy from the outside air
while boiling or evaporating. The operating cycle described above
with partial capacity operation of the primary compressor is termed
Mode 1, or M1. When the set point of thermostat 38 is reached, a
signal is sent from the thermostat to the microprocessor to
terminate operation of primary compressor 24 in M1. If the
temperature of the space to be heated again falls below the set
point of the thermostat by 0.6.degree. F.-1.2.degree. F., the
thermostat again delivers a heat calling signal to microprocessor
36, and if the temperature sensed by sensor 48 is still in the
first range of between about 60.degree. F. and up, the system is
again cycled through operation in M1. As long as the outdoor
ambient temperature sensed at sensor 48 is in the first range
between about 60.degree. F. and up, the microprocessor will only
allow operation in M1, i.e., with partial capacity operation of
primary compressor 24. Also, if the outside air temperature, as
sensed by sensor 48 is not at or below a selected upper first range
temperature of, e.g., about 75.degree. F., the microprocessor will
not allow operation of primary compressor 24, and heating operation
will not occur. This prevents inefficient use of the heating
system.
[0020] The system continues to operate in M1 until sufficient heat
has been delivered to the space being heated to satisfy the setting
called for by thermostat 38. When the setting of the thermostat is
satisfied, a signal is delivered from the thermostat to the
microprocessor, and operation of the compressor system is
terminated. However, if sufficient heat has not been delivered to
the internal space to be heated within a pre-programmed period of
time (typically from 5 to 10 minutes) or if the rate of increase in
temperature is not fast enough, the thermostat calls for stage 2
operation by sending a second signal to microprocessor 36 to call
for more heating capacity from the system. If the outdoor ambient
temperature sensed at sensor 48 is in a second and lower range of
temperature between about 38.degree. F. and 59.degree. F., the
microprocessor then delivers an enabling signal to primary
compressor 24 to operate both pistons of the primary compressor 24
to effect operation of the primary compressor at full capacity.
This full capacity operation of the primary compressor is termed
Mode 2 or M2. In M2, the flow of refrigerant through the system is
as in M1, but at a higher flow rate, whereby a greater volume of
hot vapor is delivered to indoor condenser coil 26 to heat the
indoor space to be heated. Note, again, that if the outdoor
temperature sensed at sensor 48 is not at or below the upper limit
of about 59.degree. F. of the second operating range of outdoor
temperatures, the microprocessor will not enable M2 operation of
the system. Again, this prevents inefficient operation of the
heating system. The system continues to operate in M2 until
sufficient heat has been delivered to the space being heated to
satisfy the setting called for by thermostat 38. When the setting
of the thermostat has been satisfied, a signal is delivered from
the thermostat to the microprocessor to terminate operation of the
compressor system. If the temperature of the space to be heated
again falls below the set point of the thermostat by 0.6.degree.
F.-1.2.degree. F., the thermostat again delivers a heat calling
signal to microprocessor 36, and if the temperature sensed by
sensor 48 is still in the second range of between about 38.degree.
F. and 59.degree. F., the system is again cycled through operation
first in M1 and then in M2. As long as the outdoor ambient
temperature sensed at sensor 48 is in the second range between
about 38.degree. F. and 59.degree. F., the microprocessor will only
allow operation in M1 and M2, i.e., first with partial capacity
operation and then fall capacity of primary compressor 24.
[0021] At a third and lower range of outdoor ambient air
temperatures, from about 31.degree. F. to 37.degree. F. the
temperature signal delivered by sensor 48 to microprocessor causes
the microprocessor to skip M1, and go directly to enabling or
allowing M2 operation. Accordingly, upon receipt of a heat calling
signal from stage 1 of thermostat 38 being delivered to
microprocessor 36 (as the result of the temperature in the space to
be heated falling below the set point of the thermostat), the
microprocessor delivers a signal to primary compressor 24 to
operate the primary compressor at full capacity. The system
continues to operate in M2 until sufficient heat has been delivered
to the space being heated to satisfy the setting called for by
thermostat 38. If the setting of the thermostat is satisfied, a
signal is delivered from the thermostat to the microprocessor, and
operation of the compressor system is terminated. However, if
sufficient heat has not been delivered to the internal space to be
heated within a period of time (typically from 5 to 10 minutes), or
if the rate of temperature increase is not fast enough, the
thermostat calls for stage 2 operation by sending a second signal
(calling for more heating capacity from the system) to
microprocessor 36. However, in this third range of outdoor ambient
air temperatures, from about 31.degree. F. to 37.degree. F., the
microprocessor is programmed to still only allow M2 operation upon
receiving the stage 2 signal from the thermostat. This prevents
inefficient use of the heating system as higher capacity operation
is not to be permitted by the microprocessor until it is really
needed.
