Crank Case Heater

[gregscott]

Is it necessary or beneficial for a heat pump with a scroll compressor to have a CCH?

[Cooked]

YES! Especially in Amarillo, TX.......

[gregscott]

That was my understanding. The reason I ask, was that I put a scroll compressor on a Rheem heat pump and recommended a CCH to the customer. He had just paid for a new Carrier from a larger local company that sits side by side with the unit I repaired. No CCH on the Carrier (that I we could see). The customer declined my offer. By the way, he is an engineer and stood over me for the entire repair.

Could there be an internal heater on the Carrier or something I am not aware of that does the same thing?

[Cooked]

............. By the way, he is an engineer and stood over me for the entire repair ......Freakin' engineers, I wouldn't trust 'em farther than I could throw 'em........... ;)

...........Could there be an internal heater on the Carrier or something I am not aware of that does the same thing?

If it does there will be two wires penetrating the compressor near the bottom and generally, of those two, one is tied directly to the contactor.

An "add-on" bellyband heater is cheap and easy insurance too.

[assisted]

Very important, yes.

[gregscott]

Thanks Cooked. I saw you were an engineer, you have probably done a little snooping yourself. I am not an engineer, but always drive repairmen crazy standing over them; combination of curious and paranoid. It is for this reason that I encourage customers to watch if they like. He was interesting and helpful.

I would like your advice. I am new at this business and my boss is a plumber with an HVAC license. He is very fair, conscientious, and easy to get along with, but his technical knowledge is limited.

It is my understanding that refrigerant migrated to the coldest part of the system. In the winter this would be the condensing unit. Refrigerant below the oil in the compressor will violently vaporize upon pressure decrease inside the compressor. This action will cause the oil to splash where there should only be vapor, causing damage/slugging to the compressor.

Could you correct or add to my understanding of the benefit of a CCH? Also, are there times where the CCH is not good insurance?

[gregscott]

Assisted, could you explain why it is so important?

[maxster]

keeps refrigerant from migrating and sitting in the oil sump ...if it has a heater in the OFF cycle it wil boil off the freon.York came out with an air cooled chller with (4) scrolls compressors on it and sold it for ambient applications 24/7 runs thru New York winters...:gah:.they were blue/Danfoos scrolls we'll they didn't ship them to York with CCH and York wasn't installing them on the compressors.i saw a guy go thru 2 winters lose all 4 compressors from burn outs.York changed the design on later models with Copeland scrolls and CCH they call that R&D research.the reason you want them OFF during the compressor running might add too much heat to a compressor lower section

[Cooked]

.............It is my understanding that refrigerant migrated to the coldest part of the system. In the winter this would be the condensing unit. Refrigerant below the oil in the compressor will violently vaporize upon pressure decrease inside the compressor. This action will cause the oil to splash where there should only be vapor, causing damage/slugging to the compressor.

Could you correct or add to my understanding of the benefit of a CCH? Also, are there times where the CCH is not good insurance?........

You're on the right track. The CCH keeps liquid from pooling in the sump, which if it does pool, causes all sorts hideous things and gnashing of teeth. It doesn't take much heat to keep the refrigerant boiled (or in a gaseous phase) and the CCH provides that heat through conduction to the metal parts of the compressor. You could do it with a small hair dryer or something but it's impractical and mean to make the old lady stand outside in freezing weather while you're inside watching Days Of Our Lives. Sooooo....some guy said one day, hey if we could heat up that refrigerant just a little we'd quit getting all these warranty claims and our Christmas bonus checks will be bigger.

The first CCH's I remember seeing were external belly band types and then along in the late 70's I remember seeing the internal types. They both work fine. The reason you see them on heatpumps is because HP's operate in low ambient conditions where the refrigerant does migrate to the sump during the off cycle. As maxster pointed out it is not normally necessary or advantageous to keep the CCH energized during a run cycle. The heat from the adiabatic compression is sufficient to prevent problems.

To answer your last question, you simply don't need a CCH if the AC or HP operates in a warm ambient atmosphere.

Hope this helps

Robert

[ACFIXR]

I will put heaters on scrolls, even on package units. I hate compressors starting up filled with liquid.:eek:

http://i1201.photobucket.com/albums/bb359/Chuck_Phelan/HVAC/Service/Crank_Case_Heater.jpg

[gregscott]

Good information, thank you. I believe the Rheem unit I worked on had a port on the defrost timer for the CCH. I will assume, unless I am advised otherwise, that the board will energize the CCH in the off cycle only.

Let us assume that there is no port and I would need to wire the heater in the field. I would probably use a fan relay like one I would see on an old air handler that has both a normally closed and a normally open circuit. I would use the yellow wire from the air handler that generally energizes the condensing unit contactor to energize the relay, and wire the contactor and the heater from the appropriate leads on the relay.

I make this scenario in hopes of advice for a simpler or more common method to retro-fit.

[Chris_Worthington]

Moved to tech to tech residential.

[catmanacman]

I think every unit should have a cch but the manufactures sell hundreds of thousand units times the cost of a cch ,also not in three best interest for a unit to last 20 yrs .it's a money thing:.02:

[craig1]

I make this scenario in hopes of advice for a simpler or more common method to retro-fit.

On a unit with a single pole contactor you just hook one wire from the heater to the Line terminal and one wire to the Load terminal on the switched pole of the contactor.

[monkeyspanners]

Slightly off topic,

Have seen some Maneurop units where they used the motor windings as a heater (was in a refrigeration application) but i belive many inverter mini splits do the same thing to stop the comp being the coldest part of the system.

[SBKold]

Just bought a house with a 2003 rheem unit. 1st thing I did was buy a aftermarket self regulating heater and a comressor insulating wrap for it.

Noticed the discharge temp was noticeably hotter noticeably quicker w/ heat.

This makes sense... ice cold compressor goona hafta run awhile to even start throwing toasty discharge.