Horizontal air handler condensate issue

ChrisJ

Hi all,

It's been a while, but this is one of the problems I need to button up before it gets warm out again.

As some may recall, I installed A\C in own house last year and ran out of time. I ended up rushing some things because the attic was turning into an oven. Some problems turned up, a few of which I corrected (hunting TXV etc).

On hotter days I kept having an issue with condensate making it into the blower compartment. As best I can tell, it's getting pulled a little too far just by the air as there's no pan on the blower side of the evaporator. This was happening with the original TXV as well which is how I cracked the pan, I thought the primary drain was leaking so kept tightening it.

The air handler is horizontal and has the mouth of the evaporator facing the blower, the narrow part faces the filter as per the design for this position. Air flow is from left to right as this is a negative pressure setup as usual.

Shown here :




On extreme days, the insulation on the blower side gets soaked, so then the cabinet on the bottom sweats.
Here's what I've seen if I crack open the blower side door. Notice the puddle of water on the plastic, button corner of the evaporator. It drips there, and then runs down into the insulation.




Here's a picture looking into the evaporator, but I doubt it's helpful.






I'm running 1200 CFM in high stage for 3 tons. I tried dropping it down to just under 1100 CFM for a while, it still had the problem. Total static pressure is 0.5" WC in high stage. AHU is level. My temp drop is around 20 degrees in high stage and as high as 23 degrees in low stage. Air filter is a 20x25x5 MERV 8 air bear.

My plan was to bend up an aluminum baffle to mount in the bottle and catch those drips and run them back into the evaporator. But doesn't it seem odd that I need to do that?

Thoughts?

the_donut

How’s the venting on the condensate drain? Did you use a trap in the drain line, if so, how many inches of drop?

ChrisJ

the_donut said:

How’s the venting on the condensate drain? Did you use a trap in the drain line, if so, how many inches of drop?

Venting is good, the drop isn't much as I simply didn't have the room. I had to go with an awful running trap.

But best I can tell, the pan is draining good even under heavy load. The water would have to jump a good 2 inches to make it into the blower compartment over that lip, meanwhile my secondary connection is bone dry.

the_donut

It’s possible that the vacuum is preventing water to drain until system cycles up and is only a problem after long runs. Could cycle fan off to drain.

ChrisJ

the_donut said:

It’s possible that the vacuum is preventing water to drain until system cycles up and is only a problem after long runs. Could cycle fan off to drain.

Wouldn't I have seen water in the secondary drain's float if that was the case, or not necessarily?

EBEBRATT-Ed

Maybe just running a couple of beads of caulk will do it. Any velocity over 550fpm (approx.) will pull water off a coil. Unfortunately some manufactures cheat a little on this.

Putting a baffle may increase the velocity and cause more carry over.

But you gotta do what you gotta do.

I would think dropping the airflow would help. Water from the upper half of the coil should run down hill against the air flow and drip into the drain pan. Maybe it is carrying over from the top

McGee

I would have said that the coil was backwards but you said it was per instructions. Maybe washing the coil might help, some have oil on them.

ChrisJ

> @EBEBRATT-Ed said:
> Maybe just running a couple of beads of caulk will do it. Any velocity over 550fpm (approx.) will pull water off a coil. Unfortunately some manufactures cheat a little on this.
>
> Putting a baffle may increase the velocity and cause more carry over.
>
> But you gotta do what you gotta do.
>
> I would think dropping the airflow would help. Water from the upper half of the coil should run down hill against the air flow and drip into the drain pan. Maybe it is carrying over from the top

I believe it's coming from the top.

I've wondered about what @McGee just said. The coil most certainly had oil on it when I put it in.

ChrisJ

> @McGee said:
> I would have said that the coil was backwards but you said it was per instructions. Maybe washing the coil might help, some have oil on them.

I also included a picture from the instructions showing how it's installed.

McGee

On most that I do the air is sucked thru the mouth instead of the way it is there. When installed as shown I have seen trays extended to catch blow off and drain back into the pan.

ChrisJ

> @McGee said:
> On most that I do the air is sucked thru the mouth instead of the way it is there. When installed as shown I have seen trays extended to catch blow off and drain back into the pan.

What I'd give to see a picture of one of them......just to get a better idea of what to make.

the_donut

Has to be a fair amount of water sitting to make cabinet sweat bad enough to soak insulation. A good size puddle not high enough to trigger switch that would drain down on shutdown or loss of vacuum.

I imagine those ducts are tighter than an average installation 1/2” might be enough to keep water stuck in that running trap until the head from puddling water exceeds surface tension, water runs out, and cycle repeats. Enough fresh cold condensate to keep sweating on outside.

Could be carryover condensate though. I guess you could leave the same and vacuum vent to test if silicone or a catch bottle doesn’t work.

