Aprilaire 760 humidifier installation on Trane furnace

Hello -

First post here. Forgive me, I know next to nothing about HVAC. Trying to learn though.

I just bought a house. The furnace in the attic is a Trane model XR90. There is an Aprilaire 760 humidifier installed on the side. It has been incredibly dry in the house, so I checked it out and realized the saddle valve off the hot water line that runs up to the humidifier was turned off. I checked out the humidifier, read all about it, did the yearly maintenance that's recommended (replaced water panel, feed tube, etc.). The humidifier is getting water, the solenoid valve is working, water trickles out the drain tube during operation, and it actually humidifies the house. That's all great. But, every time the furnace (and therefore the humidifier) turns off, the humidifier leaks a bunch of water out of the base. I cannot figure out why it's doing this.

I think there may be a fundamental flaw in how it was installed. When I take the cover and water panel off the humidifier, so that I can see inside the furnace, I see... what I think is a draft inducer blower??? Um, I don't think that's normal, for a humidifier to be installed right against (what I think is) a draft inducer blower?

I still don't understand why that would make the humidifier leak, only when it turns off. But this installation seems strange. Is it? If so, could it explain the leaking at the end of each cycle?

Thanks in advance for any help anyone can provide. I have to get this humidifier to stop leaking so I can use it. Everything I touch in the house gives me a static shock. Ugh.

-dave

 

Welcome to the forums.

I hope that's a heated attic.
Can you post a picture of what you have there ? http://www.doityourself.com/forum/el...rt-images.html

 

Sure thing...

Front:


Front right:


Back right:


Looking through humidifier with cover and water panel removed:


No, the attic is not heated - it's pretty much open to the outside (has one of those huge fans with just a screen over it, because it gets so hot in the summer in DC). But it's a one-story house, with pretty measly ceiling insulation, so the attic doesn't get that cold. It's 4 degrees outside right now, but not too cold up there.

 

Since you have water there you definitely don't want anything to freeze.

That is the main blower there. You have a downflow furnace. Your A/C coil is at the bottom.
Probably not the best location for it. What I can't figure out is why you get water when the blower stops running. I'd think you'd get water with the blower running unless the blower is creating a vacuum thru the humidifier and holding water inside the unit.

Thinking here about a trap for the drain.

Try this..... take a plastic bottle or bucket. Put a little water in it and drop the drain line for the humidifier into it so that the drain line is under water. Keeping the drain line submersed see if you have the same overflow problem.

I'm thinking the blower is drawing air thru the drain tube and preventing it from draining correctly.

 

Thanks for your help. Here is a video (sorry about the quality) showing it start to leak the moment the system shuts off (at 0:11 in the video). http://youtu.be/eXMJ_EmeXoM

The blower is *definitely* creating a strong vacuum. If I open the humidifier cover while the system is running, I can barely pull out the water panel because it is getting sucked back in toward the unit so strongly).

Is this just a completely stupid place for the humidifier to be mounted? I'm not sure there's anywhere else to mount it.

I'm wondering, if I just sealed the bottom of the humidifier housing with foil tape or something, maybe that will direct that momentary rush of water (that happens every time the system shuts off) down the drain spud, and this won't be a problem?

 

I doubt sealing the humidifier will help.

Try the drain idea I left you.

 

Wow, I think/hope that actually worked. Thank you! I put the drain tube down into a bucket under the water line, watched it for a full cycle, and saw two things... First, there was one continuous stream of water going down the drain tube, whereas before it would drain a little, stop, drain a little more, stop, etc. Second, at the end of the cycle when the system shut off it didn't leak!

I'll have to go back up there tomorrow and test it for several cycles to make sure. But, assuming that's the answer, what do I do now? I obviously can't keep draining it into a bucket. I assume I need to implement some type of water trap like you said, which I assume is basically a container of water where the drain tube coming from the humidifier is underwater, below the level of an exit tube that goes to my actual drain system? Are there premade traps for this purpose? And how am I going to mount something like that to the side of my furnace?

I really, really appreciate you helping me solve this. Awesome.

 

Hey, so I just put a simple loop in the clear vinyl drain tube, which seemed to create a trap (loop remains filled with water) with enough resistance to maintain the air seal and do the job. Unit is no longer leaking when it shuts off. This is so great. Once again... THANKS!

 

I was going to recommend a simple loop. You just need from having air drawn up the drain tube so if you have any issue..... increase the depth of the loop.

Since the drain line is a small diameter and will stay full of water..... you'll need to clean it at the end of every heating season.

 

OK, on to the next problem. As I let the system run like that for awhile, the drain pan beneath the whole system started filling up with water? Uggh!

Any thoughts on why that would be happening?

 

I'm guessing you're talking about the pan in the bottom of the humidifier. You need to increase the pull of the water to counteract the pull of the fan.


