Help replacing trane xl824 with nest 3rd gen

[drtiki]

Hi,

I currently have a Trane XL824 thermostat hooked up to a Trane XR95 furnace. I also have a aprilaire 550 humidifier and a Fantech HRV unit. Is it possible to connect the Nest thermostat with my current setup? I have included some pictures. I have two cables going to thermostat. One is from furnace circuit board and the other is for the humidifier and hrv. I am stuck on how to hook the Nest up. I would be happy to provide more info if needed.

Pictures - https://ibb.co/pWFW7cb and https://ibb.co/cTtHwTC
Thanks

[Admin]

The NEST can't control an HRV but it will control the humidifier.  Wire the humidfier solenoid directly to C on the furnace board and * on the NEST.

The only thermostat I know of that will control both an HRV and humidifier is the Honeywell Prestige 2.0,

https://forwardthinking.honeywellhome.com/related_links/thermostats/prestige/68-0311.pdf

[drtiki]

Thanks for the quick reply. By doing this what will change in how my current system operates? Before the Trane thermostat sensor went wacky it had a "ventilation" feature that we never used. Is this the only thing we will be missing?

[Admin]

Yes, you will lose control of the HRV.  I don't think the Fantech units have an ON/ OFF switch built onto them.  You could buy a seperate Fantech control and use it for ventilation.

[drtiki]

The bathrooms have timer switches (up to 60 mins). I suppose could manually use those.

I am not sure how the Trane thermostat determined when to run ventiliation, might have been whenever furnace fan was on.

Can you think of any downsides of not using a thermostat that controls the HRV?

[Admin]

If you're using the bathroom timers daily you'll likely provide the home with enough ventilation.

When you're cooking or cleaning with chemicals just get in the habit of using the timers to run the HRV.

The HRV is something that can be used year round whereas the humidifier is only used during the winter.  Have you considered using an Ecobee 4 instead of the NEST?  That way it can control the HRV and you can install a cheap humidistat at the furnace to control the humidifier.