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In a positive displacement compressor having a plurality of banks, operation can be multi-staged or single staged. Single stage operation can be of a single bank or plural banks in parallel. Switchover between modes of operation is under the control of a microprocessor responsive to sensed inputs. D

In a positive displacement compressor having a plurality of banks, operation can be multi-staged or single staged. Single stage operation can be of a single bank or plural banks in parallel. Switchover between modes of operation is under the control of a microprocessor responsive to sensed inputs. During pulldown under ambient or condenser entering air temperatures of 100°F., or more, suction modulation is used to limit the suction pressure thereby permitting a switchover to two-stage operation and the use of an economizer.

대표청구항 ▼

In a refrigeration means under microprocessor control for cooling a zone including a closed circuit serially including compressor means, condenser means, economizer means connected to said compressor means, expansion means and evaporator means, a method for operating the refrigeration means during p

In a refrigeration means under microprocessor control for cooling a zone including a closed circuit serially including compressor means, condenser means, economizer means connected to said compressor means, expansion means and evaporator means, a method for operating the refrigeration means during pulldown at high ambient temperature where the compressor means has three banks, a crankcase, a suction inlet connected to the evaporator, means for controlling mass flow to the three banks, and a discharge connected to the condenser comprising the steps of: supplying gas from the suction inlet to the first and second banks; supplying gas from the crankcase to a third bank of the three banks; delivering compressed gas from the third bank to the discharge; selectively connecting the first and second banks to either the crankcase or the discharge whereby when said first and second banks are connected to the crankcase they act as a first stage and the third bank acts as a second stage and when the first and second banks are connected to discharge they act as a single stage and the third bank acts as a single stage in parallel with the first and second banks; sensing at least one of ambient and condenser entering air temperature; sensing zone temperature; sensing zone set point; comparing zone temperature and zone set point and if the sensed ambient or condenser entering air temperature is on the order of 100°F., or above, the sensed zone temperature exceeds the zone set point by 5°F., or more, and the first, second and third banks are in single stage operation, performing the serial steps of: reducing the capacity of said first and second banks to reduce crankcase pressure; switching over from single stage to two-stage operation; enabling the economizer whereby capacity is increased and the pulldown is speeded up.