Humidifiers and Dehumidifiers - Furnace filter clogged 8 days after humidifier install!

I installed an Aprilaire 400A on the 30th of January. Today, only eight days later, I noticed our furnace fan running full speed with no call for heat. I discovered the pleated furnace filter was severely restricted and replacement let the fan settle down and run at idle speed. I change the filters quarterly and never had any problem with dust restricting it so severely it ramped up the fan speed. I can only assume it is dust from the humidifier. I assumed the water deposits would stay in the humidifier filters so I got a supply of them with the unit though now it looks like I'll burn through many more furnace filters instead. I'm liking this furnace mounted humidifier less every day.

That's a new one for me...

There is no dust made by the humidifier. the air is already filtered when it comes though the pad.

It's a white coating on the filter, not the usual brown dust. I had put a new one in Jan 1. We do have hard water and the fan is always running, from idle to full on heat demand. I've never seen the 400A filter damp more than two or three inches of the bottom of the filter. Seemed slow to put any moisture in the air but eventually shut off around 45%, then didn't kick back on till below 40%. That being the reading on the 400A humidistat. The cheap hygrometer I have upstairs never read much over 30%. I should put together a sling psychrometer for a more accurate reading.
The plugged up furnace filter was certainly unexpected. The humidifier is on the return four foot ahead of the filter.

This is what I am thinking.

Since the 400 isn't a flow though, and you said the pad is dry in most area, and have hard water, it may be the issue..

Hard water is mineral in the water, and when it does go into the pad, it dries up, and it's not being flushed down the drain like the regular flow though unit.

Not to hijack your thread, but when I installed my humidifer, I loosened a lot of debris with all the cutting into the plenum and the air intake, etc. Shaking everything, etc.

Could be you loosened this stuff up when you installed it and it took a couple days to "stick" to the filter. I changed mine a week later, too, and it was a fairly new furnace filter. Since then, I have had no issues.

Doesn't sound like your problem, but ya never know.

If I could post an attachment I'd post a picture of my furnace filter clogged up again two weeks after replacement. :mad: Pissed off doesn't begin to describe my mood. Not only am I burning through furnace filters but the furnace is burning up electricity running the fan at full speed to overcome the restricted filter until I discover it and replace it. This is bullcrap.

http://img23.imageshack.us/img23/6668/img0340large.th.jpg (http://img23.imageshack.us/my.php?image=img0340large.jpg)

Would be nice if strike was included in the bb code allowed...

The photo has to be on a photo host site like yahoo, or imageshack.us.

As I said before, this is the first I've heard such thing. Only thing I can think of is the water is "left" in the pad/tray, and all the minerals in the water is not being flushed down the drain as would be found in the flow though unit.

From the 400 Owners Manual:
The minerals and solid residue not trapped by the replaceable Water Panel evaporator are flushed down the drain in the Models 350, 360, 500, 600 and 700. This is the most effective and least expensive method to dispose of trouble-causing minerals. The drain also eliminates the problems caused by stagnant water.
There are some homes where drain facilities are not accessible or available. For these situations, or where high water hardness is not a problem, the newest Aprilaire, Model 400, is designed to satisfy these applications.

I have no experience with the 400, but it looks like it has no drain (except one for emergencies) so it can't flush away the minerals like most of the other units. This undoubtedly saves tons of water, but I think it guarantees that all of the mineral content in the water will become dust...

If that's true, I'd say that a steam unit like the Honeywell TrueSteam or Skuttle might have been a better choice.

I got this from the supplier of the unit and as you can see Aprilaire is in a strong state of denial: "I contacted Aprilaire about this and sent the picture also. They stated that there is no way that the humidifier can cause this. They said there has to be something in the duct or the filter itself is breaking down." Maybe poltergeists in the duct are breaking the filter down into mineral dust in two weeks time...
I think I'll send them a section of the filter to see that the minerals did indeed come from the humidfier.
http://img26.imageshack.us/img26/355/img0361l.th.jpg (http://img26.imageshack.us/my.php?image=img0361l.jpg)
http://img4.imageshack.us/img4/4525/img0363y.th.jpg (http://img4.imageshack.us/my.php?image=img0363y.jpg)

They must have some knowledge of this problem to make that statement in the owner's manual about high water hardness. A line filter was suggested by an HVAC company but then I'd be purchasing countless filters of another type with no guarantee that the problem wouldn't recur. Which begs the question, what happens with the minerals using a steam unit?

edit: The bottom of the humidifier filter is to the right in the photo, you can see the deposits accumulating.

The air filter picture, Did you cut that section out or that came apart like that?

Seeing all the deposit, that's a lot of minerals in the water after a few days. Do you know what your water hardness is?

Do you have a water softener? If you don't, I can't imagin what your water heater looks like at the bottom.


For steam unit, they flush the water down every now and then, and Honeywell has a coating on the coil to prevent heavy build up, and makes cleaning easy every spring.

Standard disclaimer...no expert here....

If you put some CLR or similar on the filter, you should be able to tell if its minerals or something else.

http://img413.imageshack.us/img413/8759/img0365.th.jpg (http://img413.imageshack.us/my.php?image=img0365.jpg)
Our showerhead needs some CLR for sure.
The water analysis from two years ago showed a total water hardness(as CaC03) of 140 Mg/L. I'm finding that is only considered moderately hard, >150 being hard, >300 very hard.
Yes, I cut the filter for samples to return w/ the humidifier and to send to Aprilaire.
No water softener. I've flushed the 15yr old water heater a couple of times since we moved in eight years ago. Still does it's job.

