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  1. #1
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    Crankcase heaters

    How crucial are crankcase heaters? I'm in the pacific NW so it's not extremely cold here. Lately I've been finding a bunch that are bad. I'm just curious as to how important they are and in what conditions? Is it mainly used when the cooling is used in low outdoor temperatures?

  2. #2
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    Very crucial. Refrigerant migrates to the coolest part of the system during off cycles. They prevent liquid refrigerant from accumulating in compressor crankcase and pumping out the oil or worse, blowing out intake and exhaust valves due to hydrostatic pressures. Just a few degrees difference between indoor & outdoor temps is all it takes for migration to start. I always check them and keep at least 1 band type on the truck. Easy repair to save a compressor, so an easy sale.

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  4. #3
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    Mixing oil and fire with a big spoon.
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    unfortunately, they are cheap so they easily break. but fortunately, they are cheap so they are easy to sell. i would always recommend them. i sometimes question their effectiveness, but they are cheap insurance if there is ever a question.
    "Right" is not the same as "Wise".

    Don't step on my favorite part of the Constitution just to point out your favorite part.

  5. #4
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    CCH are extremely important to the life of a comp. Migration takes place when the comp/CU is colder than the evap. Migration also takes place when the comp/CU AND the evap are all at the same temp as in a power outage and the outdoor/indoor temps (again) are the same. When the out/in door temps are the same, the P/T of the freon is at (lets say)90*F/168.4 psi. The oil surface vapor is at 90*F but the oil surface vapor PRESSURE is at (lets say)168.3. So, press always goes from hi to low. So the higher press r22 jumps into the lower press oil and then and there you have migration. And then and there you have the beginning of a dead comp.

    All/most AC Mfrgs(Carrier,Rheem,etc) have a chart that shows the "balance point" of the amount of freon in a system when a CCH is mandatory. It is based on how much freon can be absorbed into the comp oil w/o saturating the oil and building up a liquid level of freon UNDER the oil. That liquid freon buildup under the oil is the real comp killer. Flapping jaws, if the oil level is 2" high and migration takes place then there will be a 1" freon puddle w/ 2" of oil above the freon.

    I sell lots of CCH's and I also sell lots of 6' of #14THHN wire, which I loop into 10 loops for a "CCH amp tester" which I test on every routine. Oh yeah, I also sell lots of orange wire nuts for the CCH.

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  7. #5
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    Quote Originally Posted by heatingelement View Post
    How crucial are crankcase heaters? I'm in the pacific NW so it's not extremely cold here. Lately I've been finding a bunch that are bad. I'm just curious as to how important they are and in what conditions? Is it mainly used when the cooling is used in low outdoor temperatures?
    Their purpose is to not allow the sump of the compressor to be the coldest place in the system. If that happens, liquid refrigerant pools there by condensation, and you can wash the oil out of the lower bearing, which is bad for the bearing.

    So, I recommend them when a piece of equipment was spec'd out on the cheap.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

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  8. #6
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    with reciprocating compressors they are crucial....scrolls can tolerate liquid, but you still don't want a mix of refrigerant and oil in the crank case.

    just to add to what was said......when you have that mix of oil and refrigerant in the sump, and the compressor starts, that refrigerant basically explodes out of the oil. you instantly get a huge bubbling, boiling mass of foaming oil and refrigerant. that mass of liquid/oil/foam can break valves, etc. as it leaves the compressor. The other side effect is that you get a refrigerant/oil mix going to the compressor bearings. as it moves through, the refrigerant boils off, so you're left with much less oil at the last bearing, than the first one.

    with recip compressors, the oil is pumped through the crank shaft to multiple rod bearings, so the effect is multiplied....the first bearings get decent lubrication, but the last get very little. the scoring is very easy to see and diagnose. I have also cut open scrolls that show the same affect. the bottom bearing will be smooth and shiny, but the top will be badly scored.

    while CCH's don't completely stop migration, especially during very low ambients, they are cheap insurance.

  9. #7
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    Agree very cheap insurance, i always had a stock of the add on, wrap around, universal types, self regulating types in the truck.
    UA Local 32 retired as of Jan 2020

  10. #8
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    Some scrolls seem to handle the liquid refrigerant better than other scrolls. If the manufacturer put on a CCH, then I try to remember to always check it on a PM. Sometimes I know I forget. Had this one roof a few months back, been an account for maybe two years now. I've done a lot of service and repairs there, but never a PM, until a few months ago.

    They have 14 units, most two stage. I found somewhere around 10 CCH's that were not working. Obviously, my co-workers never checked if they were working.

    All that said, I made my home A/C a pump down system. No CCH. Figured with the CCH drawing an amp, a bit of extra effort in the install would be cheaper in the long haul.
    If you were a real tech, you'd solder a relay on that board and call it good to go.

    I do a triple evac with nitro to remove non condensables.

    I use 56% silver on everything except steel.

    Did you really need the " If you were a real tech " ??

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  12. #9
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    Most of the junk they sell now doesn't have them but the ones that do state is must be energized 24hrs before starting the unit. Go figure

    Sent from my SM-G960U using Tapatalk

  13. #10
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    It is only the scroll itself that can spread apart to tolerate a little liquid.

    Liquid is still just as bad for the bearing as it is in a recip.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

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  14. #11
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    Quote Originally Posted by Spitz View Post
    Most of the junk they sell now doesn't have them but the ones that do state is must be energized 24hrs before starting the unit. Go figure

    Sent from my SM-G960U using Tapatalk
    Energizing the CCH for 24-48 hrs allows for the very small amount heat of the CCH to slowly heat the oil and drive out the freon from the oil.

    Copeland has finally done electrically/electronically what I have been doing for 4 1/2 decades manually. Anyone familiar w/ the Copeland "EUC"(Electronic Unit Controller) CondUnit controller? Its a beautiful thing what they did! Upon start up of the CU the comp comes on for a few seconds then shuts down then starts then stops for 3 cycles. This was done to stutter start the comp and to agitate the comp oil which cause the oil to release a bunch of the migrated freon from within the oil.

    These packed RTU that require the CCH to be on for a minimum of 24hrs is another example of migration taking place on a system where the evap coil and the comp/condenser section are all at the same temp. At the same temp(evap/cond) migration still takes place.

  15. #12
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    Now think about this.....
    In commercial refrigeration application we quite often use pump down to control the compressor.
    So, no migration is gonna happen because that path has been eliminated.
    Yet I still use heaters on outdoor units for other reasons.

  16. #13
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    Quote Originally Posted by VTP99 View Post
    Now think about this.....
    In commercial refrigeration application we quite often use pump down to control the compressor.
    So, no migration is gonna happen because that path has been eliminated.
    Yet I still use heaters on outdoor units for other reasons.
    Migration is much more difficult in a properly operating pump down system...but not impossible. And if the pump down system isnt working properly (or stops working properly) then you would still need CCHs.
    "Right" is not the same as "Wise".

    Don't step on my favorite part of the Constitution just to point out your favorite part.

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