Seems residential home pre-sale inspections cannot be run for the A/C side if the outside air temp is below 60F

[trader4]

Well, Rheem, for example, must not know what they are doing then. Because here is an example of their data sheet that covers 7 typical models from 2 ton to 5 ton. Only the 5 ton has a crankcase heater installed:

The installation instructions for all the models say:

FIELD INSTALLED ACCESSORIES COMPRESSOR CRANKCASE HEAT (CCH) While scroll compressors usually do not require crankcase heaters, there are instances when a heater should be added. Refrigerant migration during the off cycle can result in a noisy start up. Add a crankcase heater to minimize refrigeration migration, and to help eliminate any start up noise or bearing =93wash out.=94

COMPRESSOR CRANKCASE HEATER (CCH) The 5-ton (-)ARL is factory equipped with a crankcase heater. Refrigerant migration during the off cycle can result in a noisy start up. The crankcase heater minimizes refrigeration migration and helps reduce start up noise or bearing =93wash out.=94 The heater is located on the lower half of the compressor shell. Its purpose is to drive refrigerant from the compressor shell during low outdoor ambient conditions (below 75=B0F), thus preventing damage to the compressor during start- up. At initial start-up or after extended shutdown periods during low outdoor ambient conditions (below 75=B0F), make sure the heater is energized for at least 12 hours before the compressor is started. (Disconnect switch on and wall thermostat off.)

Note that nowhere do they say you run the risk of damaging the unit without a heater. Seems mighty strange that they don't issue such a warning if turning the thing on at 50F is gonna cream it.

[The Daring Dufas]

I should have pointed out that reciprocating compressors are more prone to damage than the scroll compressors which have fewer moving parts. If you check out the options I would guess a crankcase heater is one of them for all the units. I have had a scroll compressor fail because of bearing failure due to low ambient operation but scroll compressors are usually more tolerant of abuse than the reciprocating units. There is a line of reciprocating compressors manufactured by Maneurop which are basically immune to refrigerant flooding. The housing acts as an accumulator and the compressors closely resemble those in Trane and American Standard AC units. Johnstone Supply used to carry the Maneurop compressors. I'm sure that the Rheem units that have/had reciprocating compressors were equipped with crankcase heaters. I have also installed low side accumulators on some systems to protect the compressor when it had to be operated in low ambient conditions. There are some crankcase heating methods that apply a low current to the compressor motor windings to provide heat. ^_^

TDD