Hi all
I want to install a Nest, but need a bit of help. We have an older house that used to have a two-wire furnace system. A couple of years ago we added a heat pump so we have a hybrid system. The installers did not replace the two wires, but instead went for a system where the thermostat connects to a control module that they put next to the furnace. That control module in turn controls the furnace and heat pump.
So I will need to run new cable and replace the control module with a junction box (any good recos? I was looking for one on Amazon that might have HVAC labels already but didn't see any). I believe I need 18/8; there are 8 wires in the control module although two are for an outdoor air temperature sensor that I expect I will not be able to use anymore.
I'm trying to determine the wiring. We normally just use the heat pump but in cold weather we have 'auxiliary heat' provided by the furnace. The manual for the existing system is at https://resource.carrierenterprise.com/is/content/Watscocom/rcd-parts_t6-prh01-b_article_14496534438... and it looks like our system is wired up like that on page 77:
Based on that, it looks like G goes to G on Nest, and C goes to C. I am fairly sure that O/B W2 terminal should go to OB on Nest, Rh should go to Rh. I'm not sure what the Y/Y2 terminal should go to on Nest; would it be Y1 or Y2? Similarly for the W/W1 terminal; I would have said W1 but I think this is what turns on the Aux heat which makes me wonder if it should go to W2 (aux) on Nest.
Thanks in advance!
