Method and apparatus for transport refrigeration system control
First Claim
1. In a transport refrigeration system of the type having the capabilities of at least heating and cooling operations, and dual compressor speed operation, and having first relay means including switch means controlling heating and cooling operations, and second relay means including switch means controlling compressor speed operation, said first and second relay means being responsive to temperatures in the served space for controlling said system normally in at least four stages of operation in accordance with the differences in temperature of the served space from the setpoint temperature, two of said stages of operation including low speed compressor operation in the temperature band encompassing temperatures closely above and below said setpoint temperature, the improvement comprising:
- auxiliary control relay means including switch means;
time delay means connected to control operation of said auxiliary control relay, said time delay means being connected to be controlled in a timed operation in accordance with the condition of said second relay following said first relay means having first operated to a heating condition position;
said auxiliary control relay being operative to maintain said compressor speed at a lower level until said time delay means operates to change the condition of said auxiliary control relay to thereby change said compressor speed to the higher level in accordance with said second relay calling uninterruptedly for a predetermined time period for compressor speed at a higher level.
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Abstract
A transport refrigeration system having the capability of either heating or cooling at high or low speed and with the compressor loaded or unloaded is controlled by a temperature control system including a heat relay 1K and a speed relay 2K, and has an auxiliary control relay CR which is operative to maintain the compressor speed at a low speed in the temperature band 48 closely above and below the setpoint temperature, and will further maintain the low speed of the compressor for a predetermined time as the temperature rises above or below the narrow temperature band through time delay means 46 which, if uninterrupted in operation for the predetermined time period will drop out the control relay so the system can resume higher speed operation.
36 Citations
12 Claims
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1. In a transport refrigeration system of the type having the capabilities of at least heating and cooling operations, and dual compressor speed operation, and having first relay means including switch means controlling heating and cooling operations, and second relay means including switch means controlling compressor speed operation, said first and second relay means being responsive to temperatures in the served space for controlling said system normally in at least four stages of operation in accordance with the differences in temperature of the served space from the setpoint temperature, two of said stages of operation including low speed compressor operation in the temperature band encompassing temperatures closely above and below said setpoint temperature, the improvement comprising:
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auxiliary control relay means including switch means; time delay means connected to control operation of said auxiliary control relay, said time delay means being connected to be controlled in a timed operation in accordance with the condition of said second relay following said first relay means having first operated to a heating condition position; said auxiliary control relay being operative to maintain said compressor speed at a lower level until said time delay means operates to change the condition of said auxiliary control relay to thereby change said compressor speed to the higher level in accordance with said second relay calling uninterruptedly for a predetermined time period for compressor speed at a higher level. - View Dependent Claims (2, 3, 4, 5, 6, 7, 12)
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8. In a transport refrigeration system of the type having the capabilities of at least heating and cooling operations, dual compressor speed operation, and different compressor loading operation, and having first relay means including switch means controlling heating and cooling operations, and second relay means including switch means controlling compressor speed operation, said first and second relay means being responsive to temperatures in the served space for controlling said system normally in at least four stages of operation in accordance with the differences in temperature of the served space from the setpoint temperature, two of said stages of operation including low speed compressor operation in a temperature band encompassing temperatures closely above and below said setpoint temperature, the improvement comprising:
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a speed control circuit including solenoid means having a high and low speed condition in accordance with energization and deenergization, respectively, of said solenoid; an auxiliary control circuit including time delay means and an auxiliary control relay in series; a loading circuit including a loading solenoid having a loaded and less loaded condition in accordance with deenergization and energization, respectively, of said loading circuit; a pilot control circuit including solenoid means for providing a cooling and heating operation in accordance with deenergization and energization, respectively, of said solenoid; a first normally open switch of said control relay in said auxiliary control circuit; a second normally closed switch of said auxiliary control relay, and a third normally open switch of said second relay in series with said speed solenoid in said speed circuit; a third normally open switch of said auxiliary control relay, and a first normally closed switch of said second relay in series with said loading solenoid in said loading circuit; a second normally open switch of said first relay in series with said pilot solenoid in said pilot circuit; a third normally open switch of said first relay in an initiate circuit connected between said third switch of said auxiliary control relay and said first switch of said second relay in said loading circuit and said time delay means; said time delay means being connected to control operation of said auxiliary control relay, said time delay means being connected to be controlled in a timed operation in accordance with the switch means of said second relay;
said time delay means being initially energized to thereby provide energization of said control relay through said normally closed first switch of said second relay and said third switch of said first relay, continued energization of said time delay means and control relay being afforded by closure of said first switch of said control relay;a time delay initiation circuit including said third switch of said second relay and a line connected to said time delay means so that initiation of a time period occurs with said time delay means energized upon closure of said third switch of said second relays;
said compressor operating at said lower speed with said speed solenoid deenergized through the open position of said second switch of said control relay until a predetermined time period expires with said third switch of said second relay remaining closed uninterruptedly. - View Dependent Claims (9)
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10. In a method of controlling a transport refrigeration system of the type having at least heating and cooling capability and dual compressor speed capability and having at least four stages of operation produced in accordance with temperatures in the served space varying more or less and above and below the setpoint temperature of the served space, the improved steps of:
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operating said compressor at the lower speed when the temperatures in said served space are in a relatively close range both above and below the setpoint temperature, and said served space temperature has dropped to below said setpoint temperature; overriding a call for operation of the compressor at the higher speed as sensed temperatures in the served space move either above or below said relatively close range until at least a predetermined period of time elapses with an uninterrupted call for high speed operation existing; and
thenoperating said compressor at said higher speed. - View Dependent Claims (11)
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Specification