[0022] At a fourth and lower range of outdoor ambient air
temperatures, from about 19.degree. F. to about 30.degree. F. the
temperature signal delivered by sensor 48 to the microprocessor
causes the microprocessor to again skip M1, and go directly to
allowing M2 operation. Accordingly, upon receipt of a heat calling
signal from stage 1 of thermostat 38 being delivered to
microprocessor 36 (as the result of the temperature in the space to
be heated falling below the set point of the thermostat by from
about 0.6.degree. F.-1.2.degree. F.), the microprocessor delivers a
signal to primary compressor 24 to operate the primary compressor
at full capacity. The system continues to operate in M2 until
sufficient heat has been delivered to the space being heated to
satisfy the setting called for by thermostat 38. If the setting of
the thermostat is satisfied, a signal is delivered from the
thermostat to the microprocessor, and operation of the compressor
system is terminated. However, if sufficient heat has not been
delivered to the internal space to be heated within a period of
time (typically from 5 to 10 minutes), or if the rate of
temperature increase is not fast enough, the thermostat calls for
stage 2 operation by sending a second signal (calling for more
heating capacity from the system) to microprocessor 36. If the
outdoor ambient temperature sensed at sensor 48 is still in the
range of between about 19.degree. F. and 30.degree. F., the
microprocessor then generates enabling signals to operate all of
the booster compressor 22, the primary compressor 24 at full
capacity, and the economizer at full capacity. This operation of
the booster compressor, the primary compressor at full capacity and
full capacity operation of the economizer is termed Mode 3 or
M3.
[0023] Referring to FIG. 2, when the system is operated in M3, the
high pressure discharge from booster compressor 22 closes check
valve 52, whereby the refrigerant vapor from outdoor coil 28 is
delivered through 4 way valve 32 and conduit segment 55 to the
inlet to booster compressor 22. After compression in booster
compressor 22, the higher pressure refrigerant vapor discharge from
compressor 22 is delivered via conduit segment 56 to primary
compressor 24 after first mixing with the additional refrigerant
saturated vapor emanating from the boiling side of economizer 30
(see description below re economizer 30). The now combined and
somewhat desuperheated vapor (after mixing) is further compressed
by primary compressor 24 and is then delivered to condenser indoor
coil 26. The increased mass flow of the refrigerant resulting from
both the high flow rate low compression booster and the heat
recovering economizer enters the primary compressor resulting in
significantly increased heating capacity for the system, which can
be transferred to the air flowing over indoor coil 26 to be
delivered to the space to be heated.
[0024] The warm liquid refrigerant discharged from indoor coil 26
is delivered to economizer 30. However, the economizer enabling
signal from the microprocessor opens solenoid valve 31, whereby
some of the liquid refrigerant is bled through bleed line 58 and
expanded through an orifice in solenoid valve 31 thereby entering
the boiling side of the economizer where it boiled (or evaporated)
into saturated vapor. This boiling liquid in the boiling side of
the economizer significantly subcools the warm refrigerant flowing
through the liquid side of the economizer as it extracts the
thermal energy originally present in the warm liquid. This results
in significantly subcooled liquid refrigerant being delivered to
expansion valve 42 of evaporator outdoor coil 28. This results in
an increased refrigerant capacity (per unit of mass flow) which
absorbs more heat energy from the ambient air passing over outdoor
coil 28 thereby further increasing the heating capacity of the
system.
[0025] The saturated refrigerant vapor from the boiling side of
economizer 30 is delivered via conduit segment 60 to a location in
conduit segment 56 between the discharge from primary compressor 22
and the inlet to primary compressor 24 where it joins and mixes
with the vapor stream going form the discharge of the booster
compressor to the inlet to the primary compressor.
