Humidifiers and Dehumidifiers - Installing HE220A

I purchased the HE220A humidifier. I plan on installing it on the return side and using a sail switch, but I dont have to. Im not quite sure where I get the power for the humidifier though. Here are some pictures of the setup. I have a 1991 comfortmaker furnance with RPJ heat exchanger. I can get model number later if needed.

power in top: (ftp://cis.bismarckstate.edu/frohlich/power_in.JPG)
controller
controller (ftp://cis.bismarckstate.edu/frohlich/control.JPG)
lower power in (ftp://cis.bismarckstate.edu/frohlich/lowerpower.JPG)
wiring diagram (ftp://cis.bismarckstate.edu/frohlich/wiring.JPG)
blower fan control? (ftp://cis.bismarckstate.edu/frohlich/lower.JPG)
whole setup (ftp://cis.bismarckstate.edu/frohlich/IMG_0819.JPG)

Really no place to get power from this furnace since it's not set up to do it.

A couple of things can be done, if your transfromer on the furnace itself is strong enough, we can tap on to the W and C to get 24 volts.

Or use the transformer that came with the unit, and add a junction box on the side to mount it, and use the sail switch or A50 Relay.

Thanks for the reply. I will probably just use the transformer that came with the unit and a junction box. Just curious though, what would happen if my tranformer on my unit isnt strong enough and I tried to use the W and C?

What would happen if my tranformer on my unit isnt strong enough and I try to use the W and C?

The valve may be clicking on and off often, or won't open. And transformer may burn out.