Will a Honeywell TH8321U work with this setup?

[markf57]

I really like the VP 8000 thermostat line. The model I have (TH8321U) can run with up to 3 heat/2 cool, but I was wondering if it can handle a dual fuel system with 2 stage HP and a 2 stage furnace? Wouldn't that be 4 heat and 2 cool? Or do the heat sources only count as 2 since neither runs at the same time?

[BaldLoonie]

2 stage comp, 1 stage backup. To do what you want, get the VP IAQ.

[markf57]

Thanks.

Would it matter if the heat pump was a 2 stage single compressor or a 2 compressor system?

[docholiday]

No, you still want the IAQ as mentioned by the bald one. If you like the 8000 series, you'll like the 9000 series better. The bonus is you get some humidity control and the ability to stage it the way it should be staged.

[ga-hvac-tech]

No, you still want the IAQ as mentioned by the bald one. If you like the 8000 series, you'll like the 9000 series better. The bonus is you get some humidity control and the ability to stage it the way it should be staged.

Vision Pro IAQ; Also known as the 9421.

[airsome]

If you have Trane equipment, the Th8321 should work in conjunction with a TAYPLUS103A dual fuel relay.
We have done this with similar tstats, such as Trane Taystat500, Taystat 540, TCONT803. We have probably done it with the Th8321U1006 (the only Vision Pro we use), but I can't swear to it.