US 5,551,248 AGranted

Control apparatus for space cooling system

AssigneeHeatcraft Inc.

InventorGregory S. Derosier

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Abstract

Apparatus for providing integrated control of a space cooling system is disclosed. The apparatus receives inputs from a plurality of temperature sensors, including a temperature sensor for measuring evaporator superheat, space temperature and compressor discharge temperature. The control apparatus incrementally adjusts the position of the cooling system expansion valve to regulate evaporator superheat and compressor discharge temperature and cycles the outdoor condenser fan on and off to raise condenser pressure in response to a low condenser pressure condition. In one embodiment, the cooling system includes a plurality of evaporators and a corresponding plurality of controllers electrically interconnected in a series loop for controlling the expansion valves and defrost heaters associated with the respective evaporators. One of the controllers functions as a master controller and receives inputs from the space temperature sensor and the compressor discharge temperature sensor as well as from the temperature sensors associated with the corresponding evaporator. The master controller activates and deactivates the cooling cycles in response to the inputs from the space temperature sensor. Both the master controller and each slave controller separately control the corresponding expansion valve and defroster. The master controller also initiates the system defrost cycle. However, once the defrost cycle is initiated, each slave controller controls the defrost cycle for its corresponding evaporator.

Claims20

Dependent claims

In a space cooling system having an evaporator in heat exchange relationship with a space to be cooled, a condenser external to the space, a compressor for circulating heat transfer fluid between the evaporator and the condenser, and an expansion valve between an outlet side of the condenser and an inlet side of the evaporator, the expansion valve being positionable in at least a fully open position to allow the heat transfer fluid to enter the evaporator and a fully closed position to substantially inhibit the heat transfer fluid from entering the evaporator, apparatus for controlling operation of the space cooling system, said apparatus comprising:

first temperature sensing means for sensing a difference in temperature between the heat transfer fluid at the inlet to the evaporator and the heat transfer fluid at an outlet from the evaporator and for generating a first electrical signal indicative thereof, said difference in temperature corresponding to a level of superheat across the evaporator;
second temperature sensing means for sensing temperature of the heat transfer fluid on a discharge side of the compressor and for generating a second electrical signal indicative thereof;
and
control means for controlling operation of the space cooling system, said control means including first means for increasing pressure of the heat transfer fluid in the condenser in response to said level of superheat indicated by said first electrical signal being greater than a predetermined level when the expansion valve is in the fully open position and the compressor is operative, said control means further including second means for disabling said first means when the compressor is operative in response to the temperature of the heat transfer fluid on the discharge side of the compressor indicated by said second electrical signal being greater than a selected temperature when the compressor is not operative.

1 more element

In a space cooling system having plural evaporators in heat exchange relationship with a space to be cooled, a condenser external to the space, a compressor for circulating heat transfer fluid between the condenser and each of the evaporators, and plural expansion valves, each of which is operatively associated with a corresponding one of the evaporators and is positionable in at least a fully open position to allow the heat transfer fluid to enter the corresponding evaporator and a fully closed position to substantially inhibit the heat transfer fluid from entering the corresponding evaporator, apparatus for controlling operation of the space cooling system, said apparatus comprising:

plural first temperature sensors, each of which is adapted to sense a difference in temperature between the heat transfer fluid at an inlet to the corresponding evaporator and the heat transfer fluid at an outlet from the corresponding evaporator and for generating a corresponding first electrical signal indicative thereof, said difference in temperature corresponding to a level of superheat across the corresponding evaporator;
a second temperature sensor for sensing temperature of the space and for generating a second electrical signal indicative thereof;
and
control means for controlling operation of the space cooling system, said control means including plural controllers, each of which is operatively associated with a corresponding one of the evaporators and a corresponding one of the expansion valves, said controllers being electrically interconnected, one of said controllers being a master controller and being operable to activate the compressor to initiate a cooling cycle and to transmit a cooling on signal in response to said second electrical signal indicating a first temperature condition in the space, the other one or more of said controllers being slave controllers, each of said controllers being operable to control operation of the corresponding expansion valve in response to the corresponding first electrical signal when said cooling on signal is being transmitted by said master controller, said master controller being adapted to deactivate the compressor to terminate the cooling cycle and to transmit a cooling off signal in response to said second electrical signal indicating a second temperature condition in the space, each of said slave controllers being responsive to said cooling off signal, said controllers being electrically connected in a series loop, each slave controller being adapted to relay a cooling on signal and a cooling off signal received from an adjacent controller upstream to an adjacent controller downstream, whereby a cooling on signal and a cooling off signal are transmitted from said master controller to said slave controllers.

1 more element

A space cooling system, comprising:

plural evaporators in heat exchange relationship with a space to be cooled;
a condenser external to the space;
a compressor for circulating heat transfer fluid between the condenser and each of the evaporators;
plural expansion valves, each of which is operatively associated with a corresponding one of the evaporators and is positionable in at least a fully open position to allow heat transfer fluid to enter the corresponding evaporator and a fully closed position to substantially inhibit the heat transfer fluid from entering the corresponding evaporator;
control means for controlling operation of the space cooling system, said control means including:
plural first temperature sensors, each of which is adapted to sense a difference in temperature between the heat transfer fluid at an inlet to the corresponding evaporator and the heat transfer fluid at an outlet from the corresponding evaporator and for generating a corresponding first electrical indicative thereof, said difference in temperature corresponding to a level of superheat across the corresponding evaporator;
a second temperature sensor for sensing temperature of the space and for generating a second electrical signal indicative thereof;
and
a plurality of controllers, each of which is operatively associated with a corresponding one of the evaporators and a corresponding one of the expansion valves, said controllers being electrically interconnected, one of said controllers being a master controller and being operable to activate the compressor to initiate a cooling cycle and to transmit a cooling on signal in response to said second electrical signal indicating a first temperature condition in the space, the other one or more of said controllers being slave controllers, each of said controllers being operable to control operation of the corresponding expansion valve in response to the corresponding first electrical signal when said cooling on signal is being transmitted by said master controller, said master controller being adapted to deactivate the compressor to terminate the cooling cycle and to transmit a cooling off signal in response to said second electrical signal indicating a second temperature condition in the space, each of said slave controllers being responsive to said cooling off signal, said controllers being electrically connected in a series loop, each slave controller being adapted to relay a cooling on signal and a cooling off signal received from an adjacent controller upstream to an adjacent controller downstream, whereby a cooling on signal and a cooling off signal are transmitted from said master controller to said slave controllers.

6 more elements

Dependencies are inferred from the claim text.