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  1. #1
    Join Date
    May 2008
    Location
    Wisconsin
    Posts
    24

    Angry Help please on this walk in freezer

    here is the story. 18 years ago, I installed a walk in freezer. Evap and condensing unit rated at 9000 btu's at -30 degrees. R-502 was the refrigerant.Everything working well and box holding at -12 degrees. We did have the ocassional electrical problem and even replaced the compressor once. The condensing unit is remoted in a room @25' away. Now, a year ago, the compressor failed electrically . It was replaced with a new one rated the same but using R-404A. Box began to loose temp. First it would maintain 0 degrees and and kept loosing a little until +20 was all it could do. In the mean time, the txv was changed, twice, and they had been adjusted and tweaked many times. No ghange in box temp. could be made. Always +20. The load that goes in is frozen meat at -12 . Nothing warmer ever goes into the box. It is supposed to be a holding locker. Customer says, put in a new compressor and evaporator and get over with it already. I get a new direct Bohn replacement evap. and copeland compressor and txv. Installed them. Everything is rated as it was from original but ofcourse new updated equipment. Started everything up and +20 is all I can get. Today, box at +22 and subcooling at 10 degrees, suction pressure at 22psig at compressor and suction line temp at compressor is +46 degrees. Bohn said open txv wide open and let run until box temp starts to fall then slowly adjust back to
    +15 to +20 degrees super heat at compressor.Opened valave and got 30psig for just a little while the n dropped to 22psig. closed txv 1 turn and pressure did not change but box dropped 4 degrees. Not enough! Why won't this thing work? The txv is a sporlan SBFSE-A-ZP.Also the correct orifice was installed in the evap.Bohn coil is a LET090BK. Condensing unit is rated for the evap and box temp and size but do not have the numbers in front of me. Have tried everything I can think of. Lines are suction = 1-1/8 and liquid 3/8. Suction reduces to 7/8 at evap and condensing unit connections. About 25 feet long. What is so puzzling is this thing worked for many years as R-502 with no problems. I have had 9 degrees diff. from outlet of txv and out let of evap. Have measured super heat at evap. at +6 degrees. Nothing that is tried makes a difference.4 defrosts a day at 1/2 hour each and coil clears nicely. Evap seems to frost evenly in all 3 circuits. Thanks for any help.

  2. #2
    Join Date
    Sep 2005
    Location
    florida
    Posts
    5,514
    Quote Originally Posted by hoofbeat View Post
    here is the story. 18 years ago, I installed a walk in freezer. Evap and condensing unit rated at 9000 btu's at -30 degrees. R-502 was the refrigerant.Everything working well and box holding at -12 degrees. We did have the ocassional electrical problem and even replaced the compressor once. The condensing unit is remoted in a room @25' away. Now, a year ago, the compressor failed electrically . It was replaced with a new one rated the same but using R-404A. Box began to loose temp. First it would maintain 0 degrees and and kept loosing a little until +20 was all it could do. In the mean time, the txv was changed, twice, and they had been adjusted and tweaked many times. No ghange in box temp. could be made. Always +20. The load that goes in is frozen meat at -12 . Nothing warmer ever goes into the box. It is supposed to be a holding locker. Customer says, put in a new compressor and evaporator and get over with it already. I get a new direct Bohn replacement evap. and copeland compressor and txv. Installed them. Everything is rated as it was from original but ofcourse new updated equipment. Started everything up and +20 is all I can get. Today, box at +22 and subcooling at 10 degrees, suction pressure at 22psig at compressor and suction line temp at compressor is +46 degrees. Bohn said open txv wide open and let run until box temp starts to fall then slowly adjust back to
    +15 to +20 degrees super heat at compressor.Opened valave and got 30psig for just a little while the n dropped to 22psig. closed txv 1 turn and pressure did not change but box dropped 4 degrees. Not enough! Why won't this thing work? The txv is a sporlan SBFSE-A-ZP.Also the correct orifice was installed in the evap.Bohn coil is a LET090BK. Condensing unit is rated for the evap and box temp and size but do not have the numbers in front of me. Have tried everything I can think of. Lines are suction = 1-1/8 and liquid 3/8. Suction reduces to 7/8 at evap and condensing unit connections. About 25 feet long. What is so puzzling is this thing worked for many years as R-502 with no problems. I have had 9 degrees diff. from outlet of txv and out let of evap. Have measured super heat at evap. at +6 degrees. Nothing that is tried makes a difference.4 defrosts a day at 1/2 hour each and coil clears nicely. Evap seems to frost evenly in all 3 circuits. Thanks for any help.
    You changed the txv and orifice.How about the nozzle after the txv?
    I love the smell of phosgene first thing in the morning:

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  3. #3
    Join Date
    Jan 2006
    Location
    Near Atlanta, GA.
    Posts
    14,626
    Did you change the entire condensing unit, or just the compressor?

    What kind of head pressure are you running?

    Also, you're suction line should be 7/8 the whole way. Gotta be extra careful with oil return when using 404.

  4. #4
    Join Date
    Jun 2005
    Location
    Las Vegas NV
    Posts
    1,152
    My bet is that the replacement compressor you got is incorrect. Do you have the original model number and the replacement number?

  5. #5
    Join Date
    Nov 2006
    Location
    Ontario
    Posts
    7
    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.

  6. #6
    Join Date
    Nov 2005
    Location
    Haymarket VA
    Posts
    642
    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
    Last edited by sarpanch2001; 09-17-2008 at 08:54 PM.

  7. #7
    Join Date
    Dec 2000
    Location
    Flat Rock, NC
    Posts
    463
    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

  8. #8
    Join Date
    Mar 2008
    Location
    Florida
    Posts
    193
    I,m with K-fridge, no mention if condensing unit was changed. 18 years old and if I read correctly condensing unit is in a room, I,m thinking condensing coil has internal build up or bad fins.

  9. #9
    Join Date
    Oct 2006
    Location
    Emerald Coast, FL 30.1N 85.8W
    Posts
    681

    superheat at compressor don't mean squat -- evap superheat tells story

    You should only be concerned about useful superheat -- the superheat at the evaporator tells the story how efficient both the evaporator & TXV are -- a useful target is no more than 5 degrees evaporator superheat for a freezer.

    I would've change the line set also -- going from 1 1/8 to 7/8 will cause heavy vapor going to the compressor and poor performance -- not to mention residual contaminants & oil.

    Man was 502 a good LT refrigerant or what?


    Quote Originally Posted by hoofbeat View Post
    here is the story. 18 years ago, I installed a walk in freezer. Evap and condensing unit rated at 9000 btu's at -30 degrees. R-502 was the refrigerant.Everything working well and box holding at -12 degrees. We did have the ocassional electrical problem and even replaced the compressor once. The condensing unit is remoted in a room @25' away. Now, a year ago, the compressor failed electrically . It was replaced with a new one rated the same but using R-404A. Box began to loose temp. First it would maintain 0 degrees and and kept loosing a little until +20 was all it could do. In the mean time, the txv was changed, twice, and they had been adjusted and tweaked many times. No ghange in box temp. could be made. Always +20. The load that goes in is frozen meat at -12 . Nothing warmer ever goes into the box. It is supposed to be a holding locker. Customer says, put in a new compressor and evaporator and get over with it already. I get a new direct Bohn replacement evap. and copeland compressor and txv. Installed them. Everything is rated as it was from original but ofcourse new updated equipment. Started everything up and +20 is all I can get. Today, box at +22 and subcooling at 10 degrees, suction pressure at 22psig at compressor and suction line temp at compressor is +46 degrees. Bohn said open txv wide open and let run until box temp starts to fall then slowly adjust back to
    +15 to +20 degrees super heat at compressor.Opened valave and got 30psig for just a little while the n dropped to 22psig. closed txv 1 turn and pressure did not change but box dropped 4 degrees. Not enough! Why won't this thing work? The txv is a sporlan SBFSE-A-ZP.Also the correct orifice was installed in the evap.Bohn coil is a LET090BK. Condensing unit is rated for the evap and box temp and size but do not have the numbers in front of me. Have tried everything I can think of. Lines are suction = 1-1/8 and liquid 3/8. Suction reduces to 7/8 at evap and condensing unit connections. About 25 feet long. What is so puzzling is this thing worked for many years as R-502 with no problems. I have had 9 degrees diff. from outlet of txv and out let of evap. Have measured super heat at evap. at +6 degrees. Nothing that is tried makes a difference.4 defrosts a day at 1/2 hour each and coil clears nicely. Evap seems to frost evenly in all 3 circuits. Thanks for any help.

  10. #10
    Join Date
    May 2008
    Location
    Wisconsin
    Posts
    24
    Quote Originally Posted by powell View Post
    My bet is that the replacement compressor you got is incorrect. Do you have the original model number and the replacement number?
    Compressor model is a copeland, CF09K6E-PFV-979 and copeland tells me it is rated at 9800.00 btu at 0'.

  11. #11
    Join Date
    May 2008
    Location
    Wisconsin
    Posts
    24
    Quote Originally Posted by powerup View Post
    I,m with K-fridge, no mention if condensing unit was changed. 18 years old and if I read correctly condensing unit is in a room, I,m thinking condensing coil has internal build up or bad fins.
    The condensing unit is only a year old. or maybe year and a half. Coli is clean and fins are in almost perfect shape.

  12. #12
    Join Date
    May 2008
    Location
    Wisconsin
    Posts
    24
    Quote Originally Posted by emcoasthvacr View Post
    You should only be concerned about useful superheat -- the superheat at the evaporator tells the story how efficient both the evaporator & TXV are -- a useful target is no more than 5 degrees evaporator superheat for a freezer.

    I would've change the line set also -- going from 1 1/8 to 7/8 will cause heavy vapor going to the compressor and poor performance -- not to mention residual contaminants & oil.

    Man was 502 a good LT refrigerant or what?
    I am seeing what you say is true, I went into attic and found what was left of old line set. 7/8 and 1/2. Will 3/8 liq. make me starve the coil like this?

  13. #13
    Join Date
    May 2008
    Location
    Wisconsin
    Posts
    24
    Quote Originally Posted by emcoasthvacr View Post
    You should only be concerned about useful superheat -- the superheat at the evaporator tells the story how efficient both the evaporator & TXV are -- a useful target is no more than 5 degrees evaporator superheat for a freezer.

    I would've change the line set also -- going from 1 1/8 to 7/8 will cause heavy vapor going to the compressor and poor performance -- not to mention residual contaminants & oil.

    Man was 502 a good LT refrigerant or what?
    I am starving the coil some how. I went into attic tonight and seen old lines were 7/8 and 1/2 . I will change them next. But even so I would think I'd get the box to at least +10 What about the liq. line? any comments on that?

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