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heilProblems 01-11-2013 09:12 AM

Heil Condensation leak from secondary heat exchanger???
2 Attachment(s)
Hi all, I am really hoping someone can help me here as I am sort of running out of options.

I have a 10 year old 90+ Heil furnace in my basement that has been leaking condensation for a few weeks now. I'll try to give as much information as possible so apologies in advance for the long post.

The furnace itself is of the N9Mp1 variety and it is installed "upflow" very similar to Figure 11 in this PDF but with the condensate trap installed outside the unit on the left hand side.

This problem started about 3 weeks ago when I noticed water on the floor of the basement. Removing the top cover revealed the black transition box was leaking. I ordered a replacement which came with a soft foam gasket in between it and the exhaust blower. If you look at the exploded diagram in the above PDF these are items "P" and "Q" in the picture.

After I replaced those I put the furnace back together and that has solved the leak there. HOWEVER two new leak have appeared which I am currently dealing with.

The first is from the black 5/8" OD 1/2" ID rubber tube running from the Exhaust pipe connector to the condensate trap. This tube is seized and badly cracked so water is leaking out of there, not a lot, maybe 5-10 milliliters every 2 hours or so, but definitely enough that it's a problem.

To fix this I have ordered a new hose which I'm waiting on to arrive.

The big problem which I've no solution for is that water seems to be seeping out from underneath the metal enclosing the secondary heat exchanger. Again, not a lot but enough that it's a problem and I've no idea where this is coming from.

Things I've done:
- I can't touch the 5/8" hose as it'll crack if I breath on it but I've taken off the other hoses, the 1/2" "elbow" and the smaller 3/16" tube and made sure these are clear.

- I've taken upper caps off the condensate and tried to clean this out with a very small (1cm diameter) bristle type pipe cleaner brush. Nothing much came out.

- I've poured a few oz of Draino into the condensate trap and let it sit for about 20mins. Then I flushed it with warm water from the kettle (not boiling). I was able to pour a constant stream of water from the kettle into the condensate trap using a small funnel and it drained away no problem.

This morning I took the cover off whilst the furnace was running and noticed water under the metal partition behind the transition box. Whilst the unit was running I noticed this water seems to "wisp" in and out almost like something was sucking on it from behind the partition but then losing suction and the water flows back towards me. I think this suction is caused by the Exhaust blower (item #11 from page 60 in the above PDF).

Couple of questions:

- Why does the manual say to "prime" the condensate trap with 8oz of water? It looks like this is just a plastic box but the fact that they suggest priming it indicates there's some kind of seal inside that needs to be wetted in order to maybe created a pressurised loop of some kind.

- The system still needs a new hose. Is it possible it's relying on pressure to pump the water to the trap and as a result of the cracked hose the water is not making it to the condensate trap?

- Is this water actually produced in the secondary heat exchanger area or is it produced in the transition box and somehow finding its way back from the transition box into that area?

- One theory I had was it's produced in the transition box and not draining out of it sufficiently fast. Then backing up into the row of circular holes in the secondary heat exchanger which the transition box covers and finally leaking down from the cover.

- Should the bottom of the metal partition between the secondary heat exchanger and the transition box be air-tight with the floor of the top part of the furnace? It currently is not and this is where I saw the water wisping in and out.

- The Exhaust blower runs AFTER the gas burners turn off. Then after a few seconds the gas blowers will turn back on and burn more. I think this is not supposed to happen but am assuming for now it's related to this leak I have.

Again, apologies for the long message. I have attached some photos to clarify some of this.

Meanwhile any and all help is GREATLY appreciated. I have been unable to locate anyone who'll touch this thing with a long stick and have been losing sleep on it for a long time now.

I would really love to just open the door some day and find the unit to be bone dry. Help me get there DIYers!!! :(

joecaption 01-11-2013 09:25 AM

Any hardware store, Box store, auto supply will stock that hose and sell it by the ft.
Never use any form of drain clean in a condinsate drain!!
Use bleachand water instead. The water may be to fill the trap in the line.
The lines form algee inside of them and the bleach will kill it.

jagans 01-11-2013 10:44 AM

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Did you use new longer screws at the location shown in the attached Picture? Looks like you punctured the box. That bar should just attach to the box lugs. After you change the gasket, gun butyl into those holes and reinstall the screws with a rubber washer on them. Should work. You could also go down to the auto parts store and get some cork gasket material, That should work well with the sealant also

I would not use a foam rubber gasket (These are bad news) I Know, why do they supply them in the first place? To seal anything. They dont work. Use a non hardening Butyl sealant on very clean surfaces. Clean with alcohol. To be honest, the stuff I see in your photo at the edge of the box looks to be some sort of fabric, like fiberglass or polyester, and not foam rubber at all.

