# Condensate only drains when blower stops



## yuri (Nov 29, 2008)

Thats a LOT of words. :yes: Take some pics of it and post them here (manage attachments) or the links to photobucket here. We really need to see what you have. I have had to put open tees on the drain where it leaves the coil and sometimes add a vertical extension piece or pipe or clear tubing on the tee to break the vacuum or alter the pressure on the drain so it will flow properly. Takes some trial and error to get it right. Did someone change the fan speed recently?


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## sethmorgan (Jun 26, 2010)

yuri said:


> Thats a LOT of words. :yes: Take some pics of it and post them here or the links to photobucket here. We really need to see what you have.


Yeah sorry for the thousand words; a picture is much better. Attached is the best pic I have for now.



yuri said:


> I have had to put open tees on the drain where it leaves the coil


If the tee is open, cold air blows into the attic. I can't imagine that would be good for efficiency.



yuri said:


> and sometimes add a vertical extension piece or pipe or clear tubing on the tee to break the vacuum or alter the pressure on the drain so it will flow properly. Takes some trial and error to get it right. Did someone change the fan speed recently?


You mean if the vertical portion of the tee is longer, it modifies the pressure in the drain? That's interesting. Didn't know changing the fan speed was possible, but I had begun running it constantly, which is what caused the overflow pan to fill up. But no, the speed hasn't been changed.

Thanks for the response! :thumbsup:


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## Marty S. (Oct 31, 2009)

Elaborate a bit about those three highest rated filters. Hopefully you don't have three of the 3m filters in one system.


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## sethmorgan (Jun 26, 2010)

Yeah, is that not good? :confused1: The whole family has allergies and they seem to help. 

3M Filtrete Ultimate and Elite Allergen filters:

20x25 - 2200 MPR
14x20 - 1900 MPR
12x12 - 1900 MPR


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## beenthere (Oct 11, 2008)

What size is the A/C?

Take another pic or 2 of the case coil set up. So we can see how the plenum is attached to it, and how the duct work is attached to the plenum.


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## biggles (Jan 1, 2008)

why are there 2 PVC lines off that air handler...do they both connect inside to the pan?the emergency pan shouldn't have a white drain pipe run to it it is only installed when the pan overflows and hits the insulation and drips out the panels...and the one shown that looks like the main condensate drain doesn't have a trap on it.there aren't options to install on the neg/pos sides it is the design where the coil and fan are that gives it that result....either or they have to be trapped


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## Marty S. (Oct 31, 2009)

biggles said:


> why are there 2 PVC lines off that air handler...do they both connect inside to the pan?the emergency pan shouldn't have a white drain pipe run to it it is only installed when the pan overflows and hits the insulation and drips out the panels...and the one shown that looks like the main condensate drain doesn't have a trap on it.there aren't options to install on the neg/pos sides it is the design where the coil and fan are that gives it that result....either or they have to be trapped


Looks to me like there's a trap in the primary side but it's in backwards. Around here there's a good chance that trap would freeze and break before drying out. Secondary goes into the emergancy overflow pan which is the piped seperate. Perfectly acceptable to do that but I prefer a float switch. Secondary has to be used here if the unit is in a hidden place, can't leave the plug in and jut let it overflow the coil into an emergancy pan.


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## sethmorgan (Jun 26, 2010)

Here are some better pictures.

Secondary pan has a float switch and also a drain that runs outside next to the primary drain line.


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## beenthere (Oct 11, 2008)

Take a piece of duct tape(or whatever). Put it over the secondary drain line, so it traps the water it there. Then see if the primary drains better.

Looks like you may have a velocity problem through the coil. The air may be carrying the condensate past the primary drain and pushing it out the secondary.

If so. Just install a small trap on the secondary(running trap, so it evaporates the water come heating season).


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## sethmorgan (Jun 26, 2010)

beenthere said:


> Take a piece of duct tape(or whatever). Put it over the secondary drain line, so it traps the water it there. Then see if the primary drains better.


I tried capping it before. The internal pan just fills up until the blower shuts off. Then all the built-up water in the pan rushes out the primary.



beenthere said:


> Looks like you may have a velocity problem through the coil. The air may be carrying the condensate past the primary drain and pushing it out the secondary.
> 
> If so. Just install a small trap on the secondary(running trap, so it evaporates the water come heating season).


