Thread: water in furnace pan

Here's a 6-yr-old furnace sitting in a pan of rusty-looking water. The homeowner said it's no big deal, just condensate - but shouldn't all the condensate be pumped directly out of the furnace, rather than draining into the pan? It looks like there is PVC coming from 3 different places out of the furnace (the clear tube is from the air exchanger), which I don't understand. One you can see in front going in about 8" from the bottom, but that continues up and heads to the rear; the other PVC joins that pipe at the floor.

Is there a leak somewhere causing water to drain into the pan, or is this normal for some furnaces?

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Originally Posted by Kristi Silber

Here's a 6-yr-old furnace sitting in a pan of rusty-looking water. The homeowner said it's no big deal, just condensate - but shouldn't all the condensate be pumped directly out of the furnace, rather than draining into the pan? It looks like there is PVC coming from 3 different places out of the furnace (the clear tube is from the air exchanger), which I don't understand. One you can see in front going in about 8" from the bottom, but that continues up and heads to the rear; the other PVC joins that pipe at the floor.

Is there a leak somewhere causing water to drain into the pan, or is this normal for some furnaces?

It has a problem.

Does it have a humidifier system on it?
What type of furnace is it?

Either way, water in the pan is wrong.
A few rusted drip spots is typical for that age but not that much water.

Nope, no humidifier. It's a Carrier direct vent, that's as much as I know. Thanks for reply - I thought it didn't seem right.

There appears to be a high water alarm on the pan.
The furnace sits on a plastic riser.
If that is condensate from the operation of the furnace, it is corrosive.
If its water from the AC condensation its neutral, but still a concern.

Cracked heat exchanger?
Or faulty AC?
Or both?

I would hazard a guess that this unit was purposely set up this way because its has been damaged in some way and somebody got a cheap furnace.

Did you remove the panels to see what further evidence existed?

Yeah, I noticed that alarm, too. And no, I didn't take the panels off. Usually that's more than we're called on to do, plus the homeowner was right there, assuring me that all was fine and normal.

I feel so dumb when it comes to HVAC, I wouldn't even know what to look for to see if the water is from AC or the furnace.

Is it possible the the furnace or AC is set up to drain into the drip pan, and the drip pan then has an outlet to carry the condensate to the floor drain?

I'm sorry! I wish I knew where to look to answer questions like these myself. I've looked at Inspectipedia, but the info there is so spread out, sometimes it's hard to find just what I'm looking for.

The pan is only there in case the primary and/or secondary drains fail. Water in the pan indicates a problem, either with the way the equipment is functioning, or the way it was set up, or both. Do not listen to anyone telling you it's ok. It ain't.

As others have said, water in the pan is wrong. Condensate from furnace is corrosive as stated, from AC not as corrosive but conducive to growth of biological organisms, (think Legionnaires Disease, worst case scenario just to drive home a point).

At the very least it will shorten the life of equipment, at worst it could make the occupant very ill. Out of your scope of work I know but it does not hurt to try to stay informed.
Keep posting, keep asking questions, you will learn, or probably have already, that a thick skin is needed here. You have shown some good insights and apparently you are willing to pay attention and to learn. Just don't be put off by some of the replies and stop trying...

The rust means the waters been in the pan for a long time. It's probably the A/C drain line is clogged and the condensate dripped down inside the furnace.

Another possibility is the direct vent condensate drain is kinked and that condensate is leaking into the pan. Either way, it's a problem that is usually an easy repair.

Thanks, guys! Man, I love this forum! I do learn so much here, and it's a great feeling. Alton, thanks especially for your kind words (there are a couple times when I have felt like not posting anymore, then someone will come along and say something like you've said, and I realize there are so many really excellent people here, it would be silly to walk away). And Darren, I love that avatar!

One of the most frustrating things about my job is that I'm not supposed to tell the homeowner when I see problems. It just makes me more convinced that one day I want to be an HI. I've a long ways to go, so much to learn, but you all are great role models!

I think I'll start doing more investigating when I see things like this, even if it takes a bit more time (this survey was a "high value," and normally worth a $46 fee though it can take 4-6 hours). Taking the panel off a furnace is pretty different from taking it off a C/B panel.

Definitely wrong. Standing water in the pan is not normal.

If you are that uncomfortable with HVAC Kristi, definitely invest in an HVAC inspection class. Ride along with an existing inspector to see how somebody else inspects HVAC systems hands on. The knowledge you gain will be invaluable and will make you much more confident when it comes to inspecting the HVAC system.