[0026] In M3, the flow of refrigerant through the system is at a
higher flow rate and pressure than in M1 or M2, whereby a greater
volume of hot vapor is delivered to indoor condenser coil 26 to
heat the indoor space to be heated. Note, again, that if the
outdoor temperature sensed at sensor 48 is not at or below the
upper limit of about 30.degree. F. of the fourth operating range of
outdoor temperatures, the microprocessor will not enable M3
operation of the system. Again, this prevents inefficient operation
of the heating system.
[0027] The system continues to operate in M3 until sufficient heat
has been delivered to the space being heated to satisfy the setting
called for by thermostat 38. When the setting of the thermostat has
been satisfied, a signal is delivered from the thermostat to the
microprocessor to terminate operation of the compressor system. If
the temperature of the space to be heated again falls below the set
point of the thermostat by about 0.6.degree. F.-1.2.degree. F., the
thermostat again delivers a heat calling signal to microprocessor
36, and if the temperature sensed by sensor 48 is in the fourth
range of between about 19.degree. F. and 30.degree. F., the system
is again cycled through operation first in M2 and then in M3. As
long as the outdoor ambient temperature sensed at sensor 48 is in
the fourth range between about 19.degree. F. and 30.degree. F., the
microprocessor will only enable operation in M2 and M3, i.e., first
with full capacity operation of primary compressor 24, and then
adding in the operation of the booster compressor and the
economizer.
[0028] For the sake of clarity, it should be noted that although
the M3 enabling signal from the microprocessor calls for operation
of both the booster compressor and the economizer, there is a
slight delay in the operation of the economizer relative to
operation of the booster compressor. The booster compressor
operates at full capacity almost immediately upon receipt of the
enabling signal from the microprocessor. However, there is a time
delay in operation of the economizer because of the time needed to
bleed the fluid through the orifice of solenoid valve 31 and
deliver the saturated vapor from the boiling side of the economizer
through conduit segment 60 to conduit segment 56.
[0029] When ambient air temperatures in a fifth range of 18.degree.
F. and below are sensed at sensor 48, and when thermostat 32 is
calling for heat in stage 1, microprocessor 36 allows and effects
operation of the heat pump system in M3, i.e., with full capacity
operation of the primary compressor, and with operation of the
booster compressor and with operation of the economizer. However,
if sufficient heat has not been delivered to the internal space to
be heated within a period of time (typically from 5 to 10 minutes)
or if the rate of temperature rise is not fast enough, the
thermostat calls for stage 2 operation by sending a second signal
(calling for more heating capacity from the system) to
microprocessor 36. The microprocessor then allows and effects
operation of backup electrical resistance heater 62, which is
positioned downstream of the air flow over indoor coil 26. This is
designated as Mode 4 or M4 operation. Note, again, that if the
outdoor temperature sensed at sensor 48 is not at or below about
18.degree. F. of the fifth operating range of outdoor temperatures,
the microprocessor will not allow M4 operation of the system.
Again, this prevents inefficient operation of the heating system.
The system continues to operate in M4 until sufficient heat has
been delivered to the space being heated to satisfy the setting
called for by thermostat 38. When the setting of the thermostat has
been satisfied, a signal is delivered from the thermostat to the
microprocessor to terminate operation of the compressor system. If
the temperature of the space to be heated again falls below the set
point of the thermostat by 0.6.degree. F.-1.2.degree. F., the
thermostat again delivers a heat calling signal to microprocessor
36, and if the temperature sensed by sensor 48 is in the fifth
range of between below 18.degree. F., the system is again cycled
through operation first in M3 and then in M4. As long as the
outdoor ambient temperature sensed at sensor 48 is in the fifth
range below about 18.degree. F., the microprocessor will only
enable operation in M3 and M4, i.e., first with full capacity
operation of primary compressor 24 and booster compressor 22 and
the economizer 30, and then adding in operation of electrical
resistance heater 62 if the thermostat is not satisfied.
[0030] It will be understood that when the booster compressor and
economizer are operating, the primary compressor is also operating
at full capacity. That is, operation in M3 includes operation in
M2. Also, when supplemental electrical resistance heat is
operation, the primary compressor is operating at full capacity and
both the booster compressor and the economizer are operating. That
is, operation in M4 includes operation in M3.
[0031] Referring to FIG. 4, a table is presented showing the
various modes of operation allowed and effected by the system
depending on outdoor ambient temperature as sensed at sensor 48.