Wow! I've never seen the shower head that bad.

I've had water softener most of my life, and didn't have it for a short time at once place I was in, the head got white, but not like yours.

I would suggest getting a water softener to save on your washer, dishwasher, and other fixtures.

I dont know why the air filter should clog the air should be getting pulled from the return duct thru the unit and into the supply side of the ducting totally bypassing the filter. Anything that evaporates should be sent out thru the ducting into the house. Do you have a picture of the installation?

http://img178.imageshack.us/img178/5029/img0302.th.jpg (http://img178.imageshack.us/my.php?image=img0302.jpg)
I think you need to rethink pressure differentials eddie.

do you have this problem only on the hot water, or in your water in general?

could be something in your hot water tank. Just a thought.

I have this weird jelly stuff coming out of my tank which I believe to be coming from the anode falling apart. But I imagine this is your water source, period. Not just hot water.

But if you get this much sediment from your water in general, you may want to drain your tank more often to get rid of it. And cleaner water will help it last longer, too.

http://img178.imageshack.us/img178/5029/img0302.th.jpg (http://img178.imageshack.us/my.php?image=img0302.jpg)
I think you need to rethink pressure differentials eddie.

According to the Aprilaire installation paperwork the main unit should be mounted on the supply side of the furnace and the intake should be on the return side. When the furnace is on you will be pushing air past the main filter and be drawing air in thru the return side. Your unit appears to be mounted the exact opposite of that.

http://www.discountfurnacefilter.com/v/Downloadable%20Resources/Aprilaire%20Documentation/400A%20Installation%20Instructions.pdf

According to the Aprilaire installation paperwork the main unit should be mounted on the supply side of the furnace and the intake should be on the return side. When the furnace is on you will be pushing air past the main filter and be drawing air in thru the return side. Your unit appears to be mounted the exact opposite of that.

Eddie,

I looked at the manual, on the first page, on the right hand side "Installation Option" it says it can be mounted on either side.

The air on all bypass unit is going to come from the supply(Under preassure) side into the return(under negative preassure) side.

Most dealer/installer prefer to mount the humidifier on the return side to less the risk of water damage to the furnace if something did go wrong with the humidifier itself.

Also, lot of furnace there is no room on the supply side to mount the humidifier on.. Like mine below in the photo below.

http://img246.imageshack.us/img246/4048/imgp0468.jpg

http://www.aprilairehumidifierparts.com/files/49460.pdf

The installation options clearly states the unit may be mounted on either the supply or return plenum.

I see what you are saying about the air pressure now it would work either way but if it could have been installed the other way you wouldnt be pushing very moist air directly into your air filter where it can dry and leave a lot of mineral deposits which is what seems to be happening to Satch. Even though they say it can be run either way it seems it would work better installed the other way except he has no room to install it that way looking at his furnace. Man my hot air furnace doesnt have half those tubes running out of it and it feeds a 3600 sq ft house.

Read again: "The air on all bypass unit is going to come from the supply(Under preassure) side into the return(under negative preassure) side."

The moistened air ends up in the return plenum no matter which side the unit is mounted.

it could have been installed the other way you wouldnt be pushing very moist air directly into your air filter
The humidity % going into the return is going to be same either way.

The only humidity you don't want going into the return is the Steam models.

Even though they say it can be run either way it seems it would work better installed the other way except he has no room to install it that way looking at his furnace.
I am curious on how or why you think it works better on supply side vs return side?


Man my hot air furnace doesnt have half those tubes running out of it and it feeds a 3600 sq ft house.
I got almost everything on my furnace.
-A/C
-90% 2 Stage (white PVC pipes)
-UV Light.
-Humidifier
-Fresh air
-Media Air filter.

I think no matter what, this water source is a problem and needs to be dealt with. Doesnt matter where those deposits accumulate whether it be in the air filter or the ducts or on the floors and walls of the house, its just a small problem that got bigger.

Yes, it's a curse. It couldn't be as simple as mounting a humidifier on the furnace. Can't assume a inline filter would stop the deposition. Don't want the expense of installation and consumables for a water softener, which can produce deposits of it's own. I've seen pictures of steam unit heating elements looking worse than my shower head in a matter of weeks. A reverse osmosis water filter to feed portable units would be expensive to purchase filters for to avoid excessive maintenance on the portables, plus time spent filling them.
I usually am able to purchase the pleated furnace filters on sale for $3.50 at Ace Hardware. Perhaps I should just plan on replacing it every two weeks through the season, might be the cheapest solution of all. The Aprilaire does it's thing without any intervention otherwise. Maybe a $20 inline filter will stretch the periods between furnace filter changes...
I need some moisture somehow. Age brought on a itching atopical dermatitis with the dry winter air that is still driving me nuts even with the humidity up around 50%.

As a reminder, if you're not on well water, it would seem that a different flow-through unit would deposit less due to it's "self-flushing" (a.k.a. water-wasting!) design.

Noted. That was Jay11J's original take on the choice of humidifiers which I did not heed. We pay three times what the communities on either side of us pay for water from the same exact pipe. 40% more for electricity. I kick myself every day for not taking the bermed house and 5 acres in the country eight years ago.:wall: