School me on this condensate drain.

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Because the pan under the air handler in the attic was full, which thankfully shut the system down. But the condensate drain is working. The pan does not have a drain itself. I sucked out two wet/dry vac loads of water out of the pan and the system is running again but I can’t figure out why the pan filled up if the condensate drain is flowing.

My first question, are all these test caps supposed to be secured on these three holes? Because they were. House is nine months old and this HVAC system is 30 years newer than the last system I tended in our last house so I’m slightly out of my depth. There’s also a piece of PVC pipe with a cap on it stuck in a fourth hole. It easily pulls out. See pic below. It looks like a secondary drain with a P-trap that is open over the pan.

Second question, assuming those four caps/lids/whatever are correct, how the heck did my pan fill up, because as mentioned, the condensate drain is flowing fine. There was some condensation on a small area of the bottom of the air handler, also pictured, but I’m guessing this isn’t what filled up my pan.

@jjwestbrook

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After evacuating the water from the pan
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Condensation on the bottom of the airhandler over the pan

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If the pan is full, and not draining, then the drain is plugged. It might be plugged right where the drain is connected to the pan. That's because what's plugging it is wet, stringy dust globs that end up in the pan when your filter gets plugged and dust blows by. It can be frustrating, when you cannot see or feel a blockage, but it's there. Keep blowing compressed air into it, while blocking the upstream end, and clean the pan if you can. You may need to modify the drain to make it easier to maintain. I made a disconnect downstream, so I could see crap coming out. I also made a disconnect just downstream of the trap. Those caps are to help you in this situation.

Change your filters!
 
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Can't say for sure because I know about as much about AC as you do but I feel like the pan should have a drain also otherwise any water that goes in it must evaporate or sit there. Might need to get a pro to check the system or you could just add a drain to the pan.
 
If the pan is full, and not draining, then the drain is plugged. It might be plugged right where the drain is connected to the pan. That's because what's plugging it is wet, stringy dust globs that end up in the pan when your filter gets plugged and dust blows by. It can be frustrating, when you cannot see or feel a blockage, but it's there. Keep blowing compressed air into it, while blocking the upstream end, and clean the pan if you can. You may need to modify the drain to make it easier to maintain. I made a disconnect downstream, so I could see crap coming out. I also made a disconnect just downstream of the trap. Those caps are to help you in this situation.

Change your filters!
The pan doesnt gave a drain. And the condensate drain is flowing. When I play around with all those caps/lids/covers over the stacks in the drain line it messes with the dynamics of water flow due to escaping air from the blower, and I see condensate being pushed out the secondary drain which overflows into the pan depending on if those caps are on or off. When I take one or more of the caps off everything flows and condensate doesn’t get pushed out that secondary drain into the pan. I just looked at my next door neighbor’s unit inside and his stacks on the Ptraps to the condensate drain aren’t capped at all.
 
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You should have a condesate drain running out of the house somewhere, usually near the compressor. Algae can block this drain causing the condesate to flow into the pan which has a shut off switch for when it gets full. Get a nozzle adapter for a wet-dry vac and go to the end of the drain line (outside) and suck out the gunk. I have to do this every year at my house.
 
You should have a condesate drain running out of the house somewhere, usually near the compressor. Algae can block this drain causing the condesate to flow into the pan which has a shut off switch for when it gets full. Get a nozzle adapter for a wet-dry vac and go to the end of the drain line (outside) and suck out the gunk. I have to do this every year at my house.

Condensate drain was never plugged best I can tell. That’s what is weird. Once I drained out the pan and dried off the shut-off sensor in the pan the system started running again. This generated condensate and it began draining outside like it should. I think there is some weird dynamic that these caps cause (pictured^^) because my neighbor's system has open stacks on the condensate drain and mine has those caps on it. I have a cap off of the stack on the p-trap for the condensate drain now and everything seems to be behaving, rather than pushing condensate out the secondary drain which overflows into the pan. At least I think that’s what’s happening.

The system is still under warranty from the installer and they are coming out to eyeball it this afternoon.
 