Others have covered this pretty well, however, if you're going to be intimidated by what the homeowner says while you're inspecting, then you need to grow a pair. Allowing a homeowner to tell you how to do your job, will eventually lead to a civil action against you, for passively allowing such defects to go unreported. You are there to observe, and write a report detailing what you observed. Regardless of what the homeowner has to say. If a contractor later determines there is no problem, then so be it.

It's a good thought, but at this stage I haven't the cash to invest in any classes, and it would be largely superfluous to my current job. I am thinking, though, that I should at least get a good HVAC book (any suggestions?).

I've also been hoping the only HI I know of around here will take me out inspecting with him, but so far he's a bit reluctant - and has his reasons for it. I should post somewhere asking about that.

Originally Posted by Kristi Silber

. I am thinking, though, that I should at least get a good HVAC book (any suggestions?).
.

.
This Amazon.com: Real Estate Home Inspection: Mastering the Profession (9780793168255): Russell Burgess: Books is an all around Generalist Knowledge Publication.
.

Thanks, Billy! Looks like it would be handy for my job now, too.

Check in to seeing if there are any local NAHI or ASHI chapters around and see if any of the inspectors in there would be open to letting you do some ride along inspections. The members of the local NAHI chapter I am in are very open to this to help new inspectors gain experience and knowledge.

Originally Posted by Jimmy Roberts

Others have covered this pretty well, however, if you're going to be intimidated by what the homeowner says while you're inspecting, then you need to grow a pair. Allowing a homeowner to tell you how to do your job, will eventually lead to a civil action against you, for passively allowing such defects to go unreported. You are there to observe, and write a report detailing what you observed. Regardless of what the homeowner has to say. If a contractor later determines there is no problem, then so be it.

Jimmy,
Kristi is not doing a Home Inspection as a HI, but is doing an inspection of the home for a blood sucking insurance company. She does a whirl wind inspection to look for potential liability exposure of the insurance company. Also, in a way she is working for the home owner since the premium is where she is paid from. Bottom line not a Home Inspection as you think of it, and for less than $10/hr.

Originally Posted by Garry Sorrells

Jimmy,
Kristi is not doing a Home Inspection as a HI, but is doing an inspection of the home for a blood sucking insurance company. She does a whirl wind inspection to look for potential liability exposure of the insurance company. Also, in a way she is working for the home owner since the premium is where she is paid from. Bottom line not a Home Inspection as you think of it, and for less than $10/hr.

Yow!!! Don't hold back Gary. Tell us what you really think.

That said.......Kristi, can you pass along the type of inspection you perform and what you are looking for as part of your inspections?

I didn't see Jimmy's post last time, but was coincidentally thinking yesterday about posting some info from the insurance perspective, even though I'm somewhat removed from the companies themselves.

The reason I was thinking of describing my job was based on questions brought up in some threads about the duty HIs have to their clients, and whether to warn them about potential future costs. Insurance is one of those costs, and some things that insurance companies look at are fairly easily/cheaply fixed and might save your clients money, like downspout runoff and railings where there are 4 or more risers leading to front or back doors. Some issues are also red flags for some companies, like aluminum wiring, inadequate C/B or fuse amperage, free-standing wood stoves, or galvanized water supply lines. (Somewhere there's a thread with a more extensive list of these "red flag" issues.)

I am assigned three main types of surveys: Exterior, Exterior/Interior, and High Value. In all surveys the main function of my job is to gather data about materials and methods used in construction, and measure the exterior of the house and sketch them online to find living area in square ft. I also look for obvious sources of dwelling and liability issues. This includes things like lack of railings, downspouts draining near the foundation or onto walkways, presence of aggressive dogs, deterioration of the property, etc. With interior surveys I also look at furnaces, water supply pipes, and fuse or circuit breaker panels, and attempt to date their installation and any upgrades since they were installed.

High Value surveys take the longest and are very detailed, including percentages of every type of wall, floor and ceiling covering, number of doors and what they are made of, built-in/ornate/special features (such as radiant ceiling panels I found in the last one I did, which the owner didn't even know about!), type of framing, brief histories of the purchase and coverage of the structure, accessibility in case of fire, alarm systems, and a million other details. This info not only goes into an online form, I have to write in a narrative style everything I learn.

