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Need Leak Finding Help

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Mac_R
Mac_R Member Posts: 117
in A-C, Heat Pumps & Refrigeration
I am working on an Armada AC unit. 

the first time I was there I hooked my test equipment up and found 50 super heat and a 40 sub cool.  Head was around 175 and low was 25psi. Charged the system to 16 super heat and 12 sub cool.  Head of just over 200 and low of 68psi.  The house temp was at 75 dry bulb coming back to the unit on the return line with about 45% humidity.  the outdoor temp was 75 dry I know the humidity was around 50%. So not that much of a load on the system.  When I took off the dust cap on the high side of the system I got a puff of R22.  So I replaced the valve core. 

that was on a Sat morning. 

Got a call Monday the house is at 78 and the unit will not shut off.

Took temp readings.  The house was at 74 dry bulb with a 50% humidity.  Supply temp of 68 Degrees and 50% humidity.  There was water laying all around the furnace so I took off the access panel and there was a clogged condensate line.  I removed the clog and cleaned the coil.  humidity dropped to 40% and supply air was at 65 degrees. 

Customer then called on Thursday saying unit was not cooling again. 

Checked supply temp and return no delta T.  Checked charge in unit and back to where we were in the first place.  I recharged the system to the specks I stated before because conditions were not that far off from the first time.  I also ran my leak detector over both coils nothing.  I then injected a tube of dye into the system.  Came back Friday and can not find any trace of dye on ether coil anywhere.  Checked charge and charge looked good for the conditions.  17 super heat 15 sub cool.  Left the unit run over the weekend. 

Customer called Monday morning saying the system is not cooling.  They have air blowing but it does not feel cold.  I checked the super heat 16 and sub cool 12.  outside temp is in the high 70s.  I was not able to gain access to the house to know what the delta T is across the coil or to know the house conditions.  I can only guess that the house is at 72 where the customer sets the thermostat because the unit was turning on and off.  I found no trace of a leak on the outside coil.  I went over every inch of the system with a high intensity UV flashlight to find the dye and found nothing.  Now that the charge seems to be okay after running all weekend.  Any advice?

Comments

  • Paul Fredricks_3
    Paul Fredricks_3 Member Posts: 1,557
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    Just a bit confused

    At the beginning of your post you state 50° SH and 40° SC. That subcool says you are over charged, but given the SH I'd guess a clogged filter/drier or a stuck TXV. But then adding refrigerant wouldn't have helped.



    Given your final numbers listed, I'd say it's OK. Wonder if someone is letting gas out of the unit. It has happened before (huffing freon).



    Note too that it can take a little while for the dye to show up. I think I've heard that it can take up to a week.
  • Mac_R
    Mac_R Member Posts: 117
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    Help

    It uses a Piston metering device.  I did not know I can take up to a week for the dye to show up.  I guess I will just need to keep an eye on the system and see what happens.  
  • Techman
    Techman Member Posts: 2,144
    edited June 2011
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    Freon leak

    .Could all of that water been from a frozen evap coil?Supply air temp  should be  15-17-20 * colder than room temp,depending ! As per Dan H.!
  • Mac_R
    Mac_R Member Posts: 117
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    Water

    I pulled the cover off the coil box and there was a large plug of gunk plugging up the condensate line.  I removed the plug of gunk and cleaned the coil and put a cake in to help prevent future buildup.  After that the system was started up again.  Everything looked good.  I got called on Thursday and the system was two pounds low.  Checked it this last Monday and the system is running fine.  The only thing I did was put in a tube of dye. 
  • World Plumber
    World Plumber Member Posts: 389
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    Indoor coil

    How clean is the indoor coil? Are the returns sized right? Are any blocked? If the coil is freezing up it will look like it is under charged. Adding will make it work sometimes, but when temperatures and humidity and load conditions change so will the charge look low or high. Also is there anything in the system that can block metering device (piston)? I have seen systems with contamination in them work fine under low load condition. But under high load and longer run times the contamination would block the piston and the system wouldn't cool. Under low load when the compressor shut off the debris fell away from the piston and the system cooled when the compressor restarted.
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