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  1. #1
    Join Date
    Jan 2005
    Posts
    8

    Question

    Hi,

    We have an add on cooling unit to our central heating. It's a Pioneer, 3 phase, 19kw unit. The house is approx. 32 squares. The heating and cooling is zoned separtely upstairs and downstairs. There is a return air vent both upstairs and downstairs. The whole system, and house, are only 3 years old. The thermostat is a Brivis Networker.

    The problem is, the larger of the two copper refrigerant pipes from the indoor coils to the outdoor unit that is covered with foam insulation(I think it's the suction line) becomes frozen because the refrigerant is being forced back to the outdoor compressor. When this happens, the copper pipe freezes up like a balloon, and the indoor temperature keeps rising. The whole air conditioner stops cooling, even though the fans and compressor keep running, and the whole system just wastes electricity.

    If the air conditioner has not been used much (ie, if there haven't been many hot days during summer), it fires up and works perfectly. However, the pipe seems to freeze whenever it's been working hard during the day, and there's a drop in outdoor temperature (such as a cool change, common in Melbourne Australia during the summer). The outside temperature will drop, inside temperature in the house will rise from about 23 degrees C to 25 or even 26 degrees C. The compressor will continue to work all night, with the pipe frozen, and the temperature will not drop unless it's significantly colder outside (yeah, I know this wastes money, but it's uncomfortably hot to sleep at night).

    Furthermore, if the unit has been working all night with the pipe frozen, and hot weather has been forecast for the remaining few days, the a/c will continue to struggle, and the pipe will remain frozen (I guess because the unit hasn't been off long enough for the refrigerant to unfreeze).

    Now for the interesting part - the a/c company who installed the system cheated on us and installed non-genuine Pioneer coils in the roof, without our knowledge or permission . We only found out when another a/c repair company inspected the coils in the roof. And of course, that same a/c company has gone bankrupt (I wonder why), no longer exist, and of course we now have no warranty .

    Some other information -

    - The first repairman was "not so smart", and reversed the polarity on the compressor, and over-filled the unit with freon, so the compressor would pop and bang when switched on, and not run at all.

    - The second repair company, sent by the builder, fixed the above, and drained and re-filled the unit again with freon. But ever since he did this, the pipe has been freezing even worse, and the cooling problems became worse. The cooling capacity was always suspect, and the pipe would always freeze to some extent, but not as badly as it has done last summer and this summer.

    - The second repairman fitted a thermostatic expansion valve (TXV) near the compressor on the outdoor unit. We both thought this would fix the problem, but when he hooked up his guages to the unit, it still did weird things, like working perfectly for 5 minutes, before sending refigerant back to the compressor again, and freezing the pipe, and then unfreezing and working perfectly again after a few more minutes.

    I have been reading the following website to try and diagnose the problem, but my knowledge of a/c units is limited :
    http://www.longviewweb.com/coolfix.htm

    In summary, considering all of the above, I can only conclude :

    a) The unit is overcharged with refrigerant. Perhaps both repairmen are incompetent, and are not sure what the correct amount of refrigerant the unit requires.

    b) There are not enough return air grills in the house for the unit. Less likely, imo, as the unit cools adequately unless the pipe is frozen, as described above.

    c) The non-genuine indoor coils are incompatible with the Pioneer outside unit.

    d) The whole compressor and outdoor unit are screwed, and need to be taken out the ocean and attached to a anchor and chain

    Any advice would be appreciated

  2. #2
    Join Date
    Mar 2004
    Location
    NJ
    Posts
    1,214
    Some of your statements have to be seriously wrong especially the one about the TXV location....Either way it sounds like atotal mess plus a few different "techs" seem to have all tinkered with it which makes it hard if someone new comes out but what I would like to know what temperature are you setting the system at 80 degrees F? 75 degressF?sorry celsius is not my gig.
    thehumid1-------I live in NJ, a state where it's free to come in but you have to pay to leave!

  3. #3
    Join Date
    Jan 2005
    Posts
    8
    The inside temp on the thermostat is never set below 22 degrees C / 71 degrees F.