This is sort of what I was thinking. Bad design?


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## beenthere (Oct 11, 2008)

Not a bad design. As much as probably not set up right.

Can you measure the air temp at the return of the furnace. And in the plenum right after the coil.
If not. then the temps at the nearest return grille and nearest supply register. Thats not as good as knowing what the temps are at the unit though.

Along with model number of the outdoor unit, the indoor coil, and the furnace model number. Furnace model number is inside the burner compartment.

With that info. We know what size your equipment is, and what size blower your furnace has. Along with temp rise across the coil. We may be able to determine if the air flow is set too high.


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## Marbledust (Jun 26, 2010)

You need an airgap...put the trap first and the airgap second.


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## sethmorgan (Jun 26, 2010)

beenthere said:


> Not a bad design. As much as probably not set up right.
> 
> Can you measure the air temp at the return of the furnace. And in the plenum right after the coil.
> If not. then the temps at the nearest return grille and nearest supply register. Thats not as good as knowing what the temps are at the unit though.
> ...


I'll get that info ASAP


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## sethmorgan (Jun 26, 2010)

Marbledust said:


> You need an airgap...put the trap first and the airgap second.


An airgap?


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## biggles (Jan 1, 2008)

you have 4 PVC lines there? the one with the trap is your main the one down to the emergency pan needs to be removed and plugged the one behing the gas valve is the emergency panel it should be on the insulated base of the fan(not off the condensate pan.right now if it is,and seems to be on the positive side of that coil it is pressurizing the atmospheric side of the main trap and that is why your no draining.the other line going into the curb..what and where is that going..but definitly cut that one behing the gas valve and drop that down to the emergency pan....TOOOOO many connection for a simple drain out of a horizontal unit:whistling2:


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## Marty S. (Oct 31, 2009)

sethmorgan said:


> An airgap?


Take your hose fitting and turn it so the opening is up. Creates a vacuum break so the line drains better. Everything is piped correctly according to the latest photos. Actually overkill with a float switch on the emergancy pan and a drain from it also. Guessing there was just a float at one time and somebody got tired of loosing cooling so added the drain line.
Check and see if the coil is level or slighty canted toward the primary drain.


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## sethmorgan (Jun 26, 2010)

beenthere said:


> Can you measure the air temp at the return of the furnace. And in the plenum right after the coil.
> If not. then the temps at the nearest return grille and nearest supply register. Thats not as good as knowing what the temps are at the unit though.


Air temp at the return of the furnace: 74.7
Air temp at nearest supply register: 69.6



beenthere said:


> Along with model number of the outdoor unit, the indoor coil, and the furnace model number. Furnace model number is inside the burner compartment.
> 
> With that info. We know what size your equipment is, and what size blower your furnace has. Along with temp rise across the coil. We may be able to determine if the air flow is set too high.


International Comfort Products:
Outdoor unit: NAC048AKC3
Indoor coil: EPM48F19CT1
Furnace model: N8MPN075F16A1


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## beenthere (Oct 11, 2008)

4 ton unit, with a 4 ton blower. So it shouldn't be a velocity issue per say. 
The low supply temp doesn't sound right though. And would indicate a air flow problem.

How much condensate are you getting out? Does your house feel clamy, like the humidity is too high.


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## beenthere (Oct 11, 2008)

4 ton unit, with a 4 ton blower. So it shouldn't be a velocity issue per say. 
The low supply temp doesn't sound right though. And would indicate a air flow problem.

How much condensate are you getting out? Does your house feel clamy, like the humidity is too high.


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## sethmorgan (Jun 26, 2010)

beenthere said:


> 4 ton unit, with a 4 ton blower. So it shouldn't be a velocity issue per say.
> The low supply temp doesn't sound right though. And would indicate a air flow problem.


I measured the temp at the nearest supply register which is in a closet, so the reading may be due to the narrower duct; maybe flow is the problem there (for measurement purposes). I can remove the coil access panel and take a measurement there, but I hate to re-mastic again 



beenthere said:


> How much condensate are you getting out? Does your house feel clamy, like the humidity is too high.


