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rosenjas 01-25-2009 09:03 AM

Generaire 1042 Humidifier Installation Question
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I have a couple of questions concerning the operation of my humidifying unit. I have always believed the unit has been installed incorrectly and would like your input on the situation.

I will describe the installation as best I can and I have attached pictures as well.

The head of the humidifier is installed on the warm air flow side and then a circular duct connects the head to the return air side.

The GeneralAire M2 humidistat is installed directly on the return air duct. The furnace is in our basement where it is already humid, so should the humidistat be installed on the return air duct in the basement?

The humidistat is wired to an electrical switch on the furnace and to the electric water valve on the side of the head unit.

In order to get the unit to operate, I have to increase the humidistat, usually between 50-60% humidity, until I hear the water valve click open. There is a constant water flow through the humidifier filter even when the furnace is not running. This seems odd to me. Shouldn't the water flow only turn on when the furnace is running?

We have a two story house, and I can never get the humidity level above 35% on the top floor. Should this be happening?

I hope my description is not too confusing. I have attached pictures as well.

Thank you for your time folks.

yuri 01-25-2009 09:19 AM

As long as the installer cut thru the insulation and thru the sheet metal so the humidistat senses the humidity IN the return duct it should work properly. It will then get an average reading for the house. That is the way I install them. The power supply for the unit should be hooked up to a 110 Volt HUM or EAC terminal on the furnace circuit board so it does not run continuosly. It can also be wired w/o the transformer and hooked up to the W and C low voltage terminals so it only works when the heat is on.

rosenjas 01-25-2009 10:02 AM


Thanks for the reply.

The transformer that is being used is a Class 2 Transformer, Model UM-12 24V, 12VA.

Is this the correct transformer? If not, could this be making the unit run continuously?

Thanks again.

yuri 01-25-2009 10:05 AM

No. Buddy just wired it directly into the power supply. Hook it up my way and it will be fine.

rosenjas 01-25-2009 10:22 AM


I have a York Diamond 90 gas furnace. Would you happen to know where I can find the low voltage terminals? Are you saying I should remove the transformer all together and just use the wires that are connected to the transformer?

rosenjas 01-25-2009 10:28 AM


I removed the bottom panel and have located the circuit board. I see the W and C on the board and will wire the switch to those posts and see what happens. Is it ok to leave the transformer installed without having anything connected to it? Thanks for all your help.

rosenjas 01-25-2009 10:38 AM


Also, what type of wire is recommended?

yuri 01-25-2009 10:43 AM

The same as on the transformer now. Looks like 18/2 LVT which can probably be bought by the metre (Canada) foot (US) at HDepot. The transformer can stay put. You can CAREFULLY pry the front off the humidistat, after removing the knob to see if Buddy cut a hole in the duct. Swing it from bottom outwards and then up.

rosenjas 01-25-2009 11:07 AM

Ok Yuri. I looked behind humidistat and all looks fine; no obstructions.

One last question, the W and C posts on circuit board already have connections to what appears to lead to air conditioning unit outside. Is it ok to use more than one connection on W and C posts.

Again, thanks for all your help. I'll head to Lowes for wire, then let you know what happens.

yuri 01-25-2009 11:15 AM

You can leave the old transformer as is. I doubt if you can ever get more than 35% RH. I keep mine at 30%. :thumbsup:The A\C will hookup to Y and C. You can hookup the humidifier to W and C and you can put 2 wires under the terminals. Keep the cat out of the fan, LOL.:thumbup:

beenthere 01-25-2009 12:46 PM

Wonder why they ran that saggy flex around the front of the furnace.
Instead of keeping it short and tight, by going around the back of the furnace.

rosenjas 01-26-2009 07:41 AM


I want to thank you for your help. The humidifier now comes on only when the heat does. House is around 35%, I'm hoping it will reach 40%. Also, I'm concerned that the unit itself is only fastened to the ductwork with tape. How do you fasten the humidifier to the duct?

yuri 01-26-2009 05:10 PM

Sheet metal screws. May need 1" long type to go thru the insulation. Tape will eventually dry up and the unit will fall off. There are mounting holes on the top/bottom and sides. Glad to help. There is a cartridge inside which may need cleaning with CLR once and a while.

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