How to install a whole house humidifier in 10 steps

If you don't have allergies or asthma, then the level of humidity in your house is not that important to you, but if you are heating your house in the winter is likely that one way or another you are being affected by this issue.

During a tough winter day, a house heated at 72 degrees has a humidity level of 6 percent - compare that to the 25 percent humidity in the Sahara Desert, and you would get the idea of how millions of people live in misery every winter because of the dry air in their homes. Furthermore, humidity greatly affects air quality. Low humidity can cause all kinds of ailments, like severely dry skin, nose and eyes, asthma attacks, increased allergies and respiratory infections. The chart below illustrates this very well:



As a solution, and since we are selling them at work (therefore I can get one very cheaply) I bought a whole-house humidifier to install in my house. I went with a Skuttle Model 2000 High Capacity Bypass Flow-Thru Humidifier. Buying the thing was the easy part - I had a heck of a time understanding how it works and even worse, how to install it. After calling several Heating and AC places to inquire about installing it, I got tired of getting the runaround, I gave up on it, and today decided to install the thing myself, and since I found zero help online and no instructions on how to do it, I put together a short tutorial on how to install a whole-house humidifier. The purpose of these steps are to help other do-it-yourself guys (and gals) do the same thing. Generally speaking, these steps should apply most other models of by-pass humidifiers.

GENERAL DISCLAIMER: Unfortunately I have to say this. These steps to install a whole house humidifier are just suggestions and you should not do this yourself unless you are a certified technician/electrician. If you cut your fingers, lose an eye, get electrocuted, flood your house or blow it up, don't come blame me for it since I did not make you do it. I am not responsible for any errors in my suggestions, typos or any other information that may lead to your injury or death. These general suggestions are not meant to replace professional training or expertise and are only serving as documentation of my own installation of a whole house humidifier.

Whatever you do, make sure you choose the right humidifier based on the square footage of your home and the "tightness" of it. Speaking with an expert or simply calling and asking the manufacturer will help you make the right decision.

Tools needed: Tin snips, electric drill and bits, flat and phillips screwdrivers, wire cutters, duct tape, leather gloves, utility knife, plumbing wrench, flash light, measuring tape.

Parts: 6 inch tin collar, 90 degree elbow (6 inch), 6 inch duct (as long as necessary), stranded electric cable (smaller gauge), electric tape, wire nuts, teflon tape, saddle valve, copper tubing, plastic tubing for draining.

Cost: Parts cost about $65, plus the wholesale cost of the humidifier.



Before you start, turn your heat off and cut off electricity from your furnace.

Step 1 - Use the tin snips and the template provided by the manufacturer to cut an opening into the plenum of your furnace (hot air main) - a reader of this blog also commented below that a Dremel cutting tool worked better than tin snips, and this is an excellent suggestion. I found that drilling large holes helps getting the cut started - when cutting a rectangle is seems to be easier if the holes are drilled in the corners. The cut edges will be razor-sharp; wear heavy leather gloves when you touch them - I got cut through my leather gloves too so be extremely careful. Also make sure to cut the opening level - remember that water will flow through this device, so it has to flow evenly.



Step 2 - Drill pilot holes into the plenum and mount the base of the humidifier securing it with screws as directed by the manufacturer.



Put the media inside and snap the cover on.



Step 3 - Mount the 6 inch duct to the humidifier using a collar and use duct tape to secure the connection. This can get a little tricky; just be patient and work the duct around the collar. If you are using a rigid duct you can use screws instead of duct tape to secure it.



Step 4 - Again, use the tin snips to cut a 6 inch round hole into the cold-air main return. The cold air return is the big duct returning cold air from inside your house back into the furnace to be heated.



Another 6 inch collar can be inserted here and mounted in order to secure the 90 degree elbow and the 6 inch duct coming from the humidifier. These "collars" can be purchased at Lowes or Home Depot. I had to use a flexible alluminum tube because of the location of my ducts.



Step 5 - With all the air ducts connected and secured, you can now run a 1/4 inch copper line from your water line to the inline of the humidifier. Use a saddle-valve to tap into your cold water line - use soft water if possible, to avoid mineral buildup inside the humidifier. Also use teflon tape for all water connections. Once you pierce the water line, double-check for leaks and tighten all your connections. Do not use plastic tubing or you risk flooding and damaging your house.

Note: A saddle-valve (pictured below) is a water valve that mounts on an existing copper water line. It is designed to provide water to appliances that require low-volume, low-pressure water sources. Once mounted on a water line, with the included rubber seal in place, all that is required is to turn the valve clockwise until it pierces the water line. When the valve handle can no longer be turned, it is done. Turning the handle counter-clockwise opens the valve. These valves can be installed without shutting off the main water supply.



