Split System Freezing Coil

Discussion in 'Maintenance and Troubleshooting' started by PAGeo, Jan 21, 2009.

  1. Geotech

    Geotech Member

    Condensation is normal on an accumulator, however ice is not, if system is performing normally there should never be ice, ice tells a tech there is a problem.It looks like I see a bulb that's not been placed on the refrigerant tubing, in your pic the bulb is just above the suction line at the compressor. I do see a bulb on the suction line which should be for the TXV this is the one for heating. Please hav:)e the tech give you the EWT and the refrigerant pressures I may know what is happening.
  2. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    I missed the photo

    The picture helps a lot.

    Geotech the clamp on the suction line may be where the bulb should go.

    I can not tell which port is inlet. Can you?

    The suction accumulator looks to be acting like a metering device.
  3. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    Help me understand thermodynamics at work here

    Many closed loop systems, including the one now being discussed, operate with LWTs and, sometimes, EWTs below freezing (32F)

    Heat moves from the 'warmer' loop water to colder refrigerant on system low side via the coax heat exchanger serving as evaporator. The refrigerant then enters accumulator and compressor suction. Those components would have to be colder than loop water for that heat transfer to have occurred. Exposed to air with a dewpoint above 32, those components would sweat and / or ice up.

    Am I missing anything? In other words, is not suction line and accumulator icing normal in systems whose loops run at or below freezing?
  4. geo fan

    geo fan Member Forum Leader

    Freeze = Fan , Filter , Freon

    other less common dirty coil , other duct/air restrictions
    metering device/reversing valve/ checks, possible but far less likely in my guess:rolleyes:
  5. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    I still want to know

    How they weigh in a charge on a miss-matched split.

    Thought they did all the air flow things.
  6. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    I like that '4-F' mnemonic - I'll shamelessly reuse it at my earliest convenience. That's the standard mantra for a frozen AC evaporator. AC is used to cool 75-80 degree air down to 55-60, so appearance of ice is a failure.

    However, since one effect of some geo systems is to chill loop liquid to subfreezing temps, appearance of ice on the pieces parts is parts doing that chilling seems to me a natural, expected result. We expect ice on some loop lines, why not on the refrigeration components near or in contact with that cold loop liquid
  7. PAGeo

    PAGeo Member

    Yes, when the tech installed a new TXV, he placed the bulb in a different position than before. What affect will this have on the unit?

    EWT = 32F yesterday, after running constantly for about 18 hours. On Tuesday the EWT = 45F

    I don't know the refrigerant pressures, but they were "good" when he started it up after changing the Reversing Valve and it seemed to be working on Tuesday.

  8. PAGeo

    PAGeo Member

    The tech took a sample of the loop mixture to be tested. They want to know the % mixture and what type of antifreeze is being used. It is original, so we don't know exactly what it is. However in the past, the tech has said it is fine. They want to make sure the antifreeze is compatible with the Florida unit. Could it be incompatible? They also said the mixture should be about 4 to 1. Is this correct?

    My concern is this, they just seem to be guessing every time. First it was the loop had air in it. Second, it was the TXV. Third, it was the Reversing Valve. Fourth, now we are back to the loop and the mixture.

    Since the freezing begins at the Accumulator, could it be the problem? I have other pics that I can upload, when time allows. Man, this is sooooo frustrating.
  9. Geo Guy

    Geo Guy Guest

    PA Geo
    Sorry to hear of your problem.
    Two things.First is there 2 TX's on the unit, one after the earth coil, and on after the A coil?
    There should be 2 bi directional TX's on a split system, so the refrigerant will stay in a gassy state in both directions of the line set. This could explains why the unit runs good in AC.
    Second, it is very difficult to weigh refrigerant into a split system and get it right. The line set is never the same length to provide the exact weigh in amount for different projects. Being the unit works well in cooling, and the frosting occurs in heating, and if there is two TX on the unit, I would look at a low charge. I always set the first charge in the cooling mode and then I add charge to get the heating side to perform. This way I am not over charged in the cooling mode.
    Hope this helps
    Geo Guy
  10. hardchines

    hardchines Member Forum Leader

    For what its worth, this type of diagnostics has been called the SHOT GUN method, but in all fairness if this was simple to diagnose everyone could do it. And after the problem has positively been identified and fixed , everyone will say I thought that was it, or thats what I would have done to begin with!
    good luck
  11. PAGeo

    PAGeo Member

    So, here is the latest: they have tested the loop material and say that it does not have enough anti-freeze. I have a few questions.

    1. What is the best type of anti-freeze to use in the Northeast (cold winters and hot summers)?

    2. Could the loop material be contaminated in any way?

    3. Should we flush the whole loop out and start fresh?

    Any suggestions or help is greatly appreciated. BTW, I am tired of the shot gun method. This will be the last shot fired by the heating company. It's my turn next.
  12. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    I had a former employer

    tell me that refrigeration, is an artistic science. I agree after more than thirty years in the field. I carry a hygrometer when testing geo loops. If it is glycol solution in the loops it could take a lab test to determine what kind it is.

    I truly hope the installing contractor is paying for this guess work.

    Keep us posted.

    I'll come fix the damn thing.
  13. Looby

    Looby Member Forum Leader

    Methanol is cheapest and most efficient, but flammable
    until diluted, and toxic. Wouldn't worry too much about
    toxicity (unless the loop is close to your domestic well);
    methanol biodegrades rapidly in soil or groundwater.
    Half-life is only 1-7 days, so if it leaks, it won't migrate
    very far before it becomes harmless.

    Ethanol (a/k/a Environol) is nearly as efficient as methanol,
    still flammable until diluted, but less flammable than
    methanol. More expensive. Non-toxic (50-proof vodka).
    Be careful that the denaturing additives are compatible
    with materials in the system.

    Propylene glycol is the least efficient, I don't understand
    why anyone would choose it -- but opinions differ.

    Mixing antifreeze types is lookin' for trouble. If you don't
    know what's already in there, flush it out and start fresh.

  14. PAGeo

    PAGeo Member

    The loop was flushed and new mixture added. We still get freezing. After a whole day of trying everything, the tech tried removing the accumulator and running the FHP. It still froze. So, the only things that have not been changed are the heat exchanger and the compressor. Now we are waiting to hear if Florida is going to "approve" a replacement unit. Shouldn't they approve it, since it is under warranty? I have already contacted my attorney.:mad:
  15. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    I'm lost again...

    I don't see a connection between icing on the low side refrigerant components and composition / choice of loop anti-freeze.
  16. PAGeo

    PAGeo Member

    I did not see the connection either, but it was all part of their "shotgun approach" to solving the problem. Since we are down to the heat exchanger or compressor, could it be either one?

    I have told them for over a month that I want this whole unit replaced. I have also asked them for a quote on replacing the 10 year old air handler, so we can match them up. I have not received any satisfaction from this contractor or FHP.


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