# Fan Powered Humidifier on Return Air Side



## JA Boomer (Sep 25, 2014)

Today's question:

We live in Alberta and the house is dry. About 20% relative humidity (RH) in the winter and 40% RH in the summer. The furnace doesn't have a humidifier so I ordered a whole house humidifier. It's a Honeywell 360 fan powered flow-through unit.

After reading the installation instructions I notice that it's to be installed on the supply (warm) air side of the furnace. After inspecting my furnace the only place to install the unit on the warm air side is blocked by the exhaust vent flexible pipe.

I try and relocate the exhaust pipe but find that it's really not that flexible and I don't really want to screw around with the furnace exhaust so I call a HVAC company for a quote to relocate the exhaust piping. He tells me that there's no reason a humidifier would have to be installed on the warm air side and to save some money and install it on the return (cold) air side.

I spend 5 minutes on google and find that fan powered units should be installed on the warm air side because:

1) The warm air has a lot more ability to absorb moisture, making it more efficient to humidify your house.

2) Because the fan powered units throw out a lot of moisture (compared by bypass units) it's not great to install on the return air side because you can get moisture collecting on the furnace filter, motor, circuits, and burner.

I also find that some people refuse to install a humidifier of any type on the warm air side of the furnace because if you ever have a leak it goes into the furnace housing and costs you a lot of money. And some fan powered humidifiers allow installation on the return air side as long as you make the supply water hot.

So what's a guy to do. Is it worth hiring an HVAC company come in and move the exhaust pipe so the humidifier can be properly installed on the warm are side. I'm also worried that the unit may melt as it would be mounted only inches up from the furnace itself.

Or should I just install it on the return air side and see how it goes.

Appreciate any light anyone can shed on the topic.

Boomer


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## yuri (Nov 29, 2008)

Why do you need a fan powered?

A simple bypass flow thru type where the air goes from the hot air thru the humidifier and back to the return will work if you have room.

Post some pics of all sides of the furnace and front and back and I can help better.

Go Advanced>Manage Attachments


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## Bob Sanders (Nov 10, 2013)

The good ole fashioned drum style humidifiers install on the return side with a 6 inch bypass duct to the outlet side. The surface area on the drum is large enough to produce adequate humidity with or without heat. The only disadvantage to them is that they need cleaning regularly. If you do it once a month or so (as I do mine) they rinse off in fresh tap water.

I have this one and I slightly modified it.

https://www.homedepot.ca/en/home/p.12-gallon--drum-furnace-humidifier.1000456408.html

The sides are held together with tray at the bottom. The tray has notches which lock into the sides. I filed those notches off and installed a threaded rod from side to side just over the tray (the threaded rod now holds the sides from spreading). No more locking notches on the tray allows me to simply turn the float sideways out of the water and the tray slides easily out for cleaning (kind of like a drawer sliding out). The drum lifts up and out. With it streamlined like this it takes about 15 minutes a month to clean (that includes removal/install of drum and tray).


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## JA Boomer (Sep 25, 2014)

yuri said:


> Why do you need a fan powered?
> 
> A simple bypass flow thru type where the air goes from the hot air thru the humidifier and back to the return will work if you have room.
> 
> ...


Well I don't need a fan powered. But I bought the 360 based on reviews and didn't realize it was warm side mounted until I opened the box today. I don't really want to pay for the shipping to send it back (from amazon.ca).

One thing I just realized is that I probably have JUST enough room on the back side of the furnace to install it. It won't be fun installing it back there (kind of like a phone booth with about 16" between furnace duct and wall), and changing the filter will be pain. But it will be out of the way and not require any additional work. Another plus is that any leaks won't proceed into the furnace body.

http://yourhome.honeywell.com/en/products/humidifier/power-flow-through-humidifier

Boomer


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## yuri (Nov 29, 2008)

I imagine it will fit , just take your time.

There should be a EAC (electronic air cleaner) terminal on your circuit board. It supplies 120 volts to what it thinks is a air cleaner. Works also for the 120 volt power supply for the humidifier and gets energized when the fan turns on. The HUM terminal is 24 volts. It may have a red plug on top of the terminal you remove. Had a poster here earlier looking for it and found it with a cap on it next to the wires for the fan.

And yeah it gets DRY in Calgary. I lived there for a few years (Bridlewood). Back when Ralphie was still getting drunk and insulting homeless people.:wink2:


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## beenthere (Oct 11, 2008)

Return it, and get a bypass humidifier.


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## JA Boomer (Sep 25, 2014)

Well. This one hour project ballooned to a day and a half. But I got it installed and functioning.

Did my first ever solder job because the valve takeoff for the humidifier water line started leaking.

I was able to wire the humidifier directly to the furnace and it operates in junction with the burner when humidity is being called for by the humidistat. The wiring was so poorly explained in the manual and DVD that I basically ended up doing it myself. 

The casing of the humidifier was a little too close to the hot water heater 3" exhaust pipe (about 2 inches) so I put a section of 4" pipe around the exhaust pipe to act as a heat guard and I've been satisfied with the results.

I probably should have returned this unit for a bypass which could have easily been installed on the return duct work, but I couldn't find any that I liked. This unit has positive reviews and hopefully it will provide us with years of good service with the proper maintenance.

Thanks for all the help and suggestions.

Boomer


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## yuri (Nov 29, 2008)

Yeah keep checking it as Calagry water can be hard. I had to install a softener when I lived there. Looks OK to me. General Aire and April Aire make good bypass units but they are hard to get w/o special ordering.

https://www.generalfilters.com/
http://www.aprilaire.com/


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## Daveisup2it (Dec 29, 2021)

Bob Sanders said:


> The good ole fashioned drum style humidifiers install on the return side with a 6 inch bypass duct to the outlet side. The surface area on the drum is large enough to produce adequate humidity with or without heat. The only disadvantage to them is that they need cleaning regularly. If you do it once a month or so (as I do mine) they rinse off in fresh tap water.
> 
> I have this one and I slightly modified it.
> 
> ...


Drum style humidifiers are obsolete and require waaayyyyyy to much maintenance, a simple bypass gets the job done, hard water makes drum humidifiers impossible to maintain, and the only moving part on a bypass humidifier is a solenoid valve you can buy on line for $25 - $50 .


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## roughneck (Nov 28, 2014)

David A. Ward said:


> Drum style humidifiers are obsolete and require waaayyyyyy to much maintenance, a simple bypass gets the job done, hard water makes drum humidifiers impossible to maintain, and the only moving part on a bypass humidifier is a solenoid valve you can buy on line for $25 - $50 .


That post is from 2016, and made by a member that is now banned from the site. 
Not good taste to bring back threads from the dead.


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## Daveisup2it (Dec 29, 2021)

Sorry, I realized that after replying, not quite sure what he was banned for but your response really wasn't very kind for a new member, fyi.


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## supers05 (May 23, 2015)

David A. Ward said:


> Sorry, I realized that after replying, not quite sure what he was banned for but your response really wasn't very kind for a new member, fyi.


Welcome to the forums. There's been a recent rash of people not checking the dates before replying. I know his post was not intended to be offensive.


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## roughneck (Nov 28, 2014)

David A. Ward said:


> Sorry, I realized that after replying, not quite sure what he was banned for but your response really wasn't very kind for a new member, fyi.


Was more intended to be direct then unkind. 
I thought the site flagged old threads when you tried to post to them. I know it does for me.
I don’t know why Bob was banned. Before you posted I didn’t even know he’d been banned.


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