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  1. #1
    Join Date
    Apr 2008
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    Pa.
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    r-22 W I C charging?

    I installed a new compressor in a walk in today for one of the company stores. I cannot read any tags except for the compressors. Its laid out with two twin fan evaps with tev's, receiver, head pressure control ect.

    I went to charge it after the replacement of compressor and weighed in 15lbs to get started cause that's what i recovered although i found a leak so it was low. I was attempting to charge by subcool and was measuring at the condenser outlet. I have 31 lbs in it right now to get 4 degrees subcooling. I figured this would suffice to get it running and till the cooler pulls down to running temp somewhere around 36 degrees. Im goin back tommorro to finish check ups.

    my readings when I left:
    ambient = 101
    cabinet =77

    liquid side:

    285 psi =127
    123 degrees b4 receivers
    = 4 degrees sc

    285 psi = 127
    118 degrees on 2nd receivers outlet
    = 9 degrees sc

    compressor sh. wanna maintain between 20-30. i didnt check evap sh yet
    70 psi lo = 41
    62.5 line temp
    22 degrees sh

    So what do I do for the subcooling to ensure its full, before or after receiver? What for subcooling number should I target for the final charge?

  2. #2
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,659
    Forget about charging to subcooling. It is what it is and you aren't going to change it a whole lot by dumping in a bunch of gas.

    Charge to a clear glass to start with.

    http://www.sporlanonline.com/90-30-1.htm

    This is the method that I use to charge. It takes a little time, but is reliable and you aren't back out on the roof in the middle of winter just adding gas because your charge "shrunk"

    Superheat is adjustable most of the time, so if you're running too rich, go tweak a valve. SH is best measured at both the evap and the unit anyway on a refer unit.

  3. #3
    Join Date
    Apr 2002
    Location
    San Diego
    Posts
    137
    Thats a whole lot of numbers when you can just fill to a clear sight glass...
    Keep it simple.

  4. #4
    Join Date
    Sep 2008
    Location
    Western PA
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    25,659
    A few additional thoughts.

    Take your sharpie and mark on the unit the computed flooding charge and the total charge. It will make the next service call easier.

  5. #5
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    Sep 2008
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    Western PA
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    Quote Originally Posted by mfry View Post
    Thats a whole lot of numbers when you can just fill to a clear sight glass...
    Keep it simple.
    You must not work where it gets down to -10 in the winter.

    Do it right and do it once.

  6. #6
    Join Date
    Jul 2010
    Location
    So-Cal
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    580
    Yup.... full sight glass is good.

  7. #7
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    Apr 2002
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    San Diego
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    Quote Originally Posted by jpsmith1cm View Post
    You must not work where it gets down to -10 in the winter.

    Do it right and do it once.
    Funny, never even thought about ambeint temps below 50 deg. living is San Diego.

  8. #8
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    Apr 2008
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    Pa.
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    Well that's diffrent.

    I charged to full glass initially and them was using water sprayed on condenser I was getting bubbles in glass, so im still low. Ill take the time to use the sporland instructions. We can see temps about 0 or lower. I'm used to using sh and sc for everything in resi/comercial heat pumps so its "cool" to learn things are done diffntly with the refer units. What about evap sh should I be around 8-10 degrees? What does everyone do when they suspect a low charge condition? do you just recover and weight back in?

  9. #9
    Join Date
    Jan 2010
    Posts
    6,290
    Quote Originally Posted by farbeondriven View Post
    Well that's diffrent.

    I charged to full glass initially and them was using water sprayed on condenser I was getting bubbles in glass, so im still low. Ill take the time to use the sporland instructions. We can see temps about 0 or lower. I'm used to using sh and sc for everything in resi/comercial heat pumps so its "cool" to learn things are done diffntly with the refer units. What about evap sh should I be around 8-10 degrees? What does everyone do when they suspect a low charge condition? do you just recover and weight back in?
    Yes 8-10* is a good number for your superheat. If you do not no were the charge is at pounds wise. You could briefly torch the receiver to check the liquid level. It is best to do as JP says and follow the sporlan method.

  10. #10
    Join Date
    Mar 2007
    Location
    Madison, Wisconsin
    Posts
    2,260
    I charge to sight glass, then check my SH at the evap and adjust the TXV to what I want to see. Then back to compressor, if it is summer, I clear the sight glass, and add about 17% more total charge to system to account for seasonal change. Check all my temps, and pressures to make sure nothing is wacky, and call it good.

    This is on a normal system, not 1000 foot line, not over/undersized, not in a basement with boxes piled on the unit,.......
    I r the king of the world!...or at least I get to stand on the roof and look down on the rest of yall

  11. #11
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    Sep 2008
    Location
    Western PA
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    Quote Originally Posted by farbeondriven View Post
    Well that's diffrent.

    I charged to full glass initially and them was using water sprayed on condenser I was getting bubbles in glass, so im still low. Ill take the time to use the sporland instructions. We can see temps about 0 or lower. I'm used to using sh and sc for everything in resi/comercial heat pumps so its "cool" to learn things are done diffntly with the refer units. What about evap sh should I be around 8-10 degrees? What does everyone do when they suspect a low charge condition? do you just recover and weight back in?

    If you're low enough to affect operation, your glass will probably be bubbling.

    When it gets tricky is the warm days and cold nights of spring and fall.

    "This thing is warm every morning, but by the time you get here, it's fine"

    That will be the complaint. What you would need to do is recover just the flooding charge (you DID write that down, didn't you?) If it's low on gas, the glass will be bubbling. Clear the glass, then put the flooding charge back in and you'll be good to go except for fixing the leak.

  12. #12
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    Apr 2008
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    Pa.
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    Quote Originally Posted by VTP99 View Post
    Yes 8-10* is a good number for your superheat. If you do not no were the charge is at pounds wise. You could briefly torch the receiver to check the liquid level. It is best to do as JP says and follow the sporlan method.
    I used the torch over the receiver the first one from the condenser was about half full and the second one was a little over half full. subcooling at receiver outlet was 10.

    How full should the receivers be? I have full glass except when i run 57 degree water over the condenser. Then i can see its about half full.

    Also got some numbers from evaps.
    the closest evap (there are two controlled from one tstat and not sure how there piped together)
    SH was 0-8 degrees 45 suction @ comp and 22-30 line temp @ bulb. allot of hunting and no place to tap suction pres at evaps

    second evap SH was more stable @ 7 degrees

    cooler @ 38 degrees , 36 degree target

    Is it typical for the suction line temps to be below freezing and icing? The coils were not freezing but the end bends and distributer tubes were icing up.

    Compressor SH was 22 degrees LO 45psi (22 sat) and suct line temp was 44 degrees. so the compressor is safe for now but I worry about the icing.
    Last edited by farbeondriven; 07-15-2010 at 11:16 PM.

  13. #13
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    Sep 2008
    Location
    Western PA
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    Quote Originally Posted by farbeondriven View Post
    I used the torch over the receiver the first one from the condenser was about half full and the second one was a little over half full. Im up to 45 lbs of r22 now.

    How full should the receivers be?
    As full as they need to be.....

    Wait. 2 receivers? Is this a dual tank arrangement? Kind of like a pontoon boat?

    No matter, the receivers are probably linked in one way or another to act as a single tank.

    Did you do the flooding calculations? If you add that amount from a just cleared sightglass you will be fine.

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