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Thread: THPRE

  1. #66
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    The compressor is hitting the high pressure switch not bypassing, unless bypassing turns the compressor and fan off. Off at 610 and back on at 400 in under 1min. From cold start up it takes about ten min to get to this point -- then it stays there! Yes I do worry about the longevity of the compressor--do scroll compressors have reed plates? Can they vary the speed of the compressor to change pressures?

  2. #67
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    Charged incorrectly the same way 3 times, is still an incorrect charge.
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    How many times must one fix something before it is fixed?

  3. #68
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    Oct 2005
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    It looks as though the evap coil is turned 90 degrees from its intended position. The top of the blower might be restricting the outlet of the coil. That would definitely explain the low static pressures. That TXV installation looks like hell. Sorry.

  4. #69
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    Fort Worth, TX
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    You could take all the ducts off, but if the charge hasn't been changed, it can still indicate as overcharged.

    A heat pump outdoor coil is sized to reject heat from the indoor coil, refrigerant superheat, heat of compression, and compressor motor heat when the system is in cooling mode. In other words, it can reject more heat than the indoor coil can pick up, in most cases. In heating mode, this margin of extra capacity is very small. The indoor coil can quickly run out of room, as far as ability to dump heat, if any one or more of the following factors are out of whack: Airflow, refrigerant charge, lineset size and length.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  5. #70
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    Most logical answer so far!! Yes check me was during the summer. Protocol he used?? Reading the report - True flow plate measured air flow1403;charge test med

  6. #71
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    Quote Originally Posted by THPRE View Post
    I think I can say optimal in that we are talking about reducing head pressure, not overall system function or performance. This test was done at the request of the Goodman representitive. I was watching the gauges when the ducts were disconnected under the house thus providing increased [optimal] air flow. I have no way of knowing what the changes were to the static pressure or the cfm with the ducts open and the filter removed but the pressures did not change. And after all the static measurements were taken with the system operational except that the filter was removed. Air flow static pressure was measured at .3 total . with fan at 144 cfm was 2140 , with fan at 88 cfm is 1647. I'm told you expect approx. 400 cfm per ton is that correct? How does a heat pump manage the difference in refergerant needs from cooling [large condenser] to heating with a smaller condenser?
    I think those numbers (144 88) are actually pressures in pascals and refer to a cross reference chart when the flow plate is used to verify air flow. Unfortunately my cross reference chart is at the shop. I'd hope he's using the value for the 20x20 flow plate and not the 14x20 plate.

    Anyway if the airflow really is that high then it was probably charged in the cooling mode every time.

    If that's the case, have the technician charge the system using the winter protocol. He probably added (and documented) 2-3 lbs of refrigerant as per the summer protocol. He can remove that amount and then adjust as per the winer protocol. Since the system utilizes an indoor txv it will adjust for the conditions.

    Again this assumes That your airflow is correct.

  7. #72
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    Jan 2013
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    Yeah--it looked better before the first time he replaced the tx valve . I told you early on he is a friend - not a the best tech. But he is a hard worker and is not charging me for all these service calls. This is why I have had another company out here doing the check me and duct work. They are well regarded in this area for their expertise. I guess I have no idea if the evap coil is oriented correctly or if it restricts the air flow. Pictures have been sent to Goodman they should know.

  8. #73
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    Quote Originally Posted by THPRE View Post
    Most logical answer so far!! Yes check me was during the summer. Protocol he used?? Reading the report - True flow plate measured air flow1403;charge test med

    Make sure you Read my last post.

    Our target airflow should be 1600. With your low static readings it should be easy to achieve the 1600 CFM that's recommended. Assuming that the blower isn't on it's highest speed already. The blower default is 2000 CFM so it likely has been adjusted down.

    I'm still Leary of that coil position.

  9. #74
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    Quote Originally Posted by THPRE View Post
    Most logical answer so far!! Yes check me was during the summer. Protocol he used?? Reading the report - True flow plate measured air flow1403;charge test med
    That would be low air flow for a 4 ton.
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  10. #75
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    Everything you say sounds correct as to the measurements. The system has been charged at least twice for winter and then will not cool in summer without adding refergerant. This system has been charged so many times I have lost rack - but is always the same result - take it out for winter and add it back for summer.

  11. #76
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    What would you expect?

  12. #77
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    Pacific Northwest
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    Quote Originally Posted by THPRE View Post
    Everything you say sounds correct as to the measurements. The system has been charged at least twice for winter and then will not cool in summer without adding refergerant. This system has been charged so many times I have lost rack - but is always the same result - take it out for winter and add it back for summer.

    That's a classic airflow problem. The 4860 evap coil should be the right coil.

  13. #78
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    Quote Originally Posted by THPRE View Post
    What would you expect?
    1600 as per post 73. 1400 CFM is allowed to pass the check me test. The test allows for airflow as low as 330 CFM per ton.

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