JPS6450103A - Control method for number of sets of compressor - Google Patents

Abstract

PURPOSE:To realize a long service life of a compressor by selecting preferentially the compressor whose integrating time for the operation time is minimum, in case there are plural compressors of the same rating belonging to a designated rank to equalize the total operation time of each compressor. CONSTITUTION:A set number controller 4 has an operation time monitoring timer part 41, and the timer part 41 has timers TM11-TM1N for inputting start commands S1on-SNon given to each compressor 11-1N and starting the integrating time counting. These timers are reset, for instance, at every 24hr. In case for instance, the load use quantity increases and the discharge pressure has dropped to the lower limit set pressure PL, the device 4 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 when there are plural sets of compressors having a designated rated air quantity in the rank, the respective timer time counting times are compared by a program and the compressor whose time counting time is small is selected preferentially, and it is started.