We are getting ready to buy around ten 15KW to 30KW single phase 240 vac generators in our neighborhood.
The Generac company and several other generator suppliers state that the LRA (locked rotor amps) spec on the AC compressor is what you size the generator for.
My review of the internet and NEC states that the LRA is to allow proper sizing of the cable and disconnect, so that no damage occurs before the breaker blows, and has nothing to do with compressor surge when starting.
Many sources state that the starting surge for a AC compressor is based on RLA (running load amps) and the ampacity spec on the compressor nameplate, which is 1.25 x RLA. You have to add for the compressor fan and house blower.
These sources also state that proper sizing of the single phase 230 generator includes 1.25 x ampacity, and you will have plenty of power to start the compressor. Of course other resistive and reactive loads need to be considered for overall sizing, but lets keep this discussion just focused on the AC compressor.
Question, should we use LRA, which will require a larger generator (LRA is 129 amps for my AC which would require 30KW, or assuming 1.5 surge generator capability 20KW + 10KW fo my other loads for 30KW total)
OR
ampacity x 1.25 (31.3 x 1.25 = 40 amp) 40 x 230 = 9.2KW + 10KW for my other loads for 20KW total?
Regards,
Greg Arneson
The Generac company and several other generator suppliers state that the LRA (locked rotor amps) spec on the AC compressor is what you size the generator for.
My review of the internet and NEC states that the LRA is to allow proper sizing of the cable and disconnect, so that no damage occurs before the breaker blows, and has nothing to do with compressor surge when starting.
Many sources state that the starting surge for a AC compressor is based on RLA (running load amps) and the ampacity spec on the compressor nameplate, which is 1.25 x RLA. You have to add for the compressor fan and house blower.
These sources also state that proper sizing of the single phase 230 generator includes 1.25 x ampacity, and you will have plenty of power to start the compressor. Of course other resistive and reactive loads need to be considered for overall sizing, but lets keep this discussion just focused on the AC compressor.
Question, should we use LRA, which will require a larger generator (LRA is 129 amps for my AC which would require 30KW, or assuming 1.5 surge generator capability 20KW + 10KW fo my other loads for 30KW total)
OR
ampacity x 1.25 (31.3 x 1.25 = 40 amp) 40 x 230 = 9.2KW + 10KW for my other loads for 20KW total?
Regards,
Greg Arneson