How many wires needed for thermostat?

[scorpionleather]

I just noticed my existing wire bundle going to the thermostat has 4 wires but I am having a new variable speed two stage furnace (Trane XV80) installed with the existing one stage condenser. I looked in the Honeywell VisionPro thermostate install guide and it looks like I might need at least

5 or 6 wires. The installer will discover whatever needs to be done, but just wondering ahead of time if they will have to replace this wire because it goes through some tricky wall sections.

[Uncle Monster]

There is a product available for this situation. If your HVAC tech is not familiar with the item, print out the information for him/her/it.

[8~{} Uncle Monster

[Old AC Guy]

he will either run a wire bundle that has enough wires or jump w1 and w2. Just stay out of the way and let them do their job.

[Blattus Slafaly]

Only 2.

[scorpionleather]

If heat relay 1 and 2 are jumpered together, what functions of the Honeywell VisionPro thermostat would I be giving up? I would guess that the thermostat separates them for a reason. I would like to decide if it is worth the effort to run more wires through the wall or if that would be a waste because the thermostat does the same thing when it is jumpered.

[Rick-Meister]

If you're going to get the Honeywell Vision Pro, spend a few extra bucks and get the Vision Pro IAQ. The relay module is located down by the furnace and it only needs 3 wires up to the T-stat. You will save more by buying the IAQ than it will cost you to run extra wires.

It's ALWAYS better to use a 2-stage thermostat than to use the default mode on a 2-stage furnace control board. If you jumper the W1 and W2 on the Vision Pro, you're defeating the whole purpose of getting a

2-stage thermostat.

[Lp1331 1p1331]

If W1 and W2 are jumpered, the furnace will start the heat cycle on low stage heat and will automatically kick up to high after a certain time-- I think about 7 minutes. A/C will not be affected. If there is any way to run new wires, do so. If it is absolutely impossible to get wires through the walls without tearing drywall up, see if there is any other location to put the thermostat. If you are going to go to the trouble of running wire, run 9 conductor wire for any future needs. Good luck!

[Bubba]

IAQ. The jury is still out. Expensive stat. Wait till it fails and Honeywell stats DO fail. I do like the Vision Pro. Two stage furnace deserves a two stage stat. The wiring and all should be included with the install. You DONT wire a two stage furnace for single stage operation. Total waste of money. Very "hack-a-fied". Keep in mind, if you want the vision pro, it also has a neat little feature where you can install a outdoor sensor so you can see the outdoor temperatue at your thermostat. This does however require a separate stat wire (2 conductor) that cant be in the same wire bundle of the stat wires. Bubba

[Tony Hwang]

Hmmm, I just went to wireless thermostat. Couldn't run any extra wires easily.