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Pumping AC unit down in winter

ChrisJ
ChrisJ Member Posts: 16,369
edited January 1 in A-C, Heat Pumps & Refrigeration

I need to pump a 5 ton cool only unit with a scroll down to move it. I'm sure the 20f ambient will make it easier on the condenser but I'm concerned about starting the unheated compressor.

Should I try to heat the compressor? Any tricks anyone could add?

I was thinking about letting a 1500w ceramic heater blow on the compressor for a few hours.

Single pipe 392sqft system with an EG-40 rated for 325sqft and it's silent and balanced at all times.

Comments

  • pecmsg
    pecmsg Member Posts: 5,545

    it should have a crankcase heater.
    just listen or Throttle the suction service valve valve maintaining 25-50 #’s

    ChrisJ
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,898

    Not supposed to pump down a scroll. You can pump it down partially and then recover the rest.

    When you evacuate the lines set and open the valves then warm the compressor if it is cold out. Depending on the temperature. You can also throttle the suction valve as @pecmsg said.

    When they first came out with scrolls they said they could "eat liquid" and no CCH was needed. After compressors were failing CCHs became the thing. Carrier especially was famous for units with no CCHs.

    ChrisJ
  • pecmsg
    pecmsg Member Posts: 5,545

    you can use Emerson’s method……..

    3 quick short starts

    ChrisJ
  • ChrisJ
    ChrisJ Member Posts: 16,369
    https://forum.heatinghelp.com/discussion/comment/1831291#Comment_1831291

    I had thought about disconnecting the start cap and letting it go out on overload a few times but I'm betting it won't make enough heat to matter.

    How short are the starts, like 5 seconds each?

    After doing the 3 do you wait for the oil to settle down or just let it run?

    Single pipe 392sqft system with an EG-40 rated for 325sqft and it's silent and balanced at all times.

  • ChrisJ
    ChrisJ Member Posts: 16,369

    Off the top of my head I think Copeland said it's fine as long as you don't go below 50 psi. I was going to aim for that and then recover the rest.

    I'm betting as long as you keep the low side slightly positive the scroll would be fine.

    Single pipe 392sqft system with an EG-40 rated for 325sqft and it's silent and balanced at all times.

  • pecmsg
    pecmsg Member Posts: 5,545

    there 1 or 2 second bursts 3 times then run.

    ChrisJ
  • pecmsg
    pecmsg Member Posts: 5,545

    scrolls have very little oil in them and it doesn’t take much to heat it.

    ChrisJ
  • HVACNUT
    HVACNUT Member Posts: 6,470

    If you're using the recovery machine anyway, why not just recover all of it? Is the condenser moving to a new location where a change in pipe length will effect the existing charge?

    mikeapolis
  • pecmsg
    pecmsg Member Posts: 5,545

    Easier to just pump all the refrigerant into the condenser with the compressor.

    ChrisJ
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 16,898

    Unless the condenser won't hold the charge

  • pecmsg
    pecmsg Member Posts: 5,545
    https://forum.heatinghelp.com/discussion/comment/1831417#Comment_1831417

    Then yes recover the rest.

  • mikeapolis
    mikeapolis Member Posts: 47

    R22 or 410?

  • ChrisJ
    ChrisJ Member Posts: 16,369
    https://forum.heatinghelp.com/discussion/comment/1831428#Comment_1831428

    410

    Single pipe 392sqft system with an EG-40 rated for 325sqft and it's silent and balanced at all times.

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