Crankcase heaters

[BBeerme]

Poorly insulated ?

[71CHOPS]

Well, If you have a 3 watt heater, with the mass of a compressor, and 5* ambient.....what’s going to win?

[Chev5372]

The little bit of heat that is put in even at 5 degrees OSA will still cause the refrigerant to migrate else where in the system. The refrigerant wants to go where it’s colder.


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[timjimbob]

Thanks for the info guys!!

How about the ones that have a temp sensor, seen several on the Trane units that close at like 40 degrees or something.. any benefit to that instead of on 24/7?

Energy savings. 480 volt unit have a transformer with stat to power CCH. Way to many parts. Trane use to trickle current through windings to generate heat

[timjimbob]

Allied RTU do not come with CCH. Ordered a factory low ambient kit for RTU. Still not included. So, I guess they don't think it the risk is there for damaged compressors.

[TechmanTerry]

At Copeland school 25 years (Gene maybe?) ago we were told crankcase had no effect below 50F.

Gene? Or Glenn Hannagan?

My Copeland info in a Application Engineering Bulletin states that 0*F ambient is the boarder line for overpowering the heat produced by the properly sizes CCH.

[heatingelement]

This may be related..
Today I noticed a larger carrier RTU maybe 15 ton. On the side of the compressor contactors it had a separate contacts which were closed but open when the contactor pulls in. Is this for the crankcase heater? It didn't have a wire diagram to look through. What is the technical term for these contacts? Should they be replaced at the same time contactors are replaced?

[Spitz]

Those would be called auxiliary contacts they are used for a few things including deenergizing the CCH while the compressor is on.

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[timebuilder]

Yes. Aux contacts (which are specific to the brand of contactor for reliable fit) should be replaced when the contactors are replaced.

[heatingelement]

Yes. Aux contacts (which are specific to the brand of contactor for reliable fit) should be replaced when the contactors are replaced.

Thank you

[heatingelement]

Yes. Aux contacts (which are specific to the brand of contactor for reliable fit) should be replaced when the contactors are replaced.

What is the best thing to do when the aux. Contacts are not available anymore? Carrier has contactors but the aux contacts aren't available. Go with a different brand of contactor?

[Spitz]

Leave them on all the time or you can go across one leg of the contactor.

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[Chev5372]

Parallel the coil of contactor with a small relay to control heater on/off. See if you have enough room for a small relay and the coil of that relay’s amp draw won’t cause problems on the controller that tells the compressor contactor to pull in.
This just adds more things to go wrong . Best may be to get all new contactor and six. switches. KISS (keep ,it, simple , stupid) No offense!!


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[timebuilder]

Or, you can let them run. Most of the units I see do not turn off the heaters when the compressors run. I see maybe 5% that turn them off.

[pecmsg]

On all the time or relay