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  1. #14
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,879
    The main unit with the drain problem may be as simple as the trap isn't deep enough.
    Or the return is a little small, which means you need a deeper trap since you won't get anybody to spring for return duct renovations.
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    How many times must one fix something before it is fixed?

  2. #15
    Join Date
    Feb 2008
    Location
    Western NC
    Posts
    2,504
    ok...

    so the fuction of reheat is not to cool the space but to instead remove more moisture.

    And it does this by cooling and then "reheat"ing(duh) the air. Thus the system continues to run without dropping the indoor temp. But the RH in the conditioned space does drop.


    So my next question would be this......does reheat only come on when the system has satisfied the temp but not the humidity? Or will the system energize the reheat valve even if the space is not down to desired temp?
    I fully support the military and the War on Terrorism.


    If you don't know, then don't do. If you don't know and still do, then be prepared to pay someone else a lot to undo what you did and then do it right.

    If you do know, then do. But do it right. Otherwise, you may not be doing it long.

  3. #16
    Join Date
    Mar 2004
    Location
    Austin, Texas
    Posts
    1,959
    If I recall the sequence correctly and the RH is above the RH set point -

    both stages of cooling calling - runs in 2nd stage cooling with no reheat

    one stage of cooling calling - this is the one I can't remember for certain but I think it goes into reheat

    no stage of cooling calling - definately goes into reheat

    There is one more 'gotcha' - it goes into reheat about every 20 minutes of compressor operation for 30 second to a minute to keep the oil from getting trapped in a shut off reheat coil.

    So the unit will run in some stage of cooling and/or reheat until there is no call for cooling or dehumidification.
    If "I have always done it this way" is a good reason to do it again, how many times do I have to do something wrong - before it becomes right?

  4. #17
    Join Date
    Feb 2008
    Location
    Western NC
    Posts
    2,504
    ok cool. Sounds good.

    Now what other information can you spit out there for all to read?


    Like I said before, this was the first time I saw these particular units. And I'm sure there are others out there that have been afraid or unsure as to how to ask the questions.

    Me, on the other hand, will come out with some pretty stupid questions. Just ask those in the refrigeration forum. They got a good laugh outta me here a few days ago.


    Again, thanks for all the info. I will be sure to pass it along to my fellow techs.
    I fully support the military and the War on Terrorism.


    If you don't know, then don't do. If you don't know and still do, then be prepared to pay someone else a lot to undo what you did and then do it right.

    If you do know, then do. But do it right. Otherwise, you may not be doing it long.

  5. #18
    Join Date
    Apr 2008
    Location
    Nashville
    Posts
    1
    Reheat on these units should not come on until the space temperature is within 1 or so degrees of space temperature setpoint. Cooling should take priority over dehumidification, as unit is dehumidifying during a cooling cycle. If dehumidification were to have priority during periods of high cooling demand the space temp would rise to an unsatisfactory level. Operating pressures will be as previously described- lower hp higher subcooling sp should be about the same as during the cooling cycle. I have seen these units in the field installed without a dehumidistat and the reheat will not ever work. As with alot of Trane equipment the wiring and options are usually all listed and it is sometimes difficult to know what options are installed on your particullar unit. The OM manual has a breakdown of the model number that will identify what options are on your unit. For example if the sixth digit is a 2 the manual will have a particular option so as factory installed reheat.

  6. #19
    Join Date
    Dec 2006
    Location
    Middle Tennessee
    Posts
    11,347

    *

    now if you really want to get confused wait till you see a set of heat pipes around an evaporator!

    its free reheat, which is totally unconected to the systems refigeration circuit, therefore you don't get the inherited oil migration scenario!



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