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Thread: glycol chiller troubleshooting in espanol

  1. #1
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    glycol chiller troubleshooting in espanol

    Copeland Scroll 7.5hp, 3 Phase Compressor, med temp
    55 gal reservoir made from blue water barrel, uninsulated as of yet
    Bell & Gossett BP422 Heat Exchanger
    3/4hp pump

    we cant get the glycol below 37ish. and its not even "glycol" yet, still 100% water.

    compressor is rated 58k btu at 20F. right now there's 1" lines running from HX to reservoir, uninsulated as of yet, but only about a 25' run. cant imagine we're losing THAT much heat to ambient. ran unit for about 20-30 minutes, went from 70 ambient down to 40s pretty quickly, then stalled around 37-38.

    the ac tech says he thinks the compressor is bad, but im worried he's taking the easy way out by advising we get a new compressor. its a little difficult to get into a super technical discussion with him (granma didnt teach me HVAC spanish), but he went from initially not knowing why it wouldnt get cold enough to now saying that the compressor doesnt sound right and its probly going bad.

    its entirely possible that this is the case, but before we shell out for new compressor im hoping to see if there's any thing we can do to double check.

    electrician insists its wired correctly and is fully powered. (dont recall if its 208 or 230)
    gas is fully charged
    compressor does not seem to be leaking gas
    no refrigerant leaking from HX into water that we can tell (it would be oily right?)
    all the pumps and condensor fans seem to be working fine

    37F is pretty cold vs 70F ambient, so its obviously working- but only partially. which is why i just wanna be sure we're not missing something small or silly before we get a new unit. should we try and throttle down the recirc pump? would the uninsulated recirc lines really lose that much heat? drain/change refrigerant gas?

    any advice greatly appreciated.

  2. #2
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    It could be you're getting freezing in the HX between your water and refrigerant. If the chiller is rated at 20 oF your refrigerant may well be down in the twenties or teens and you're getting ice build up inside the HX which is killing the heat transfer. You should take a look at what temp the refrigerant gas is at and see if that may be the issue.
    Not having insulation makes a bigger deal than you'd think, but I have a feeling that's not the problem at the moment.
    Manuel

  3. #3
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    Quote Originally Posted by mmussen View Post
    It could be you're getting freezing in the HX between your water and refrigerant. If the chiller is rated at 20 oF your refrigerant may well be down in the twenties or teens and you're getting ice build up inside the HX which is killing the heat transfer. You should take a look at what temp the refrigerant gas is at and see if that may be the issue.
    Not having insulation makes a bigger deal than you'd think, but I have a feeling that's not the problem at the moment.
    I second the above. You could seriously damage your equipment by running water at those temps. You should have a glycol mixture that has a freezepoint 20F BELOW your setpoint. If you freeze the heat exchanger you will get no or little flow, you could crack the heat exchanger, etc.
    Luch Scremin
    Engine 15 Brewing Co.
    luch at engine15 dot com

  4. #4
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    "it's still 100% water"

    Definitely icing in the HX. Your refrigerant is below 32F, 0C, so of course the water is freezing in the HX. You don't mention what kind of HX you're using--some can be permanently damaged by freezing.

    A proper glycol mix (about 26 Brix), like insulation, is not optional, even for testing.
    Timm Turrentine

    Brewerywright,
    Terminal Gravity Brewing,
    Enterprise. Oregon.

  5. #5
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    Quote Originally Posted by mmussen View Post
    You should take a look at what temp the refrigerant gas is at and see if that may be the issue.
    .
    how would we go about this?

  6. #6
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    Quote Originally Posted by TGTimm View Post
    "it's still 100% water"

    Definitely icing in the HX. Your refrigerant is below 32F, 0C, so of course the water is freezing in the HX. You don't mention what kind of HX you're using--some can be permanently damaged by freezing.

    A proper glycol mix (about 26 Brix), like insulation, is not optional, even for testing.
    Bell & Gossett BP422 Heat Exchanger. standard plate HX.Name:  IMG_1568.jpg
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  7. #7
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    Quote Originally Posted by clydemule View Post

    If you have 37F in your barrel, and only getting 5 F across the brewery and the the Evap takes out 10 you are definitely freezing the sucker up.

    If the actual leaving temp of the evaporator is 37F then there is probably something else wrong.
    so just to clarify, we're not running the cellar/conicals/brewhouse loop at all, just the recirc loop from reservoir to HX and back (about 25 feet). and no evaporator per se, just the glycol heat exhanger (GHX), which i guess functions as the evap.

    so- either we f'd it or we didnt. the gas is still charged up, so hopefully that bodes well for the GHX. and if the gas was leaking into water inside our GHX, i assume i would see oily film in the water? on in the inside of the reservoir walls? would i smell it? or is some sort of UV/leak detection kit required here?

    at this point, im guessing the proper course of action would be:
    1- test the HX for leaks
    2-have tech check gas pressure make sure its appropriate
    3- assuming 1 and 2 are good, then whip up a small batch of glycol mix to run through the cooling/recirc loop.

    seem reasonable?

  8. #8
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    That is a brazed-plate HX, the absolute worst kind to freeze. If you got away with it this time, buy a lottery ticket!
    Timm Turrentine

    Brewerywright,
    Terminal Gravity Brewing,
    Enterprise. Oregon.

  9. #9
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    Quote Originally Posted by TGTimm View Post
    That is a brazed-plate HX, the absolute worst kind to freeze. If you got away with it this time, buy a lottery ticket!
    i hope to hell we did finally get lucky for once.

    as i said, it only ran at a stopped 37ish for a few minutes before we shut it off. might not have had time to build alot of ice, and the pump was pushing that water pretty fast so no noticeable pressure drop either. maybe it didnt build enough ice to cause a problem. fingers crossed.

    in any case- how best to test for leaks of either gas/water?

  10. #10
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    I'd cap off one end of the glycol side and put a sensitive pressure gauge--like 0-30 psi range--on the other. With the motor electrical disconnected, open the solenoid valve to allow the HX to pressurize. Leave it for a day or so and see if the pressure is climbing on the glycol side. If not, you're in luck!

    Just as a note--we started our brewery with a shop-built "frankenchiller". One of my happiest days on the job was the day we decommissioned that beast and replaced it with a professional system!
    Timm Turrentine

    Brewerywright,
    Terminal Gravity Brewing,
    Enterprise. Oregon.

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