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1. The holes on the air handler are the primary drain off the condensate pan under the coil. The second one is a higher level drain off the same pan. Both have a p-traps it looks like. One hole should be slightly higher than the other off the air handler.
2. The red caps remain plugged and are for adaptations and cleanouts to use a brush.
3. The pvc riser with a cap is usually not glued nor does it need to be because it is above gravity flow. Some installers do not put a cap on it but air will be sucked out of the attic into the unit and that takes more energy and adds humidity.
4. If you pour water into the pipe which is slightly lower than the other AND water exits the pipe outside, the issue is not the drain. See 5.
5. If you have low air flow from dirty coil, dirty filter, or a motor not operating at speed the coil inside the attic or crawl space air handler OR you have a leak and the coil is freezing into a layer of ice. The ice will melt outside of the dimensions of the pan. The pan is only slightly wider than a coil. When it thaws it will drip into the air handler cabinet and leak into the secondary safety pan which will activate the drain pan safety level switch.

Note: Change filter, determine if air entry side of coil is clean. Shine light thru the coil on the return duct side. Clean if a layer of dust or crust is on it. If it’s clean make certain the fan is turning at maximum speed. Do not run the fan in the on position. Run it in auto fan. Make certain all supply registers are open and not blocked by rugs and furniture ( never, ever, ever shut registers in any room). If the above items are good then you most likely are low on refrigerant which causes the coil to freeze into a black of ice until it goes into the off cycle.

Note 2: It appears to be a gas furnace with a cased AC coil attached. The way it’s installed is normal but not ideal. You will never clean that coil without sliding out the coil and that’s not going to happen with refrigerant in the system.
 
Installer sent out a tech who seemed competent. He took one of the caps off as pictured below, added a stack to the Ptrap in the primary condensate drain, and added a union to the condensate drain to make it easier to blow out or suck out that line with the shop vac. He wasn’t happy how the ptrap on the secondary drain was cut off and will refit a different set up there with a cut off switch later.

Filters are clean, and unit is only nine months old. It worked fine immediately after I drained the pan, and has been working fine all day. Hopefully it will continue to do so.

IMG_2126.JPG
 
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WTH? At this angle it looks entirely different. Is the unit hole on the left still open somehow to the outside? Jeez what a mess.
 
WTH? At this angle it looks entirely different. Is the unit hole on the left still open somehow to the outside? Jeez what a mess.
I just called. They are coming back out tomorrow. He twisted that secondary to the right to get the open end of the ptrap higher that you see on the left, but it’s still filling up with water. He’s talking about removing that and putting another shut-off switch on it somehow. I’m at somewhat of a loss.
 
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I just called. They are coming back out tomorrow. He twisted that secondary to the right to get the open end of the ptrap higher that you see on the left, but it’s still filling up with water. He’s talking about removing that and putting another shut-off switch on it somehow. I’m at somewhat of a loss.
Shut off switch for what? Did it not shut down the outside unit when the galvanized pan filled up with water? Is that brown switch not the cutoff switch when detecting water? The answer is yes.
 
Shut off switch for what? Did it not shut down the outside unit when the galvanized pan filled up with water? Is that brown switch not the cutoff switch when detecting water? The answer is yes.

I believe he’s talking about a second shut off switch that has something to do with that secondary drain. I’m pretty competent mechanically but I don’t know wth he was talking about. It will get discussed tomorrow. I have a highly competent guy I have used for years on multiple properties I manage, but I have been deferring to the original installers of this Trane system in this new house since it’s still under warranty.

The current shutoff switch in the pan worked last night thankfully. It will remain. I’ll know soon enough about this second shutoff he’s talking about. I might have to veto it.
 
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I believe he’s talking about a second shut off switch that has something to do with that secondary drain. I’m pretty competent mechanically but I don’t know wth he was talking about. It will get discussed tomorrow. I have a highly competent guy I have used for years on multiple properties I manage, but I have been deferring to the original installers of this Trane system in this new house since it’s still under warranty.

The current shutoff switch in the pan worked last night thankfully. It will remain. I’ll know soon enough about this second shutoff he’s talking about. I might have to veto it.
Good luck. Not being on site is like a doctor diagnostics over the phone.
 
Good luck. Not being on site is like a doctor diagnostics over the phone.
I understand, and appreciate the counsel. It’s been a wonky thing. New system worked great all summer. If they don’t straighten it out tomorrow, I am pretty sure my guy can get ‘er done, even though it is under warranty. I don’t mind throwing a couple hundred bucks at a problem if I can make it go away.
 