  4. #4
    Join Date
    May 2003
    Location
    Dixie
    Posts
    1,344
    filter dirty, coil dirty, low on ref. to name a few....find yourself a compentent tech

  5. #5
    Join Date
    Jan 2005
    Posts
    8
    Thanks for your help.

    The filters in the return air vents are not dirty. They are cleaned regularly. Both techs went into the ceiling and said the coils weren't dirty. Is incompatible coils the answer, or is there not enough airflow to the unit (ie, not enough return air vents) ? Is there any way to adjust the fan speed to the return air vents ?

    Could there be any reason why the system is blocking excessively with ice now ? It's only been worse after the second tech filled with freon. The pipe has always frozen to some extent since day one, but not to the extremes it is now, and before the techs touched it, the system still cooled even if the pipe was a little frozen.

    Thanks !

  6. #6
    Join Date
    Mar 2004
    Location
    NJ
    Posts
    1,214
    It should never freeze and 71 degree setpoint on 100 degree F day in the outback isnt going to happen but there are way too many variables for me to even suggest what the problems are... starting from what seems to have been a bad install to the other info given find someone competent like was said.
    thehumid1-------I live in NJ, a state where it's free to come in but you have to pay to leave!

  7. #7
    when you get someone to look at it have them recheck the amount of refrigerant,expansion valve,and make sure the evaporator fan is working.also make sure the sensing bulb is installed correctly.if that dont work visit your inlaws for a while.

  8. #8
    Join Date
    Jun 2001
    Location
    San Diego, CA
    Posts
    1,149
    This is not a problem with a simple solution. The entire system needs to be evaluated. If it's a good design, any good technician will fix it easily. If it's not a good design, he'll tell you that too.

    Could be a fan problem, could be a refrigerant problem. Could be the components are mismatched, could be the TXV is not adjusted or installed properly. Could be there's air in the system. All of these need to be considered and any tech worth a bag of hammers will check all of this and find the problem.

  9. #9
    Join Date
    Jan 2005
    Posts
    8
    Techs were back again today.

    I showed them a copy of the Pioneer a/c installation sheet I had lying around from when the unit was purchased. Seems that the liquid line is smaller than it needs to be. Spec sheet says half a inch, the line running to the ceiling is smaller. The installers welded a smaller liquid line to the half inch pipe inside the a/c condensor unit.

    They will come back next week and replace the liquid line and fit a TXV next to the condensor unit.

  10. #10
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    Originally posted by losiho
    Hi,

    We have an add on cooling unit to our central heating. It's a Pioneer, 3 phase, 19kw unit. The house is approx. 32 squares.
    I think you lost most of us at that point.

    What is a "square"?
    What capacity in BTU's would 19kw translate to?

    Most of us on this forum are in north America and have no experience with the equipment you have. Hopefully one of the Brits or someone will be along soon and have some ideas for you.
    If more government is the answer, then it's a really stupid question.

  11. #11
    Join Date
    Apr 2004
    Posts
    10
    I think we are all in serious need of more data to be able to help. If I had to guess, your system is suffering from a lack of airflow. An expansion valve maintains a specific amount of superheat so with a low airflow situation the superheat will drop. This will cause the valve to close off even more thereby dropping the suction pressure which lowers the saturation temperature of the refrigerant well below freezing and it only gets worse after the coil starts to frost up, it is a vicious cycle that snowballs (no pun intended) the longer the system runs. I would like to know what the temperature split is across the evaporator, superheat, subcooling, pressures, etc. Also, what type of refrigerant??? R-22???

  12. #12
    what kind of ref is in this system maybe r22 with a 410a exp?
    had that happen before. works great till you get a hot day!

  13. #13
    Join Date
    Nov 2004
    Posts
    2,927
    Originally posted by mark beiser
    Originally posted by losiho
    Hi,

    We have an add on cooling unit to our central heating. It's a Pioneer, 3 phase, 19kw unit. The house is approx. 32 squares.
    I think you lost most of us at that point.

    What is a "square"?
    What capacity in BTU's would 19kw translate to?

    "Square"=10ft. by 10ft.=100sqft.=3200sqft.
    A term mostly used by roofers.Metric might be different.

    1 watt=3.41 btu
    19 kilowatt=64790btu

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