I want to install a whole house humidifier in a home with a Lennox Pulse furnace (Model Number G2103-80-1.) There's a schematice on the unit. I don't think it has a provision to provide power to the humidifier only when the heat is running, but I wanted to make sure. This is a really nice feature on the furnace in my home. I think this one might be too old (circa 1994.)

Does anyone know if the furnace provides a 120V output that only comes on when the ehat is running?

Thanks.

Darryl

Probably not, most of these I've seen use a current-sensing relay clamped around the heating-speed blower motor lead and wired in series with the humidifier control circuit. If you go this route make sure you get the right one for the voltage you will be applying to it.

Thanks for the quick response. I have been looking at both the schematic & the unit I bought. The unit needs 24VAC, and the schematic indicates circuitry for 24V (not sure if it's AC or DC.)

So, I think I'm getting close. If anyone knows for sure, please post, otherwise, it'll be a little probing with the multi-meter in the next day or two.

Thanks again.

Darryl

I would recommend an AP-50 relay, wired in series with the humidifier, humidistat, and low voltage power supply. Attach the relay to the heating speed blower motor lead.

OK. Where do I get an AP-50 relay? And I assume it's a 120V relay, so I just run it to an outlet, and plug the power supply into the outlet? Thanks.

Is there a hum, or acc terminal on the control board. If so, check to see when you get voltage at this terminal. If you get 24v when blower kicks on, then you can power the humifier, through the humidistat directly from this terminall. If you get 120v when blower kicks on, you will need to use the factory supplied transformer( most humidifiers will supply a 120-24v tranformer)

Quote:

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Originally Posted by KC13

I would recommend an AP-50 relay, wired in series with the humidifier, humidistat, and low voltage power supply. Attach the relay to the heating speed blower motor lead.

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Did you read all of this? Pulse control board does not provide accessory terminals. Perhaps you should have a pro do this for you.

Quote:

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Originally Posted by junkdls

OK. Where do I get an AP-50 relay? And I assume its a 120V relay, so I just run it to an outlet, and plug the power supply into the outlet? Thanks.

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The AP-50 relay is a switch that will allow the control of a humidfier. It senses the current flowing through the power wire going to the blower motor. This will allow the humidfier to onlt run when the blower motor is working. You do not want the humidfier to run all the time since that is a waste of water and will not help humidfy the air during that time.

Many humidfiers come with a wall plug in 24 volt control transformer but some do not. No matter since the transformer only supplys the voltage to the humidstat then to the water valve to turn the humidfier on and off while that is wonderful it still offers no control of the blower which the AP-50 does.


SEE additional diagrams here.

http://www.alpinehomeair.com/view.cf...1-3B9839F377F0

Thanks for the schematic. It is close to what I had expected from KC13's reply. No its crystal clear.

So, where does one acquire the relay? One of the box hardware stores, or do I need to see an HVAC guy? A quick Google search on AP-50 got a lot of stuff that was not HVAC related.

Thanks again.

In the above: "...now it's crystal clear..."

The model 50 relay is available at HVAC supply houses for sure but I am not sure if available at Home Depot or Lowe's.

OR Ebay


APRILAIRE #50 Humidifier Current Sensing Relay 24V - eBay (item 310094284248 end time Jan-20-09 16:31:22 PST)

Got it. Thanks everyone for your help!