JPS6450102A - Control method for number of sets of compressor - Google Patents

Abstract

PURPOSE:To always secure the safe operation of a compressor and to raise the reliability by selecting a substitute machine, as for the compressor whose elapsed time after the operation has been stopped in within a prescribed time, among the compressors belonging to the designated rank to limit a start frequency. CONSTITUTION:A set number controller 40 has a start frequency monitoring timer part 41, the timer part 41 has timers TM11-T1N for inputting stop commands S1off-SNoff given to each compressor given to each compressor 11-1N and starting the time counting, and when a prescribed time T0 elapses after the time counting has been started, each timer becomes time-up and sends out a start permitting signal. In case for instance, the load use quantity increases and the discharge pressure has dropped to the lower limit set pressure PL, the device 40 selects a rank of a higher level being higher than the present in the total discharge air quantity, from the generated rank pattern table, generates a rank-up command and executes a prescribed set number control, but in this case, when the time T0 does not elapse after the compressor 1N to be moved newly has topped, the compressor having an equal function is selected as a substitute machine from an operable machine list and started in conformity with a program.