Step 6 - Again, make sure you CUT OFF ALL ELECTRICITY to your furnace, and set your thermostat to OFF.

Step 7 - With all the water lines connected and secured, take the cover off your furnace (if it has a cover) and locate the wires going to the blower (the blower is simply a motor spinning a fan that pushes hot air through your furnace). Most furnaces wired to standards have a white and a black wire running into the motor. You need to tap into these two wires; either cut them both and run a third wire from each one, into the transformer that came with your humidifier, or you can strip a small area of the plastic insulation and connect the transformer wires to that - make sure you use electric tape or wire nuts to insulate the connection.

Note: The by-pass humidifier came with a 24 volt transformer that regulates electricity to a solenoid water valve. This transformer needs to be powered up by the furnace blower, thus water flows through the humidifier only when the air moves through your ducts (when the blower spins). The solenoid valve is simply a water "switch" - when electricity is off, the valve stops water flow; when electricity is applied, water is allowed to flow through the valve into the humidifier.



Step 8 - With the transformer connected to your blower motor, cut another opening into the cold air return, in which you will mount your humidistat.

Note: The humidistat measures humidity and controls the humidifier based on your settings...think of it as a thermostat, but for humidity instead of temperature. Do NOT mount the humidistat on the hot air plenum. You will damage it permanently. The humidistat should be mounted either on the cold air return, or on a nearby wall.



Step 9 - Wire the humidistat, the transformer and the humidifier valve according to the schematics provided by the manufacturer. This was the hardest part to do for me. Double-check your wiring to make sure you are not shorting out your furnace, burning up the blower, or worse. If you have a gas furnace, be careful when you work around the gas lines with electricity...don't blow up yourself and your house.

Step 10 - Connect a 1/2 inch (inside diameter) plastic tube to the bottom of the humidifier with a 1/2 inch clamp to allow water to drain. Run the tube in a constant decline to a nearby drain. Turn your furnace back on, and set your thermostat to HEAT. If you hooked everything up correctly, your furnace should fire up and when the blower kicks in, you should see a stream of water coming through the draining tube. This means the media inside the humidifier is getting wet and evaporating water into the hot air that is being bypassed back into the furnace. You will not notice any change in the air at all immediately. It will take up to 2 weeks for everything in your house to "humidify"; only then will the air saturate and be at the level you set on your humidistat.

The happy humidifier running - you can see the water draining through the draining tube:




As a side note, the humidifier can also be mounted on the cold air return, but I am not sure if the output will be affected; my Skuttle 2000 can evaporate up to 14 gallons a day - that's quite impressive if you ask me. I also suggest buying a digital hygrometer, which allows you to monitor the level of humidity in your house. Amazon.com has one hygrometer on sale for $10...not a bad deal at all. It will also keep you from getting your humidity too HIGH in your house, which can also be a bad thing: mold, mildew and bacteria all love high humidity. An ideal setting would be anywhere from 38 to 45 or 50 percent humidity. Because of this you will also be able to save money on your heating bill: you can turn down your thermostat a couple of degrees and it will feel just as warm.

I hope others can find these instructions helpful and save the $300 they would otherwise have to pay to get a humidifier installed - it took me about 4 hours to get this done, but most of the time was spent researching and reading schematics. A well-skilled worker should be able to get this install done in one and a half hour.

You can buy a Skuttle Humidifier and parts from Dayton WinAir on Stanley Ave. right off I-75 (937-223-1218) or your local WinAir company: http://www.winholesale.com/Winair/index.htm

You can also check out Skuttle's website at http://www.skuttle.com - you can buy parts for the Model 2000 here on this website.


21 Nov, 2005 | Virgil
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Comments


by Psychohmike - 21 Nov, 2005 - 16:55:40
Or you could just move to Southern California 8-). Although you can't be a gun carrying cowboy here.

by Virgil - 21 Nov, 2005 - 17:31:47
Mike...southern california? Not in a million years. With my salary I would be able to put down enough for a 300 square foot, 1 bedroom house in suburban LA. :)

by Psychohmike - 21 Nov, 2005 - 20:03:41
or you could just get three jobs...there are plenty of them. Yeah, real estate out here is nuts. I was lucky enough to get mine before the boom. I will be able to move out of state when I retire and live off of the equity. Who needs a 401k when you can own a home in SoCal. 8-)

by Jl - 22 Nov, 2005 - 08:30:19
Mike,

It only works if you get out before the bust.

Where in SoCal are you located? I'm near Disneyland.

