Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit

Condensation in the air handler

When in doubt... TRAP


  • Mikey B
    Mikey B Member Posts: 9

    I just installed a Heil 13 seer A/C unit and it condensate so bad that it pours out of the cabinet and into the secondary drain pan. The air handler looks the same as i use to install years ago beside TX valve. what can cause such a problem> air handler not insulated proper. drain has a vent and blower in not sucking from coil, drain great? i am at a lost of how or what to fix?
  • Techman
    Techman Member Posts: 2,144

    Hi!Pressurers are needed!Trap first, then vent.Condensate is one thing(drain) ,condensation(of the cabinate)is another.Measure the ammount of drain water in an ammount of time.Air flow problems are more related to condensation.Have Fun!(Betterer? M.T.)
  • Empire_2
    Empire_2 Member Posts: 2,343
    Laughing Techman,,,,,....

    You'll see on the other post....:-) Also check the Pan itself...It's not common but I have found them cracked from shipping.....Also,..Which way is the "A" as in coil facing? just currious. You may have volocity issues..

    Mike T. Enjoy.....:-0
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    A number of issues

    1 - in order for the condensate to drain properly, the pressure at the inlet of the drain line (at the unit) must be higher than the pressure at the drain line termination point. If such is the case, the pan should drain properly. If not, see #2.

    2 - If the drain line in on the negative pressure side of the blower, the drain line must be trapped in order to allow the water to drain properly.

    3 - With the blower off, pour water into the drain pan and verify that the water will drain. Next, with the blower on, pour water into the drain pan and place the service panel back on the system. If the water does not drain, you are in need of a trap. To eliminate the need for this step, see #4.

    4 - Install a trap on the drain line. If the drain line needs a trap, it will thank you. If the drain line does not need a trap, no harm no foul, as the drain line will not hold this against you.

    5 - If you are referring to condensation on the equipment itself, you may very well have an airflow problem.

    6 - If your ductowrk is sweating, you have an insulation problem.

    7 - I am thinking that you definitely have a trapping issue, as the secondary drain line should always be completely dry.

    8 - If you are sweating, you are too hot... grab another beer.

  • bob_46
    bob_46 Member Posts: 813

    for carry-over ie water blowing off the coil or out of the pan down the duct.
  • Mikey B
    Mikey B Member Posts: 9

    I was always told by my old boss not to put traps in, due to it freezing and cracking. the A coil Facing ( < ) Could the blower be pulling off the coil as it condensates due to no trap? the flow of the Acoil pan and drain pan good. The drain pan are not built the greatest and always leave about 1/4" of water due to locating of fitting. I thank you all alot. Any more helpful hints would be great and I try it out. Thanks Mike
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    Oh Really?

    Think about it this way...

    If you have an ideal coil temperature of 40 degrees, the lowest possible temperature of the condensate on the coil will be, under absolutely perfect condition, 40 degrees.

    There is no way the condensate can freeze at 40 degrees.

    Even if the evaporator coil is completely frozen, the ice will just above 32 degrees, as the ice acts as an insulator between the return air and the refrigerant in the evaporator coil. Once again, no freezing.

    In order for condesate to freeze, it must come in contact with a surface or substance that is cooler than 32 degrees.

  • rucomfy
    rucomfy Member Posts: 43

    maybe his boss was referring to winter ambient and the standing water in the trap freezing.... Have never ran into this myself, but I guess there is always a first time.... For purposes of this discussion we will assume that the AHU is level and plumb. Possible coil blow off , some mfg will provide a baffle for this condition. Proper air flow did we use our magnehelic or just "assume" that we have the correct speed tap or board configuration for the nominal tonnage look for 350 per ton for optimum humidity control.... what is the TESP and is our velocity within range.. These suggestions may help.
  • larry_27
    larry_27 Member Posts: 1


    If you have a coil on the discharge of the blower motor there is no need for a trap because the air is blowing the condenstate out of the evaporator but if it is on the suction of the blower it is bring moist air into the evaporate to condestate which make more work for the compressor to cool properly that is the best way to think about it.

  • Techman
    Techman Member Posts: 2,144

    Morning!I find Traps solve condensate problems ,even when located on the positive press side of the blower. The positive press blows the condensate away from the drain fitting and air comes out of the drain not water.Enjoy your day!
  • jim lockard
    jim lockard Member Posts: 1,059
    And vent

    Always trap as Profes. said and then vent your drain line so as to not get the "pepsi in the straw" effect. J. Lockard
This discussion has been closed.


It looks like you're new here. If you want to get involved, click one of these buttons!