Seems like quite a bit of condensate drains out. When I was running the blower 24/7, the secondary pan had an inch of water in it within 12 hours. We're humid here in the south, but my indoor hygrometer reads between 45% and 50%. The house doesn't feel clammy but I may just be used to it.


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## beenthere (Oct 11, 2008)

Removing the panel would give a false reading. Since some of the air would bypass the coil. And give you a colder air temp coming out of the coil.

One thing you can do. And yep, you'll have to remastic the panel.

Is get a sheet of plex glass. Cut the same size as the panel. Remove the panel, and seal the plex glass in its place. Run the A/C, and watch what happens to the condensate. And see if its is being blown off of the coil. Or help toward the upper end of the drain pan.

Or if the drain pan is leaking(cracked maybe).

Sometimes a cleaning of the coil, will eliminate this type of condensate problem, sometimes not.
I've seen more then one coil that became so dirty, that the air that bypasses the coil near the drain pan is so much, that it blows the condensate off the drain pan.

You need to look at the coil side toward the furnace. The top side(discharge) can look clean, while the other side looks like its covered with a blanket.


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## sethmorgan (Jun 26, 2010)

beenthere said:


> Removing the panel would give a false reading. Since some of the air would bypass the coil. And give you a colder air temp coming out of the coil.


I meant removing the panel to insert the thermometer, then remastic.



beenthere said:


> One thing you can do. And yep, you'll have to remastic the panel.
> 
> Is get a sheet of plex glass. Cut the same size as the panel. Remove the panel, and seal the plex glass in its place. Run the A/C, and watch what happens to the condensate. And see if its is being blown off of the coil. Or help toward the upper end of the drain pan.
> 
> Or if the drain pan is leaking(cracked maybe).


Great idea! I'll try that and let you know.



beenthere said:


> Sometimes a cleaning of the coil, will eliminate this type of condensate problem, sometimes not.
> I've seen more then one coil that became so dirty, that the air that bypasses the coil near the drain pan is so much, that it blows the condensate off the drain pan.
> 
> You need to look at the coil side toward the furnace. The top side(discharge) can look clean, while the other side looks like its covered with a blanket.


I foamed the coil thinking if it was clogged with dirt, the air would pass around the sides to where the drain is located, but that didn't seem to help.

I appreciate all the help.


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## beenthere (Oct 11, 2008)

If a coil has a blanket on its inlet side. Foaming cleaner won't get through the blanket.

I wish it would.


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## sethmorgan (Jun 26, 2010)

I think I've discovered the problem. Where the inlet side of the coil mates up with the framework is a little space that looks like it allows air to blow by. Raising up the coil makes it flush. And is it supposed to be this rusty?


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## mastertech (Mar 14, 2011)

*condensate issues*

ok sir from reading the different posts in my opinion this should help you out.#1 this is a gas furnace so the need for the p trap is useless.The p trap is designed to keep the unit blower from creating a negative pressure on the drain while its running.This is a gas furnace and the blower is making it a positive pressure.Im not sure but is the air vent before the trap? I would remove the ptrap and just run a line straight out.You can put a tee in the line to allow air to help it drain and yes the air will come out the fitting.You can just allow the condensate to drain on its own.:thumbsup:to be honest with you the things you are posting is when a system doesnt have a ptrap and the drain is a negative pressure.The system wont drain untill the unit shuts off.In my neck of the woods people dont know how to plumb the a/c condensate line correctly and you see it happen ,the unit stops and water gushes out onto the roof.Its kinda funny!:thumbsup:


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## hvactech126 (Nov 11, 2010)

1mastertech said:


> ok sir from reading the different posts in my opinion this should help you out.#1 this is a gas furnace so the need for the p trap is useless.The p trap is designed to keep the unit blower from creating a negative pressure on the drain while its running.This is a gas furnace and the blower is making it a positive pressure.Im not sure but is the air vent before the trap? I would remove the ptrap and just run a line straight out.You can put a tee in the line to allow air to help it drain and yes the air will come out the fitting.You can just allow the condensate to drain on its own.:thumbsup:to be honest with you the things you are posting is when a system doesnt have a ptrap and the drain is a negative pressure.The system wont drain untill the unit shuts off.In my neck of the woods people dont know how to plumb the a/c condensate line correctly and you see it happen ,the unit stops and water gushes out onto the roof.Its kinda funny!:thumbsup:


You realize this thread is from 2010?


