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  1. #14
    Join Date
    May 2008
    Location
    Wisconsin
    Posts
    24
    Quote Originally Posted by codgy View Post
    that coil is 9000btu at 0 deg. I think your old unit being rated at -30 is your problem. you need a 3hp system to reach those temps and capacity. coil coil and unit need to be derated to -30 for true capacity. sounds undersized
    Gave specs of everything to Bohn today, they say I need 9800 btu

  2. #15
    Join Date
    May 2008
    Location
    Wisconsin
    Posts
    24
    Quote Originally Posted by sarpanch2001 View Post
    if am not wrong you said evap coil is -12 deg and you got +6 deg ? superheat at you evap outlet thats your 18 deg superheat high.again make sure on pump also .post model # for pump also sounds like to me evap starving.diff on after txv and evap out let you have to be verry accurate to find out like that . i would say stay with superheat just post evap outlet temp and presure at evap coil thats only way get accurate way to get superheat
    suction line temp at txv bulb = 12/ and suction pressure at evap = 24. box temp 28'/ suct line temp at comp. = 9/ suct. press. at comp.= 22/ liq. line press. 250/ and liq. line temp.= 88

  3. #16
    Join Date
    May 2008
    Location
    Wisconsin
    Posts
    24
    Quote Originally Posted by coolaide View Post
    If you did not change the defrost timer yet - that's likely the problem. Once I had the exact scenario - the contacts on the timer welded together - so that even during the regular freeze cycle, the heaters would remain energized never allowing the box to reach temp.
    Timer o.k. clearing coil good and I checked power to heaters while in refrig. cycle and there is no power to the heaters then. I was hoping it was that simple too.

  4. #17
    Join Date
    May 2008
    Location
    Wisconsin
    Posts
    24
    Thank you all who replyed with your help to this problem. I have tried to reply the info you asked as well. I really appreciate everyones help.Got more work to do on that thing and will let everyone know.Thanks again.

  5. #18
    Join Date
    Sep 2008
    Location
    Cedar Rapids, IA
    Posts
    486
    As old as this unit is the insulation in the box walls may have deteriorated. Have you checked for ice in the walls? Is there condensation on the exterior?
    Are seams caulked vapor tight?

    How's the door/ door gasket / floor sweep.

    Being 800 btus short shouldn't raise your box temp by 30 degrees.

  6. #19
    Join Date
    Jul 2004
    Location
    NJ
    Posts
    1,793
    Seems like that compressor has 7040 btuh capacity at -25F evap.temp.It's 2000btuh shorter than your original compressor.
    Still,
    because of the progressive nature of your problem and 6* evap superheat you were able to measure at high box temp(22F?) I would focus on infiltration.I have had a box that had the walls seperating.
    I am sure you already monitored the thermostat..
    Last edited by wannafreeze; 09-18-2008 at 02:02 AM.

  7. #20
    Join Date
    May 2000
    Location
    Monmouth Junction-NJ-USA
    Posts
    6,002
    I am inclined to agree with bob sch_scheel and wannafreeze. The only information missing here is the SIZE of the box and the composition of it. Please supply that information so that we can get a more clear picture of the entire installation.
    If you really know how it works, you have an execellent chance of fixin' er up!

    Tomorrow is promised to no one...

  8. #21
    Join Date
    Nov 2005
    Location
    Haymarket VA
    Posts
    642
    Quote Originally Posted by hoofbeat View Post
    suction line temp at txv bulb = 12/ and suction pressure at evap = 24. box temp 28'/ suct line temp at comp. = 9/ suct. press. at comp.= 22/ liq. line press. 250/ and liq. line temp.= 88
    12 deg evap outlet -10 deg evap coil 22 deg superheat high
    and 19 deg SH at comp ?
    104 deg condensing 88 deg liq line temp 16 deg subcooling
    try to lower your superheat if you can or find out what cause starving evap .whats liq line temp before it enter txv . what is box size ?indoor or out door what was ambeint
    if it comes thru attic make sure you are not boiling off way before txv
    Last edited by sarpanch2001; 09-18-2008 at 09:21 AM.

  9. #22
    Join Date
    Nov 2005
    Location
    Haymarket VA
    Posts
    642
    Quote Originally Posted by wannafreeze View Post
    Seems like that compressor has 7040 btuh capacity at -25F evap.temp.It's 2000btuh shorter than your original compressor.
    Still,
    because of the progressive nature of your problem and 6* evap superheat you were able to measure at high box temp(22F?) I would focus on infiltration.I have had a box that had the walls seperating.
    I am sure you already monitored the thermostat..
    22 deg evap SH

  10. #23
    Join Date
    Jul 2004
    Location
    NJ
    Posts
    1,793
    Quote Originally Posted by sarpanch2001 View Post
    22 deg evap SH
    I think he says box temp.22F.And evap SH 6*.

  11. #24
    Join Date
    Sep 2005
    Location
    florida
    Posts
    5,506
    This sound's like the same walkin frz thread to me.http://www.hvac-talk.com/vbb/showthread.php?t=181429
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  12. #25
    Join Date
    Nov 2005
    Location
    Haymarket VA
    Posts
    642
    i think if he comes with box size and liq line temp before enter txv he can get right answer

  13. #26
    Join Date
    Nov 2005
    Location
    Haymarket VA
    Posts
    642
    Quote Originally Posted by wannafreeze View Post
    I think he says box temp.22F.And evap SH 6*.
    Pt chart was just front off me so i got right

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