When the outdoor ambient temperature is in the first range between
about 60F and up, operation only in M1 is allowed and effected
regardless of whether stage 1 or stage 2 of the thermostat is
calling for heat. When the outdoor ambient temperature as sensed at
sensor 48 is in the second temperature range between about
38.degree. F. and about 59.degree. F., operation first in M1 is
allowed and effected when stage 1 of the thermostat is calling for
heat, and operation in M2 is allowed and effected when stage 2 of
the thermostat is calling for heat. When outdoor ambient
temperature as sensed at sensor 48 is in the third temperature
range between about 31.degree. F. and about 37.degree. F.,
operation only in M2 is allowed and effected, regardless of which
stage of the thermostat is calling for heat. When outdoor ambient
temperature as sensed at sensor 48 is in the fourth temperature
range between about 19.degree. F. and about 30.degree. F.,
operation first in M2 is allowed and effected when stage 1 of the
thermostat is calling for heat, and then operation in M3 is allowed
and effected when stage 2 of the thermostat is calling for heat.
When outdoor ambient temperature as sensed at sensor 48 is in the
fifth temperature range below about 18.degree. F., operation first
in M3 when stage 1 of the thermostat is calling for heat, and then
operation in M4 is allowed and effected when stage 2 of the
thermostat is calling for heat.
[0032] In an alternative embodiment of the heat pump system, an
on-off booster operation may be utilized to reduce the net capacity
being delivered to the system condenser when more heat capacity
than M2 is needed, but when full M3 system capacity is not
absolutely necessary. As an example, instead of allowing full Mode
3 operation as the outdoor temperature falls into the fourth range
of temperatures (from about 19.degree. F.-30.degree. F.) and the
thermostat is calling for heat, microprocessor 36 is programmed to
first allow and effect booster compressor 22 to start and stop for
pre-determined relatively short periods of time until the outdoor
temperature eventually falls to a point where it is desirable to
allow continuous M3 operation. This cycling mode of operation of
booster 22 is designated as Mode 3-C (M3-C) and will be
incorporated approximately half way down in outdoor temperature
between where M2 operation and the full M3 operation are allowed as
indicated previously (e.g., for a temperature range of from about
24.degree. F. to about 30.degree. F.). Full M3 operation would be
enabled for the lower half of the M3 operating temperature range.
The booster "on" and "off" intervals can be of equal time or
unequal. Alternatively, the relative "on" and "off" times for the
booster compressor can be made to vary in steps as outdoor air
temperature falls through the entire outdoor door temperature range
for M3 operation, with booster "on" time being lowest when outdoor
air temperature is higher in the M3 enabling temperature range and
booster "on" time being highest when outdoor ambient temperature is
lower in the M3 enabling temperature range. This variable on-off
time ratio inversely proportional to the outdoor temperature may
further enhance operating efficiency.
[0033] Referring to FIG. 4A, another modification is illustrated if
the M3-C mode of operation is utilized. In this modification, M3-C
operation is allowed and effected when the sensed outdoor ambient
air temperature is in the third range of from about 31.degree. F.
to about 37.degree. F. and stage 2 of the thermostat is calling for
heat; and M3-C operation is also allowed and effected when the
sensed outdoor ambient air temperature is in the fourth range of
from about 19.degree. F. to about 30.degree. F. and the first stage
of the thermostat is calling for heat.
[0034] In another embodiment intended for use warmer winter
climates such as in the southeastern or southwestern U.S., the
heating demand on the system may be reduced. For use in such
climates, economizer 30 can be eliminated from the system, and M3
or M3-C operation would then involve only full capacity operation
of primary compressor 24 and operation of booster compressor 22
[0035] It is typical to incorporate a defrost cycle or operation in
heat pump systems to prevent accumulation of ice on the outdoor
evaporator coil. In the system of the present invention,
temperatures are not low enough for icing of the evaporator coil to
be a problem where only M1 operation is enabled. Accordingly, no
provision is made for defrost operation whenever the system is
enabled for operation only in M1.
[0036] However, whenever the system is enabled for operation in M2,
(M3-C if that embodiment is incorporated), M3, or M4, provisions
must be made for defrost cycling or operation. In the present
invention, defrost cycling is accomplished on a demand basis, i.e.,
when defrosting is needed, as opposed to systems where defrosting
operation is always initiated on a timed basis, whether needed or
not.
