Dual Power Connector wiring for separate heat/cool thermostats

[DougSlug]

My house has separate thermostats for heat and cool control, each located in a different part of the house.  It's a single-zone forced air system for both heat and cool.  The existing thermostat wiring is minimal: 2 wires going to the heat thermostat (R, W) and 3 wires going to the cool thermostat (R, Y and G).  No spare wires are available in the walls for a C-wire connection.

I want to replace both existing thermostats with separate Nest thermostats.  I believe I need a separate Power Connector for each thermostat to provide the virtual C-wire connections.

I am seeking confirmation that the following proposed wiring is correct and would not cause any problems:

Thanks,

Doug

[zoeuvre]

Hi DougSlug, 

Thanks for posting. To confirm the proposed wiring for replacing your existing thermostats with separate Nest Thermostats, you can follow these guidelines:

For the heat thermostat:

• Connect the R wire from the HVAC system to the R terminal on the Nest Thermostat.
• Connect the W wire from the HVAC system to the W terminal on the Nest Thermostat.

For the cool thermostat:

• Connect the R wire from the HVAC system to the R terminal on the Nest Thermostat.
• Connect the Y wire from the HVAC system to the Y terminal on the Nest Thermostat.
• Connect the G wire from the HVAC system to the G terminal on the Nest Thermostat.

To replace your existing thermostats with Nest Thermostats, use a Power Connector, also known as a Common (C) wire adapter, to provide the virtual C-wire connection. The Power Connector connects to the C terminal on the Nest Thermostat, providing the necessary power. Follow Nest Power Connector installation instructions here in this guide. 

Let us know if that helps.

Best,

Zoe

[DougSlug]

Zoeuvre,

Thanks for your reply, but it didn't quite address my main concern, which is whether it is OK to connect two Power Connectors as shown in my proposed wiring diagram (repeated below in this reply).  None of the installation instructions I have seen address multiple Power Connector arrangements.  I wanted to be sure that hanging the two Power Connectors in parallel across the R and C connections would not cause any unintended loading or current leakage paths that could cause unexpected behavior of one or both of the control loops.

Thanks,

Doug

[DougSlug]

For some reason, my house uses separate thermostats for heat and cool control, each located in a different part of the house.  It's a single-zone forced air system for both heat and cool.  The original thermostat wiring in the walls has only 2 wires going to the heat thermostat (R, W) and 3 wires going to the cool thermostat (R, Y and G).  No spare wires are available in the walls for a C-wire connection.

I obtained two Nest thermostats free of charge with a rebate from my local utility, and I'd like to replace both existing thermostats with separate Nest thermostats (I know, not the best solution, but probably easiest and cheapest approach).  Based on what I've read online, I believe I need a separate Power Connector for each thermostat to provide the virtual C-wire connections.

The existing wiring is a bit unconventional (see diagram at https://drive.google.com/file/d/1Iej9qCYaCF3qveEp3U8GRTdHaoOY5Bp1/view?usp=drive_link).

I am looking for confirmation that the following proposed wiring would not cause any issues...the main concern is whether it's okay to wire the two Power Connectors in parallel for the R and C connections at the furnace terminal block, with the W and Y connections routed through their corresponding Power Connectors:

ABBREVIATIONS: HTS = heat thermostat, CTS = cool thermostat, HPC = heat power connector. CPC = cool power connector, FTB = furnace terminal block

HEAT THERMOSTAT:

HTS (R) -- HPC (R gray)

HTS (W) -- HPC (W/Y gray)

HPC (R white) -- FTB (R)

HPC (W/Y white) -- FTB (W1)

HPC (C white) -- FTB (C)

COOL THERMOSTAT:

CTS (R) -- CPC (R gray)

CTS (Y) -- CPC (W/Y gray)

CPC (R white) -- FTB (R)

CPC (W/Y white) -- FTB (Y)

CPC (C white) -- FTB (C)

G wire goes straight through from CTS (G) to FTB (G)

Thanks,

Doug

[DougSlug]

Existing wiring diagram: