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  1. #1
    Join Date
    Jul 2010
    Location
    Denver, CO
    Posts
    435

    Carrier Ductless Split System

    I installed a Carrier Ductless split (Outdoor M# 38HDF036, Indoor M# 40QNC036) about a month ago as secondary cooling for a sever room and have yet to get it to run correctly. I have 140 feet of line set with 20 feet of lift. I followed the long line guide to a T, putting the correct calculated charge (10lb 10oz total) in the unit and the correct piston size (66). Two days after it was running I found it with the evaporator completely frozen and both the suction and mixed phase lines frozen. I had to take out the freeze stat clean it and put heat conductive compound on it and got it working, but then it would cycle every 10 to 15 minutes. I was running 75psi suction, about 15 degrees. I removed the charge and verified I had the proper charge. I took out the piston and looked for debris and cleaned it, I replaced the liquid line dryer, I scoured the entire line set for a restriction and found nothing. I was still running 75psi suction. I finally added 3lb 8oz of R410a and got my suction up to 95psi but this is still only 28 degrees. I am not cycling the freeze stat every ten minutes, it is now about 20 minutes. I feel like I have exhausted every possibility I can think of. The kicker to it all is that another contract installed an identical unit to this one andit also is running 75psi of suction, they apparently don't care enough to get it running correctly.

    If anyone has experience with these units any advice or direction on how to get my suction up to an acceptable pressure would be appreciated.

  2. #2
    Join Date
    Nov 2009
    Location
    Saskatchewan
    Posts
    492
    If you figure it out let me know. I got a night mare going on also. Mine does not freeze up because it has a freeze stat built into the wall unit. Do you have the fan cycle kit? Baffles?
    Is the arrow pointing to the condenser on the piston holder? Is the piston At the condenser not the evap? I am running 89 psi and zero superheat at the accumulator. Carrier hot line keeps having techs calling me telling all is well, no worries.

    I am worried. I put a water cooled back up in just incase for when the real hot weather gets here. You can always call Carrier for help. I always find they never have the answer. Like the time they forgot to some screws in the back of a heat exchanger....... or the time transformers were labeled wrong and kept melting down........

    Anyway, the ductless splits are..... well keep us in the loop. They are fustrating as heck.

    Hey, you have the same exact same stuff as me. I am 83 feet, 6 lift.

  3. #3
    Join Date
    Aug 2007
    Location
    Oregon
    Posts
    226
    Sounds like its under charged to me .....What is the SH and SC and ambient conditions ?

  4. #4
    Join Date
    Jul 2010
    Location
    Denver, CO
    Posts
    435
    I have the metering piston at the condenser, pointed the right direction (towards the condenser), I have a liquid line solenoid installed, I have a fan cycling swtich. Like I said, I followed the instructions to a T.
    I have talked to Carrier tech support on this quite a bit and they are just as stumped as I am at this point (while telling me a few times that 90 psi suction is not uncommon, even though I dont want to be running my evaporator at 26 degrees) and they are going to come out and go over the system with me this week and see what we can figure out.

    So on the orginal, calculated charge, I was running 75psi suction, 310 psi discharge, 28 degrees superheat and 16 degrees subcooling. With the additional refer I put in the system I am running 95psi suction, 350 psi discharge, 4 degrees superheat, and 36 degrees subcooling. It is definitley not under charged, it is acting as if it has a restriction but as I have stated I could not find one any where.

    The only thought I have on this is that the piston sizing chart is wrong or the piston I was shipped was not bored correctly (though I do not find this very likely).

  5. #5
    Join Date
    Sep 2007
    Location
    Boise, ID
    Posts
    4,247
    Check the LL solenoid. Do you feel TD? Make sure arrow points towards indoor unit.

    What does install ins. say about max line set length....seems awfully long for a ductless system.
    If a nation expects to be ignorant and free, in a state of civilization, it expects what will never be. (Thomas Jefferson 1816)

  6. #6
    Join Date
    Jul 2010
    Location
    Denver, CO
    Posts
    435
    Quote Originally Posted by Gib's Son View Post
    Check the LL solenoid. Do you feel TD? Make sure arrow points towards indoor unit.

    What does install ins. say about max line set length....seems awfully long for a ductless system.
    I have checked and there is no TD across the solenoid and I have good power, I am confident it is opening fully and the arrow is in the correct direction. The maximum line set, according to Carrier is 200ft, so my 140ft is acceptable, theoretically.

  7. #7
    Join Date
    May 2006
    Location
    toronto
    Posts
    46
    put some gas in this thing, liquid charge right ?

  8. #8
    Join Date
    Jul 2010
    Location
    Denver, CO
    Posts
    435
    I had Carrier out today to help me figure out this system. We removed the 66 piston (as calculated from the long line guide) and installed a 74 (which makes more logical sense to me) and removed the extra refrigerant I had put in the system. After this I was running 95psi suction with 0 degrees superheat (showing a flooded evaporator) and 310psi discharge with 10 degrees subcooling. This is apparently how the system should run (according to the Carrier tech).

    I won't be happy with it until I see everything is all good on Monday. I am happy with it thus far though.

  9. #9
    Join Date
    Jul 2007
    Location
    Mount Airy, MD
    Posts
    7,281
    I just had a tech call me about one of these that seems to be eating compressors on a year old system for my 2 cents.....

    I am seeing the same as you and am questioning this whole "0" superheat thing as well as the piping on the accumulator, Inlet on the bottom and discharges out the side, 5-10 "cooler" coming out of the accumulator?

    Did you ever hear/see anything else on these systems?
    Last edited by Chris_Worthington; 08-13-2012 at 08:54 PM. Reason: sp

  10. #10
    Join Date
    Jul 2012
    Location
    Southwest
    Posts
    114
    I have never quoted a Carrier. We have an account with about 12 and all 12 are not working.

  11. #11
    Join Date
    Jul 2007
    Location
    Mount Airy, MD
    Posts
    7,281
    Quote Originally Posted by B1978 View Post
    I have never quoted a Carrier. We have an account with about 12 and all 12 are not working.
    same unit?

  12. #12
    Join Date
    Dec 2000
    Location
    Flat Rock, NC
    Posts
    463
    crap, crap, crap Go Daikin and never look back.

  13. #13
    Join Date
    Jul 2010
    Location
    Denver, CO
    Posts
    435
    Chris, after installing the new piston I didnt have any more issues until about a month ago. It shelled the compressor at about 1 year old... I question the accumulator to, it looks like its made to slug the compressor, and with it shorting to ground I think thats exactly what happened. I do not like the set up nor the 0 superheat, but what can you do?

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