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  1. #1
    Join Date
    Sep 2005
    Location
    Woodbridge, VA
    Posts
    5

    Confused Heat craft walk-in cooler got me stumped

    I got called for a walk- in not cooling properly. Was told by the owner that the unit was cooling properly then the temp started climbing. He had a company before me come in and they adjusted the TXV. After that the temp would climb a few degrees and hold for a day or two and rise again. I attempted to set it back to the factory setting so I could find the original problem but quickly realized that the spring had broke. I replaced the TXV as well as installed new liquid line and suction line driers. Pulled a good vacuum (400 microns) and held it for an hour. Then recharged the unit by sub cooling. It's a R-22 system. I have 11degrees sub cooling, suction is 35 degrees and the head is 175. Superheat remains high at 15 deg. I spoke with heatcraft tech support and was told that because of TXV bulb placement that the TXV would have to be adjusted. After all of this the compressor keeps going off on thermal overload and can't keep the system running long enough to set the Superheat. I tried to adjust the TXV hoping that it would open more, cool the compressor allowing it to run but no luck. It's a 35 deg box and a 25 deg coil I'm out of ideas. Any suggestions would be appreciated

  2. #2
    Join Date
    Sep 2007
    Location
    NH
    Posts
    1,136
    Could just be a bad compressor.. Have you tried to pump it down to see if the valves will hold?
    Amp draw would be handy too.

    Also you should never charge by subcooling if you have a receiver, just clear the sight glass and add winter charge if needed... Do you have a receiver?

    What do you have for sh at the compressor?? And what's the discharge line temp??

  3. #3
    Join Date
    Oct 2011
    Location
    Chicagoland Area
    Posts
    4,509
    First off, How could you attempt to set it back to factory setting? Never heard of a factory setting on a WIC, and without knowing what the previous company did, the statement you made doesn't make sense. Broken spring is a new one on me. How did you determine this? Suction is 35 degrees? Suction what is 35 degrees? Saturation temp? Box will never get to temp. 175 head? What's your ambient and do you have ambient controls?
    Officially, Down for the count

    YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET

    I know enough to know, I don't know enough
    Liberalism-Ideas so good they mandate them

  4. #4
    Join Date
    Sep 2005
    Location
    Woodbridge, VA
    Posts
    5
    Quote Originally Posted by 2sac View Post
    First off, How could you attempt to set it back to factory setting? Never heard of a factory setting on a WIC, and without knowing what the previous company did, the statement you made doesn't make sense. Broken spring is a new one on me. How did you determine this? Suction is 35 degrees? Suction what is 35 degrees? Saturation temp? Box will never get to temp. 175 head? What's your ambient and do you have ambient controls?
    According to sporland you can reset the TXV to factory setting by figuring out how many turns it takes to go from closed to open and then set it half way. I determined the spring was broken when I pumped down the system and took the TXV apart to inspect it. Ambient was 80 deg. No ambient controls, pump down, and it's air defrost. Sorry, I should have added more info. I have not been back to the job yet because the owner said he doesn't want to sink a lot of money into a 25 year old system and just wants us to install a new one

  5. #5
    Join Date
    Feb 2004
    Location
    Western New York
    Posts
    1,042
    175# head at 80 deg ambient, and a 35 deg SST?

    I agree with replies above. Something is wrong in the compressor... likely bad valves.
    Experience is what you have an hour after you need it.

  6. #6
    Join Date
    Sep 2011
    Location
    Plainfield IL
    Posts
    101
    Sounds like a bad compressor to me. A broken TXV spring means the system would have flooded out the compressor most likely causing mechanical damage. When recharging a system with a txv you should charge it to a clear sight glass. Does your unit have a reciever and sight glass?

  7. #7
    Join Date
    Oct 2011
    Location
    Chicagoland Area
    Posts
    4,509
    Quote Originally Posted by pfinnmccool View Post
    According to sporland you can reset the TXV to factory setting by figuring out how many turns it takes to go from closed to open and then set it half way. I determined the spring was broken when I pumped down the system and took the TXV apart to inspect it. Ambient was 80 deg. No ambient controls, pump down, and it's air defrost. Sorry, I should have added more info. I have not been back to the job yet because the owner said he doesn't want to sink a lot of money into a 25 year old system and just wants us to install a new one
    Reason I asked is txv should be adjusted upon instalation. No factory setting per say. Example: Install a 9000 btu coil and a 1 ton valve. More than likely the valve will need to be throttled down to hit your desired SH. Too many variables in the equasion.

    If he wants you to install a new one then go right ahead. Make the man happy.
    Officially, Down for the count

    YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET

    I know enough to know, I don't know enough
    Liberalism-Ideas so good they mandate them

  8. #8
    Join Date
    Apr 2012
    Location
    winnipeg
    Posts
    1,330
    what was the purpose of the suction scrubber.....
    it was working.... played with it.... now its broke.... whats the going hourly rate for HVAC repair

  9. #9
    Join Date
    Oct 2012
    Location
    Las Vegas, NV
    Posts
    6
    DO YOU HAVE A HEAD MASTER?!?!?

  10. #10
    Join Date
    Jul 2012
    Location
    Western KY
    Posts
    1,221
    Gotta assume it has a receiver, or it would never work in low ambient, and a head master, for same reason. Wouldn't scrap comp yet. Check head master.

  11. #11
    Join Date
    Oct 2011
    Location
    Chicagoland Area
    Posts
    4,509
    Head at 175. +/- headmaster's ok. If the saturation temp is 35 degrees
    suction is 35 degrees and the head is 175.
    ain't gonna get to temp.
    If you mean't to say suction is 35 psi and head is 175psi....well you have other issues......which are pretty obivious
    Officially, Down for the count

    YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET

    I know enough to know, I don't know enough
    Liberalism-Ideas so good they mandate them

  12. #12
    Join Date
    Jul 2012
    Location
    Western KY
    Posts
    1,221
    Quote Originally Posted by 2sac View Post
    Head at 175. +/- headmaster's ok. If the saturation temp is 35 degrees ain't gonna get to temp.
    If you mean't to say suction is 35 psi and head is 175psi....well you have other issues......which are pretty obivious
    Yep. Check the headmaster! Is it bypassing? Since there was no mention of sight glass and charged by subcooling I suspect it is. So why would it be?

  13. #13
    Join Date
    Oct 2012
    Location
    Las Vegas, NV
    Posts
    6
    Quote Originally Posted by Tommy knocker View Post
    Yep. Check the headmaster! Is it bypassing? Since there was no mention of sight glass and charged by subcooling I suspect it is. So why would it be?
    Sometimes it will flood the liquid line. Meaning that the condensor coil would act over sized. This happens when the restrictor piston gets stuck from bad seal or when it is over extended from "dead heading" this is caused from charging in the discharge line when breaking a vacuum.

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