Bryant Heat Pump VPS Switch.
Model Number 650ANX036000ADAA
Outdoor coil had iced up in heat mode because the outdoor fan
was off. Outdoor fan is powered through VPS switch. VPS-Vapor
Pressure Switch. I assume it is a low-pressure switch, and it (definitely)
is on the (A/C) suction line.
First question: Is the "suction" (fat) line low-pressure in heat mode?
I wouldn't think so. The switch kept the outdoor fan off in both
heating mode and cooling mode. I jumped it out and both modes
then allowed condenser fan operation. Note that there is a low-pressure
switch on the liquid line (in A/C parlance).
Second Question: Why the heck would they do it that way? Why
wouldn't they run the contactor through the VPS in order to kill
I ran the thing in cooling mode and it had (I have a bad memory)
a 20+ degree temp drop, but ambient was 46 degrees. Inside
return air was 65.
I was going to get the heat-mode temp rise but the heat
strips came on immediately despite a 3 degree temp difference
between room and setpoint temps. I think it was due to the
adaptive feature of the thermostat--it knew it needed to
turn them on. So I have no idea if it heats well, but the
homeowner seemed to think it was weak without heat strips.
I was going to disable the heat strips but it was getting late
and homeowner was cool and suggested we do it in two days
when he had time off. With heat strips on, temp rise was
a modest 26 degrees, so I am inclined to believe it is not
heating well. But how could it cool so well but not heat well?
I'm going back the day after tomorrow to either charge the thing
or determine that the VPS swith is indeed nuts. I am hoping
for 55+ ambient temps so I can (yes?) then rely on the
nameplate subcooling value to tell me whether the charge
is low. Today, at 46 F, the subcooling was only 5 degrees
and nameplate was 14 F, but I wasn't sure where "design
conditions" really deviated from actual operation.
ALL of today's calls were heat pumps. It was a bad day.
Will days ever be all good no matter what I encounter?
I mean before retirement.