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Phil
Phil, Mechanical Engineer
Category: HVAC
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Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Lennox furnace leaking water from blower motor. How to fix?

Customer Question

I have a Lennox C33-36B-2F-4 furnace and it is leaking water which appears to be coming from the blower motor. When I take off the black cap labeled drain on the right side of the furnace (exhaust vent side) water comes out. If I let it all drain out then recap the drain, it stops leaking from the blower motor, but it will be leaking again soon if I let it sit for a while.

Submitted: 5 years ago.
Category: HVAC
Expert:  Phil replied 5 years ago.

Phil :

Is this the furnace you have? Are you operating in heating or cooling mode?

http://imgs.ebuild.com/xCat/ebuildWebB/15?ObjectID=19645&Variant=Original

JACUSTOMER-x9h9y6fb- :

No that is not my furnace, cooling mode

I have model number: C33-36B-2F-4

That pdf appeared to be for some G model

Phil :

In cooling mode water leaks are always with no exceptions from the cooling coil drain pan sitting on top of the furnace

They clog with slime and mold.

JACUSTOMER-x9h9y6fb- :

Yeah I figured that

Phil :

Its $250 or so to have it cleaned

Let me know if you want to clean it yourself

JACUSTOMER-x9h9y6fb- :

Nothing I can do then?

I would love to

Phil :

Find there the white plastic drain line attaches above the furnace. The 2 copper tubes for cooling attach just above it.

That is the cooling coil cabinet

Remove the insulation.

Remove the 14 screws that hold the 20 x 20" cover in place

Remove the cover

Observe the drain pan, and drain... clean it up

Pour a few cups of warm water down the drain to blow any debris out of the trap

JACUSTOMER-x9h9y6fb- :

Sounds like this would require some insulation/heat tape to fix what I am undoing

Phil :

Yes, a bit of duct insulation wrap and duct tape you can buy at a big box home repair type store... or just the duct tape to put the existing insulation back on

JACUSTOMER-x9h9y6fb- :

Ok

If that trap is clogged then how is water getting down to the black box on the right side of the furnace under the exhaust vents (the hole labeled drain with a rubber cap on it)

Seems like if it got that far, then it would just drain through the pipe that runs into the concrete slab

Phil :

That is a very good question... the exhaust vent with the rubber cap only has water in it when the furnace is in heating mode. Since the furnace is in cooling mode the only way water can get into the exhaust vent is by leaking into the burner box or through the power vent fan etc...

JACUSTOMER-x9h9y6fb- :

Which you are suggesting is happening because of the trap being clogged?

Phil :

Those are sealed components. Water from above should have no pathway to the inside of the vent as you are reporting except through a cracked heat exchanger or some such.

And that is a dangerous situation, carbon monoxide leaking is an issue and that needs to be tested by a licensed and qualified Lennox furnace specialist.

JACUSTOMER-x9h9y6fb- :

I'm not running the furnace though

Phil :

The clogged trap, allowed the evaporator coil drain pan to over flow onto the furnace heat exchanger and other furnace parts

You are running the cooling only of course, but that drain pan leaks onto the furnace heating element, heat exchanger

That is apparently cracked, or with some other defect... allowing water inside and into the vent trap

This definitely needs an onsite inspection. Odds are in the 70% range that a dangerous condition exists that can put carbon monoxide into the home

JACUSTOMER-x9h9y6fb- :

Ok, I opened the cabinet

Tray looks pretty clean

I poured water into the tray, it drains as expected

Coils look very clean, no slime or build up

Drain pipe is not clogged

Thoughts?

Phil :

Inside the A coil is the inlet face of the coil. It collects dirt and hair etc over time and can create a water drip bridge around the drain pan, so that water drips past the drain pan onto the top of the furnace heat exchanger

To access that area. Remove a 6" square panel that is screwed into place where the cross bar is on a capitol A.

JACUSTOMER-x9h9y6fb- :

Update: I removed the black cap from the drain box

Phil :

Use a flash light. You will see the inlet side of the coil and can clean it using a coil cleaning kit, that includes a 'green fin comb'... big hardware stores carry the kit

JACUSTOMER-x9h9y6fb- :

I poured water in the drip tray

The water flowed right back out of the drain box

Sounds to me like the drain pipe that runs into my concrete slab might be blocked up near where it enters the slab

Phil :

I can't see it from here of course, but it sounds like the 'drain box' is actually a box with a pump in it. That pumps the condensate from the boiler and the condensate from the cooling coil outside.

