I am somewhat confused about the need to preheat the crankcase oil and refigerant of a heat pump before starting.
I am having a Carrier 25HNA6 3 ton heat pump installed. The installation manual clearly states that the unit should be connected to the source power for a minimun of 24 hours before the compressor is run. Specifically for my unit the manual states that : "... starting the compressor without a minimum of 12 hours of crankcase heat prior to initial start-up may result in a compressor chattering noise and possible damage to the compressor".
The installer stated that this was not necessary at the current outside temp (55 F). How do I reconcile these two opposing statements. Also, if the crankcase heat is that critical why is there not a thermistor that prevents operation of the compressor unless it is at a certain temp. It would not be unheard of for the power to fail for several hours while the occupant is not at home in the winter with outside temps well below freezing. In such a case the compressor would automatically restart when the power was resumed -?damaging the compressor. The manufactures statement seems critical and alarming, yet I suspect most heat pump owners are oblivious to this concern and the manufacturer does not include any design features to deal with the issue. This is very confusing for the consumer. Does anyone know the truth?