GW

So it’s flying off and missing the pan? Or the pan gets too full?

ChrisJ

> @the_donut said:
> Has to be a fair amount of water sitting to make cabinet sweat bad enough to soak insulation. A good size puddle not high enough to trigger switch that would drain down on shutdown or loss of vacuum.
>
> I imagine those ducts are tighter than an average installation 1/2” might be enough to keep water stuck in that running trap until the head from puddling water exceeds surface tension, water runs out, and cycle repeats. Enough fresh cold condensate to keep sweating on outside.
>
> Could be carryover condensate though. I guess you could leave the same and vacuum vent to test if silicone or a catch bottle doesn’t work.

No no, the insulation gets wet from the water dripping off the evap into the blower side of the cabinet. It's totally missing the pan. Then the ahu sweats as its in an attic. I only get a few drips into the secondary pan during this

ChrisJ

> @GW said:
> So it’s flying off and missing the pan? Or the pan gets too full?

90% sure it's totally missing the pan as there is no lip or anything on that side of the coil

GW

But your positive the pan isn’t overflowing? Like 100% positive?

And your drain is on the negative right? Your not hanging up your water are you?

I have a Unico job that’s flying its water so I know it’s a real pain

Edit, its not it’s, stupid phone

ChrisJ

> @GW said:
> But your positive the pan isn’t overflowing? Like 100% positive?
>
> And your drain is on the negative right? Your not hanging up your water are you?
>
> I have a Unico job that’s flying it’s water so I know it’s a real pain

I guess I'm 99% sure...my secondary float stays bone dry. And now that I think about it I had watched the drain when the blower shut off a few times and never had a burst of water from it. As far as I can tell the pan drains well.

What are your plans for the Unico

the_donut

Could use an endoscope to be sure. With panel open you are breaking 1/2” seal.

JUGHNE

I am sure I mentioned this before. Had problem with a counterflow gas furnace with coil under burner/blower. Positive pressure.
This was a modular home with a return air hallway blaster filer grill.
But they had a basement and would get water dripping out of the duct work straight below.

I sprayed the coil with Dawn soap/water mix. Just soak the hell out of it. Bubbles in the duct only freshen things up IMO.

This is like "Wetter Water" that we use in the fire department.
It gives water a clingy feature, spray something and the wetter water will cling to it to prevent re-ignition.
Makes water heavy and can not be blown/sucked away as easily in the wind.

Cheapest and easiest to try.

Also for a trap I build one deep enough to go between the floor joists go get heat from the ceiling and cover it with insulation blanket.

McGee

Can you cut a piece of plexi glass for a door and watch it? It would help if you posted model numbers. If I get some time tomorrow I’ll see if I can dig out some literature.

ChrisJ

> @McGee said:
> Can you cut a piece of plexi glass for a door and watch it? It would help if you posted model numbers. If I get some time tomorrow I’ll see if I can dig out some literature.


I considered doing that but am hoping it can be avoided. Ahu is an Amana (Goodman really). AVPTC37D.

JUGHNE

Chris will probably put a small WIFI camera in there to watch at work. Just say it is a doorbell alarm and you have to check it out.

the_donut

JUGHNE said:

Chris will probably put a small WIFI camera in there to watch at work. Just say it is a doorbell alarm and you have to check it out.

He’d have to install a booster to get through attic and handler. Hardware it, cat6 shielded.

HVACNUT

Is it possible the manufacturer left out a part? Do you have an exploded parts diagram to check? I shouldn't ask but the upflow pan is plumb?
Good to hear from you again!

GW

My Unico issues, someone mentioned (maybe here) that the coil may not be wet enough (not enough refrigerant). So it’s a super long run. About 70’ R22. Pressures are weird. We went back and installed an adjustable txv to open up the valve some. Didn’t help, affected sub cool. Anyway when it’s warm we’ll make a other run at it.

GW

Also can you check the static pressure?

Is this an variable speed, basic ecm or basic PSC?

Can you get the condensate flowing, quickly shut it down and throw a video cam smart phone in there with a flashlight or something? Yes I know it’s winter, but someday summer will be here

Are you pitched properly? Maybe stick a small level on the pan itself. Putting a level on the unit is fine but the coil is what reallly matters (yes, they should be equal)

Mike

Did you flip the coil, to make it horizontal right? Some manufacturers want the top of the "A" coil blank off plates turned also.

ratio

I've seen coils with extensions that are (field added) to the leaving side of the coil, presumably to catch the water, but if it's not mentioned in the IOM this must not be one of those.

I would second (third?) the soapy cleaning of the coil, like @JUGHNE said. My Old Guy used to say that excessive oil will let the condensate fly off the coil at a lower velocity.

icy78

You have protective oil on the coil, (from the manufacturing process) and it's not allowing the condensate to stick to the coil and run down and off. A citrus type cleaner will fix it. Like a bottle of lime juice.
Spray it on with an atomizing sprayer.
Should do the trick.

