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  1. #53
    Join Date
    Mar 2015
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    Medford, N.Y.
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    Quote Originally Posted by Olivero View Post
    Probably just kept running and ran air over it. I see a lot of air defrost and it'll do it on it's own, just takes forever.
    I agree, but this system did not reach temp to do an air defrost.

  2. #54
    Join Date
    Oct 2016
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    Clearwater, Florida
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    This doesen't really make sense.

    The walk in's I take care of can get down to about 25* or so before reaching the end of their capacity, at least most of them. So if you are having trouble going below 35* that's an outpoint in itself.

    Terry,

    I think you are correct, there's a bit of stuff not adding up with this.

    OP,

    If you want to fix it for real, we can help you or at least verify everything is in order, but so far it sounds like a lick and a promise kind of fix.

  3. Likes Cdh11192 liked this post
  4. #55
    Join Date
    Dec 2014
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    Quote Originally Posted by Cdh11192 View Post
    A thermostat adjustment.
    The system had needed a new txv and thermostat before I made the post. Then the coil started icing up. I didn't dial the thermostat in, which caused the system to run continuously.

    Sent from my SM-G977U using Tapatalk
    Yeah....what I ment to say when I said calibrate the thermostat.
    Spell-check made it thermometer.
    I probably said thermo and it changed it to thermometer.

    Sent from my SM-G950U using Tapatalk

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  6. #56
    Join Date
    Dec 2014
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    Quote Originally Posted by icy78 View Post
    Yeah....what I ment to say when I said calibrate the thermostat.
    Spell-check made it thermometer.
    I probably said thermo and it changed it to thermometer.

    Sent from my SM-G950U using Tapatalk
    Good chance the coil iced up from hot pull-down/long runtime and too low set point. Not unusual.
    Add a defrost clock for next time theres a issue of some kind.

    Sent from my SM-G950U using Tapatalk

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  8. #57
    Join Date
    Oct 2016
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    Clearwater, Florida
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    Could be, I've seen that before.

    Just in combination with odd pressures, if they did exist at one point, makes me thing there's more to it.

  9. #58
    Join Date
    Mar 2015
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    Medford, N.Y.
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    Quote Originally Posted by Olivero View Post
    Could be, I've seen that before.

    Just in combination with odd pressures, if they did exist at one point, makes me thing there's more to it.
    I agree.

    My experience w/ a slightly under sized CU is the comp runs and runs and build frost from no off time. So, I install a defrost clock to shut the comp off and defrost the evap. By doing this "step down" it allows the under sized comp to pull the box down in steps.

  10. #59
    Join Date
    Jan 2019
    Location
    Akron ohio
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    Thread Starter
    Quote Originally Posted by Olivero View Post
    This doesen't really make sense.

    The walk in's I take care of can get down to about 25* or so before reaching the end of their capacity, at least most of them. So if you are having trouble going below 35* that's an outpoint in itself.

    Terry,

    I think you are correct, there's a bit of stuff not adding up with this.

    OP,

    If you want to fix it for real, we can help you or at least verify everything is in order, but so far it sounds like a lick and a promise kind of fix.
    I got called out to some other jobs but I will be checking on them tomorrow morning. I'll Post all my pressures and my findings then. Thank you.

    Sent from my SM-G977U using Tapatalk

  11. #60
    Join Date
    Dec 2014
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    Quote Originally Posted by Olivero View Post
    This doesen't really make sense.

    The walk in's I take care of can get down to about 25* or so before reaching the end of their capacity, at least most of them. So if you are having trouble going below 35* that's an outpoint in itself.

    Terry,

    I think you are correct, there's a bit of stuff not adding up with this.

    OP,

    If you want to fix it for real, we can help you or at least verify everything is in order, but so far it sounds like a lick and a promise kind of fix.
    Explain that first paragraph.

