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Trane YCD 300 Series

clammy Member Posts: 3,111
Besides the driers has anyone cycled all the condenser fans ,checked outdoor fan relays(check contractor), fan motors and pitch on fan blades and has anyone done a good condenser coil cleaner to help drop the head pressure,also check to ensure that all coindenser fan are running at full speed ,has any one installed a low ambient kit or a fan head pressure controller on one of the condenser fans possible ,Also when inm total doubt try giving your local trane tech service they are allways helpful .peace and good luck clammy
R.A. Calmbacher L.L.C. HVAC
NJ Master HVAC Lic.
Mahwah, NJ
Specializing in steam and hydronic heating


  • scott bailey
    scott bailey Member Posts: 3
    Trane YCD 300 series RTU pressures

    I have a 7 year old RTU in which both compressors were recently replaced. One was grounded and one was open. The building has a history of electrical issues such as a loss of power. The problem is on both compressors we have both the high and low sides constantly going up and down. The pressures act as if it has a fan control. (it don't) the high side will go up the low side down. Ten to 15 second later the high side goes down the low side goes up. The system was brought down to 500 microns on the change out, and the driers changed. We actually did this twice thinking a possible issue with the driers. The unit will trip a high pressure switch on a hot day.
  • tim smith
    tim smith Member Posts: 2,752
    Pressures fluctuating too much

    Is it piston, cap tube or expansion valve. I would suspect expansion valve and you may have a problem in the expansion valve. There also could be some clogging in the strainer screen of expansion valve. May have to pump down and change out. Just a thought.
  • scott bailey
    scott bailey Member Posts: 3
    YCD 300

    The condensor coils are clean one of the condensor fan motors is new, the system is not TXV, the rotations on the CFM,s is also correct.
  • jim lockard
    jim lockard Member Posts: 1,059

    I understand that you have pumped the unit down.(did you do a 3 minute rise test and what was it?) Have you checked the oil for acid which would come from trapped moisture. I am thinking that if both the red and blue gauges are moving, the blue to the left and red to the right there noncondensables in the system. Best Wishes J.Lockard
  • Techman
    Techman Member Posts: 2,144
    Ups and Downs

    Hi ! First,what is the head press and what is the temp of the air going into the cond coil?Then ,is the liquid line "full" going into the metering device?Is the TXV thermalbulb nice and tight to the suction line? And insulated? What is the superheat at the compressor?And tripping the Hipress safety!Is the cond fan motor{s} also tripping off?Is the cond fan motor capacitor the proper size ?On certain motors the cap is a different size for 208v and different for 230v.Electrical problems in the blgd should then require a "compressor protector device" saving the comp's life!And a few others posibilites if none of these help!
  • Empire_2
    Empire_2 Member Posts: 2,343
    Hi Scott

    All points here a good ones and I'll add another. While non condensables is a possibility, it will increase total system pressure as it goes thru the compressor. Almost sounds like a moving restriction to me. How did you charge the system? Weigh it in or other? Acid should be a major concern here since burn outs can wreak havoc even after the system has been cleaned. Also, I know this sounds foolish, but are you sure that when replacing the LL Dryers, The lines weren't accidentally crossed?

    Mike T.
  • hvacfreak
    hvacfreak Member Posts: 439
    past experience

    There is a brand of computer room equipment ( that I won't name ) that I see a similer problem from time to time. These units have HGBP and TXV's ...so it really messed me up when I first saw this problem. To make a long story short , I solve this by changing the refrigerant ( I suspeect moisture contamination causes this ).

    You could check into the metering devices ( txv bulbs tight , etc. ) ...but I suspect contaminated charge ( your seeing this in BOTH circuits I'm assuming ). And as someone pointed out , the 500 micron level is to be a STANDING check ( with the vacume pump isolated and the micron gauge reading system vacume ). My pump will pull 500 with a small leak in place ( measured while running ).

    If you have new refrigerant in the system , than I would say it has to be dirty inlet strainers ( liquid line before metering device ). Please let us know what you find for sure. - Freak
  • Mitch_4
    Mitch_4 Member Posts: 955
    had this happen once too

    I could not figure it out for the longest time. (Different model though), bu the basic pressure bouncing like it had head pressure controller was the same.

    Found that there was a small copper shaving fromthe original installer when he reamed the tube, that got to the metering device, and would affec the pistons back and forth motion. The pressures wouold build, then drop, run fine, then start over, occasionally trip the HP safety.

    You have said that it is not TXV, and everything eslse seems to check (except acid test, haven't seen a reply there)

    Check the evap at the metering device for contaminate, other than that, I lean to recover, purge system with nitro, triple evac, and fresh refrig.
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