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  1. #1
    Join Date
    Aug 2013
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    Condensate puddle in drain pan.


    I just wanted to know if the following conditions are normal, or they are problematic and need to be solved - not searching DIY's.

    I live in a humid desert, where in summers the dew point becomes like 25 deg C (Outdoor temperatures 40+ deg C).

    My building has central a/c, that is we dont have to pay for air-conditioning only - it is exempt from electricity bills.

    I dont know what is the outdoor unit like, whether the whole building has combined outdoor unit, or each flat has separate outdoor unit, dont know about about outdoor unit if its water cooled or whatever...

    Indoor, above the false ceiling in our flat, we have the fan-coil unit. The capacity of my fan-coil unit is 6.4 tons (77200 Btu/hr). Each flat has their own fan coil unit. There is one fan coil unit for the entire flat, which provides air to different rooms using ducted system.
    (Ducts supply air to Home=Kitchen+Hall+Bedroom+Bedroom+Another Room)

    Last summer I had severe problem of moisture in home, which could either be due to-

    1) Over-sized Air-conditioner - not running long enough / cooling very quickly

    2) Air infiltration from outside - humid air leaking into home which condenses since the temperature indoors is below due point of outside air. We discovered a small hole in the wall above the false ceiling, which was near the fan coil unit. So once the air conditioner is done cooling, the fan would still work, however part of the air going into the fan coil unit could be outside air, which is "humid air" which can spread everywhere. "Possible cause"

    3) Or combination of both of the above.

    We had overcooled the home during this period to keep the compressor running longer, and this had abnormally overcooled the floor tiles. This was further contributing to the problem since any of outside air entering the home (while opening the door) would condense on the floor because it was cold as ice.

    Anyways i am trying on small fixes to limit the problems before summer comes such as trying to reduce air infiltration by filling a cloth in wall (blocked 80% of hole), trying to cool the home only as much required and not overcooling to keep floor temperatures suitable. And changing the air flow in each room such that better results are achieved (the room receiving almost no sunlight has the least airflow so it doesnt overcool in long run - this was one of the most affected rooms by-the-way, so better to keep it little warmer). Preparations in progress before peak summer arrives. So far so good.

    Now i am searching for a thermostat with auto fan function so it goes off after its done cooling, since my thermostat has no auto fan function, only 1,2, and 3.

    Coming back to the point, i recently discovered an old cloth lying in the drain pan, which the technicians must have left which installation of our fan coil unit last year. So i decided to throw it, since it looked moldy,slimy and all. After removing the cloth i found out there is about 1 inch - 3/4 inch deep puddle of water in the drain pan. Its an open drain pan. The drain pan has a drain pipeline to drain water. The water in the drain pan was all dirty, slimy, moldy and dirty.

    So i somehow made the drain pan dry and cleaned it. Just to check if the drain line was not blocked, i poured more than 5 liters of water to check for overflow. It didnt look blocked. What i guess is that drain line is not placed properly such that water can properly flow through the line until it reaches a certain height of say 1 inch. So there is always standing water of 1 inch and any more water will automatically flow in the drain line.

    I wanted to know if this lying water contributes to the moisture problem?
    Because as of this month (when outdoor temperatures are around 25 deg C - 38 deg C) when i use the air conditioner regularly with quite lots of air infiltration reduced from that hole, all things stay good when the compressor is on, but just after the compressor turns off, it starts feeling stuffy and uncomfortable in fan only mode. Infact it feels better without the fan after the compressor goes off.
    So i wanted to know can this lying water in drain pan cause this problem of moisture and stuffy air?? Is this normal, or do i need to get rid of this standing 1" water.

    Two major problems-
    1) Moisture/condensation on floor during peak summer.
    2) Stuffy/humid/uncomfortable air coming after compressor switches off.

    Some pictures of my indoor fan coil unit can be found on this link. There are a couple of videos too, please forgive the rotation of the video.

    Thanks for reading so much, I guess the more I elaborate, the more you professionals can understand and help me identify my problem.

  2. #2
    Join Date
    Sep 2003
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    Maybe you could give us an idea of square footage in your flat.

    Leaving a rag in a dark wet place (evao coil) invites all kind of nasties to grow on it.

    Good catch

    I would also try and find out what unit that serves this fan coil unit.

    Unless your place is taj mahal like in size, I would suspect it is oversized

    But more info is needed.

  3. #3
    Join Date
    Aug 2013
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    Thread Starter
    Ok a very very rough measurement.

    Maybe its like 105 metre square or 1130 ft square.
    Very approximate - +/- of 50 ft square possible.

    So before closing the false ceiling, just decided to pour 2 more liters of water..

    Found this on the video that only the top layer of water being drained slowly
    The pipe is place in such a way that drain line cannot rely on gravity until the certain height of 1 inch is reached as I mentioned before.
    Another picture/video added in same link. It'll take a while to upload and appear.

  4. #4
    Join Date
    Aug 2013
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    Thread Starter
    Found out some more info about the fan coil

    Fan coil unit pdf :
    Model Number - dyp 18/60 LH WG

    direct drive series
    ceiling suspended with plenum
    18 unit size nom. x 100 cfm
    6 rows for cooling coil
    0 rows hot water coil
    Type of cooling coil - Chilled Water Coil
    Galvanised Finish

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