JACUSTOMER-x9h9y6fb- :

Is there any way I can upload a pic?

Phil :

Yes

JACUSTOMER-x9h9y6fb- :
Full Size Image

The black box I have shown here

In this pic the plastic cap is on

You can also see how the drain pipe turns before entering the slab

The clear U trap is also clean

See what I mean?

Phil :

Thanks, great pic

That is a totally unusual condensate trap arrangement. Its functional though.

JACUSTOMER-x9h9y6fb- :

See what I mean about the drain pipe and the slab

I think the clog is there at the bend before the floor

JACUSTOMER-x9h9y6fb- :

Logically if I pour water in the tray, and the clog is at the bend near the floor, then the water would back up into the black box

Phil :

I have absolutely no idea what the black box is and the condensate going into a hole in the slab is not legal. It could be a problem for your foundation/ slab if the soil under the slab doesn't drain well

JACUSTOMER-x9h9y6fb- :

Not legal in a specific State or Nationally?

I ask because I had a home inspector look at this house before I bought it

Phil :

You can but a 3/4" PVC 'repair coupling' cut the pipe, clean the clog and then fit the coupling

If the soil doesn't drain well you could have water backed up as a result of that as well

JACUSTOMER-x9h9y6fb- :

So what I was saying probably makes more sense to you now because of the picture

Phil :

Its not legal according to the US building codes, some rural unincorporated areas do not have code enforcement. Some inspectors could miss that as well

Yes the picture helps, but I have no idea what the black box is

It would not need to have a pump in it, I don't see a pump either, and I can't see what function the black box might have from here

JACUSTOMER-x9h9y6fb- :

There are two rubber tubes that come away from the area

Near the blower motor

That runs into the black box

Not shown in the picture

Phil :

Can you access the inside of the box and tell me what you see... the entire job is quite unusual. The condensate trap and the pipe into the slab. That black box makes no sense either

JACUSTOMER-x9h9y6fb- :

The box appears to be one unit, no hardware to remove to see the inside

Phil :

We are looking at a home built system by someone who has done that type of work before and just dreamed it up

JACUSTOMER-x9h9y6fb- :

Let me grab another picture quick

Home is less than 3 yrs old

Built by a building company

Its a townhouse

Phil :

Its a loopy condensate design. The drain into the slab is illegal, but an easy fix. Just run the condensate outside if you can find a gravity flow route

If not cut the pipe and put a condensate sump and pump assembly in

Then you can pump it to a drain/ it cannot be hard connected at the drain. There has to be an air gap.

JACUSTOMER-x9h9y6fb- :

Two more pics of rubber hoses running to black box

You can see the black box at the right in the second pic

Blower motor is by my thumb

Phil :

Rubber hoses probably go to the furnace condensate trap. Its a high efficiency condensing furnace. The black box is probably not necessary. The furnace condensate can be piped to any drain

JACUSTOMER-x9h9y6fb- :

My floor has a drain in it

White PVC drain cap with holes in it

Can it drain through there, don't know what else the drain is for

Floor slopes somewhat towards the drain

Phil :

If there is a floor drain there, the condensate pipe has to terminate one inch above the drain so that there is an air gap, that is to preclude sucking sewer gasses onto the AC system.

JACUSTOMER-x9h9y6fb- :

Ok

Phil :

System should work but it was not installed by anyone with training. These need to be properly set up. I recommend you call a Lennox dealer to do a service call on it..

Notice the pipe dope on the gas pipe union?

JACUSTOMER-x9h9y6fb- :

Unfortunately it was installed by a Lennox dealer

Phil :

There is supposed to be none on the piece in the middle of the union

JACUSTOMER-x9h9y6fb- :

No pipe dope on the middle of the union

?

