This is my first post to commercial. I have pretty much confined all
prior posts to the safe residential zone.
However, today I was presented with troubleshooting a 10 (12?) ton
commercial heat pump and the schematic only got me so far.
There must be about 15 wires into the defrost board, a sharp contrast
to one for residential.
I googled the operaton info for the Carrier (50HJQ012-631) but it did not
give me any info about the inputs/outputs of the defrost board.
As memory best serves me, the #1 compressor worked fine, giving
about a 15+ temp rise at the unit. But the #2 compressor would
run for about a minute and stop. For those who are intimately
familiar with such units, the relay (CLO2) seemed to have only one input
pin 2, and one output, pin 3. But pin2 came, I think, from the defrost
board. And it had maybe 15 wires to it and the operation info presented
absolutely no info about operaton of the board.
It seemed strange to me that there did not seem to be merely a duplication
of circuits of #1 for #2. They seemed different.
The two safeties, LPS and HPS , lie after the CLO2 board, and just before
the contactor for the compressor. The defrost sensor, I forget, but I think
goes to the defrost board. On the running compressor, comp1, pins 2 and 3 of
CLO1 have control voltage. On the stopped compressor, pins 2 and 3 of
CLO2 have no control voltage. As I said, the LPS and HPS lie after
CLO2 so I leaned toward them not influencing signals TO CLO2,
but maybe I'm wrong?
Basically, if I knew what ALL of the terminals on the defrost board meant,
I would be in a LOT better shape to troubleshoot this thing.
Can anybody enlighten me? I go back tomorrow at 7:00am.
I am SO glad I will be merely facing low 30 temps, that I don't
live back east (or midwest where I grew up). I don't know how
HVAC men back there make it through the cold season without
death finding them. You all don't get paid enough to be on a
rooftop in freezing temps. Then again, maybe you all have
more sense than to install heat pumps rather than gas-packs.
Thank you for any help.