Problematic A/C condenser attic drain

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Giantsean

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Hi All,

Our upstairs air handler (installed in attic) has a problem with leaking, and because our installers were pretty much hacks, it's been a long struggle. This summer I finally want to get it right and prevent what happened last year (overflow into the ceiling joists/insulation). On occasion it backs up and I suspect it is not venting well (I added the 45 bend and long pipe to allow for a little more overflow space... before that it had a small cleanout stub w/ a cap..

The hacks installed a drain pan which is fairly well sealed. They also installed a float switch to shut off the unit, but it never triggers because the real problem is that the p-trap for the condenser is outside the reach of the pan, and was overflowing out of the top of the trap cleanout.

The A/H sits on foam blocks on a board across the joists, so my only choice to move the pan is to remove the trap, suspend the unit, and slide the pan over. I should have enough room to just make it. Have attached a few pics to illustrate.

This setup does not touch the sewer line or is exposed to sewer gas until the basement. The line drops from the attic down a vertical chase, then does a couple 90's until it dumps into a reducer set up as a catch pan. The reducer attaches to the sewer and is trapped.

Questions as follows.

- Should the vent be in front of the trap? (see example pic below inline), I assume in this drawing it just drains outside and not into the sewer line or else it could be exposed to gas.
- Knowing my setup is not exposed to sewer gas, do I even NEED to trap at the handler? (maybe I can just vent). I am thinking I could get a better slope without it.
- Any advice on how to keep the general area as dry as possible? I will try to seal/dope the pipe where it threads into the A/H. as mentioned will also try to move the pan under the pipe openings to better catch water.

I know it's a weird setup so appreciate any advice!

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Breplum

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1. The trap should have a vent as the illustration in bottom pic shows...so, a tee on its back with a stup up high enough, after the trap for the vent. Then a cap on the existing tee to prevent air wasted into unconditioned space.

Did the secondary/overflow hole get plugged? should not be plugged.
2. The second "overflow drain" port (it is there for a reason) that every coil pan has, should get a special overflow switch made for the secondary drain that will be wired with the thermostat to shut things off in the case of overflow. https://www.amazon.com/Rectorseal-9...&sprefix=ac+coil+saftey+switch,aps,141&sr=8-1
 

Giantsean

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Did the secondary/overflow hole get plugged? should not be plugged.
2. The second "overflow drain" port (it is there for a reason) that every coil pan has, should get a special overflow switch made for the secondary drain that will be wired with the thermostat to shut things off in the case of overflow. https://www.amazon.com/Rectorseal-97637-Safe-T-Switch-Ss2/dp/B005D4RFEM/ref=sr_1_1?crid=KFULOZ88764Q&keywords=ac+coil+safety+switch&qid=1687203586&sprefix=ac+coil+saftey+switch,aps,141&sr=8-1
There is no secondary in the pan... it does not sit high enough to make the drop (or they just cheaped out). A secondary drain may have helped take up some of the water from the pan but the real problem was not the pan overflowing but the water coming out of the cleanout outside of the range of the pan.

Thanks for the link I will definitely look into the switch.. when you say the 2nd port do you mean the one directly next to the existing outlet (ie this pic, not my unit but same corner)

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BTW do you have any recommendations for the pan switch aside from the one I already have? hopefully the one you recommended will solve the immediate problem but I could always use a good backup
 

Breplum

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Yes, secondary port is always next to "primary" port.
If no secondary, then maybe two tees, one for the vent on the long pipe run, one for a wired float switch.
A drain for the pan is also normal. There are off the shelf products too. Yes, the pan switch is good if everything around it were set up properly!
Dirtbag installers, for sure.
 

John Gayewski

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You need the trap. You'll be blowing cold air through your pipe without it. Not to mention other things that can happen.
 

John Gayewski

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Get an easy clean trap they have plugs on them. You should have a vent after the trap to allow atmosphere into your drain pipe especially as it drops a long way into the basement. So e-z trap, then pipe to where it drops, then use a tee as a 90 with a vent on top as it drops into the chase.
 

Jeff H Young

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I would not remove the trap, If positive pressure cold air will escape true , As it would from the secondary line? So I dont fully understand why or how it exactly matters one pipe blowing cold air better than 2 .
I dont think you have a problem with fall unless you have a bow or hump near the unit it appears it might .
I routinely see " safe t switches" installed in primary lines and secondarys very often plugged off I think many figure whats the need? The switch will shut down the condensor unit right? So a switch inside a pan (with no drain) and a plugged secondary I have seen , often the pan is added to a old system that presumeably didnt have a pan and it might not be connected to a drain.
I run condensate drains close to the units and leave all the traps and switches to the HVAC guy .
My quetion to anyone is how does the cold air not run out a open secondary line? putting a trap is pointless it will dry out
 

