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I’ve seen a version of this question in a few places but nothing really fits.

I have a boiler and hot water baseboards. It’s a three zone system and I installed 3 Nests but there is not C wire and no easy way to run one. A friend of mine said they had the same set up and the transformer keep burning out on them so I started looking into using a 24v transformer for each thermostat. I just can’t find an easy guide on how to wire it.

This is the transformer I bought three of: Help me decide on this product: C Wire Adapter 24 Volt Transformer Compatible with Nest Honeywell Ecobee Emerson Sensi Smart WiFi (White) https://a.co/d/dsCTR9U

And here is a photo of the current wiring on the Nests: enter image description here

I really need help with this as HVAC systems are not my wheelhouse :)

Unhuman
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    run a new thermostat cable with 7 wires. You might need some in the future. Find the 24 Volt transformer on the furnace and use it to get C wire from the transformer – Ruskes Feb 12 '23 at 21:58
  • How is your 3 zone system current wired? Keep in mind that the so-called C wire is just one side of the transformer, nothing magical about it. – SteveSh Feb 12 '23 at 22:08
  • If the 24v transformer on the furnace can't provide enough current to power all three, you can install a separate 24v transformer and power them that way. The instructions that come with the thermostat should describe several alternatives. My smart thermostats also support an adapter (at extra cost) that can run power and signal across the same wires, if you really can't pull new wire. – keshlam Feb 13 '23 at 00:19
  • @SteveSh the thermostats all have the same two wires as in the photo, but if you mean how is it wired at the furnace, I’ve no idea unfortunately:( – Unhuman Feb 13 '23 at 00:36
  • @keshlam unfortunately the transformers I got didn’t come with instructions so I spent the day on google and wound up here, I may just return them for better ones that include documentation. Thanks! – Unhuman Feb 13 '23 at 00:37
  • If you only have two wires, transformers alone will not solve your problem. I was referring you to installation instructions for the thermostats, which ***may*** have a way to cheat this with additional equipment or may not have an alternative to a separate 24v wire. – keshlam Feb 13 '23 at 01:10
  • Are you (OP) saying that each Nest/thermostat location has a red and white wire going to it, like in the picture? – SteveSh Feb 13 '23 at 04:13
  • And you might find this post useful, which describes how a simple 2-wire thermostat connection works. https://diy.stackexchange.com/questions/10482/how-can-i-add-a-c-wire-to-my-thermostat – SteveSh Feb 13 '23 at 04:16
  • @SteveSh Yes, each thermostat location has a red and white wire, like in the photo. I'll check out the other post you mentioned. Thanks! – Unhuman Feb 13 '23 at 15:51

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