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  1. #1
    Join Date
    Jan 2012
    Location
    tennessee
    Posts
    18

    reach in freezer help needed

    I deal mostly in residental hvac but take care of a store close to my house. I'm having trouble with a Howard McCray GF75LBM reach in freezer. It uses 404a refridgerant . I moved the condensing unit two years ago from inside the cabinet to the other side of the wall betwwen the walk-in and outter store wall around 2 years ago . The system has ran just fine and still runs great as far as keeping the temp inside the freezer where it should be. Recently the customer told me he was hearing a loud vibrating noise coming from the unit after defrost. What I found is the noise is coming from the crank case pressure regulater. My head pressure gauge vibrates so fast you can't hardly see it until the suction pressure goes down to aroun 35 or so psig , then the noise stops and all is well . I know the CPR is working because the suction climbs only up to around 48 psig while the systen is in defrost. The CPR does not vibrate during a regular cycle , only in defrost . This system does not have a soleniod . My super heat and subcool is very high SUCTION PRESSURE 20 PSIG ---LINE TEMP 69.5 ---- HEAD 315---- LINE TEMP 184
    I am going to clean the condensor coil tommorow and already have the new CPR valve ready to put it on . I just want to be sure when its on and cleaned we don't have the same problem.
    The unit seems to run really well other than the problems I mentioned , ant suggestions would be greatly appreciated

  2. #2
    Join Date
    Oct 2012
    Posts
    10
    Does the compressor have a sight glass where you can see oil level in it?

  3. #3
    Join Date
    Oct 2011
    Location
    Chicagoland Area
    Posts
    4,617
    How do you know the cpr is ok? Nothing you stated tells me so. The cpr is there to control the load on the pump after defrost under high load conditions. You need to set it according to amp draw and not pressure.
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  4. #4
    Join Date
    Jan 2012
    Location
    tennessee
    Posts
    18
    Yes sir Mr. halsay it sure does and Ive noticed the oil is trickling down over the knobs in the sight glass as the systems running and when its off at best the glass is quarter full . I'm gonna put some POE in tommorrow but not sure thats the problem unless otherwise convinced .
    2sac I considered the CPR good because the suction wasn't rising above 48 PSIG , my amp draw off the compressor is at best when running close to 3 amps while the RLA is rated for 9.9 . I'm getting this reading from the common . I've not tried ajusting the CPR maybe I should?

  5. #5
    Join Date
    Oct 2011
    Location
    Chicagoland Area
    Posts
    4,617
    The cpr should be set right at defrost termination. I'm wondering why you're only running 3amps when rla is 9.9 especially with the head being so high. I'm going to assume there is no receiver and you cannot pump the system down. I'm also assuming it's a semihermetic. Have you tried front seating the suction service valve to check for bleed thru?
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  6. #6
    Join Date
    Jan 2012
    Location
    tennessee
    Posts
    18
    No the system does have a reciever and no I've not tried front seating the suction kingV , and as well it is a semi . I do believe I will try front seating the king tommorow just to see about that . As of now my plan is to go in clean the condensing coil until it looks like a prize trophy , then pump refridgerant into reciever , change CPR , roll back my defrost time on the dixell from 30 min to 20 , most likely put a little POE in , leak test , vacuum , and see what the amp draw is after defrost . It doesn't need to be set to 9.9 does it? I'm really not sure . I just know I'll be sick if it does the same thing as before . What will bleed thru on the suction king tell me ? and I'm concerned about the super heat and sub cool . Also I talked to the howard McCray tech support guy and he thinks the CPR may have something going on internally and to solve the prob just replace it . My whole reason for asking all this is to be sure it may not be being caused by something else

  7. #7
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    18,547
    When you relocated the condensing unit, how long was the system open?
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  8. #8
    Join Date
    Jul 2012
    Location
    Western KY
    Posts
    1,221
    I'm not familure with that unit so I'll ask. Does it have a DTS with fan delay?

  9. #9
    Join Date
    Jan 2012
    Location
    tennessee
    Posts
    18

    Confused

    If the system noise is coming from the cpr that wouldn't make the needle on my high side shake so fast you can't even see it would it? Could the system possibly be flooding back after defrost for some reason? I moved the condensing unit about 2 years ago and don't understand why it would just now be causing trouble . The condensor was only moved about 5 feet on the other side of the wall and it is inside and in conditioned space , but it possibly needs a solenoid?

  10. #10
    Join Date
    Jan 2012
    Location
    tennessee
    Posts
    18
    yes

  11. #11
    Join Date
    Oct 2011
    Location
    Chicagoland Area
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    4,617
    Are you taking the high side pressure of the discharge line? It's somewhat common to get a flutter under a high load. I'm wondering if the compressor may be bleeding thru the valves and that may be causing the noise issue and low amp draw. I'm guessing the noise is a damaged bellows or diaphragm, and I'm concerned what may have caused the damage. Would hate for you to do all that work to have to go back in a week because the new one is damaged. Are you taking the suction pressure of the service valve or of the cpr?
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  12. #12
    Join Date
    Jan 2012
    Location
    tennessee
    Posts
    18
    yes i'm taking the high side pressure of the discharge line at the service port at the comp not the reciever and the suction pressure at the compressor as well . This cpr does not have a servive port , this is a sporlan cpr not for sure the actual numbers but i am pretty sure the second number is 6 and the last 0/60 I think....

  13. #13
    Join Date
    Oct 2011
    Location
    Chicagoland Area
    Posts
    4,617
    It's oem without a tap. The 0/60 is just the operating range. See if it pumps down. See if the valves hold. If that's ok, go ahead and change it. If not, you may be looking at a new pump in addition to the cpr.
    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

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