My reports first go to my employers for quality control, and only once they've passed that do they go to the underwriter for whatever insurance company requested the report. They then base their premiums on it, taking into consideration both the replacement cost estimates (totalled by the program I use before I submit my data) and the "hazards/concerns" I've found during my survey.

So, yes, I do indirectly work for "blood-sucking" insurance companies, and that makes my job quite different from yours. It is the insurance companies that pay for the surveys, but it comes out of their overhead; it is not billed to the policyholders directly.

My training left a lot to be desired, and the problems we're trained to look for are pretty minimal. But I like to do my job well; the things I learn about here I often do end up reporting, like this furnace. Even though it's frustrating that I can't share my findings with the policyholder, I understand the reasoning behind it: if I did, and they did something about whatever the problem is, the info the policy is based on would no longer be accurate. It is up to the insurers to tell the PH (or the PH to ask...or an HI to tell them) what things they could do to bring their premiums down, if any.

It's kind of interesting seeing replacement cost estimates that are triple the current market value of a home.

That's probably more info that you wanted, but there it is!

(If anyone is interested, here's an example of one of my High Value narratives about the physical structure and systems in a home. Not all the surveys I do are whirlwind!
Risk was built in 2005 on foundation of a rambler that was torn down, apart from the area at the rear that is built on a crawl space, which is new. Foundation is concrete block. First story floor is reinforced concrete, supported by concrete and steel pillars. Ceiling of pantry and a closet behind it is also concrete; member states that rest of risk has wood joists, but FR suspects the entire second story floor is concrete. Member further states that above the basement is wood joist and stud framing, but FR suspects at least some steel studs and/or steel/concrete posts/beams to support concrete floor areas, especially considering the boxed in areas of the first floor ceiling (visible, for example, in the photo of the dining area). Risk also has some very thick (12") exterior walls, suggesting the possibility of reinforced concrete there as well - see, for example, the photo of the family room. On the left side of risk is a built-in garage, which has a reinforced concrete ceiling and a shop area to its right. Above the garage is a large open room with a cathedral ceiling. Roof here is rafters; elsewhere it is most likely trusses. Siding is HardieBoard planks and shingles, with HardieTrim around doors and windows. Windows are 80% double-hung and 20% fixed; they have thick glass with beveled grids mimicking panes. Roof has architectural shingles. Risk has 2 furnaces, one in the basement supplying heat to the first floor, one on the second floor, supplying heat there. Second floor furnace is equipt with air exchanger. Both are within 36" of combustibles. The second floor furnace has a pan under it that has about 1" of rusty water in it; after discussing it online with some housing inspectors, it appears there could be multiple reasons for this, but none of them good. There are radiant ceiling panels in the master bathroom. One 200 Amp circuit breaker panel is in the basement, one 100 Amp panel on the 2nd floor. Water supply lines are nearly all copper, with the exception of a little bit of PVC connected to bathroom fixtures, and flexible steel lines between risers and faucets. All systems apart from the 2nd floor furnace are in good condition.)

Nick,
I try to be restrained at all times. My comment was a restrained one.

Kristi,
Thanks for the example.
And thanks for the background, gives me an idea of what you may be familiar with and understand for future reference.
I am surprised that Unk wasn't using glue.

Regarding OP. If you see a few nail pops - like taxes, get use to it. If you see a ceiling with hundreds then there is something to explain as to cause.

I have a feeling that we will be seeing an increase in the numbers as time goes by, building faster and cheaper.

Since the pictured device in the safe pan has what appears to be loose yellow wiring to/from the back wall, in the safe pan and the back wall side of the furnace/safe pan seems to the possible origination area of the clear tubing drainage, I suspect this sensing device was not merely an alarm, but to close contacts to allow a pump to run.

The proximity of the folding chair and other inappropriate area storage leads me to believe that quite possibly damage to the installation, wires have been pulled and/or the pump has been disabled or perhaps just the sensor switch has been dislodged or disabled.

Also appears the sensor may be resting or mounted above the bottom of the safe pan (i.e. sitting upon something), perhaps the ajacent is a retention clip (white?) for the hose has been dislodged or removed (first picture along wall behind box or crate resting upon wall) or the pump has lost its prime or been disconnected. (Although you insist there isn't a humidifier present, it would be unusual to not in MN, and that clear tubing is usually included with same.

Some provide audible alarm, some also a light display, some also close contacts to allow a pump to run.

I do not see a trap for the coil's condensate drain either.

