Electric power demand limit for variable speed heat pumps and integrated water heating heat pumps
First Claim
1. Method of operating an integrated heat pump and hot water system that is capable of providing heating or cooling to an environmental comfort zone, said heat pump and hot water system including a variable speed compressor whose operating speed is substantially linearly related to the difference between outdoor air temperature and indoor air temperature in the comfort zone, and also including means to receive a utility peak demand limit signal to initiate automatic power limiting to reduce the power demand imposed by the heat pump and hot water system, the method comprising sensing the outdoor temperature TOD ;
- sensing the indoor temperature TID in the comfort zone;
sensing the speed S1 of the variable speed compressor; and
in response to receiving said utility peak demand limit signal DLS calculating a reference speed SR for the compressor as a function of said speed S1, said outdoor temperature TOD, said indoor temperature TID, and predetermined values that correspond to a reference indoor temperature TID and a zero-load temperature difference Δ
TZ that corresponds to the difference between the outdoor and indoor temperatures that result in a zero load requirement on said compressor; and
during occurrence of said signal DLS operating the compressor at a reduced operating speed limited to a predetermined fraction, less than unity, times said reference speed SR.
1 Assignment
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Accused Products
Abstract
An integrated heat pump and hot water system provides heating or cooling of a comfort zone, as required, and also provides water heating. As a power management feature, the speed of a variable speed compressor is reduced to a predetermined fraction, e.g. 80%, of its normal operating speed, in response to a demand limit signal provided from the electric power utility during times of peak electrical load. A reference compressor speed is computed based on the current compressor speed, indoor temperature, outdoor temperature, and zero-load temperature difference. If the system is between operating cycles when the demand limit signal is received, a stored speed is used which corresponds to the compressor speed at a predetermined outdoor-indoor temperature difference. This system produces graceful reduction in comfort cooling during demand limit periods.
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Citations
12 Claims
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1. Method of operating an integrated heat pump and hot water system that is capable of providing heating or cooling to an environmental comfort zone, said heat pump and hot water system including a variable speed compressor whose operating speed is substantially linearly related to the difference between outdoor air temperature and indoor air temperature in the comfort zone, and also including means to receive a utility peak demand limit signal to initiate automatic power limiting to reduce the power demand imposed by the heat pump and hot water system, the method comprising sensing the outdoor temperature TOD ;
- sensing the indoor temperature TID in the comfort zone;
sensing the speed S1 of the variable speed compressor; and
in response to receiving said utility peak demand limit signal DLS calculating a reference speed SR for the compressor as a function of said speed S1, said outdoor temperature TOD, said indoor temperature TID, and predetermined values that correspond to a reference indoor temperature TID and a zero-load temperature difference Δ
TZ that corresponds to the difference between the outdoor and indoor temperatures that result in a zero load requirement on said compressor; and
during occurrence of said signal DLS operating the compressor at a reduced operating speed limited to a predetermined fraction, less than unity, times said reference speed SR. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
- sensing the indoor temperature TID in the comfort zone;
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10. Method of operating a heat pump system that is capable of providing heating or cooling to an environmental comfort zone wherein said heat pump system includes a variable speed compressor whose operating speed is controlled to vary with an imposed heat transfer load on the system;
- controller means providing a speed control signal to the compressor to control its speed, the speed control signal being supplied under normal conditions at a normal speed value to operate the compressor at a normal condition speed; and
demand limit signal receiver means coupled to the controller means to receive a demand limit signal to initiate power limiting the method comprising supplying said speed control signal at said normal speed value when said demand limit signal is not being received by said receiver means; and
supplying said speed control signal at a reduced value below said normal speed value when said demand limit signal is being received. - View Dependent Claims (11, 12)
- controller means providing a speed control signal to the compressor to control its speed, the speed control signal being supplied under normal conditions at a normal speed value to operate the compressor at a normal condition speed; and
Specification