I have a Goodman GMH8 Furnace/AC unit I had a TH5110D T-Stat.
I added a Honeywell HE260A Bi-Pass Humidifier with the H-Stat that came with it.
I have purchased a RiteTemp 6080 Programmable Stat with Humidistat built in.
I have installed the new stat and the furnice and AC work great. No long/short cycling. Program works great.
I want to now get rid of my old h-stat and use the built in h-stat on the RiteTemp unit.
I have not changed any of the wiring on the humidifier except to remove the line that goes from my transformer to the old H-Stat and the line that goes from the old H-Stat to my Sail Switch.
If I run a line from the transformer (where the old H-stat was connected)to the sail switch (where the old H-stat was connected) and the solenoid on the humidifier opens and water flows like it should.
My instal guide states that my humidifier control line runs from my H terminal to my humidifier relay.
I think that I need a relay to use between my transformer and my sail switch, but I don't know what type I would need.
So, you have two power supplies at the furnace. One transformer integral to the furnace, then a separate externly mounted transformer, dedicated to the humidifier.
Then, yes, you will need a 24v single pole, single throw relay. Pay close attention to C on the drawing. Your 24v from H on the stat to one side of the coil, and C from the furnace to the other side of the coil.
And on the top of page 18 there is a diagram showing how to hook it up with an external 24vac power source. So I took one wire and put it to my R terminal on my furnice board from the other post on my transformer and voila it works!
Thanks for your help. If this diagram didn't appear, and didn't work I would have tried your SPST suggestion.