Phil :

Pipe dope only goes on the pipe threads on each end.... not in the middle. That gets into the gas flow and can cause problems with your gas valve... its the sign of a person with no clue about the trade

The picture showed what appeared to be pipe dope

JACUSTOMER-x9h9y6fb- :

Which pic? 1, 2, or 3

Phil :

2 I think

JACUSTOMER-x9h9y6fb- :

Yeah I see what you mean

Phil :

The black box came with that model furnace

JACUSTOMER-x9h9y6fb- :

I also think that there was no need to bend the drain pipe right before the floor other than the fact that the installer did not line it up correctly

However, apparently it shouldn't be done that way at all

Phil :

Its a bad install but easily fixed

JACUSTOMER-x9h9y6fb- :

I can't easily run the drain pipe outside, but I could run it to the drain in the floor

Phil :

Find out which Lennox dealer installed it, and call a different one

JACUSTOMER-x9h9y6fb- :

Any idea why the black box came with the furnace?

Phil :

Just to collect the condensate and equalize the pressure between the condensate trap and the condensing chamber. Its not common with other condensing furnaces. Lennox is known for its unique approaches

JACUSTOMER-x9h9y6fb- :

I looked at my home inspection report and the report merely says that the condensate line is installed

Here is the pic he took during the walkthrough

JACUSTOMER-x9h9y6fb- :

You can see the drain in the floor

You can see that the trap is different too

Phil :

gasp..... give me a moment to recover...

JACUSTOMER-x9h9y6fb- :

Somebody came when it was under warranty and fixed a freon leak, noticed that the trap couldn't be cleaned and installed one that could be cleaned

JACUSTOMER-x9h9y6fb- :

What?

Phil :

The second photo lists the inspector's remarks... the term ludicrously incompetent comes to mind

JACUSTOMER-x9h9y6fb- :

What makes you think that, obviously I wouldn't know

Phil :

The top photo seems to show a floor drain about 12 inches away. From there the 3/4 plastic appears to be going into the floor...are you sure it goes into the floor? Maybe its just sitting there

Phil :

Tell me what business you are in and I will give you a parody

JACUSTOMER-x9h9y6fb- :

I thought that too and I checked

It definitely is concreted into the floor

Can't be moved at all

Phil :

Its illegal

JACUSTOMER-x9h9y6fb- :

I'm in electrical engineering

Phil :

Ok here is a parody of a bogus electrical inspection

"Wires are red and some green, with a black one... be sure you check these once a year to be sure they are not faded, or that the wire is still in the metal casing tube."

JACUSTOMER-x9h9y6fb- :

hahah, okay I see what you mean

Phil :

"once a year wipe off the wires with an oily rag to prevent rust"

JACUSTOMER-x9h9y6fb- :

Great

I feel like a dumb ass for hiring this guy

Phil :

The inspector advised oiling the electric motors with engine oil... wrong stuff.. you need electric motor oil or turbine oil, etc

You are not the man with the problem

You have no way of knowing ahead of time

JACUSTOMER-x9h9y6fb- :

True, but ultimately I am left to deal with incompetence of these men

Phil :

You find these things out later

Its getting worse by the micro second

Brace yourself

Lucky for you this is all an easy fix

JACUSTOMER-x9h9y6fb- :

What is the fix?

Phil :

But have a good Lennox dealer to a proper start up on it

JACUSTOMER-x9h9y6fb- :

Just to run to that drain in the floor

Phil :

Run the condensate to the drain, with a one inch air gap

Have a good Lennox dealer do a proper start up on it.. it takes special instruments

Flue gas analysis etc

JACUSTOMER-x9h9y6fb- :

I don't want to have the Lennox dealer do everything I just did, and end up with the same solution for $$$ reasons

Phil :

Its important

JACUSTOMER-x9h9y6fb- :

Ok

So its a safety thing

Phil :

Yes

You can do the condensate drain fix yourself

JACUSTOMER-x9h9y6fb- :

Yes, for sure

Phil :

To be doubly safe I would put a trap at the end of the condensate as well just before the drain

JACUSTOMER-x9h9y6fb- :

To catch anything that might clog my floor drain?

Phil :

Trap is so air cannot be sucked back into the system, and to prevent any combustion gasses from escaping past the black box. Its over kill but I can't be sure the black box was installed correctly and do not want to take the chance... Another reason for the Lennox dealer inspection

You could wait until the Lennox dealer arrives on the added trap.. I tend to be over cautious, and am probably being over cautious here.

JACUSTOMER-x9h9y6fb- :

I'm going to schedule an appointment tomorrow morning and see when they can come out

I have no way of knowing which dealer installed the unit

Phil :

Stay in touch as you need to

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