Connecting Nest adapter on unusual boiler wiring.

betterwingedicarus

Hey folks!

I've been looking for an answer for this for a few days, and the only place I've seen my situation mentioned is this video:

https://www.youtube.com/watch?v=1o88SE0nUVA

But it didn't answer my question. So, here's the issue:

My transformer's connections look like this:

R      C
    G
W     Y

And the wires coming from my current thermostat connect like this:

Thermostat Red Wire -> Transformer G
Thermostat White Wire -> Transformer Y

The instructions for connecting the Nest adapter look like this:

So when I connect the adapter, on the boiler side of the adapter's connection...

Do I connect Adapter R to Transformer G, because Thermostat Red Wire is connected to Transformer G currently?

Or do I ignore Transformer G and just connect Adapter R to Transformer R?

And then do I connect Adapter W/Y to Transformer Y? Or do I connect it to Transformer W instead?

Any help, even just pointing me to where I might find this answer, would be appreciated. Thank you!

Jamie Hall

Your transformer connections seem... unlikely at best. As well as incomplete -- there are other connections, perhaps, to the transformer? And maybe some wires to the boiler or zone valves or control board?

EdTheHeaterMan

Not enough information to answer your query. That is because some of the steam boilers that are using the transformer with R W Y G and C terminals are not connecting the R from the old thermostat to the R on the transformer. A brand and model number for your boiler or a photo of the wiring diagram will go a long way to solving your problem.

EdTheHeaterMan

If you have the Weil McLain standard wiring diagram, there is a little rewiring you need to do in order to get the NEST to work and you do not need a relay or power converter if you have a third conductor (18-3 wire) in the wall behind that old thermostat. I posted this comment earlier last year https://forum.heatinghelp.com/discussion/comment/1783725#Comment_1783725

EdTheHeaterMan

If you have only 2 conductor wire (18-2) from the thermostat to the boiler room than you can add the NEST power converter the same way as you would connect the Nest Thermostat using the same instructions for the Red Jumper, the Yellow Wires from the limit to the LWCO and the three wires from the Nest Power Converter R W C as shown in this illustration.

It is a little more than you may want to do so you may need a Nest Pro to install your thermostat and power converter if needed. If you are a fairly patient person with an aptitude for electrical circuits you may be able to DIY this one.

Feel free to ask any question. There are no stupid questions only ****** people who decide to not ask! You can PM me if needed

pecmsg

You all know my love of the NEST!

anything is better!

EdTheHeaterMan

pecmsg said:

You all know my love of the NEST!

anything is better!

You never let one go, do you? LOL

betterwingedicarus

EdTheHeaterMan said:

If you have only 2 conductor wire (18-2) from the thermostat to the boiler room than you can add the NEST power converter the same way as you would connect the Nest Thermostat using the same instructions for the Red Jumper, the Yellow Wires from the limit to the LWCO and the three wires from the Nest Power Converter R W C as shown in this illustration.

It is a little more than you may want to do so you may need a Nest Pro to install your thermostat and power converter if needed. If you are a fairly patient person with an aptitude for electrical circuits you may be able to DIY this one.

Feel free to ask any question. There are no stupid questions only ****** people who decide to not ask! You can PM me if needed

Thank you! I appreciate all of your info on this. It is in fact just a 2 conductor wire like you describe, but I do want to get the brand and model number of the boiler, make sure that those yellow connections already exist on it, and look up the wiring diagram. I will probably PM you, if that's alright.

betterwingedicarus

Jamie Hall said:

Your transformer connections seem... unlikely at best. As well as incomplete -- there are other connections, perhaps, to the transformer? And maybe some wires to the boiler or zone valves or control board?

Yes, I should have clarified, there are a lot of connections around the boiler! Especially between the transformer and the control board. But the wires to G and Y are the only connections I can identify as coming from the thermometer.