Possible that the dawn soap mentioned above, will do it for you too.

ChrisJ

Thank you all for taking the time to respond.

Right now, it sounds like I need to wash the evaporator good and see how it does this summer before I fabricate or modify anything.

If you look at the third picture in my first post you can see drops of water all over the upper half. I watched it dripping all over the place, but I assumed it was normal.

This is also their high efficiency version of the air handler, so the coil is closer to the size of a standard 4 ton unit rather than 3 ton so I doubt velocity is an issue.

@GW I can easily check static pressure, if you recall I have a magnehlic mounted in my wall by the bedroom that shows my total static pressure. But seriously..........I do.

clammy

Do you have a trap on your coil ,i have seen coil pans without hold water until the fan cycles off then the coil drains .A trap will give u a seal and prevent air from being sucked tjrough your condensate line and after your trap you can cut in a tee for a drain vent .I always put a union before and after my trap makes it easy to remove clean and blow out condensate lines .Is your air handler installed level some like to pitch there air handler ,thinking that will ensure better drainage i ve always installed level and never have had a issue .peace and good luck clammy

GW

OK so you're at .8? Where are your reading points? Just the duct work or is that the coil drop? in other words where is the filter?

Just curios on my other questions too

icy78

@ChrisJ . This is a typical horizontal issue. It won't show on vertical installs because the drip angle is different. Not to say that it happens on most horizontal, just that it is most likely to occur there.
On an interesting side note here's a scenario for you. Side by side evaporator coils in a duct. 1 first stage 1 second stage. First stage makes condensate, resistance to airflow increases so more air goes through the second stage coil. Then the second stage calls and starts making condensate and the higher velocity through that coil now starts throwing drops of water off it. We've seen that a few times.
On another note; with your system you may very well get away with as low as 320 CFM per ton . This will improve your dehumidifying capacity. (And make your coil drip more

DZoro

Slope of the unit to the left 1/4", to the front 1/4". Install with a baffle they don't always come with a baffle. If your coil was in the other way I would suggest looking at the Suction, and liquid lines inside the box have had them "drip" out side of the pan. Basically had to slope those also. Maybe something to look at in your case also. Were you able to at least get a 4" trap? And a tee vent on the other side of the trap? Like others said too lower your cfm if possible. Good luck!

McGee

That static psi is high but also interested in where it is taken. Bottom

McGee

Whoops don’t have my glasses on, bottom line is if cleaning the coil and making sure it is trapped, only thing left is installation problem.

ChrisJ

Gentlemen,

@McGee, @GW
You're looking at the adjustable flag on the magnehlic, that's not the pressure. In that picture the gauge wasn't even hooked up yet, the red needle was at 0.

The pressure runs at 0.5" WC in high stage, that's the highest it's been. When I dropped speed to under 1100 CFM it was around 0.4". Low stage runs around 0.2".

Pressure is taken from the AirBear filter housing on the air handler side, and from the supply plenum before it splits into two trunks. This shows the total static load on the air handler.

I had considered plumbing it into the suction side of the blower just after the evaporator as it would also show a dirty evaporator then, but I decided not to as I didn't want to put holes in the air handler.

I'll see if I can get some videos when I pull the cover off but it's going to be a while. Air handler is a variable speed ECM setup.

unclejohn

I used the plastic door method on the one AH I had trouble with. It;s really helpful when you can actually see where the water is coming from.

pecmsg

Its not the P-Trap. Traps are required when the coil is on the negative pressure side, yours is positive pressure. All the trap will do is close a 3/4" hole from spilling air.

Assuming the static pressure is fine and FPM over the coil is within specs:
New coils can allow the condensate to bead up more then normal and be carried off. One solution is spraying with a coil cleaner to remove the oils used in manufacturing. Being that its going on a year old you may not have that issue this season! Try running it and see what happens.

ChrisJ

So, am I correct in that water should never drip from the upper half of the evaporator to the bottom, it should run down the evaporator?

I just want to confirm that because right now I'm planning on ordering some aluminum evaporator cleaner

I saw tons of it dripping off all over it and assumed it was normal. That's why I couldn't understand why they would leave that tapered edge running into the blower compartment so close to where water is falling.

If you enlarge this picture you can see tons of water laying in the fins and dripping off. This was after the system was off for long enough for me to climb up into the attic and pull the blower cover off.




I'm guessing this is likely from the oil that's still on it?



@pecmsg I wish, mine is negative pressure, the blower is pulling through the coil backwards, as designed for this position.

pecmsg

According to Fig 5 it blows thru.

Draw thru Must have a trap. A running trap may not have enough water weight to hold back the incoming air. with .5 SP i would like to see at least 1" of water in the trap.