Heat pump with adaptive frost determination function
First Claim
1. A method for detecting the formation of frost in a heat pump having a compressor, an interior heat exchanger, an exterior heat exchanger, an exterior fan for moving exterior air past the exterior heat exchanger, and a thermostatic control means for cycling the compressor ON and OFF in accordance with heating demand, the improvement comprising the steps of:
- repetitively forming the difference between the exterior ambient temperature and temperature of the exterior heat exchanger during operation of the compressor;
repetitively comparing said difference to a frost formation difference function of the exterior ambient temperature during operation of the compressor;
interrupting the operation of the compressor and defrosting the exterior heat exchanger if said difference exceeds the value of said frost formation difference function for the current exterior ambient temperature;
measuring the length of time of said defrosting of the exterior heat exchanger; and
altering said frost formation difference function if said measured length of the time of said defrosting of the exterior heat exchanger deviates from a predetermined length of time.
1 Assignment
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Accused Products
Abstract
The present invention is an adaptive method and apparatus for detecting the formation of frost in a heat pump. The compressor cycle is interrupted and a defrosting operation is begun if the difference between the exterior ambient temperature and exterior heat exchanger temperature exceeds a difference function of the exterior ambient temperature. The length this defrosting cycle is measured and the difference function is altered if the measured length deviates from a predetermined length of time. The frost formation difference function is initially set as a linear approximation. Thereafter the difference function value at the particular exterior ambient temperature is increased if the length the defrosting is greater than an upper limit value of six minutes and decreased if the length the defrosting is less than a lower limit value of four minutes. In the preferred embodiment, the exterior heat exchanger temperature is measured by a sensor and the exterior ambient temperature is determined once each compressor cycle from this measured temperature.
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Citations
34 Claims
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1. A method for detecting the formation of frost in a heat pump having a compressor, an interior heat exchanger, an exterior heat exchanger, an exterior fan for moving exterior air past the exterior heat exchanger, and a thermostatic control means for cycling the compressor ON and OFF in accordance with heating demand, the improvement comprising the steps of:
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repetitively forming the difference between the exterior ambient temperature and temperature of the exterior heat exchanger during operation of the compressor; repetitively comparing said difference to a frost formation difference function of the exterior ambient temperature during operation of the compressor; interrupting the operation of the compressor and defrosting the exterior heat exchanger if said difference exceeds the value of said frost formation difference function for the current exterior ambient temperature; measuring the length of time of said defrosting of the exterior heat exchanger; and altering said frost formation difference function if said measured length of the time of said defrosting of the exterior heat exchanger deviates from a predetermined length of time. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 31, 32)
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17. An electronic thermostat for control of a heat pump for heating an interior space, the heat pump including a compressor, an interior heat exchanger, an interior fan for moving interior air past the interior heat exchanger, an evaporator, an exterior heat exchanger and an exterior fan for moving exterior air past the exterior heat exchanger, said electronic thermostat comprising:
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an interior temperature sensor for generating a digital interior temperature signal indicative of the ambient air temperature within the interior space; a desired temperature means for generating a digital desired temperature signal indicative of a predetermined desired temperature; a first control means connected to the compressor, the interior fan, the exterior fan, said interior temperature sensor and said desired temperature means for cycling the compressor and the interior fan ON and OFF to warm the interior space based upon the relationship between said interior temperature signal and said desired temperature signal; an exterior heat exchanger temperature sensor for generating a digital exterior heat exchanger temperature signal indicative of the temperature of the exterior heat exchanger; an exterior ambient temperature determination means for generating a digital exterior ambient temperature signal corresponding to the exterior ambient temperature; a frost determination means for repetitively forming the difference between said digital exterior ambient temperature signal and said digital exterior heat exchanger signal during operation of the compressor and generating a frost signal indicative of the formation of frost on the exterior heat exchanger if said difference exceeds a frost formation difference function of the exterior ambient temperature during operation of the compressor; a second control means connected to the compressor, the interior fan and said frost determination means for interrupting the operation of the compressor and the interior fan, and defrosting the exterior heat exchanger if said frost determination means generates said frost signal; a timer means connected to said second control means for measuring the length of time of said defrosting of the exterior heat exchanger; and a frost formation difference function adjustment means for altering said frost formation difference function if said measured length of the time of said defrosting of the exterior heat exchanger deviates from a predetermined length of time. - View Dependent Claims (18, 19, 20, 21, 22, 23, 25, 26, 27, 28, 29, 30)
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24. The electronic thermostat for control of a heat pump as claimed in claim 24, further comprising:
an operator input means for entering an operator selectable lower limit value.
