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Thread: THPRE

  1. #53
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    Jan 2004
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    Lancaster PA
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    Quote Originally Posted by THPRE View Post
    Ok but if the system was wide open in the return and had a 16in. duct removed from the plenum and I was still watching 610psi to 400psi in under 1 minute cycles there must be a further prob;lem? I mean that with sstatic pressure minimal and cfm close to 2100 there should not be an air flow problem causing the 610 high side?
    Might mean they had to over charge it in cooling mode to make it work with the low air flow.
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  2. #54
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    Jan 2013
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    TRAIL,OREGON
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    THPRE

    The return air pressure was taken at the air filter louvered opening with the filter removed and with the outside air vent open and closed. open was .04 and closed was .05. the other reading was right at floor level under the coil and blower. this was .25. These two readings gave the total of .30. The air handler sits in a very tight fitting closet,it is larger than the original electric heat unit. We had to remove the door and the door frame to get the unit in. The face is closed with a removable piece of sheet rock. This will be made permanent once the unit works. so above the air handler there is a space close to the same size as the air cabinet and approx. five feet tall above the air handler with the outside vent at the top and the filter opening on the front side. below the air handler there is a reasonable sized plenum with the original rectangular duct on one side and the new 16in. duct on another side. The 16in. was removed when we were on the phone with Goodman and there was no change in refergerant pressures. We were not reading static air pressures at this time .

  3. #55
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    I must have misled you somehow. The two reading are different. Return is .05 and supply is .25 giving the total of .30. Yes I am in Oregon. 25miles up the Rogue River from Medford. The coil cabinet is on top with the blower underneath. Whole unit is about 6 inches off the floor on a sheet metal duct the same size as the air blower cabinet--this goes directly through the floor and becomes the under house plenum. This plenum is at least 24in. deep
    under the house not including the part on top of the floor or the thickness of the floor. I will try to get pictures. Thanks THPRE

  4. #56
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    So was the air filter removed, along with the outside air vent open, when it was charged in cooling mode.

    Now, put the filter in, keep the louvered door closed, and then take the static pressure. Static pressure must be taken with the system operating in its normal set up to be accurate, or any indication of what is going on. The removal of the filter is not part of its normal operating conditions, so those static checks are meaningless.
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  5. #57
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    Ok but with filter out and duct off under house the air flow is optimal and the system was still not functioning. 610 to400 psi cycles in less than one minute. And yes everything was in place when the system was charged.

  6. #58
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    Then the cause goes back to low air flow when it was first commissioned. And you haven't had a good tech out there yet. Seen what you describe more then once already.
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  7. #59
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    pictures from THPRE

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  8. #60
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    Not great pictures and no I'm not going under the house if I can help it!

  9. #61
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    Aug 2003
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    Fort Worth, TX
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    Quote Originally Posted by THPRE View Post
    Ok but with filter out and duct off under house the air flow is optimal and the system was still not functioning. 610 to400 psi cycles in less than one minute. And yes everything was in place when the system was charged.
    Then it's likely overcharged, just as beenthere said.

    You can't say airflow is "optimal" until it has been correctly measured. Judging by your prior posts, we don't yet have an accurate assessment of airflow. You have to assure correct airflow on a heat pump or its a nightmare of problems, as you are seeing firsthand. This can't be measured by intuition or hope. Only by correctly obtained data.
    • 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.

  10. #62
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    Jan 2013
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    TRAIL,OREGON
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    The unit has been charged at least three times with present air flow. Still the basic question - cools well with proper pressures,heat mode with optimal air flow pressures 610 high side? How come?

  11. #63
    Join Date
    Oct 2005
    Location
    Pacific Northwest
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    2,266
    This is a variable speed blower. How are static pressure readings going to tell us the air flow for certain anyway?

    The "check me" diagnostic test was developed to verify that the correct speed settings were chosen by the installer for the variable speed motor.

    The test is also supposed to verify that the charge level is correct.

    Did your installer use the summer or winter protocol for the "check me" diagnostic test?

    I've personally done many check me tests. I've learned that the summer protocol is useless for heat pumps. The problem is that the summer protocol forces the technician to charge to a specific subcooling value. This is guaranteed to produce an over charged heat pump in the heating mode especially on goodman equipment. The factory target subcooling value is just to high.

    The winter protocol for the check me diagnostic test should be used.

    The technician should be installing the flow plate for the test in the air handler or duct work. It sounds as though he's putting the plate in the filter grille?

    I suspect that the blower speed selection is to low and the check me test may not be accurate.

  12. #64
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    Aug 2003
    Location
    Fort Worth, TX
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    Quote Originally Posted by THPRE View Post
    The unit has been charged at least three times with present air flow. Still the basic question - cools well with proper pressures,heat mode with optimal air flow pressures 610 high side? How come?
    It has been charged three times with nobody verifying if airflow was correct or not. You need to realize that with heat pumps, there is more "slop factor" on the cooling side than the heating side regarding airflow. Not that this is a good thing. It just allows subpar techs to get by until the compressor dies. If none of the techs who charged this system while it was in cooling mode paid any attention to superheat or subcooling readings, they were not in a good position to catch refrigeration cycle problems. If airflow is not good on this system, which seems evident, then it will indicate such in both heating and cooling modes when measuring the refrigeration cycle.

    As for why your head pressure at the moment keeps swinging back and forth, the compressor could be internally bypassing. It won't live much longer if that is the case.
    • 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.

  13. #65
    Join Date
    Jan 2013
    Location
    TRAIL,OREGON
    Posts
    68
    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?

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