[0037] In the present invention, microprocessor 36 uses an
algorithm to calculate a defrost trigger temperature T1 based on
the outdoor ambient temperature sensed by sensor 48. A second
temperature sensor, sensor 50, is positioned on conduit 34 just
upstream of the entrance to outdoor evaporator coil 28, whereby
sensor 50 senses the temperature T2 of the boiling refrigerant
entering the evaporator coil, and a signal commensurate with T2,
i.e., the temperature of the boiling refrigerant entering the
evaporator coil, is sent to microprocessor 36. When T2 is less than
or equal to T1, i.e., T2.ltoreq.T1, for a predetermined period of
time, e.g., ten minutes, thus indicating a possible icing condition
at outdoor coil 28, then defrost operation is triggered. In the
present invention, separate algorithms are used to calculate the
defrost trigger temperature (DTT) depending on whether the system
is operating in M2 or M3.
[0038] When the system in operating in M2, a typical algorithm is
as follows:
Mode 2 DTT (T1)=0.850.times.A.degree. F.-10.50
[0039] When the system is operating in M3, a typical algorithm
is:
Mode 3 DTT (T1)=0.7075A.degree. F.-19.625
where, in both cases, A.degree. F. is the outdoor ambient air
temperature sensed by sensor 48 and delivered to microprocessor 36.
These algorithms, which are linear functions of outdoor air
temperature, are illustrated in FIG. 5. Referring to FIG. 5, line
100 represents the outside air temperature; line 102 represents a
temperature commensurate with the temperature of boiling
refrigerant in outdoor coil 28 when the coil is free of frost or
ice in M2 operation of the system; line 104 represents a
temperature commensurate with the temperature of boiling
refrigerant in outdoor coil 28 in M2 operation with a sufficient
accumulation on the coil of frost or ice to trigger defrost
operation if the temperature sensed by sensor 50 stays at or below
line 104 for a predetermined time; line 106 represents a
temperature commensurate with the temperature of boiling
refrigerant in outdoor coil 28 when the coil is free of frost or
ice in M3 operation; and line 108 represents a temperature
commensurate with the temperature of boiling refrigerant in outdoor
coil 28 in M3 operation with a sufficient accumulation on the coil
of frost or ice to trigger defrost operation if the temperature
sensed by sensor 50 stays at or below line 108 for a predetermined
time.
[0040] When microprocessor 38 determines that T2.ltoreq.T1 for ten
minutes, the microprocessor generates a signal to commence defrost
operation. That defrost operation signal effectively puts the heat
pump system in the cooling mode of operation (See FIG. 3). To that
end, a signal is delivered from the microprocessor to 4 way valve
32 to move the valve to reverse the flow of refrigerant in conduit
system 34. A signal is also delivered from the microprocessor to
primary compressor 24 to operate the primary compressor at full
capacity, i.e., in cooling M2. The booster compressor and the
economizer are not operative in the defrost mode. During the
defrost operation, airflow over outdoor coil 28 is terminated, but
airflow over indoor coil 26 is maintained in order to absorb
sufficient thermal energy to effect ice/frost removal on the
outdoor coil.
[0041] As shown in FIG. 3, with 4 way valve 32 moved to the cooling
position to effect defrost operation, refrigerant vapor discharged
from primary compressor 24 is delivered to outdoor coil 28, which
is now functioning as a condenser. The vapor gives up its heat of
condensation as it cools while circulating through outdoor coil 28
thus melting any ice or heavy frost that has accumulated on coil 28
to effect the defrost operation. The refrigerant then flows through
check valve 46 and around expansion valve 50 and is delivered as
cool liquid to the liquid side of economizer 30. The liquid
refrigerant flows through the liquid side of the economizer and is
expanded through expansion valve 40 and is delivered as cool liquid
(along with some flashed vapor) to indoor coil 26 which is now
functioning as an evaporator. The resulting cool refrigerant vapor
is then delivered through 4 way valve 32 and check valve 52 in
conduit 54 to the inlet to primary compressor 24 to continue the
defrost cycle.
