CCH aren't rated by a *F, or C. They are rated by wattage. The wattage required to keep the oil at X*. The temperature they reach in *F/C, is determined more by their physical size, and what surrounds them to absorb the heat.
Bristol had (kinda old now) a .pdf that basically says 20ºF warmer than the coldest section of the system.
It's suppose to be to inform the public and last revision was 2/27/98
To inform the customer of the following:
¨ Importance of a crankcase heater and the need for system evaluation to assure necessity
and proper sizing of the heater for each application.
¨ Compressor charge limitation.
¨ Systems exceeding the compressor charge limitation.
¨ High and low ambient liquid refrigerant migration and methods to correct.
¨ Important factors and test procedures to determine need and/or sizing of a crankcase
"The crankcase heater size (in watts) depends on the following factors:
¨ Differential temperature (between compressor sump and system) which is necessary to
move/keep liquid refrigerant out of the compressor.
¨ Total system charge and potential overcharge.
¨ Time the heater is energized before compressor starts up.
¨ Maximum system ambient (indoor section and outdoor section).
¨ Sun load on condenser (louvered, covered or exposed coil).
¨ Type of system: split, package, air conditioning, heat pump, chiller, close coupled, long
line sets, etc.
¨ CFM of air across compressor.
¨ Type/location of heater – in well or wrap around."
Pretty interesting it talks about reverse migration in high ambient conditions.That's was new to me.....didn't know it could help in high ambient also.