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Twinning units

Discussion in 'Residential' started by jamesyarbrough, Jun 6, 2017.

  1. jamesyarbrough

    jamesyarbrough Amateur Gynecologist

    Messages:
    3,466
    Location:
    Denison TX
    What do you guys know about twinning compressors? What would it take to set 2 condensing units and have them share a lineset and stage them?

    We got a couple 1 1/2 ton heat pumps sitting around new in box. I wonder if i could make a 2 stage 3 ton heatpump with a single ahu
     
  2. LemonWizard

    LemonWizard Blinky Lights Wizard

    Messages:
    1,971
    Location:
    Ohighyo
    I would think at first stage your evap would be oversized. That may result in lower than expected pressures and cause premature freeze ups.

    You may or may not be able to fix that with a txv, but I think you'd also need a first and second stage txv for the different rates of refrigerant flow.
     
  3. icy78

    icy78 New Member

    Messages:
    504
    Balanced Oil return would be a problem.

    Sent from my SM-G930V using Tapatalk
     
    frozensolid and newtech like this.
  4. flange

    flange Act like you care and do SOMETHING!!

    Messages:
    12,613
    Location:
    IMT--in my truck
    spend the extra 150 bucks and run two linesets, you will thank us later
     
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  5. tuna

    tuna New Member

    Messages:
    2,886
    Id either buy two ahu's and have two zones, or wire them up to run together if connecting to one ahu. Would be afraid the oil would log in the indoor coil if only one ran for extended period. I think it would be okay with one line-set as long as they ran together. :dunno:
     
    Daryl_Dixon likes this.
  6. icy78

    icy78 New Member

    Messages:
    504
    Somehow you have to insure equal oil return and I don't think you can do that unless you have oil equalizing piping between compressor sumps.

    Sent from my SM-G930V using Tapatalk
     
  7. pecmsg

    pecmsg Junior my ASS

    Messages:
    19,862
    Location:
    Eastern LI
    Split an A coil in half. Two line sets.
     
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  8. Catpower

    Catpower The Crowd Pleaser

    Messages:
    21,639
    Location:
    in the Cabana
    Do what flange said you will be much happier
     
    icy78 likes this.
  9. flange

    flange Act like you care and do SOMETHING!!

    Messages:
    12,613
    Location:
    IMT--in my truck
    I had two --twenty ton splits serving a bar in the old stadium. they were piped to the opposite condensers, but wired to the right ones. damn things ran that way for YEARS. one day they lost a compressor and the piping mistake was found. not sure how it eve worked except they likely had pretty even runtime due to only being used on game days.
     
  10. Catpower

    Catpower The Crowd Pleaser

    Messages:
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    Back in the days when Trane Was Trane they made two stage units down to 3 tons the evap coils and condensor coils had two separate separate circuits. They worked pretty good
     
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  11. jamesyarbrough

    jamesyarbrough Amateur Gynecologist

    Messages:
    3,466
    Location:
    Denison TX

    Yeah thats my main concern. I dont think you can just drill a hole in a herm compressor and pipe them together.
     
  12. jamesyarbrough

    jamesyarbrough Amateur Gynecologist

    Messages:
    3,466
    Location:
    Denison TX
    Hell i may just take advantage of the tech rebate and get a 5 stage inverter! .....or i may let it run till it craps out and put something together from the scrap pile. :D
     
  13. jamesyarbrough

    jamesyarbrough Amateur Gynecologist

    Messages:
    3,466
    Location:
    Denison TX
    Hell i may just take advantage of the tech rebate and get a 5 stage inverter! .....or i may let it run till it craps out and put something together from the scrap pile. :D
     
  14. frozensolid

    frozensolid Psychologist's Dream

    Messages:
    11,978
    Location:
    Earth
    Oil is the obvious problem. But there is another. Where is the liquid going to go when one condensing unit is off. I have seen a setup where someone effed up and did something similar to what you are talking about. They tried to deal with it by putting a check valve at the LL on each circuit. Epic fail. After the third compressor replacement they finally took my advice and bought a new unit.

    It was a hard sell because my Company's previous owner did the install. I had the place for like six months and the customer was not real understanding. I just told them If I had done it I would fix it. But I did not, so sorry. I spent at least a hundred grand fixing resi stuff effed up by the prior owner. I finally said no more. This was a Commercial Trane 15 or 20 ton two circuit condenser that should have been a single circuit. Two circuits one unit is the same basic thing as two smaller units.
     
  15. jamesyarbrough

    jamesyarbrough Amateur Gynecologist

    Messages:
    3,466
    Location:
    Denison TX
    I guess if i had an A coil i could split it in half by seperating the distribution tubes and suction header. Then i would need to find a way to change fan speeds with y1 and y2. A couple relays could do that.
     
  16. pecmsg

    pecmsg Junior my ASS

    Messages:
    19,862
    Location:
    Eastern LI
    Why change fan speed? The 1/2 of the A coil that's cold will still be pulling moisture and temperature.
     
  17. Randysmit1986

    Randysmit1986 New Member

    Messages:
    41
    I've seen 2 evap coils piped to one condenser when I first started out...mind was blown lol
     
  18. jamesyarbrough

    jamesyarbrough Amateur Gynecologist

    Messages:
    3,466
    Location:
    Denison TX
    Well it seems all of the coils we get are aluminum now. So i wont be splitting one.

    Hell with it. We'll just let them units sit. Someone will eventually need a couple 18k btu heat pumps
     
  19. Catpower

    Catpower The Crowd Pleaser

    Messages:
    21,639
    Location:
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    I got a TIG welder, you could use it
     
  20. heavyevans

    heavyevans FNG

    Messages:
    1,198
    Location:
    Indy
    Air will follow the least path of resistance. Once the active side is wet, air flow goes to the dry side. So don't stage the two circuits. Best to do this with interlaced coils.
     
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