Help installing nest thermostat gen 4 to boiler system

Rifat1

Hello everyone. I have a one pipe steam boiler system at my house (model #gsa-125-n-sp). I wanted to replace my honeywell thermostat with the nest thermostat gen 4 for better control. Currently there is 2 wires in my thermostat, white into W and red into R then there seems to be a jumper between R and RC. I followed google's instructions and connected white to W1 and red to rH. Initially the thermostat didn't turn on, so I charged it with an external usb c cable then plugged in again but now during setup it says rH doesn't have power.

After unsuccessful attempts I switched it back to the honeywell and it works fine. Not sure if I have a faulty thermostat or wiring. Just need some advice before calling a pro. Any help is appreciated!

Steamhead

That Nest will never work right until you have a third "common" wire.

Jamie Hall

And more to the point — it won't control your system any better than the old Honeywell. It's fun, perhaps, to mess with these things — but it's no improvement.

pecmsg

https://forum.heatinghelp.com/discussion/comment/1833976#Comment_1833976

the 1st 5 words are correct!

EdTheHeaterMan

The Nest R terminal needs to be connected directly to R terminal of the Transformer. On your boiler the regular 2 wire thermostat is not connected directly to the R of the Transformer. That is because the LWCO control and the Vent Damper MUST be connected to the transformer. There are only 2 wires that can connect directly to the transformer that would the R (where the LWCO is connected) and the C (where the Damper is connected) If you can follow the wiring diagram it is very clear

In order to connect the Nest thermostat you will need to provide another transformer with an isolation relay. This can be a DIY project if you are good with electrical circuitry. If this is over your head, then you will need a professional to get the job done.

If you are up for the DIY method, I can help you thru the steps and parts you will need. First. thing, you need to own and know hw to use a Multi Meter.

Ironman

Connect about a three foot long piece of thermostat cable to the Nest while it’s off of the wall. Take it outside, sling it around above your head several times as hard as you can, then release it and let it fly as far as you can. Don’t go after it, just leave that piece of junk where it lands.

You’ll have done yourself the biggest favor possible.

EBEBRATT-Ed

Some people love them. Not me.

jesmed1

Or trade it for an ecobee.

HVACNUT

Switch the wires at the thermostat. It'll work for a little while.