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33. A method for detecting the formation of frost in a heat pump having a compressor, an interior heat exchanger, an exterior heat exchanger, an exterior fan for moving exterior air past the exterior heat exchanger, and a thermostatic control means for cycling the compressor ON and OFF in accordance with heating demand, the improvement comprising the steps of:
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repetitively measuring the temperature of the exterior heat exchanger; determining the exterior ambient temperature once each compressor on/off cycle by repetitively measuring the temperature of the exterior heat exchanger immediately following the thermostatic control means cycling OFF the compressor until said measured temperature of the exterior heat exchanger reaches a plateau temperature other than freezing, operating said exterior fan immediately following the thermostatic control means cycling OFF the compressor at least until the exterior heat exchanger reaches said plateau temperature other than freezing, and determining the exterior ambient temperature as said plateau temperature; repetitively forming the difference between the exterior ambient temperature and temperature of the exterior heat exchanger during operation of the compressor; repetitively comparing said difference to a frost formation difference function of the exterior ambient temperature during operation of the compressor; interrupting the operation of the compressor and defrosting the exterior heat exchanger if said difference exceeds the value of said frost formation difference function for the current exterior ambient temperature; measuring the length of time of said defrosting of the exterior heat exchanger; and altering said frost formation difference function if said measured length of the time of said defrosting of the exterior heat exchanger deviates from a predetermined length of time.
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34. An electronic thermostat for control of a heat pump for heating an interior space, the heat pump including a compressor, an interior heat exchanger, an interior fan for moving interior air past the interior heat exchanger, an evaporator, an exterior heat exchanger and an exterior fan for moving exterior air past the exterior heat exchanger, said electronic thermostat comprising:
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an interior temperature sensor for generating a digital interior temperature signal indicative of the ambient air temperature within the interior space; a desired temperature means for generating a digital desired temperature signal indicative of a predetermined desired temperature; a first control means connected to the compressor, the interior fan, the exterior fan, said interior temperature sensor and said desired temperature means for cycling the compressor and the interior fan ON and OFF to warm the interior space based upon the relationship between said interior temperature signal and said desired temperature signal; an exterior heat exchanger temperature sensor for generating a digital exterior heat exchanger temperature signal indicative of the temperature of the exterior heat exchanger; an exterior ambient temperature determination means for repetitively comparing said digital exterior heat exchanger temperature signal with the prior digital exterior heat exchanger temperature signal immediately following said first control means cycling OFF the compressor until said digital exterior heat exchanger temperature signal reaches a plateau temperature other than freezing, operating said exterior fan immediately following thermostatic control means cycling OFF the compressor at least until said digital exterior heat exchanger temperature signal reaches said plateau temperature other than freezing, and generating a digital exterior ambient temperature signal as said plateau temperature; a frost determination means for repetitively forming the difference between said digital exterior ambient temperature signal and said digital exterior heat exchanger temperature signal during operation of the compressor and generating a frost signal indicative of the formation of frost on the exterior heat exchanger if said difference exceeds a frost formation difference function on the exterior ambient temperature during operation of the compressor; a second control means connected to the compressor, the interior fan and said frost determination means for interrupting the operation of the compressor and the interior fan, and defrosting the exterior heat exchanger if said frost determination means generates said frost signal; a timer means connected to said second control means for measuring the length of time of said defrosting of the exterior heat exchanger; and a frost formation difference function adjustment means for altering said frost formation difference function if said measured length of the time of said defrosting of the exterior heat exchanger deviates from a predetermined length of time.
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Specification