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  • condinsate traps

    im curiouse why allot of guys i talk to in the states trap their ac condinsate lines. i understand the purpouse when it comes to high efficient appliences, to keep gasses going out the exhaust not through the drain. but on ac? if it is running into a floor drain there is no sewer gasses. please explain. i see the trap a a place to cause blockages and a mold growing ground educate you canadian freind
    how is it that so many answers are in the instructions

  • #2
    Re: condinsate traps

    Originally posted by proplumb View Post
    im curiouse why allot of guys i talk to in the states trap their ac condinsate lines. i understand the purpouse when it comes to high efficient appliences, to keep gasses going out the exhaust not through the drain. but on ac? if it is running into a floor drain there is no sewer gasses. please explain. i see the trap a a place to cause blockages and a mold growing ground educate you canadian freind
    This is just a thought pro,but since mold is a concern,and the unit can draw air from the line,wouldn't the trap minimize spore content.

    This is only a thought.No hard evidence or proof.I Have to inquire from knowledgable A/C for the reason.

    Comment


    • #3
      Re: condinsate traps

      Im newish to the trade...but my understaning is a condenstae trap is required by code..also drain must be 12" from the wall to prevent termites or something like that....worked for 2 companies and on installs both put them in....and doing service usaly see them on installs done by other companies.

      I've always put 2 90's togher to get the trap. It keeps air but also insects and such out of the condensate line.....found a few frogs seting up house inside some non traped lines....comeing out of the wall... I got the ac leaking calls....removed the frogs and traped the line about 4" off the ground.


      from a personal stand point. I prefer to install a "French drain" under the condensate trap....plastic edgeing circle filled with some rocks about 6-12" deep....I think it makes a new change out/install look better than the trap just dribing on the grass.

      Comment


      • #4
        Re: condinsate traps

        Insects are a big part of condensate traps, also, in some states condensate drains are allowed to be tied to a vent system, nothing can be tied to a waste and vent system without a proper trap.

        Don't forget about your vent, installed before the trap, between the trap and the unit, to keep the trap functioning properly.

        Condensate drains also need to be drained in an approved location, an example would be that they are not allowed to drain on a sidewalk, etc. check your local codes.
        sigpic

        Robert

        Comment


        • #5
          Re: condinsate traps

          On a standard residential upflow/downflow system, I never trap the condensate line coming off the evaporator. I dont see a need to. I do install vents on all condensate drain lines. If its a horizontal application where the evaporator is in the return air stream, then it should have a trap otherwise it will suck air through the condensate line. Most often they will not drain until the blower shuts off. I've seen systems run for 15-20 minutes and not show a drop of condensate. Then the thermostat satisfies, the blower shuts down, and water comes running out like its a faucet. I've seen the same thing happen to condensing furnaces which have faulty drain system, because both heat exchangers are under a negative pressure.

          Keep in mind 99% of my condensate drains just dump into a floor drain in a basement. If there isnt a floor drain close I usually install a pump like the Little Giant VCM-15ULS and pump the condensate over to a washer stand pipe. Very very rarely I have a gravity drain that runs outside.
          Last edited by Ruudacguy; 10-07-2007, 06:47 PM. Reason: spelling

          Comment


          • #6
            Re: condinsate traps

            Just to add with what Ruud said. I had a very smart HVAC instructor who showed us how a condensate trap also causes a pressure drop allowing it to drain. He tried to explain it and he's an oustanding instructor but this ended up being one of those things that confused everybody. If this guy tells me something about AC then I take it as is and don't try to figure it out.
            Buy cheap, buy twice.

            Comment


            • #7
              Re: condinsate traps

              i never have drains go outside, so bugs are not an issue. i agree with allot of what ruudaguy had to say about the condensate being held in untill the call for heat has been meet.

              im curiouse about whar gearjunie has to say, on the two furnace brands that i put in the most they come with traps and of coarse they get used. the preassure drop idea is one that does seem like it would have some merrit to it, not sure where i can reaserch it further though. im a strong believer in venting my drains if they are changing allot in elevation or allot of turns.

              if there are anyother ideas or thouhgts allong with what you guys suggested im allways all ears
              how is it that so many answers are in the instructions

              Comment


              • #8
                Re: condinsate traps

                Ok, I will try to explain this,

                On a typical blow-through system (most common in residential) think of your condensate drain as a 3/4" hold in the duct, you are pushing conditioned air through the drain.