Oh... wait a minute... the pan under the unit is filling up ?

You need to see where the water is coming from.
It's either draining down the inside of the furnace or the drain line leaving the attic is plugged or frozen. My guess..... it's frozen or sitting in a block of ice.

 

Yes, the pan under the entire furnace is filling up. It filled up pretty fast - in like 3 heat cycles (5-10 min each).

I do not think the PVC drain line connected to the furnace is leaking, or frozen. The water appears to be coming down from the inside of the furnace. I'll need to watch it a bit to be sure (the insulation around the base of the unit is now wet, and the drain pan isn't level, so it's hard to get it completely dry to watch it from scratch).

If the water is draining down from inside the furnace, what does that mean?

I'm trying to figure out if it's still filling up even tough I've turned the humidifier off for now. I hope I don't now have a separate furnace problem.

 

As an aside, it doesn't seem like the little float safety valve in the drain pan is operating. When I pull it up so it clicks, the system does not turn off.

Crimony, I think I need an HVAC visit. I don't want to flood my house.

 

Ok... get a grip.

The float switch is probably only wired to the A/C compressor which in your case is incorrect.
If you turn the water off to the humidifier there should be no further water entering the pan.

If that drain pan is filling with water then there must be a drain problem.

I would check and see if the AC / humidifier drain line is connected to the same line as the overflow pan.

 

It looks like all the drains are sharing a common line leaving the area which is also incorrect. The lower drip pan is supposed to be on a separate drain line.

 

oK, sorry.

Yeah the two drain lines coming out of the furnace, one higher up on the left, one lower down on the right, join together and exit the attic, down through my utility closet on the main floor (which I think at one point housed the old furnace), and through the floor of the utility room out the bottom of the house. As best I can tell, that PVC drain line is not frozen anywhere I can access it. Possible it's frozen under the house.

Since I've shut the humidifier off, the safety pan is no longer filling up with water.

I don't think the PVC drain line was leaking. I think the water was, like you said, draining down the inside of the furnace. Would that mean that the humidifier + main blower are just pulling way too much water (droplets) inside the system, and it's not all vaporizing but rather just getting sprayed around inside and dripping down the walls of the furnace? If so, is that because installing a humidifier right over a main blower is a stupid place for it?

 

Confirmed that it's definitely water draining down from inside the furnace and pooling from under the bottom of the furnace. It's not a PVC pipe leaking. It starts to seep out about 5 min after I turn the humidifier on.

Any thoughts/suggestions?

 

If anyone has any suggestions for why my furnace might be leaking now, I'd really appreciate it. Thanks.

 

The last we spoke here I asked you if the drain could be plugged. You said the pan was filling with water which would suggest a clogged drain line. Even if the humidifier was leaking water into the furnace..... it should drain into the pan and the pan should empty.

If the drain line was plugged or frozen... the water that was draining from the humidifier was backing up and coming out into the pan thru the drain line.

 

I now understand what you mean that if the PVC drain line coming out of the furnace is blocked or frozen, then when the humidifier runs and drains into that line, water is going to back up into the furnace, the internal drain pans will overflow, and water will leak down the inside of the furnace and pool in the emergency pan.

It was ridiculously cold (single digits) here all of a sudden this past week (well, cold for DC), and I was not running the humidifier during that time, so maybe there was/is standing water at some spot in the drain pipe under the house that froze. What I don't get is why it takes like 5 minutes each time I run the humidifier for everything to start overflowing into the emergency pan. Maybe that suggests a slow, but not completely blocked, line.

Any tips on how I could figure out where the PVC drain line may be blocked or frozen? In case it helps, here is a picture of that drain pipe coming down into the utility closet on the first floor. It connects to that black plastic pipe (where there's a capped off tee), which runs out the bottom of the house (there's just a few feet of open crawl space / earth below) and I assume joins with the main lateral drain line that goes from the house to the city pipe under the street. Nothing else in the house (sinks, showers, toilets) is currently backed up or running slowly.



Thanks for your help. At least this is a learning experience. I should know the basics about how the appliances and utilities in my house work.

 

Update: It was warmer today and it seems the pipe unfroze. Furnace and humidifier has run a number of cycles now without leaking. I heated up a pot of water (not boiling) and poured it down the humidifier drain, then went downstairs and could feel that drain pipe get warm. When the furnace kicked back on and the room temp / cool water from the humidifier started running, I felt the downstairs pipe get cool pretty rapidly. So water seems to be running through it. Hopefully it doesn't freeze again (it's going to get cold here again in the next few days). With the humidifier working now, so running and having water flow with every heat cycle, hopefully that periodic water movement will prevent the pipe from freezing.

Thanks, seriously, for your help in diagnosing and solving both of these problems (leaking humidifier, leaking furnace). I really appreciate it.

 

You are very welcome. Good luck there.