Air Conditioner: Cold Air blowing hard out the PVC Drain?

Question

I have a brand new house and all summer long have had problems with my air conditioner. I was in my attic tonight and noticed that there is cold air blowing hard (harder than it blows out of the vents in my house) out of the PVC drain pipe. The pipe comes out of the AC unit and T's immediately. The bottom portion of the T forms a "U" and then runs Parallel with the ground and goes out of the attic. The top portion of the "T" is open and that is where the extremely cool air is blowing out.

The unit is a 3 ton, 12 SEER American Standard. 1800 Sq Ft House.

What vents do you think are closed? The vents in the house are open and on one end of the house air blows fairly strong. The other end air blows very weak. I'm not sure what vents you think are closed, please explain.

I think capping it would be a huge mistake if it did get plugged up. Any other ideas?

That still doesn't explain why the air is coming from the PVC pipe. Even without the dampers set, would the air just blow harder out the other end of the house? Should air be blowing out the drain pipe? I went in my neighbors attic and his wasn't blowing out the drain pipe.

Answer 1

only a few things can cause what you have explained,,, the one most often is the coil is stopped up,,,needs cleaned or the filter is stopped up,,, causeing blow back, the second thing is ,,, that the coil has been placed on the wrong side of the air handler, mabe there was not room to put it in the return side so they installed it in the supply side,,,, this sounds like what you have,,, this is installed wrong,,, you will have alot of problems out of it,,, it will become stopped up very often and you are very likely to have water damage not far in the future if not corrected,, the way to check for this is take the cover off unit, feel the air blowing,,,,,, the fan should be pulling through the coil,,,not pushing through it,,,, hope this helps,,,,

Answer 2

I have this same issue. Place a PVC cap on the open pipe, but as another poster said, don't glue it. Why? Because you need to be able to pour a little diluted bleach in there to clear anything that might grow and plug the drain. I do that every spring to make sure that the drain is clear. Also, I do the same for the secondary drain that goes from the external drain pan to outside the house. The trick there is to get the diluted bleach into the drain only - not in the galvanized pan (it can corrode it). Good luck.

One poster wrote:

"the fan should be pulling through the coil,,,not pushing through it"

Not necessarily . If you have a gas furnace (as I do) the blower will be forcing air over the cooling coil, not drawing air through it - this is what produces the positive pressure and air coming out of your drain.

One poster wrote:

"Do not cap that tee. You may cause an air-lock by doing so and cause water to overflow."

Simply put, this is impossible. The drain is connected to a free flowing air stream - YOUR AC!

Answer 3

The pvc pipe is supposed to be dripping water, condensation, not so much air.

You have a blockage, I bet none of your vents are open. Get a flashlight and look up in those vents. They MUST be closed.

Usually, in mine, there is a small slotted piece of plastic for a screwdriver to fit that can turn EASILY to open the vents or some other type of way.
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Ok well, if you are sure all the vents in the house are open and the one side of the house is blowing weak then it's got to be a damper that is closed on the duct work in the attic.

In the attic, try to trace the duct going to where the air is weak. Start from the output of the ac unit. Somewhere on the duct there has to be a small metal handle. It will only turn 1/4 turn, clockwise and counter-clockwise, don't force it. It's probably near the junction between the ducts that blow hard and those that don't. This damper acts to balance the flow of air around the home, but it's turned all to one side, the nut holding it together might be loose.
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If you don't find a damper handle and the vents are really open then, there must be some other blockage on the inside of the duct. Get a good duct cleaning person who has a camera to send up there and have a look see.
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Right, not much air should be coming out of the drain pipe. For the amount of air that you say is coming out of the pipe, there must be a clog or blockage that is preventing the air to go through your house. It has no where to go but out the drain pipe. It sounds like the ducts that go to one end of your house are turned off or otherwise blocked.

Answer 4

Don't plug it if it shares a drain line with your furnace.

• If an air conditioning coil is installed with the furnace, a
common drain may be used. An open tee must be
installed in the drain line, near the cooling coil, to
relieve positive air pressure from the coil’s plenum.
This is necessary to prohibit any interference with the
function of the furnace’s drain trap.

Answer 5

Do not cap that tee. You may cause an air-lock by doing so and cause water to overflow.

It is normal for some cold air to blow out of the tee, but it is not normal to have minimal air flow on one side of the house. Have your builder call the company that installed your HVAC system and ask them to do a courtesy check.......... Good luck.

Answer 6

http://www.google.com/search?hl=en&lr=&safe=off&q=Cold+Air+blowing+hard+out+the+PVC+Drain%3F

Answer 7

cap off the top of the tee. master plumber

Answer 8

Put a cap on it but don't glue it.