My old system did this all the time. I just took the air compressor and blew air up the drain lines and all was good. Every once in a while pour a little Clorox down the line if you can.
 
My old system did this all the time. I just took the air compressor and blew air up the drain lines and all was good. Every once in a while pour a little Clorox down the line if you can.
I suctioned mine out about 5AM when I discovered the full pan, and reversed the wet/dry vac to blow this afternoon, and blew it out this afternoon after the tech put a union on the line that makes it easier to accomplish. It’s still misbehaving somewhat. We’ll see what their plan B is tomorrow
 
I know this is a Captain Obvious call but, is it possible the drain line doesn’t have a continuous and sufficient fall?
 
Just out of curiosty and guessing here but does that sump pump in the pan normally pump the water out to the drain or is it normally gravity from the unit, if normally pumped is it on a gfci breaker? Just curious if that wire that is not attached and wire nutted might be hanging down in the water and tripped it out?
 
At the condo I have a float switch that fits into the condensate drain, maybe he’s talking about installing one of those.
 
Just out of curiosty and guessing here but does that sump pump in the pan normally pump the water out to the drain or is it normally gravity from the unit, if normally pumped is it on a gfci breaker? Just curious if that wire that is not attached and wire nutted might be hanging down in the water and tripped it out?
That’s just a sensor in the pan to shut down the system when the pan fills up.
 
I know this is a Captain Obvious call but, is it possible the drain line doesn’t have a continuous and sufficient fall?
Possible. The system in on cinder blocks in the floor of the attic. The drain line travels maybe
I know this is a Captain Obvious call but, is it possible the drain line doesn’t have a continuous and sufficient fall?
The air handler sits on blocks in the attic, and the drain travel maybe 15-18 feet to the wall and then drops one floor where it drains
 
Possible. The system in on cinder blocks in the floor of the attic. The drain line travels maybe

The air handler sits on blocks in the attic, and the drain travel maybe 15-18 feet to the wall and then drops one floor where it drains
Check to be sure there’s good fall all the way along that run. When they installed mine, the total fall was sufficient but there were a couple “high spots”. If it isn’t falling all the way, the liquid never gets to the point where it drops downstairs.
 
Also, even assuming the fall is continuous, you might wanna measure the height of the pipe on both ends of the run (at the bottom of the p-trap on the air handler side) to see how much total fall you have over that distance.
 
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Check to be sure there’s good fall all the way along that run. When they installed mine, the total fall was sufficient but there were a couple “high spots”. If it isn’t falling all the way, the liquid never gets to the point where it drops downstairs.
I did have a low spot I corrected earlier today.

The condensate drain has drained all summer, visibly outside. Just not sure what happened last night. There are some weird dynamics with having those stacks over the two p-traps closed. The tech opened one, and hopefully we’ll get some corrections on that secondary drain tomorrow that drains into the pan.
 
Something else to check... I had a system installed and they didn't remove the knock-out plug before screwing in the pipe nipple for the drain. Didn't find out until the humidity got high and it dripped faster than it could evaporate.
 
When they put in that union today, did they put one at the other end too? If so, you could take the pipe off and look through it to make certain there’s nothing left inside.
 
When they put in that union today, did they put one at the other end too? If so, you could take the pipe off and look through it to make certain there’s nothing left inside.
It runs out over rafters to where it would be hard to get to. It would be a pain to put another union on it. I don’t think the primary drain is the problem. Something hinky with the secondary ,and that’s what is filling up the pan, I’m pretty sure.
 
Last idea...

You mentioned that the unit worked perfectly up until this week. I assume the amount of water you had to suck out with the shop vac was more than would have been expelled in all the months you’ve run the ac. In other words, it was drainig just fine, even with the strange plumbing they did, until recently. That says to me (and I’m not a tech nor did I stay at a Holiday Inn last night) that their plumbing isn’t the major issue and that something recently got (and remains) plugged up with grunge.
 
The drainage drama settled down after I quit screwing with it yesterday afternoon, and 24 hours later every thing appears to be working like it’s supposed to.
 
Which air handler drain hole is higher than the other in the picture. Left or right? You only need the lowest one to have a adequate drain. The higher one can have everything everything removed and the p-trap with stand pipe installed to the lower one.

If the coil is freezing up inside the cabinet it will not be a drain pan or drain line issue.
 
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