NFPA 90A & 90B can be viewed on line at NFPA.org. I note what appears to be the manuals located at the return.

Would a humidifier be invisible, i.e. inside the furnace? I've seen some humidifiers around here, but they aren't ubiquitous, and they've been on the outside of the furnace.

The clear hose is coming from an air exchanger.

Originally Posted by Kristi Silber

Would a humidifier be invisible, i.e. inside the furnace? I've seen some humidifiers around here, but they aren't ubiquitous, and they've been on the outside of the furnace.

The clear hose is coming from an air exchanger.

They all have some visible sign at the exterior. Some are small and typically are a spray or atomizer type, but all will have a water line running to them.

The vinyl line you referenced earlier in the thread is typically the type of overflow used for humidifier, thermal expansion device (on cold water supply line), and condensate pump discharge. The pictures don't show enough to tell what this one is for.

There have been many threads regarding the condensate plumbing which is what has caused the water in the bottom of the auxiliary drain pan. With the location and time of year, I would suspect it is from a condensing furnace. The most likely cause is a loose connection inside the furnace where a black rubber hose has pulled loose from a connection that is held in place with a hose clamp. The rest of the installation looks very professional and I doubt there is a problem with the way the condensate drain has been installed (can't see so can't be sure). In any case, as stated by others, there is a problem that needs to be addressed.

The float switch in the auxiliary pan is to stop condensate from being produced in the event it reaches a level close to the overflow of the pan. The switch is typicaly in line with the condenser control low voltage wire and stops the compressor if it opens. The switch can be wired in line with the low voltage supply wire which would stop everything as opposed to just the compressor. In this case the water has not reached a level to open the switch or its wired to stop the compressor.

This in the photo below is what the clear tube is coming from. Air exchanger, no? And yes, it's a condensing furnace; I saw no sign of a humidifier, and I do specifically look for those. The house had another furnace, also with no humidifier - no pan under it, either - why the homeowner thought it was normal to have rusty water under this one, I don't know.

The pump for my condensing furnace is outside the furnace itself, but I gather they can be inside, too.

I suspect the floor drain has a trap in it, though I didn't think to look for one. The house seemed to be built pretty well as a whole, and I would think they'd do that part right, too.

Really wish I'd taken the front panel off to have a look! Oh, well, next time.

...Hmm, just noticed the brown marks on the vents above the exchanger.

Originally Posted by Kristi Silber

Here's a 6-yr-old furnace sitting in a pan of rusty-looking water. ...

Is the furnace installed over a livable or damageable area? What you see is what's called a "Secondary Drip Pan" by some, and may be required if a HVAC unit is installed over a space that may be damaged should water overflow from the internal drip pan that came with the evaporator coil unit. In my experience the drip pan would be installed as you see with a drain or a pump, and sometimes an alarm of some type should the drain line become clogged. This could be just an audible alarm or it may shut the AC system down until restored.

Being that the high level alarm wiring appears to have been installed when the unit was installed, it appears that the AC unit will stop until the water level is reduced.

It looks to me that the internal drip pan is not connected, not functioning, not level, drain pipe(s) clogged, or all of the above. Is it normal? The pan and alarm may be, but the sitting water isn't. Based upon the water level there also may be damage to the furnace shroud.

Originally Posted by Kristi Silber

...The pump for my condensing furnace is outside the furnace itself, but I gather they can be inside, too...

I've never heard of a condensate pump being inside a furnace.

Yes, it's installed on the 2nd floor (there's one in the basment as well). I was thinking maybe the branch PVC that went toward the back along the floor might be a drain for the drip pan. Then the branch that goes up appears to enter the furnace at two places - once about a foot above the floor, and once a few inches from the top. Would the top part then be draining the internal drip pan? And the other part be connected to a pump?

One thing I wondered about was whether the open end of the PVC was messing up the pumping mechanism.

Originally Posted by Kristi Silber

Yes, it's installed on the 2nd floor (there's one in the basment as well). I was thinking maybe the branch PVC that went toward the back along the floor might be a drain for the drip pan. Then the branch that goes up appears to enter the furnace at two places - once about a foot above the floor, and once a few inches from the top. Would the top part then be draining the internal drip pan? And the other part be connected to a pump?

One thing I wondered about was whether the open end of the PVC was messing up the pumping mechanism.

I would assume that the pipe going to the rear is for the pan drain. But, unless you are going back---we won't know. Maybe there is a dead mouse blocking the drain!