                If it happens to be a draw-thru system, you are pulling untreated air in system.

                IF you had a 3/4" in hole in your supply duct, you would patch it.

                For a trap to work properly, it should be such the "weir" depth is greater than the external static pressure the unit is capable of overcoming. Not trying to confuse anyone, I try and post a .pdf file of a detail I use on my mechanical designs.

                Regards,

                Comment


                • #9
                  Re: condinsate traps

                  Condensate drain, the main note is for a drawthrough, meaning to overcome the negative pressure, same holds true for blowthrough as well.
                  Attached Files

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                  • #10
                    Re: condinsate traps

                    So Biscuit, to get the depth of the trap right you need to know the negative pressure of the duct system?

                    Also, I thought most jurisdictions wouldn't want condensate dumped into the sanitary especially from high efficiency furnaces.

                    Comment


                    • #11
                      Re: condinsate traps

                      I'm new to this forum, so excuse me if I butt in on a conversation, but one major consideration for a condensate trap hasn't been talked about. I've found that without a trap, some units with negative pressure at the condensate line will draw air in with enough force that it will prevent the condensate from flowing out, leaving all the water in the condensate pan in the unit. On a long run-time, as under design conditions, the condensate pan will fill until it overflows into the unit. When the unit fan shuts off, the condensate will flow out, and the tech investigating the overflow will not find the condensate pan filled.

                      Comment


                      • #12
                        Re: condinsate traps

                        We are pretty informal here Ice no need to butt in

                        If you have something to say by all means speak up

                        We are a little short handed on HVAC guys but growing everyday it seems

                        Stick around and welcome to the Forum
                        Last edited by plumberscrack; 10-08-2007, 07:47 PM.

                        Comment


                        • #13
                          Re: condinsate traps

                          Originally posted by plumberscrack View Post
                          So Biscuit, to get the depth of the trap right you need to know the negative pressure of the duct system?

                          Also, I thought most jurisdictions wouldn't want condensate dumped into the sanitary especially from high efficiency furnaces.
                          You need to know the external static pressure, either positive or negative depending on fan arrangement. The coil section will either be under positive or negative pressure.

                          I have not seen a problem with jurisdictions in my area addressing your concerns.

                          I typically see residential piped into the sanitary and commercial usually piped to a storm drain if available for rooftop equipment and if inside, they are typically taken to the nearest floor drain.

                          Hope I have helped and not confused anyone.

                          Regards,

                          Comment


                          • #14
                            Re: condinsate traps

                            Originally posted by iceandfire View Post
                            I'm new to this forum, so excuse me if I butt in on a conversation, but one major consideration for a condensate trap hasn't been talked about. I've found that without a trap, some units with negative pressure at the condensate line will draw air in with enough force that it will prevent the condensate from flowing out, leaving all the water in the condensate pan in the unit. On a long run-time, as under design conditions, the condensate pan will fill until it overflows into the unit. When the unit fan shuts off, the condensate will flow out, and the tech investigating the overflow will not find the condensate pan filled.
                            iceandfire, welcome to the forums,

                            You bring up a valid point. I have seen similar situations on medium to large commercial equipment that was not trapped properly (not the correct weir depth) where the unit would retain water to a point and cause problems.

                            Regards,

                            Comment


                            • #15
                              Re: condinsate traps

                              Originally posted by iceandfire View Post
                              I'm new to this forum, so excuse me if I butt in on a conversation, but one major consideration for a condensate trap hasn't been talked about. I've found that without a trap, some units with negative pressure at the condensate line will draw air in with enough force that it will prevent the condensate from flowing out, leaving all the water in the condensate pan in the unit. On a long run-time, as under design conditions, the condensate pan will fill until it overflows into the unit. When the unit fan shuts off, the condensate will flow out, and the tech investigating the overflow will not find the condensate pan filled.
                              Welcome. Actually that has been brought up in post number 5 in this thread.

                              Comment

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