JL

by Chris - 22 Nov, 2005 - 08:59:34
I still think that house in the first picture looks like it's taking a dump.

by Psychohmike - 22 Nov, 2005 - 20:45:14
Hey JL you need to get a hold of me. I live in Lakewood and work in Santa Ana. I actually work for KWVE 107.9. My employer is Calvary Chapel of Costa Mesa. And if by some strange chance you listen to KWVE, (probably not for the dispy teaching) you just might have heard me. I do alot of commercial work and am on air from 7 to 12 midnight. How cool. I've been dying for some local preterist fellowship. Feel free to call me. 5627878344 I'm usually up till about 5am working.

by Brian - 29 Nov, 2005 - 17:30:23
VERY IMPRESSIVE!! I am a heating and air technician. I have installed many, many by-pass humidifiers in my day. Looks like you did an awesome job. I can't believe you figured out how to wire it, very impressive. Installing a central humidifier is definitely not a do-it-yourself kind of job, you should be proud.
I'm surprised there were no heating contractors who would do the work for you. It's a pretty common installation here in the Atlanta area.
The only problem that I see is the humidistat is mounted below the by-pass duct, which means the already humidified return air is hitting the humidistat, which will keep the humidistat from calling. (does that make sense?) but, if you turn the humidistat all the way up ( I would) it probably will stay on all the time anyway. It's not a big deal. However, it would be a little more accurate if you moved the humidistat above the by-pass duct. If you have any questions feel free to e-mail me. Good job. Godspeed. Brian. Newnan, GA

by Virgil - 30 Nov, 2005 - 10:58:29
Brian, thanks for the comments. You are absolutely correct...the humidistat IS installed incorrectly, below the bypass duct, which means it is measuring the already humid air. Per your suggestion, I will move it above the bypass duct.

by Rick - 02 Dec, 2005 - 18:01:46
Hi Virgil, great tutorial!

One question - I have no drain where my forced air furnace is. Is there any way around this?

Can I tap into the condensation pump from the furnace?

by Jerome - 30 Dec, 2005 - 12:09:48
Great detailed instructions. Today I installed a whole house humidifier. Printed out your instructions to use as a reference and used the humidifiers instructions. Everything works. One question do you know how long it takes to get the humidity level up to the correct level. I had a relative humidity of 20% before install and set the humidistat to 40%. Outdoor temp is approx 30 deg.

by Virgil - 07 Mar, 2007 - 11:31:34
Rick, I do not know if you can drain water into the condensation pump; that should be possible but I suggest you contact an air conditioning expert and double check.

Jerome, it will take 2 weeks or so for the humidity in your house to reach "normal" levels. I suggest buying a hygrometer to measure humidity.

by online questioner - 22 May, 2008 - 02:42:33
I paid an hvac guy to install a humidifier on the gas furnace -- not happy with results -- turned water flow off and heard I can reroute tube into garage not having to pay extra cost to heat garage - is this true????????????? and what about the tube he made to come off the furnace -- it did leave room for water flow if it would run off, I suppose -- anyway now the tube lets warm air out of it -- should I seal that tube off now that I'm not using the humidifier at all?

by David - 04 Dec, 2008 - 19:45:36
Two problems with your install, minor really but still, I feel are important. Excellant install by the way! Here are the things, never,ever, ever , ever, ever, ever, use teflon when you are connecting a compression (nut and ferrell) fitting. You risk cracking the nut! They will not leak when installed correctly. I have plumbers who insist on teflon as well but they are just wrong! I worked in Machine repair with air and water systems, believe me, I know what I'm talking about. Finger tight on the nut and then no more than one complete turn and that might be too much! Also, you can use plastic tubing as long as you use the plastic ferrell and the brass/plastic tubing insert, this gives the ferrl some purchase against the tubing.
Second item is this; I see where you wired your transformer to the furnace blower directly, this is okay as long as you have a single stage blower. Almost 100% of todays furnaces have 2 and 3 stage(speed) blowers, this is achieved by varying the voltage to the blower motor, you could seriously damgage your transformer. Take a look at the solid state control for your furnace, there is usually a terminal (120v) there for a humidifier control.
Overall great looking job!

by Virgil - 04 Dec, 2008 - 19:49:46
David, thanks a lot for your comment - I had no idea that you should not use teflon because of what you mentioned, so that's a good point.

Also, how would I know if the the blower is single stage or not?

by David - 04 Dec, 2008 - 19:59:07
I would check the model and serial number against the manufacturers web site or give them a call. If you still have your I/O manual, you can check there. Also, give the thing a listen, you can hear it change stages. The humidifer control terminals are indicated on the wiring schematic included on the door of the maintenace hatch/blower cover.

by Todd - 06 Dec, 2008 - 23:14:22
Great step by step guide :) I just installed one myself today and it went pretty well.

One question that I can't seem to find an answer for. Which way is more efficient, installing the humidifier on the hot air side and the duct to the return, or install it on the return and the duct to the hot air?

