Humidifiers and Dehumidifiers - Honeywell HE220A Bypass Humidifier Install question

Hi folks,
I am new to the forum, and I haven't had time to lurk for long so please excuse my post if this has been asked and answered...also I am in the middle of an install and searches have not been sucessfull so......here goes.

I am installing a Bypass unit. It is pretty easy and I have all the parts installed, Ducts, Humidistat on the duct, and Sail switch.

I am getting ready to do the Plumbing and Electrical and I have questions on the electrical part.

I like to run the furnace fan all the time. I have allergies and our house is hard to balance so running the fan seems gives me a bit of filtering and keeps the temp more even.

If I install the normal way, the humidifer will run while I am circluating cold air. I am a bit concerned about this so what is the best way to controll the humidifier for three cases,

Fan is on (Sail Switch)
Humidity need (Humidistat)
and....
I would like to activate the valve only when the system is calling for heat.

I figure I could take 24volts of the thermostat lead that calls for heat and feed that into the Humidistat and Sail switch, or Mount a relay on that line. I don't really want to go with a rigged up solution for our furnace but it would work.

Anyway, would it be bad to take 24v off the furnace transformer instead of using the included one, or are there any other suggestions.

Thanks in advance

How old is your furnace?

Make and model?

Why do you onlyl want the humidifer to come on when there's heat call and not as needed when the fan is running?

I'm not home now and I don't recall the make....maybe it was Bryant?
ANyway it is quite old, probably 40 years.

I am concerned that if I blow cold air through the humidifier and circulate it into cold ducts I could get condensation and mold.

The furnace size seems right, it kicks in frequently when it gets cold out, but if I find that I am not achieving the correct humidity levels I could defeat this and let the humidifier run even if the system is not calling for heat.

I figure I would start conservatively and avoid the possiblity of mold or condensation in the duct work.

Keith

Chances are the transfromer on that old equipement is not large enough to handle the extra load. You are best to use the current transfromer that came with the humidifer.

No, you will NOT get mold with the room temp air going in the humidifer.

You are safe to run it when the fan is running by itself, just shut it off in the summer.

40 years old equipement is most likley oversized! When it's really cold out it should run steady, not going on and off. And if your furnace don't run much on a normal winterday, the humdity in the home will not be where you'd like it.

OK,

Thanks...I will give it a go. A little more work and I will be all set for next winter.