[0042] The defrost cycle continues to operate until the condensed
liquid refrigerant exiting the outdoor coil becomes sufficiently
warm thus indicating complete removal of ice or heavy frost from
the outdoor coil. At this point, responding to a now warm T2 (about
70.degree. F.) the microprocessor sends a signal effecting 4 way
valve movement to the position shown in FIGS. 1 and 2, and the
system resumes operation in the heating modes.
[0043] To operate the system in a cooling or air conditioning mode,
thermostat 38 is moved to its air conditioning position, whereby a
first stage signal is delivered from the thermostat to
microprocessor 36 whereby a signal is delivered from the
microprocessor to 4 way valve 32 to position the valve as shown in
FIG. 3, and to enable operation of only primary compressor 24.
Without regard to the outside air temperature signal from
thermostat 48, when cooling is called for by the room temperature
exceeding the thermostat setting, the signal from the
microprocessor to primary compressor 24 operates the primary
compressor first in partial capacity mode M1 to circulate
refrigerant flow as described above for defrost operation. Air
flowing over indoor coil 26 is then cooled to cool the space to be
cooled. If partial capacity operation M1 proves insufficient to
satisfy the thermostat after a predetermined time, or if the rate
of the temperature of the temperature of the air being cooled is
not fast enough, the thermostat delivers a stage 2 signal to the
microprocessor, and the microprocessor operates the primary
compressor in full capacity M2.
[0044] In the preferred embodiment of this invention, neither M3
nor M3-C operation is enabled for cooling operation. However, for
very hot climates, such as the southern or southwestern U.S. in
summertime, an alternative embodiment would enable M3-C and/or full
M3 operation of the system in cooling operation. In this
embodiment, M1 and M2 operation are effected by the microprocessor
when the signal from air temperature sensor 48 indicates an outdoor
air temperature in a first range of temperatures, and the first and
second stages of the thermostat call for M1 and M2 operation,
respectively. For an outdoor air temperature sensed by temperature
sensor 48 above the first range of temperatures, microprocessor 36
would effect full capacity operation of primary compressor 22,
booster compressor 24 and economizer 30 for cooling operation (M3),
or cyclical on-off (M3-C) operation of those components, if
operation in M2 is not sufficient to satisfy the thermostat
setting. The M3 or M3-C operation in cooling is shown in FIG.
3A.
[0045] The heat pump system may also include a refrigerant charge
compensator that acts to reduce the refrigerant charge active in
the system condenser during any operating mode causing booster
compressor operation. Whenever the booster compressor is idle for
any significant period of time, a significant amount of refrigerant
vapor will condense into the booster oil in the booster sump. This
occurs because the refrigerant is essentially 100% miscible in the
oil. The refrigerant vapor condenses into the booster oil when
agitation ceases upon shutdown of the booster compressor, and
continues to condense as the booster oil temperature falls with the
end result being that about 10% more refrigerant charge must be
added to the system charge to ensure all operating modes without
the booster will always have sufficient operating refrigerant
charge. However, the refrigerant thus absorbed into the booster oil
comes out of the booster oil-refrigerant solution very quickly upon
booster startup and can overcharge the refrigerant system. This
excess charge can cause a backup of liquid refrigerant in the
condenser, thus reducing the effectiveness of condenser operation.
This, in turn, can result in the primary compressor drawing more
power and result in a reduction in the overall efficiency of the
heat pump system. This problem can be avoided by incorporation of a
refrigerant charge compensator 64 in the system (see FIG. 6). The
compensator vessel 64 can be located almost anywhere in the cold
air stream leaving the system evaporator 28. Charge compensator 64
is connected via conduit 65 to conduit 60, and thus it is connected
both to line 56 and the discharge from booster compressor 22.
Compensator 64 serves to condense and accumulate the excess
refrigerant charge coming out of the booster oil whenever the
booster is operational. This happens because the compensator is
connected to the booster discharge line, and the pressure in the
booster discharge line always exceeds the saturation
temperature/pressure existing in the cold compensator vessel
whenever the booster is operating. When the booster is not
operating the refrigerant liquid charge accumulated in compensator
64 is released from the compensator and is subsequently reabsorbed
by the oil in the booster sump.
[0046] While preferred embodiments have been shown and described,
various modifications and substitutions may be made thereto without
departing from the spirit and scope of this invention. Accordingly,
it is to be understood that the present invention has been
described by way of illustration and not limitation.
* * * * *