Attic Air Handler Dripping Water into Emergency Pan

futbole10June 19, 2011

Hello everyone,

I bought a house in Northern Virginia a year and half ago and the attic air handler is filling the emergency pan in about 5-6 weeks of use with the temperature set at 75 during the day and then 72 between 6 pm and 8 am. This unit has a Vision Pro stat on it (TH8321U1006). A week before my summer contract maintenance, I drained 3 gallons of water from the emergency pan when the unit was shut down by the float switch in the pan.

I have a contract for twice a year maintenance with one of the best HVAC companies in the entire DC area. They installed a Trane XL15i with humidifier and Honeywell VisionPro stat (TH8321U1006) last year for us on the heat pump for the main level and basemenet. It is great. It gets the humidity down to 41-42% on days where the heat index hits 105 and works wonderfully in the winter, where it has rarely used the heat strips (staged by the way using a thermometer installed outside).

In the summer checkup, they drained the attic condensate line and then used a high powered shop vac to vacuum the drains where they exit on the side of the house but the unit is still dripping into the emergency pan. I do see drips of water, and lot of it when it is really hot and the upstairs unit is running perpetually to keep the temperature setpoint. When they opened the unit they said the insulation was wet but the plastic pan inside the unit did not appear to be cracked. They said a new p-trap might solve this problem but they can't guarantee it because the unit is so old. I took many pictures of the water and the drip appears to happen underneath the drain port that has a cap on it. The underside of the air handler has droplets on it and the area closer to the drain ports is wet and dripping. Last year, there was water in the pan but that was an insulation issue where it was too loose and once the contractor fixed that, the sweating/water stopped.

I have already put in $600 into this unit and am not sure I want to throw more money at it if a p-trap can't guarantee this water issue will stop. What do you all think? Should I get a p trap? Are those waterless p traps better for this situation?

Please see the pictures.

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wet insulation provides zero insulation.
My thinking is that the attic temps are high
insulation is minimal inside unit. condensation forms.
over time the condensation wets the insulation
as it is saturated and can not absorb more water
it drips.
we have this in my area also.
dry existing insulation as much as possible.
sealing the pipe, electrical and mechanical & plenum connections will stop hot air from entering the unit.
(as hot air meets cold temps dewpoint is reached and condnesation forms)
insulate unit with R-8 ductwrap on all sides
even bottom.
the air sealing will stop attic air entry
the added insulation will lessen temp difference on

best of luck.

    Bookmark   June 19, 2011 at 2:41PM
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I want to thank everyone for their help and very good input. My awesome HVAC team put in an EZ Trap hooked up to kill the unit if the trap fails and a regular trap on the secondary. Since then the pan was dry but now a month after the install, there is a little water in the pan. I think it's from condensation with water dripping off the unit where the blower pumps the air into the main ducts. When I feel under there, I can feel droplets of water and these seem to be slowly dripping into the pan. The pan only has a 2 mm of water in it. This is the maximum amount of water in the pan and always in the same place and I've been checking every 4 hours.Is this a small amount of condensation dripping a big deal or something to be expected with an attic HVAC install? Is there anything I can do about it? Is there anything wrong with my unit? Please see photos below.

Here is a link that might be useful: Small Amount of Water in Pan after traps installed

    Bookmark   July 14, 2011 at 10:04PM
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If the backup pan has water it means the main pain is NOT draining correctly.

Use a shop vac to suck the drain clean.

    Bookmark   July 18, 2011 at 1:48PM
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so they drain the pan, but did not figure out what is causing enough condensation to fill it?

the pan filling up is a symptom
the problem is the excessive condnesation.

you've got a handle on where the water is dripping from.
if you open the unit the insulation inside the unit is wet
and exits where you described.
mastic seal unit connections and plenum connections
and externally insulate the unit.

its a good thing that your hvac company got the pan to
drain properly, but problem solving rather than part changing would solve the cause of condnesation.

    Bookmark   August 20, 2011 at 9:36AM
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Make sure you have a positive slope along the entire drain line. Years ago when I had a new unit installed in the attic they installed a new P trap where there was none before (now required.) At the right angle turn for the line below the main floor (basement ceiling) there was a section of the line that was negative slope which transitioned into positve. This negative section was acting as a P trap all along. Now, with the new P trap installed in the attic I had in effect TWO p traps causing an airlock in the line thus causing overflow into the pan. One P trap will prevent back suction. TWO P traps will prevent proper drainage of condensation

    Bookmark   August 25, 2011 at 4:41PM
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