Replace all hoses with Gates Radiator, or Vacuum hose as appropriate, and use all stainless breeze clamps.

Remove the trap and clean it properly, and never never never use draino on anything, not even plumbing.

It is pretty clear from your photos that you have had a leak in the collector box for a long long time, judging by the corrosion that is visible there. That ill designed gasket is the culprit IMO Use Cork. Hint. If you have a copy machine or scanner, place the box back down on the scanner. Scan, There is your template for your cork gasket. :thumbsup:

You have to prime the trap to prevent loss of draft which can trip the pressure switch.

heilProblems 01-11-2013 03:02 PM

Hi guys, thanks for the replies.

To answer your questions: I used 2" self-tapping sheet metal screws, an exact match to what was in there already. I don't think I punctured anything.

When you say "punctured the box" which box do you mean?
And what bar are you referring to? If you can clarify there I'll take a look.

I should clarify, the black transition box came as a single sealed unit. The screws were 2" and help attach the transition box to the plate that covers the secondary heat exchanger. There is a gasket in between the transition box and the sheet metal but this is not leaking.

There is no water coming from the new transition box or from the exhaust blower. It's coming from behind the sheet metal (which I never removed).
It's hard to tell from the pictures but only the crevice between the metal is wet, the top of the metal is bone dry.

Thanks again, really hoping I can get this solved.

jagans 01-11-2013 04:19 PM

If you look close at the screw head where I circled it in yellow, it is fairly apparent that water is leaking at that screw.

It is not unusual for HVAC equipment to be designed or manufactured without proper attention to waterproofing of the unit. I have seen this on $20,000 + Commercial rooftop units, and have solved problems in many of them that caused extensive leaking into commercial buildings.

It is hard to get by the fact that the HVAC mfgr would mess this aspect up, but it happens all the time. It sounds like the MFGR might have missed a seal between the flange of the secondary heat exchanger, and the back face of the cabinet. The key is to beleive it when you see it, not say "naaaaa they couldnt have done that"

Ill look at the manual you posted and see if anything jums out at me.

jagans 01-11-2013 04:36 PM

Can you post a few more photos, wide view especially? Your condensate lines do not appear to be configured like the manual you posted. Where is your trap, How is your drainage configured etc. etc. Most of the illustrations show the trap centered and low. I cant even see where yours is.

Marty S. 01-11-2013 05:59 PM

Take the blower out and look for leaks in the secondary heat exchanger. It will be white spots from the acids in the condensation.

heilProblems 01-11-2013 06:19 PM

1 Attachment(s)
Thanks Jagans. I am attaching a wider shot. Hopefully you can see everything's routed as it should be.

I found some hose but it's much heavier duty but I stuck it in there anyway. It's the one in Red on the left.

The manual I linked to is not the exact match for my model but I know that the setup (Upflow with trap on the left) is legit and it seems to be fine. It's worked for 10 years don't forget ;)

Also, I tested a bit and it seems this system is relying on pressure from the exhaust blower. E.g. if I disconnect the small 3/16 hose going from the trap to the pressure switch everything shuts off immediately. Similarly, if I disconnect the other 3/16" hose which runs from the top right of the transition box to the trap there is suction from the transition box. This makes me thing the blower actually sucks water into the trap by applying negative pressure via this small hose.

Could that be right? And could it be that my cracked hose was causing a lack of pressure, leading to all these leaks?

jagans 01-11-2013 06:46 PM

Honest answers now.

In the 10 years since you have owned this furnace have you ever cleaned out the trap and condensate lines with bleach and hot water?

And, is this the first time in 10 years you have had any trouble with the furnace?

