2 stage variable speed operation

[joepuwi]

FYI Carrier/Bryant products now have the capacity to do full 1/2 stage cycling without timers using just 4, #18 t-stat wires.

Really? Which thermostats can do that with 4 wires?

[Waterloo]

Really? Which thermostats can do that with 4 wires?

the VisionPro IAQ only needs 3. The wires actually feed to an equipment module (which you locate next to your furnace). From the module to the furnace is where you get all the wires necessary (9 in my case).

[mayguy]

I agree on the IAQ. I have 12 wires tied into the moduler.

[ptbrunet]

From Mayguy:

2nd stage should kick in any time you bump up the temp a couple of degrees.

Is the set up menu set right?

#170 to 8

They wire up W2 at both t-stat and furnace?

Yes on the #170, and swapped TStats in process of elimination. Hopefully just a wiring problem on the furnace controller board. I'm just testing my system to make sure everything is running right. The installer will be here next week to fix it.

BTW, here is a response from Honeywell when I asked them how to get the RTH7400 to make a stage 2 call:

The algorithm inside the thermostat works on proportional and integral control. Please increase the set temperature by 5 to 6 degrees and the thermostat can call for the auxiliary heat. As mentioned earlier, the thermostat will not show any indication of calling for second stage of heating.

I'd be interested in learning more about "proportional and integral control".