"Zypher" wrote in message
ink.net...
Most (not all) outdoor condensers (air conditioners) have a compressor
crankcase heater that should be left on. It's job (keeping the compressor
warm) will prevent liquid refrigerant from 'migrating' to the compressor
and
mixing with the compressor oil. The heater (residential) uses about 22
watts of power and has minimal cost. If you start the unit without the
heater have been on at least 24 hours MAY damage the compressor from
refrigerant migration.

I believe that the current situation with the heaters is that "Some Do, and
Some Don't.'

My present heat pump doesn't have the heater (Ruud) and the unit it replaced
(Lennox) didn't either.

I suggest that reason the companies "don't bother" is because there a plenty
of situation where the unit would have to start without the benefit of 24
hours of heater power. One example would be re-staring after a power
failure when no one is "at home." Failures would still be covered so the
makers would have an incentive to make the design function without the need
for the heater being powered 24/7.

BTW: the "customer" handout my HVAC gave me DID say to leave the machine
powered on for 24 hours before placing a heating or cooling demand. When
my HVAC guy said there was no heater, I just tossed the instructions.