John Gayewski

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I would not remove the trap, If positive pressure cold air will escape true , As it would from the secondary line? So I dont fully understand why or how it exactly matters one pipe blowing cold air better than 2 .
I dont think you have a problem with fall unless you have a bow or hump near the unit it appears it might .
I routinely see " safe t switches" installed in primary lines and secondarys very often plugged off I think many figure whats the need? The switch will shut down the condensor unit right? So a switch inside a pan (with no drain) and a plugged secondary I have seen , often the pan is added to a old system that presumeably didnt have a pan and it might not be connected to a drain.
I run condensate drains close to the units and leave all the traps and switches to the HVAC guy .
My quetion to anyone is how does the cold air not run out a open secondary line? putting a trap is pointless it will dry out
I've never ran a secondary line, they always get plugged. I'm not sure sure it's actually a secondary line. I think you use either/or depending on how the unit is oriented. They can flip vertically or on their side.
 

WorthFlorida

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First check the PVC after the trap. From the pictures it appears to go uphill just a bit then slopes down. If this is correct, you have is a double trap that will never drain. The trap does not need a vent since there is air behind it.

This is my air handler in a second floor closet. The drain line is on the left to the TEE. The cap is for flushing out the drain should it back up. The trap is actually outside. The goes down below the slab, then outside with elbows to crate a trap. The secondary or overflow is the one on the right. It's about 1/3" higher and the main drain. The pipe has a SAFE-T-SWITCH that cuts out the 24v (Red Wire) to the compressor so it turns off the compressor and no longer cooling creating condensation. The air handler fan will still run. Some are wired that disconnects the red wire to the thermostat and shuts down the entire system.

For an attic system and the condensate line cannot be sloped properly, use a condensate pump. At my church with the same setup, only the overflow pan has a water sensor. If there is no other drain connection to the drip pan, I would install a SAFE-T-SWITCH in addition to the pan overflow at the tee before the trap. There are a few different models, one of which is built into a tee for this application.

In home attics the overflow pan should also have a drain line straight pipe to the out doors usually just tucked under roof line and past the facia. If you see water dripping then you know the main drain is blocked up. Over time it is very common for the main drain to plug up with mold and gunk. With Florida heavy humidity it happens quite often. There are tablets that you place in the drip pan to minimize mold growth.

IMG_6945.jpeg

shopping

 
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John Gayewski

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First check the PVC after the trap. From the pictures it appears to go uphill just a bit then slopes down. If this is correct, you have is a double trap that will never drain. The trap does not need a vent since there is air behind it.

This is my air handler in a second floor closet. The drain line is on the left to the TEE. The cap is their for flush out the drain should it back up. The trap is actually outside. The goes down below the slab, then out side with elbows to crate a trap. The secondary or overflow is the one on the right. It's about 1/3" higher and the main drain. The piping had a SAFE-T-SWITCH that cuts out the 24v (Red Wire) to the compressor so it turns off the compressor and no longer cooling creating condensation. The air handler fan will still run. Some are wired that disconnects the red wire to the thermostat and shuts down the entire system.

For an attic system and the condensate line cannot be sloped properly, use a condensate pump. At my church with the same setup, only the overflow pan has a water sensor. If there is no other drain connection to the drip pan, I would install a SAFE-T-SWITCH in addition to the pan overflow at the tee before the trap. There are a few different models, one of which is built into a tee for this application.

In home attics the overflow pan should also have a drain line straight pipe to the other doors usually just tucked under roof line and past the facia. If you see water dripping then you know the main drain is blocked up. Over time it is very common for the main drain to plug up with mold and gunk. With Florida heavy humidity it happens quit often. There are tablets that you place in the drip pan to minimize mold growth.

View attachment 93058
shopping

Your trap should not be that far below the coil.
 

Jeff H Young

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I've never ran a secondary line, they always get plugged. I'm not sure sure it's actually a secondary line. I think you use either/or depending on how the unit is oriented. They can flip vertically or on their side.
typical here on attic units is primary to a lav where we tie in with a wye branch tailpiece . and secondary dumps over a window so you are alerted that ther must be a back up.
when its a verticle unit in garage a lot of them dont have secondary lines this is my area my experiance and observation , I guess other places vary
 

Giantsean

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First check the PVC after the trap. From the pictures it appears to go uphill just a bit then slopes down. If this is correct, you have is a double trap that will never drain. The trap does not need a vent since there is air behind it.
The picture is a little deceptive, the pipe makes a slow bend down then drops where 2x10 joists become 2x8 (it's an added-on-to old house). That said, I definitely want to move those PEX pipes over the top of the drain pipe and isolate them better when I clean up that trap setup... all that plastic together makes an ungodly racket rubbing all over themselves when there is a call for heat :D

Sincere thanks for the great info fellas! I will definitely invest in a Safe-t-switch and try to back it up w/ the pan switch (maybe cut the AC call w/ the pan or just wire them both w/ R in series.
 
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