Also, you are dead right. If the furnace has worked fine for 10 years it is set up right. I think the issue has been lack of maintenance, but dont feel bad, almost everyone does the same thing. We just expect them to work, and dont get into How they work till there is no heat, or there is water all over the floor. :(

Frankly, I really like the engineering in the Heil Furnaces, they are laid out very nicely. The only drawback is the quality of some of the components, but Im not sure if any of the manufacturers use USA made motors anymore, and all the boards are made in Taiwan or China.

Am I to understand that you replaced the entire large black panel behind the inducer fan?

heilProblems 01-11-2013 06:52 PM

Never cleaned out the lines or the trap with anything. Just draino 1-time the other night and I won't be doing that again ;)

Last year the furnace leaked when the old transition box (the black plastic box in these pictures) leaked. That time I took it off and found a crack that had developed along where the two parts of it come together. I sealed up the crack with some marine-grade adhesive from the big box store.

It's always run ok but it's probably been leaking a good while without me even noticing.

Last answer, it's never been serviced in 10 years. Definitely shame on me there :) my wife got stage IV cancer some 5 years back so that was a major "distraction" you could say. (she's fine now but it definitely rocked our world). Anyway, back on topic...should I throw a bit of bleach in the trap? The lines themselves seem clear and everything *seems* to be flowing ok, except for the leak.

heilProblems 01-11-2013 07:04 PM

"Am I to understand that you replaced the entire large black panel behind the inducer fan?"

Yes. I'm calling that the "transition box" or "transition assembly" as it's referred to in the manual. The one in the pictures you see is brand new and it's not leaking at all. The water is coming from behind the metal panel that the black box is attached to.

It's seeping out the bottom where the metal panel covering the secondary heat exchanger meets the top of the lower box.

jagans 01-11-2013 07:26 PM

First of all, I am very sorry for what you had to go through, and I am happy that your wife is OK, and yes, a damn furnace would be the last thing on my mind too.

I lost my beautiful oldest daughter at 33 years old two years ago this May, and my wife and I have resolved ourselves to the fact that we will never get past that, we just kind of exist until its our turn, if you know what I mean. I guess we all have our crosses, but this one is really heavy.

Well, as you say back on topic.

Plasticizers leeches out of PVC lines slowly and serve as a food source for mold. I have found horrible black mold problems in evaporator pans which, in an effort at continually cheapening HVAC components are made of plastic. Non chlorinated plastic.

This mold can literally clog off a 1 inch diameter line in short order. Chlorine Bleach in soapy water takes care of it. You can disconnect that red hose up top, put a big funnel in there, and pour a gallon or so down there and into a bucket. You will be surprised what comes out.

As far as the leak goes, try this first. Back out those screws that I circled all along the bottom of the black plastic box. Gun polysulfide sealant into each hole, coat screw and reinstall. See what happens. I have a sneaking suspicion those screws are the source of your leak. Polysulfide works in water.

I now use CPVC whenever I install a condensate drain. CPVC= Chlorinated Poly Vinyl Chloride. Key word Chlorinated.

heilProblems 01-11-2013 08:10 PM

Sorry to bring up such bad memories. I can't imagine how tough that must've been. My wife was 32 when diagnosed w/colon cancer (they don't screen until 50). My heart goes out to you and your family. We have been very lucky despite the struggle of surgery, chemo, radiation etc. My wife now volunteers for the Cancer Hope Network to help other newly diagnosed patients get to grips with things. Everyone has a story and I really wish you and your family peace. Again, apologies, didn't mean to turn the conversation.

I will definitely try what you mentioned. I'm going to tackle this beast fresh tomorrow and will start with the bleach flush and see what pops out. Regarding the sealant, does "Life Caulk" fit the bill?

Again, thanks for all your help. It's been really hard to find folks who know what they're talking about with these machines. Really appreciate it.

jagans 01-11-2013 08:27 PM

No Worries, You did not bring anything up. Its never out of my mind. God Bless your wife and her work. I lost my Brother in law at 58 to Colon Cancer. That damn cancer is tough to beat.

Trying to help on these forums is a welcome distraction for me. The reason I recommend polysulfide in this application is that it works in water. If you can shut her down and get her dry, you can use silicone or urethane. Ill take a look at life caulk and get back to you.

Yup thats the stuff. Boatlife.

jagans 01-11-2013 09:17 PM

Put rubber washers under the Hex Washer head screws after you inject the sealant.

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