I installed the same way as you did Virgil, the installation instructions said it could be installed either way, just curious if one way was better/preferred over the other?

by Virgil - 06 Dec, 2008 - 23:20:23
Todd, my opinion (and it's just that) is that a humidifier would evaporate more water when installed on the hot air side of the furnace. I am saying this because (1) the air is more dry because it was just heated and (2) it is hotter. Both these factors should allow it to catch more water from the evaporator and make the evaporator more efficient.

I could be wrong on both counts, and I have no data to support my assumptions though...

by Todd Taylor - 04 Jan, 2009 - 23:37:41
Funny that while searching the 'Net for tips on installing a humidifier, I find the best article on a fellow Christian's web site ;o)

Thanks for posting this article. Between the article and the tips in the reader comments, they really helped me get my Aprilaire 500A installed this weekend with few issues.

One tip I might add is that rather than use a tin snips for cutting the hole for the humidifier, a Dremel tool with a steel cutting blade works great and is very fast. They have new "quick connect" discs that are a little larger and cut through the steel almost like butter (and as a bonus, there were all sorts of sparks shooting everywhere.)

I bought a circle cutting tool for the 6" hole from Menards for ~$38... I didn't think there was any chance in heck I'd be able to cut a round hole with either the Dremel or a tin snips.

After all the time and research I spent before and during this install, I think Aprilaire should give me an installers license!

by Virgil - 05 Jan, 2009 - 08:59:15
Todd, thanks for stopping by. I will update the article accordingly to illustrate your experience with the Dremel tool, that makes a lot of sense. I'll check out your blog :)

by Steve - 14 Apr, 2009 - 12:53:11
Virgil,

This is absolutely great information! Thanks. A question I'm currently trying to answer before I purchase a humidifier for my house is is this type of humidifier is better/worse/thesame as one of the modern 'steam' type humidifiers. Any thoughts?

Steve

by jonathan - 28 May, 2009 - 16:16:24
I live in TX and am putting in a humidier on the A/C return side. The "plenum" is the duct board style rather than tin. Am I missing the boat or is this just a difference in need and application?

by Jim Boger - 16 Jan, 2010 - 15:21:04
Excellent blog. I bought a house 7-8 years ago and noticed the home humidifier was not working. I completely disassembled it and all the water lines were plugged, the solenoid valve was stuck and the guts were caked with scale. I have cleaned all and freed up the valve, bought a new filter. I have noticed some concerns. One the unit has a humidity control in the main living area that can be adjusted to control level but the way the unit was wired it will open the water flow anytime the control is calling for moisture, it is not tied into the blower. I can fix that. The other issue is they installed the unit on the return air supply duct? I would think that would make the unit noneffective as the moisture would likely evaporate during the heating cycle. I thought I was looking a the vents wrong but the duct the unit is mounted to goes down to the bottom of the heater and through the filter and the filter pulls into the heater unit away from the unit. They did put a return duct on it but I'm convinced it's in the wrong duct.
any thoughts?
thanks
jab

by Eric - 31 Jan, 2010 - 16:40:40
Following Todd's question. I have a space issue and can not for the life of me fit the humidifier unit on the warm supply air plenum. However, there is enough room to get the 6" duct into it and I can easily fit the humidifier on the cold air return. My understanding is that the draw of the air will pull the water vapor through the by-pass duct and not ruin my electric furnace. Is this correct? The only other thing I could do is cut out a steel support poll which is into the concrete floor and currently blocking the only space on the warm air supply plenum. I would replace it of course a few inches away but this is not something I want to do.

by Eric - 31 Jan, 2010 - 16:44:38
I also disagree with Brian from 05 where he says that the humidistat is mounted in the wrong place below the by-pass duct. How is that in the wrong place if it is on the return air and the humidifier is on the warm supply air?

by lenpat - 02 Mar, 2010 - 10:24:10
my humidifier blow motor does not come on when the furnace is running. Any idea what is wrong. water is continually running out of the tube?

by Virgil - 02 Mar, 2010 - 10:30:32
Lenpat - probably your motor is fried..try replacing it.

by Virgil - 02 Mar, 2010 - 10:31:36
Eric, if you have an electric furnace, you may have to ask a professional about it. At the same time, I really doubt that your humidifier will put out enough humidity to ruin your electric furnace. It's vapor, not mist or water spray. My opinion: you should be ok.

by Don - 09 Mar, 2010 - 09:56:12
I am here because I plan to install a humidifier. It appears to me that it does not matter which side of the furnance you install a bypass unit and location is only decided by access. The air is going to move from pressure side to suction side (hot air to return) it either installation. I also agree that the sensor should be located above the bypass line to sample the air returning from the living space. Thanks to someone on the heads up about the humidifier 120v terminal.
Thanks for the site and the info, just wish I had more help in choosing which is the best unit to buy.
Thanks again for everyone's input....Don

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