As for the piping in the front, it appears to be OK. Follow the path, it starts out at the drain, first goes to the furnace condensate drain (the "T" fitting with venting at the top), then it goes between the return air duct and the furnace (hidden in photo), and up to the evaporator drain on the side of the supply duct.

Originally Posted by Rich Goeken

I would assume that the pipe going to the rear is for the pan drain. But, unless you are going back---we won't know. Maybe there is a dead mouse blocking the drain!

As for the piping in the front, it appears to be OK. Follow the path, it starts out at the drain, first goes to the furnace condensate drain (the "T" fitting with venting at the top), then it goes between the return air duct and the furnace (hidden in photo), and up to the evaporator drain on the side of the supply duct.

Forgot to add that I don't know what the first connection is for---any help from HVAC folks out there?

Originally Posted by Vern Heiler

They all have some visible sign at the exterior. Some are small and typically are a spray or atomizer type, but all will have a water line running to them.

. . . . . . .

Actually Vern, the most common type of residential humidifier by far is an evaporative media. Spray or atomizing humidifiers are mostly seen in commercial/industrial/institutional applications.

Originally Posted by Rod Butler

Actually Vern, the most common type of residential humidifier by far is an evaporative media. Spray or atomizing humidifiers are mostly seen in commercial/industrial/institutional applications.

Actually Rod, I see them in residental as often as evaporative media.

Ah, a water line to the furnace - that's what that would be for, a humidifier! I remember seeing that once and not being able to figure it out. The humidifier wasn't obvious in that case, but maybe I didn't look hard enough for it.

I've never heard of a condensate pump being inside a furnace.Today 06:11 AM

So, if the condensate is acidic, does that mean it could corrode drain pipes?

Originally Posted by Kristi Silber

Ah, a water line to the furnace - that's what that would be for, a humidifier! I remember seeing that once and not being able to figure it out. The humidifier wasn't obvious in that case, but maybe I didn't look hard enough for it.

I've never heard of a condensate pump being inside a furnace.Today 06:11 AM

So, if the condensate is acidic, does that mean it could corrode drain pipes?

The humidifier will be installed in the plenum, down stream of the furnace. While the furnace condensate is acidic, I don't think you need to break out the rubber apron and gloves. Just don't water your favorite plant with the stuff. All of the condensate drain line I have ever seen has been made of plastic material.

I was thinking more of the house drains.

Originally Posted by Kristi Silber

Ah, a water line to the furnace - that's what that would be for, a humidifier! I remember seeing that once and not being able to figure it out. The humidifier wasn't obvious in that case, but maybe I didn't look hard enough for it.

I've never heard of a condensate pump being inside a furnace.Today 06:11 AM

So, if the condensate is acidic, does that mean it could corrode drain pipes?

Originally Posted by Kristi Silber

I was thinking more of the house drains.

There is a lot nastier stuff going down waste plumbing than furnace condensate.

Originally Posted by Vern Heiler

The humidifier will be installed in the plenum, down stream of the furnace. While the furnace condensate is acidic, I don't think you need to break out the rubber apron and gloves. Just don't water your favorite plant with the stuff. All of the condensate drain line I have ever seen has been made of plastic material.

K.S. is in Minnesota not the SE.

The humidifier will oftentimes be mounted on the cold air return, especially if there is an AC coil in the plenum above the upflow furnace.

Perhaps the "ventilator" is an ERV.

Originally Posted by H.G. Watson, Sr.

K.S. is in Minnesota not the SE.

The humidifier will oftentimes be mounted on the cold air return, especially if there is an AC coil in the plenum above the upflow furnace.

Perhaps the "ventilator" is an ERV.

That is a good way to rust out the heatexchanger!

Originally Posted by Vern Heiler

That is a good way to rust out the heatexchanger!

Nonsense!

Originally Posted by H.G. Watson, Sr.

Nonsense!

Why do you think the evaporator coil is always down stream?

Originally Posted by Vern Heiler

The humidifier will be installed in the plenum, down stream of the furnace.

I disagree. A humidistat or hygrometer is not a humidifier. A humidifier is not a dehumidifier, quite the opposite. A humidifier is not an evaporator coil. The OP has pictured an UPFLOW furnace - to have placed where you suggest not only would it not perform and function as intended, it would interfere with effective AC and would quite probably subject the furnace to damage, should the (most common) HUMIDIFIER's drain, pan, pad, valve, etc. fail or not be placed correctly, or become encased with sediment and/or biologics, become clogged, pinched, etc. and be located where YOU suggested (gravity, surface tension) we don't want the furnace, its controls, etc. flooded by a failure at the Humidifier. We also don't want to overload the recirculating air with TOO MUCH absolute humidity. The RH drops as the air itself is heated with all other things remaining equal in other than a bell jar environment. Furthermore, the OP has indicated the pictured and discussed IS a Direct Vented Installation, modern (6 y.o.) Carrier Furnace.

Originally Posted by H.G. Watson, Sr.

K.S. is in Minnesota not the SE.

The humidifier will oftentimes be mounted on the cold air return, especially if there is an AC coil in the plenum above the upflow furnace.

Perhaps the "ventilator" is an ERV.

Originally Posted by Vern Heiler

That is a good way to rust out the heatexchanger!

Originally Posted by H.G. Watson, Sr.

Nonsense!

Originally Posted by Vern Heiler

Why do you think the evaporator coil is always down stream?

And what does that have to do with your assertion regarding the humidifier location? Are you under some mistaken belief the OP is discussing a split HP with gas heat backup? or that Minnesota Climate necessates humidifying or swamp cooling in the summer (such as in the desert SW) or that your region's climate is in anyway similar to Minnesota? She isn't, it doesn't, and it isn't.

You're talking in circles and have either confused yourself yet again, or are having some sort of serious disconnect!

You quoted and responded regarding potential, regular, and usual location of a humidifier (not a humidistat) in a NORTHERN CENTRAL (Minnesota!) CLIMATE upon a fuel fired direct vent furnace, not a dehumidifier, nor the Latent Cooling Capacity (ability to REMOVE MOISTURE FROM THE AIR) of an air conditioning system, not a humidistat, nor a dehumidistat. The OP is discussing an upflow furnace with obviously an upflow coil (the "norm" in MN). In case you didn't notice, the pictured is withIN the thermal envelope and installed in finished, conditioned space (unlike your usual findings in SC).

YOU claimed the Humidifier should be located where the AC evaporator Coil should be located, in a humid summer, dry/sub-zero cold heating climate; when installed! I disagree completely. Then you start carrying on as though someone (noone did but you) suggested a split ac evaporator coil shouldn't be where it belongs !?!.


RH vs. absolute humidity and differential - more RH is not always better. We avoid condensation on the windows and walls and actually adjust RH DOWN as the temperatures plummet outside.

Evaporator Coil: Located inside the home, a series or network of tubes filled with refrigerant that remove heat and moisture from indoor air as liquid refrigerant evaporates.

Return Air: Air drawn into a heating unt after having been circulated from the heater's output supply to a room.

Upflow: A type of air conditioning system that discharges air into the conditioned space via a top-mounted discharge plenum or through an overhead duct system.

Upflow Furnace: A furnace that pulls return air in from the bottom and expells warm air from the top.
.

H.G., I like you "really", but stay away from HVAC. I will respond when you have returned to earth.

Watson said,

The humidifier will oftentimes be mounted on the cold air return, especially if there is an AC coil in the plenum above the upflow furnace.

After doing a little reading (yes, H.G., I do read stuff on my own) and looking at the photos I have of furnaces with humidifiers, this does indeed seem to be the case. Some humidifiers seem to be mounted within the cold air return, and some mounted semi-externally, drawing cold air through them which then bypasses the furnace completely, shunting it directly to the plenum.

Then there are the steam-type humidifiers, which apparently can be mounted anywhere within 25 ft of the furnace.

Reading the Aprilaire site also alerted me to the fact that humidifiers themselves are often drained - "extra" water flushes the deposits off the screen and away.

Originally Posted by Kristi Silber

Watson said,


After doing a little reading (yes, H.G., I do read stuff on my own) and looking at the photos I have of furnaces with humidifiers, this does indeed seem to be the case. Some humidifiers seem to be mounted within the cold air return, and some mounted semi-externally, drawing cold air through them which then bypasses the furnace completely, shunting it directly to the plenum.

Then there are the steam-type humidifiers, which apparently can be mounted anywhere within 25 ft of the furnace.

Reading the Aprilaire site also alerted me to the fact that humidifiers themselves are often drained - "extra" water flushes the deposits off the screen and away.

Ok Kristi, here's another $0.02.

