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Where to connect the c wire for a nest

Hey guys,
I’m trying to help a neighbor set up a nest and the nest is requiring a c wire in addition to the red and white. Luckily the cable in the wall has the additional wire but tracing it back to the furnace it’s not hooked up to anything. So my question is where to put it?

Comments

  • JUGHNE
    JUGHNE Member Posts: 9,365
    Many here have advised to call Nest tech support for the answer.
  • WarrenPFJr
    WarrenPFJr Member Posts: 11
    edited January 2021
    Here are a few pics. I have a cable from the boiler control, another to the shut off, 2 up to 2 zone valves and one to the hot water. They all seem to use 2 wires and most seem to pig tail right in front of the zone valves
  • Steamhead
    Steamhead Member Posts: 15,050
    Does the thermostat wire connect to the Honeywell control in the first pic, or to one of the zone valves in the last pic?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • Ironman
    Ironman Member Posts: 6,705
    That's the worst stat that could be used with a hydronic system. It won't save any energy and will sacrifice comfort in the process.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Zman
    Zman Member Posts: 7,138
    It goes on the same terminal as the white wire on the transformer.
    I would personally get rid of that mess of wires and install one of these https://www.supplyhouse.com/Taco-ZVC403-4-3-Zone-Valve-Control-Module-with-Priority
    If you do it that way, it is super clean, you land the t-stat wire on R-W-C.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • WarrenPFJr
    WarrenPFJr Member Posts: 11
    Thanks guys for all the responses. The point of the nest is that no one lives in the house full time anymore and we need to monitor the house temp remotely. I had checked on the house 10 days ago but when I checked yesterday, either the batteries in the original stat died or the unit itself died and it was below freezing inside. I’m dealing with frozen pipes now.
    The stat wire is 3rd from the left in the birds nest of pigtails and appears to connect directly to one of the zone valves.
    Zman- thanks for that link. I actually installed on of those modules in my own house. Until I can get my hands on one I’ll try hooking the blue wire to the transformer.
  • Steamhead
    Steamhead Member Posts: 15,050
    Honeywell makes Wi-Fi thermostats that work much better than the Nest.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • HomerJSmith
    HomerJSmith Member Posts: 1,421
    edited February 2021
    I don't like thermostats that spy on you, does Nest spy on you? hmmm. Does Google spy on you? hmmm. Does your Nest call home? hmmm. You will need a router and internet for remote access to the thermo.

    One side of the secondary of a 24V transformer (usually the red lead) goes to the R on the Nest and the C connection on the Nest goes to the other side of the secondary of a 24V transformer, commonly called, the Common. That would allow charging of the Nest.
  • pecmsg
    pecmsg Member Posts: 2,569
    Steamhead said:

    Honeywell makes Wi-Fi thermostats that work much better than the Nest.

    Everyone makes a better t-stat!
    Zman
  • WarrenPFJr
    WarrenPFJr Member Posts: 11
    So I got my 3 zone valve control today. Am i simply removing the existing transformer attached to the shut off and hooking up those power feeds to the transformer in the control? That would be my power supply and then its just cleaning things up by wiring up the T stat, water heater and 2 zone valves?