    What WIC is going to off-cycle defrost at 25-33f?
    Most at that temp have electric defrost. ie meat coolers. (<34‐35f) Different animal.
    And in that case they are sized for it.
    A fail-safe, solution is sensing the tail coil temp with the tstat or KE2 control.
    Or pressure control.
    Or combination pressure/timed defrost

    Altho we all use it, IMO, timed off-cycle defrosts can allow too many unnecessary defrosts.

    Sent from my SM-G950U using Tapatalk

  12. #61
    Join Date
    Oct 2016
    Location
    Clearwater, Florida
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    What I was getting at was the walk in coolers I have are not "defrosting" per say, they don't have a clock or heaters, they rely on hitting setpoint and thawing themselves out. None of my units except the freezers have electric defrost, including the meat fridge which is kept between 32 and 36*F

    He said the thermostat was set too low so it kept cooling, the lowest point we've heard so far was 35*F so if the unit kept cooling and couldn't get below 35*F and then froze up trying to do so, to me that's an outpoint, that's all I was trying to say above.

  13. #62
    Join Date
    Sep 2002
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    Let's look more closely at your numbers - because some of them don't make sense:

    That condensing unit is good for about 4000-5000 BTU's
    That evaporator number looks like it's 6500 BTU's

    A box that size needs about 2000 BTU's for a 16 hour refrigeration day

    85º air does not result in 130º condensing (a 210 head pressure on R-134) - unless something is wrong with the condenser on the outside (clogged) or on the inside (overcharged or non-condensables)

    A 35 lb. / R-134 suction is 40º - unless the stat's set point is +50º - it's not off-cycling on the stat. How can it "be coming down to temperature" ?

    High side pressure 210 psi = 130º
    Outlet of condenser 126º = 4º subccoling
    Low side pressure 35 PSI = 40º
    Inlet of compressor temp 76 degrees = 26º superheat

    PHM
    -------


    Quote Originally Posted by Cdh11192 View Post
    I recently replaced the condensing unit for this walk in. It hasn't worked since. It will come down to temperature for a couple of days and then the evaporator ices up. I ended up replacing the TXV and it still didn't help. It also has a new thermostat. I have to overcharge the system based on the receiver capacity just to clear the sight glass. I'm at a loss, please help.

    model M7ZH-H067-CFV-272
    Evap model ADT065AK
    Receiver holds 1.5 lbs of 134a at 90% capacity
    I had to add 2.5 lbs to clear the sight glass
    Indoor condenser, ambient air 85 degrees
    High side pressure 210 psi
    Low side pressure 35 PSI
    Outlet of condenser temp 126 degrees
    Inlet of compressor temp 76 degrees
    Outlet of evaporator temp 50 degrees
    10 degrees of superheat
    About 7 degrees of subcooling
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  14. #63
    Join Date
    Mar 2015
    Location
    Medford, N.Y.
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    Another thing that has me wondering is that 1.5 lb receiver and the SC#'s. I worked on a Traulsen RIR today and it had a Copeland CU w/ a small 1.5 lb receiver. So a WIR has to have a bigger receiver. So I'm thinking that the 1.5 lb is chock full and the refrigerant is backing up into the cond coil to give you the 7*SC, So possibly adding a 2nd receiver just might help.

  15. #64
    Join Date
    Sep 2002
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    With more than double the required cooling capacity available I think there will be plenty of off-cycle defrost time. <g>

    PHM
    -------


    Quote Originally Posted by icy78 View Post
    Good chance the coil iced up from hot pull-down/long runtime and too low set point. Not unusual.
    Add a defrost clock for next time theres a issue of some kind.

    Sent from my SM-G950U using Tapatalk
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  16. #65
    Join Date
    Jan 2019
    Location
    Akron ohio
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    Thread Starter
    New readings from today.

    R134A 2.5lbs. 1 lb over the receivers 90% capacity to clear the sight glass.
    High side 180psi
    Low side 24psi
    Condenser coil outlet 113°
    Compressor inlet 72°
    Evap outlet 36° fluctuating to 40°
    Subcooling 10°
    Superheat at compressor 45°
    Superheat at evaporator about 15°
    Box temp is about 40° to 44°

    Sent from my SM-G977U using Tapatalk

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