For the record, the proper place to install a humidifier is on the downstream side of the heat exchanger. The higher temp encourages better evaporation and better absorption of the air. That doesn't mean that they may not be installed on the return air duct, it's just incorrect.

The drain from an Arpilaire humidifier is the excess water falling from the evaporative media and is supposed to flush away the stuff as you mentioned. However the media still clogs with deposits and detritus and should be replaced from time to time.

Steam or atomizer humidifiers for residential applications are unheard of in these parts but it is still better to install them downstream from the heat exchanger.

I realize this is way more info than ever intended from your original post but dang I just feel like reaching out today.

And I might add, that reading and posting on Inspection News IS research in my book. That is why I come here.

Well, that and to spout of from time to time.

Originally Posted by Rod Butler

And I might add, that reading and posting on Inspection News IS research in my book. That is why I come here.

Yes indeed! Full agreement there! And the best thing that can happen, to my view, is to have a thread about something specific wander off into the general, or to another specific - you just keep learning! Another really excellent facet of this forum is that debate is acceptible and normal; debate is such a good way to learn. That's why I get involved in discussions like this, even though I don't have the background to go with it.

For the record, the proper place to install a humidifier is on the downstream side of the heat exchanger.

Depends on the type of humidifier.

What is a typical Aprilaire Installation?

1. <LI class=bodybold>All power units must be installed on the warm air plenum with the humidistat on the return or new outdoor sensor.
   
   <LI class=bodybold>By-pass models can be installed on the return drop or warm air plenum with 6" venting.
2. Make sure humidistat is higher than unit for proper reading.

Wanted to respond to Watson:

The OP has pictured an UPFLOW furnace - to have placed where you suggest not only would it not perform and function as intended, it would interfere with effective AC Why do you say this? and would quite probably subject the furnace to damage, should the (most common) HUMIDIFIER's drain, pan, pad, valve, etc. fail or not be placed correctly, or become encased with sediment and/or biologics, become clogged, pinched, etc. and be located where YOU suggested (gravity, surface tension) we don't want the furnace, its controls, etc. flooded by a failure at the Humidifier. If the humidifier is mounted on the outside, how would the damage occur? Even if it overflowed it would drain down the inside of the furnace wall and into the drip pan (or onto the floor). We also don't want to overload the recirculating air with TOO MUCH absolute humidity. The RH drops as the air itself is heated with all other things remaining equal in other than a bell jar environment. As far as I can tell, with the humidifiers installed today, the RH is automatically adjusted based on outdoor temperature, and the RH sensor would measure at the same place and time air temp is measured, so I don't understand what you're gettting at with all this RH business. Please explain (...to this lazy and ignorant insurance surveyor).

Just as big an issue with the OP is the fact that standing water can perpetuate mold and mildew issues as well as attract bugs and critters!

When I inspected furnaces having humidifiers attached, anywhere, I made a point of pulling the access cover panels (top and bottom) off the furnace cabinet to check for obvious rust. Nearly always found it somewhere. Then of course the concern for heat exchanger corrosion and CO intrusion is heightened.

On approximately 100% of the furnaces with humidifiers attached, the home owner either had no idea how to regulate the unit depending on the outside and ambient temps, or didn't care, and so they would run too much water and overflow or allow excess moisture to run everywhere. That was a given.

Talk about a red flag? Plenum or duct mounted humidifiers are the biggest!!

Kristi,

There is absolutely something wrong with that system. I'm not a home inspector, but an HVAC technician. Based on what I can see in the pictures you've got a condensing furnace and an evaporator coil. Both of these can produce condensation, and both have drains that, if working properly, will remove the condensation. That little switch connected to the pan that has the two yellow wires coming out of it is an overflow safety switch. It is used to turn off whatever is producing the water before it overflows the pan. Oh, and the pan under the furnace is called a "secondary drain pan." It's called secondary because there is a primary drain pan. In a perfect world the secondary drain pan would never see water, ever. If there is ever water in that pan something is wrong.... period.

I hope that helps.

Thanks, Bob and Ray. I called it in my report; now I wish I'd said something to the homeowner, too - although, since it's not an imminent safety issue (is it?), that would have gone against the rules for my job. Sigh.

Originally Posted by Kristi Silber

...although, since it's not an imminent safety issue (is it?)...

Not to beat you up here Kristi, but FYI...

