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Thread: New Condenser

  1. #1
    Join Date
    Aug 2004
    Location
    Lansing, MI
    Posts
    192
    I handle Maintenance at a church. We have 14 5 ton carrier units. I called a tech out to service one of our new CKC060 condensers Day 1 he says that the compressor has tripped out on thermal overload and he would be back when it cools. Day 2 he tests the unit and and says the unit is equalizing so he removes the refrigerant then recharges by a digital scale. The factory charge is for 15 feet of lineset. Once the factory charge is in the pressure read 10 suction 165 head (I am Peaking over his shoulder trying to learn he doesnt mind I asked before hand) This is the part I dont understand. The tech seems to think that the valves are going bad. I'm no expert, but after reading here awhile, dont the pressures need to be more close in proximity to one another for the valves to be bad? I guess the unit could be undercharged but I watched the scale and it was on the money. The lineset is approx 50 feet, taking that into account I can see why the unit could be undercharged but the tech thinks that the pressures are way to low even for the extra length. The tech kept adding charge but the pressures would not go up at all. The suction line temp was at 76 deg the liquid line at 84 deg. Outdoor temp 92 deg. Now getting to the point is the tech right about the valves or is the unit undercharged. FYI the Condenser is 1 week old it was changed by another company who refuses to come and look at the unit.
    Any help would be appreciated thanks


  2. #2
    Join Date
    Nov 2001
    Location
    east kansas
    Posts
    8,033
    Looks like undercharged or restriction

  3. #3
    Join Date
    May 2004
    Location
    Memphis,TN
    Posts
    91
    The compressor is pumping but the refrigerant is not flowing.Have you checked the drier for frost,also make sure the service valves on the condenser are both open,sounds like the unit is pumping down,is there a solenoid valve in the liquid line,does the unit have an expansion valve or a fixed oriface.I hope this helps let me know ok .How much refrigerant has been put in? it could just be way short on charge.

  4. #4
    Join Date
    Jul 2004
    Posts
    19
    Where was he checking the liquid line temp? If measured outside at the condensing unit, there must be a restriction before the point the temp reading was taken.

  5. #5
    Join Date
    Aug 2000
    Location
    USA
    Posts
    4,993
    Doesnt sound like the compressor to me. Youve got a restriction someplace. IE; drier, txv, crushed line, etc. They change the compressor and nothings going to change except someones getting a bill.

  6. #6
    Join Date
    Aug 2004
    Location
    Lansing, MI
    Posts
    192
    Thanks for the replies gents. Here is a little more info the temp was taken right at the liquid line just after the service valve. The unit is fixed oriface. The liguid line filter dryer did not get changed when the condenser got replace and it is located 2 feet from the evap coil the lineset is 7/8 3/8 and due to the length and the difficulty in installation the linset was not changed either. Could the unit have a restriction and be undercharged? As far as pumping down I dont believe it was done I think the tech pulled out the entire charge left the service valves open and vacumed the system. Then weighed in a charge. I believe that another 3 lbs of 22 was added and still no change in the pressures or superheat. I dont think the tech was aware that the filter dryer had not been changed. I will inform him in the morning. Should it be replaced or eliminated? Thanks again

  7. #7
    Join Date
    Jun 2004
    Location
    Richmond Virginia
    Posts
    1,078
    You absolutely have a restriction. A simple check across the liquid line drier for a temperature drop will eliminate that. It is better for the drier to be close to evaporator but for ease of service most put them at the condensing unit. It's good practice to always replace the drier if the system is opened. I'm betting on trash in the orifice. Check to see if your head pressure is higher on start up but is then "dragged" down by the suction. Also, how quickly are pressures equalizing when the system is shut down. Many don't believe those two things will tell you much but with practice I think they do.

  8. #8
    Join Date
    Oct 2003
    Location
    Florida's space coast
    Posts
    2,538
    Why did the previous condenser fail?

    Always a good starting point with repeat failures.
    We've been doing so much,for so long,with so little, that now we can do almost anything, with nothing at all.

  9. #9
    Join Date
    Aug 2004
    Location
    Lansing, MI
    Posts
    192
    Don: Our church uses year round AC the old maintenance staff was susposed to put crank case heaters and fan cycle controls on all of the compressors but they missed 1 so it ran all winter and finally went out.

    thanks again I will inform the tech of the filter dryer.

  10. #10
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,358
    You have a one week old condensing unit that the installing company won't stand behind, and also a tech that can't find a restriction. What a mess!

    The installer should've swapped out the liquid line drier, pulled a deep evac on the system, etc. But that's water under the bridge, apparently. He did gas and go on the thing and so far seems content to give you a taillight warranty, that being his vehicle's taillights were the last you'd ever see of him or any warranty.

    I agree with the others. No matter what, have the tech you're using now swap out that liquid line drier. If the previous system was a burnout, a suction line drier should be added, then monitored for any increase of pressure drop as it works to clean up the system. Being you've indicated the unit blew operating under low ambient conditions, it's possible it blew debris all over the inside of the system when the compressor valves failed. And that's what's clogged up your drier or piston or both.

    BTW these aren't heat pumps, are they? Reason I ask is that heat pumps sometimes invite the scenario where someone slaps a liquid line drier on the discharge line of the compressor. Don't think that ever happens with a split system? Some clown at my building did it on a split system heat pump when he had all the room in the world on that rooftop to add a biflow drier to the liquid line outside the unit. When the thing finally blew it destroyed the interior of the condenser coils, which had to be replaced. Unfortunately we caught it too late to go after whoever did it, and it would be like pulling teeth to get any redress on something like that anyway.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  11. #11
    Join Date
    Aug 2003
    Posts
    242
    Originally posted by bedlamx
    The suction line temp was at 76 deg the liquid line at 84 deg. Outdoor temp 92 deg.
    The liquid line temp can't be lower than the ambiant temp unless there is a restriction before the point you are taking the temp reading. You say you are taking the temp just past the liq service valve. Most units have a small bullet type drier or strainer inside the unit just in front of the liquid line service valve. Have your tech check this internal drier and make sure the liq line valve is fully open.

  12. #12
    Join Date
    Aug 2003
    Posts
    49
    Dryer is restrcted. They should change it at first place. Before installing new dryer remove old one, purge evaporator coil with high presure nitrogen <200psig from suction side out through liquid line, then install a new dryer.
    you can bill the contractor who changed the compressor at first for not following the right procedure.

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