OK if cold air from condensate tube?

cdsolAugust 29, 2007

Central A/C unit located in attic. I had to unclog my primary condensate line when I noticed water accumulating in the pan that was coming from the secondary drain tube. Is it normal for cold air to blow out of those tubes? I assume the relatively small amount of cold air discharged into the attic doesn't amount to much, and to close it off would defeat its job of draining condensation. Am I missing something?

Thanks!

Carl - Dallas TX

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garyg

Usually, the air handler fan sucks air in from the condensate drain if there is no p-trap installed in the drain.

    Bookmark   August 29, 2007 at 12:35PM
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don21

The P-trap usually keeps any cold air from blowing out the condensate line because the trap is full of water and the air pressure isn't high enough to blow the water out

Don

    Bookmark   August 29, 2007 at 9:04PM
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cdsol

Thanks for replies. My terminology may not be exactly correct, but here's how things unfolded. There was no water in the line connected to the T-tube. I'm assuming that is the primary condensate line. Water was dripping like crazy from the other tube sticking out (I'll assume that's the secondary condensate line)and into the pan. I poured water into the T-tube and it flowed freely downstream, so I ran a wire up the other direction and also blew it out with compressed air, then water trickled down that tube and the secondary tube went dry. It's the secondary tube that's blowing out cold air.

    Bookmark   August 29, 2007 at 9:28PM
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garyg

Without the P-trap, my air handler sucks air from the condensate drain. It doesn't blow air from the drain, as the drain is on the suction side of the blower.

I once had to cut the PVC drain to re-route it (removed the p-trap), and left a bucket temporarily under the cut piece. Once the a/c and air handler turned off, water gushed from the cut drain pipe. The condensate was able to overcome the suction of the air handler after it filled the drain pan and built up enough head pressure. With a p-trap, condensate water flows easily into the drain. I never realized how important the p-trap is to drain flow until after I temporarily removed it.

    Bookmark   August 29, 2007 at 9:31PM
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brickeyee

"It doesn't blow air from the drain, as the drain is on the suction side of the blower."

The vast majority of systems have the evaporator coil after the fan, and thus at a higher pressure.
A squirrel cage blower is better at pushing than pulling.

    Bookmark   August 29, 2007 at 10:22PM
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cdsol

Well the tube with an open end coming out of my unit (which is the tube that was dripping before I cleaned out the one with the T-tube)is the one blowing cold air. But I mean it's BLOWING cold air! Could it be that in my unit it tube is on the wrong side of the fan?

    Bookmark   August 30, 2007 at 6:54AM
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garyg

"The vast majority of systems have the evaporator coil after the fan, and thus at a higher pressure."

- I guess I'm the odd man out with a heat pump and back-up electric strips. From the bottom up: it's the A-coil, then the blower, then the electric strips. Air is drawn thru the A-coil at the bottom and blown out the top of the air handler.

    Bookmark   August 30, 2007 at 10:23AM
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dallasbill

OK... this has me really confused.

On our system, there is a secondary line for the overflow pan.

The is also a primary condensate line, with a p-trap, that feeds into the sink in the bathroom below. On that line, one foot out where it leaves the coil box, it has an upside down T that is open, and cold air blows out of it. What is that for? My HVAC guy said it's OK to cover it with tape -- I just use it in heating season to pour a bleach-water mixture in so that the p-trap stays full.

Can I cover up a similar T in the other system (it blows cold air out) that uses an external pump (with overflow safety) to move the condensate out to the drain?

    Bookmark   August 30, 2007 at 11:13AM
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brickeyee

If there is a pipe stub get a cap and push it on.
If the stub was omitted you could glue in a stub (you only need about 2-4 inches of pipe) and then push a cap on.
The pressure is so low (less than a few inches of water) the cap will not pop off if you push it on firmly.

    Bookmark   August 30, 2007 at 9:20PM
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cdsol

Well I thought of capping it off, but that would defeat its purpose in the event the primary condensate tube became clogged again.

    Bookmark   August 31, 2007 at 12:28AM
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dallasbill

Thanks brickeyee.

cdsol... Not in my case -- there is already a secondary. This is a T stubbed up on the primary line.

    Bookmark   August 31, 2007 at 11:02AM
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brickeyee

"Well I thought of capping it off, but that would defeat its purpose in the event the primary condensate tube became clogged again"

What?
If the line gets clogged the pan will spill on the floor, the same as the tube.
If the unit is over finished space that could be damaged a secondary pan and drain is required.

The T is to clear the line, not act as an overflow.

    Bookmark   August 31, 2007 at 7:53PM
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cdsol

Brickeye - thanks for your reply.

I think you misunderstood. I didn't mean capping off the stub. I meant capping off the secondary tube (the one without the T and drips condensation into the pan if the one with the T fails). That's the one blowing cold air, not the one with the T. Of course I won't cap it off 'cause it wouldn't drain if it had to.

I'm simply trying to understand whether I need to be concerned because that secondary drain tube is blowing cold air into the attic.

Carl

    Bookmark   September 2, 2007 at 8:23AM
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garyg

I would not want any conditioned air blowing (wasting) into the attic.

    Bookmark   September 2, 2007 at 8:58AM
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brickeyee

The secondary pan is not usually even be in the air handler.
It is a pan under the air handler with a separate drain.
They are not usually trapped since they are not under any air pressure.
What kind of equipment is this?

    Bookmark   September 3, 2007 at 3:11PM
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cdsol

How 'bout if I email'd you guys a digital pic? Is there a way to include an image with a post? Otherwide I'd have to send it to each of you individually.

/Carl

    Bookmark   September 3, 2007 at 7:40PM
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saltcedar

I much prefer to upload my FULL sized photos to Photobucket.com, (it's Free!)
then just copy the "HTML Tag" Just Below each photo on your photobucket
page. Next paste that "Tag" into the message (right here) in the body
of the post on GardenWeb.
You can also do multiple Pic's in the same post. Simple and
no resizing and you can see your pictures when you preview the
post before you click the "submit message" button.

HTH
Chris

    Bookmark   September 3, 2007 at 8:08PM
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mr_havac

Uhhh, hey, is that like some kind of picture of the rolling stones? :-)

    Bookmark   September 3, 2007 at 8:14PM
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saltcedar

Seeds Man! Seeds;-)

    Bookmark   September 3, 2007 at 8:21PM
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garyg

Those look like kidney stones. Ouch, that musta hurt.

    Bookmark   September 6, 2007 at 7:48AM
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