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## sethmorgan (Jun 26, 2010)

1mastertech said:


> ok sir from reading the different posts in my opinion this should help you out.#1 this is a gas furnace so the need for the p trap is useless.The p trap is designed to keep the unit blower from creating a negative pressure on the drain while its running.This is a gas furnace and the blower is making it a positive pressure.


Doesn't the P-trap also act as an air barrier to prevent some of my "bought air" from just blowing outside?



1mastertech said:


> Im not sure but is the air vent before the trap? I would remove the ptrap and just run a line straight out.You can put a tee in the line to allow air to help it drain and yes the air will come out the fitting.You can just allow the condensate to drain on its own.:thumbsup:


Yes, the air vent is before the trap. You can see how it's set up in the pictures on page 1. If I remove the vent cap this accomplishes the same thing.



1mastertech said:


> to be honest with you the things you are posting is when a system doesnt have a ptrap and the drain is a negative pressure.The system wont drain untill the unit shuts off.In my neck of the woods people dont know how to plumb the a/c condensate line correctly and you see it happen ,the unit stops and water gushes out onto the roof.Its kinda funny!:thumbsup:


I just had the spring maintenance/inspection done on the system. My HVAC guy seems to know what he's talking about and told me he's seen plently of incorrectly installed systems. And this one was installed correctly. Thanks for chiming in, even though the thread is from last year. I have just resigned myself to having the vent cap off.


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## mastertech (Mar 14, 2011)

I would like to know why is there such old posts left on this site.That seems kinda shall we say a waste of everybodys time? If the post is that old why leave it up there.Im sure the people that posted it definitly got there answers Im sure.Anyway it seems a waste of timwe to post on something thats that old.


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## beenthere (Oct 11, 2008)

1mastertech said:


> I would like to know why is there such old posts left on this site.That seems kinda shall we say a waste of everybodys time? If the post is that old why leave it up there.Im sure the people that posted it definitly got there answers Im sure.Anyway it seems a waste of timwe to post on something thats that old.


Because many people do a search for the answer to their problem, and find the answer in old post, instead of having to ask the same question in a new thread.


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## sethmorgan (Jun 26, 2010)

I'm still having the problem, am still living with it, and would still love to find a solution.


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## Hubcap626 (Feb 12, 2011)

I've seen when the trap is the wrong size or it's not primed air will suck in not allowing for it to drain out until the fan shuts off.


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## sethmorgan (Jun 26, 2010)

Hubcap626 said:


> I've seen when the trap is the wrong size or it's not primed air will suck in not allowing for it to drain out until the fan shuts off.


Does lack of prime also apply to a positive air pressure situation? Air blows out of the trap on my system.


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## Hubcap626 (Feb 12, 2011)

sethmorgan said:


> Does lack of prime also apply to a positive air pressure situation? Air blows out of the trap on my system.


Yea it could just dump some water down that cleanout and make sure the trap is filled with water. If that doesn't do it I would be willing to bet that trap is not the right size.


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## Technow (Nov 12, 2010)

No, positive pressure drains shouldn't have traps. Doesn't matter if the trap is filled or not on positive pressure drains.


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## sethmorgan (Jun 26, 2010)

Interesting. So it's normal to have cold air blowing to the outside? Not trying to contradict the professionals, I'm actually wondering this. Seems to go against all the preaching about sealing air leaks in the home. I thought another reason to have a P-trap with a water barrier was to keep critters from getting inside. I shudder at the thought of a palmetto bug (roach) getting into my HVAC system and dropping out of one of my vent registers.


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## beenthere (Oct 11, 2008)

Many techs don't trap positive pressure drains. Myself, I do.


