fraserjim
Member
- Location
- Denver, CO
Customer has two HVAC systems. Each system has two compressors. Stage 1 and Stage 2.
We got called in to help troubleshoot Buss LPJ-30SP 30amp. fuses blowing on Stage 1 of both systems. The systems runs at 480 volt (measured 485V). We measured 24.2 amps while the Stage 1 compressor was running.
Manufacturer's datasheet states: RLA of 27.6 at 460volts.
Each system has a Control Panel with a "Power Block". Control Panel is part of the system. The Power Block feeds the two fuse blocks, single-phase monitors, and contactors.
Last month a HVAC service tech. measure 29amps. running and reduced the refrigerant charge by 2lbs. Still blowing fuses.
Vendor has asked if they can upsize the fuses. Manufacturer states that UL will not allow them to upsize.
Since the Control Panel / Fuse Blocks / Fuses are integral to the system, I do not know what ULs rules are for sizing.
Also, I have never seen a compressor pull that close or over its RLA.
Can someone tell me about how UL sizes fuses and any other things to look for??
Thanks,
FraserJim
We got called in to help troubleshoot Buss LPJ-30SP 30amp. fuses blowing on Stage 1 of both systems. The systems runs at 480 volt (measured 485V). We measured 24.2 amps while the Stage 1 compressor was running.
Manufacturer's datasheet states: RLA of 27.6 at 460volts.
Each system has a Control Panel with a "Power Block". Control Panel is part of the system. The Power Block feeds the two fuse blocks, single-phase monitors, and contactors.
Last month a HVAC service tech. measure 29amps. running and reduced the refrigerant charge by 2lbs. Still blowing fuses.
Vendor has asked if they can upsize the fuses. Manufacturer states that UL will not allow them to upsize.
Since the Control Panel / Fuse Blocks / Fuses are integral to the system, I do not know what ULs rules are for sizing.
Also, I have never seen a compressor pull that close or over its RLA.
Can someone tell me about how UL sizes fuses and any other things to look for??
Thanks,
FraserJim