It COULD be if the water/moisture were contacting the heat exchanger on its travels downward and corroding it. (CO poisoning?) The right way to verify that is not happening is to remove the exchanger and inspect it.

Or, some metal portion of the exhaust flue may be corroding. Again, introducing CO into the home.

Or, if mold became an issue, then respiratory problems or worse may become the issue.

Or, and this may be a stretch, if the water was left in contact with the metal of the furnace bottom or feet long enough, it may cause so much corrosion that the cabinet may drop or move possibly causing a breach in the exhaust flue piping.

Or, again a possible stretch, the water may be traveling across the electrical connections of the fan motor or some other electrical or electronic connections and eventually may damage them to the point that they may short out and/or catch fire.

Yeah, I'd have said something to the owner about having it professionally looked at, for his and his families safety. Just a CYA thing.

Given the amount of BTU's being cranked through today's furnaces in the form of huge volumes of burning gas and the pressures developed forcing the gases through the system, not to mention the very thin metal walls of the heat exchanger for higher efficiency, it's my opinion that metal (particularly thin metals) + moisture or high humidity = a potentially very dangerous situation. It's a huge red flag combination that begs to have a professionally done, thorough inspection of the internal components of the furnace to avoid life threatening scenarios should a leak occur.

Thank you, Bob, you've convinced me...I have a moral obligation to talk to the homeowners about things like this, and I don't take that lightly. That's not beating me up, it's setting me straight, being informative, and I appreciate it.

Originally Posted by Kristi Silber

Depends on the type of humidifier.

What is a typical Aprilaire Installation?

1. <LI class=bodybold>All power units must be installed on the warm air plenum with the humidistat on the return or new outdoor sensor.
   
   <LI class=bodybold>By-pass models can be installed on the return drop or warm air plenum with 6" venting.
2. Make sure humidistat is higher than unit for proper reading.

At the risk of kicking a dead horse . . . I still say the proper place for a humidifier is on the leaving side of a heat exchanger where the air is (hopefully) warmer during the heating/humidifying season. I agree it is acceptable to install on the upstream side but, well, it just ain't proper.

Imagine the loss of sales at Aprilaire if they suggested that the only place to properly install a humidifier were on the leaving side of a heat exchanger!

If your concern is that warm air flows through the humidifier, it does so wherever its placed. I'm pretty sure it's the difference in pressure on either side of the furnace that makes air flow through bypass-type humidifiers, so it's always going to have warm air flowing through it wherever it is. The ductless ones should be on the warm side, though, I agree.

Here's part of an installation guide for a Desert Spring furnace humidifier:

". Selecting a Location

• If mounted on the COLD air side, air is supplied to the humidifier with a flexible duct connected to the air take-off (with sliding damper) mounted on the HOT AIR SUPPLY coming out of the furnace.
• If mounted on the HOT air side, air is supplied to the humidifier after coming out of the furnace. It is the returned to the furnace with a flexible duct connected to the air take-off (with sliding damper) mounted on the COLD AIR SUPPLY.
• Follow the instructions on the humidifier TEMPLATE to locate and cut holes for the humidifier and take-off.
• The COLD air return is preferred for the Desert Spring Humidifier.
• Mount the take-off so that the damper can be easily opened and closed.
• The Desert Spring Humidifier does not wet the furnace filter.

"

Kristi,
A good guide for inspecting HVAC can be bought at "Saturn Resource Management". Look in their bookstore. They have field guides, technical sheets, and guides all geared toward HVAC. We use them in our training classes and my inspectors carry them with them in the field. Even our seasoned inspectors use them to help the client understand (Lots of pictures) what they are trying to show them and how the system should run. They are written by some very smart people in this industry.

I highly recommend them.

Dave

Thanks, Dave - looks like some good books there.

Not sure if this ever got resolved. I did notice that in one of the pictures (labeled extra pipe here or here?) there is a drain piece missing. Above the furnace is the inside evaporating coil. The refrigerant evaporates in this coil using the heat load from inside the house for the heat. That is to say removing the heat from inside the house and carrying is outside -this is for AC during the warm months of course.

The coil sits on top of the furnace/air handler (for up-flow installation) - it should have a male pvc fitting attached to the opening (that has the female side of the threads...). As the conditioned air passes over the coil it is cooled and moisture is removed. That male pvc fitting attaches to a drain pan INSIDE the coil box, and pvc piping should carry the water outside or to a condensate drain.

The water in the secondary pan MAY be from that and is draining down through the furnace...