Preparing for Nest thermostat installation

[bsw1]

I have what I think is called a heating-only "taco" system ... 3 RM832A switching relays, a unit that I think is a zone controller (R/W wires on T1/T2 terminals and 2 dials set at 100F and 180F), and 5 thermostats (2-wire). [There is a 6th thermostat for a separate A/C system.] My problem is I don't see any 24 Vdc for the Nest Power Connector, and I only have 4 thermostat wires (one of them is cut) coming into the furnace room (but I have 5 thermostats). Could some of my thermostats be wired in series/parallel? And how would that impact their operation?

I've already purchased Nest thermostats & the Power Connector, but I don't want to pay a tech to show up only to say that my system is unworkable.

[zoeuvre]

Hi bsw1, 

Thanks for posting here in the Community forum and for showing interest in our Nest Thermostats. Based on the data you have given, it seems like you own a multiple-zoned heating system that has three RM832A switching relays, a zone controller, and therefore five thermostats. Perhaps some of your thermostats can be wired in series or parallel, which might affect their current performance and interaction with Nest thermostats.

In a typical setup, each thermostat should have its own dedicated pair of wires running to the zone controller or switching relays. However, if multiple thermostats are wired in series or parallel, it can cause issues with the functionality of the thermostats and may not be compatible with the Nest Thermostats.

In order to get the actual wiring configuration and compatibility of your system with the Nest Thermostats, please send us a picture of your current thermostat wiring configuration so I can look closer.  Use our Compatibility Checker to see if a Nest Thermostat will work with your heating and cooling system.

Keep us posted.
 

Best,

Zoe

[bsw1]

Here is a diagram. I think I see now where the other 2 thermostats come in. There are 5 circulating pumps in all; the 3 originals are Sunstrand & Myson, and 2 new pumps (Taco) for in-floor heating of bldg expansion. Those Taco pumps use Infloor model PC090 controllers. I've already purchased 6 Nest thermostats and the Power Controller because the compatibility guide seemed to indicate that it would work with my system. So my question is, will it work? And if so, how do I wire in the Nests?

[bsw1]

The 2 Taco controllers do not tie into the White-Rodgers furnace control; they only control the 2 pumps. Each of the 3 Honeywell RA832A's are wired to their respective pumps, as well as having their thermostat signals in parallel to the master.