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## Artco (Sep 23, 2010)

Why don't you get the installation instructions of the coil for a horizontal installation. It looks like the drains should be on the opposite side of the coil and usually on a blow through coil you don't need a p trap. Some horizontal installs require you to relocate the pan.
How is the coil install? verticle or pitched towards the air handler or away from the air handler? Is it a flat coil or "A" type coil?
Did this system operate OK in the past? Maybe the three filters are causing too much air restriction and causing the coil to ice up.
Are all the supply registers open?
Is the return grille blocked?


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## sethmorgan (Jun 26, 2010)

That makes sense that the drain should be on the opposite side. So I guess it was installed wrong. The previous three HVAC techs that have come out to do bi-yearly maintenance all confirmed that everything looked ok so go figure.

The coil is an "A" type, with the base of the A facing the blower and the tip facing downstream towards the direction of airflow.
The cleanout tube was discovered removed when I bought the house. When I replaced it this issue was discovered.
All the supply registers are open and none of the returns are blocked.

Thanks for the input.


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## Artco (Sep 23, 2010)

Are both the inside and outside of the coil clean?
Are you getting good airflow through the supply registers?


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## sethmorgan (Jun 26, 2010)

The outside of the coil is clean, but I can't see the inside to tell. Is it possible to view the inside from the blower area? I flushed the coil with low pressure water from the top last year when I was initially troubleshooting this so hopefully it's clean on the inside too. The air flow from the registers seems sufficient; it's not blowing my hair if I stand under one or anything, but the unit is able to maintain the thermostat set point without being on an inordinate amount of time.


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## Artco (Sep 23, 2010)

Maybe with a mirror & light thru the blower compartment.
There may be a dust build up.
Is air bypassing around the outside of the coil?
Has the system ever drained right?


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## sethmorgan (Jun 26, 2010)

I'll check this tonight.

The system hasn't drained right since I discovered the cleanout tube wasn't installed and reinstalled it.


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## Artco (Sep 23, 2010)

CHECK OUT THIS SITE. IT MAY BE HELPFUL TO YOU.
http://www.ashireporter.org/articles/articles.aspx?id=1648


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## sethmorgan (Jun 26, 2010)

I haven't had a chance yet to check the coil for blockage. However, with the system running, air flow from a register near the main duct seemed weak.

Thanks for the article; it was very informative and it appears my trap is designed properly. The only thing that may be deficient is the depth of the trap, but there is always water in it when the unit is operation (not too shallow to get blown out, which is moot since it only has the possibility of blowing out with the cleanout removed).










This is really puzzling. Without the cleanout installed, I'm having symptoms of a draw-through system that is missing the cleanout.


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## Artco (Sep 23, 2010)

Maybe you should try only one drain hooked up. There may not be enough air pressure to overcome the water in the trap the second drain. Try a screw in plug for the other drain and put a cap on where it connects to the main drain line.
I dont think you really need two drains.


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## sethmorgan (Jun 26, 2010)

I reinstalled the cleanout for the primary drain and capped the secondary drain. I opened up the panel to take a look at the coil again. I could see the inside of the coils by removing the plate at the tip of the "A". They appeared pretty clean, no dust or other visible obstructions.

Since temps have been so mild here, there haven't been many opportunites to run the A/C. So the pan was bone dry. The trap from the primary drain still had water in it. I'll report back when conditions are better suited to test.

One last thing: when the blower comes on, with the primary drain's cleanout removed, and the secondary drain uncapped, the air flow out the primary is much greater than the secondary.


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## Artco (Sep 23, 2010)

You may find that the trap has to be removed because when it is full of water the air pressure is not enough to push the water through it.
Without the trap there is not much air loss to worry about when cooling is on because condensate is flowing and restricting a lot of air loss in the condensate pipe.
It will not affect your units cooling capacity.

I do commercial hvac and on some carrier and other mfg. Units if the drain is upstream of the blower they do not want a p trap installed because of the restriction put on the drain.


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## sethmorgan (Jun 26, 2010)

I just wanted to update this thread with the solution. According to the installation documentation for the evap coil regarding the condensate drain:

"A trap must be used when the coil is installed on the
return air side of the system. When coil is installed on
the supply side (outlet air) it is not necessary to install
a trap *and better drainage is usually achieved without*​*the trap*."

My coil is installed on the supply side, so I guess I need to remove the trap to resolve this. Thanks to all for the input.


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