Humidifiers and Dehumidifiers - Can I wire the Aprilaire 700A to do this?

I have an American Standard 80 variable speed just installed about 2 years ago. I have just installed the Aprilaire 700A currently working in manual mode. It is currently wired to run with continuous fan.
w/g->G
Cf->common
on the furnace terminal strip.
My thermostat is just a simple setback for a single stage furnace.
I usually turn the fan at the thermostat to Auto at night so I don't blow cold air around but I would like the Aprilaire to come on when the furnace fires up in the morning.
Is there anyway to wire things so that the humidifier will work without the heater during the day (its really dry here and I need the extra humidifier time) but be able to turn that off at night and have the humidifier kick in in the morning with the furnace?

I have an American Standard 80 variable speed just installed about 2 years ago. My thermostat is just a simple setback for a single stage furnace.
Why are you "Crippling" that nice furnace on a single stage t-stat?


I have just installed the Aprilaire 700A currently working in manual mode.
Do you have the transformer? Why Manual Mode, and not the Auto Mode?

Is there anyway to wire things so that the humidifier will work without the heater during the day
Yes, we could wire it up to make it work, but from my experience, you are not really going to gain anything since the air flow is room temps, and it's not going to help with the water evaporation off the pad. So, the humidifier is going to run a lot more to add the humidity into the air, and lot of wasted water down the drain.

I tired this once on mine, and it ran almost all the time with the fan, and I rewired up to only come on with the call for heat, and it kept up just fine with it on only heat.

I would suggest having the t-stat changed out to a two stage stat, and that will allow the furnace to run longer in 1st stage, rather than cycling off on 2nd stage right away.

The furnace installer said we didn't really need a 2 stage thermostat and to try it and see how we liked it. Stage one seems to run for 5-10 minutes before stage 2 kicks in. About the only time we hear stage 2 is first thing in the morning.

We started in manual mode just for simplicity to make sure it was working. Plan to change to auto but have yet to run the sensor outside. Did not use the transformer but are using the furnace terminals R & B/C to power the humidistat.

I'll try just having it go with the heat but after running most of 2 days, the humidity only gets up to 27% and the humidifier never turns off.

The furnace installer said we didn't really need a 2 stage thermostat and to try it and see how we liked it. Stage one seems to run for 5-10 minutes before stage 2 kicks in.
So you are saying your furnace runs less than 10 min most of the time? Where are you out of, and how big is the home and furnace? Also age of the home?

Did not use the transformer but are using the furnace terminals R & B/C to power the humidistat.

We are going to use it.. Behind this cover (Turn power OFF), there a wire tapped "HUM" on it.. There knock out to mount the transformer to as seen below.
http://img522.imageshack.us/img522/5061/imgp0383up4.jpg

The two low voltage wires from this goes to the humidistat's W/G and Cf.

Then the R and C wires from the humidistat goes to R and B/Com on the furnace.


I'll try just having it go with the heat but after running most of 2 days, the humidity only gets up to 27% and the humidifier never turns off.
we'll wait and see what you come back with on my first questions, also are you tied to cold or hot water?

The house is 2700 sq ft, built in 1990, very well insulated, just outside of Denver at 8400ft. Thermostat is usually set to 66. Stage 1 may run 15 minutes, I've never timed it. With daytime temps at 35 or higher, I rarely hear stage 2 kick in except for an hour or so of morning heat to get back to 66 from the setdown. Occasionally I'll hear it in the evening. Weather has been pretty mild this winter. The furnace model is UD100R9V5k, so 100,000BTU. Aprilaire tied to hot water.

100k, is not too large, I'd guess an 80k would been fine, but not knowing with out the manual J done.

Anyway, You can try hooking it up to EAC wire instead of the HUM wire I mention about earlier.