Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.

If you've found help here, check back in to let us know how everything worked out.
It's a great way to thank those who helped you.
Need to contact us? Visit

Steam-Help with Thermostat wiring, New Yorker 2 wire

NysteamerNysteamer Member Posts: 22
Hello Everyone,
Current setup
-New Yorker Boiler.
- T Stat something no longer made
looking to put in a Wifi Thermostat for remote functionality.
Only steam heat no AC.

I am certain this topic has been answered somewhere, however I have not been able to pinpoint some finer details reading through various discussions. I am trying to identify how I can add a C Wire to the current wiring scheme. Upon review of one of the manuals diagrams it appears there are two places the t stat wiring goes to which is blue and brown on each one. I don't know if it is possible to connect a third wire somewhere to be "C" or do I need to apply one of the methods noted throughout the web, which is adding an external transformer, add a wire etc for an Ecobee or nest t-stat.

Attached you will find the wiring diagram pulled from the manual.
Thanks in advance!


  • ratioratio Member Posts: 2,329
    Blue from the boiler to R on the stat, brown to W, yellow to C.

    Be sure to configure your new stat correctly, esp WRT number of heating cycles per hour.

  • NysteamerNysteamer Member Posts: 22
    hello ratio!

    Thanks for the super fast response! I will get on this. One question in regards to the current transformer. Is the 40va enough? or would it be a problem in terms of the connected loads. Draft vent, pressuretrol, lwco etc? I've come to read that these t stats draw a bit of power
  • ratioratio Member Posts: 2,329
    Hard to tell without knowing the current load & the load of the new stat, but if it's undersized it'll just blow the fuse/CB. Try it & see is the cheapest solution.
  • Jamie HallJamie Hall Member Posts: 12,696
    ratio said:

    Hard to tell without knowing the current load & the load of the new stat, but if it's undersized it'll just blow the fuse/CB. Try it & see is the cheapest solution.

    It would be nice of it if that's what happened. Doesn't always -- if the load is very close, it may just drop voltage enough to cause various odd gremlins to appear. If that happens, you may need a larger transformer.
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • NysteamerNysteamer Member Posts: 22
    Hello @ratio , I have the wires connected as you described. However, the nest does not turn on with the C wire- now connected downstream to yellow in place. When I remove it, everything turns on. No clue what thats about.
  • ratioratio Member Posts: 2,329
    It may be trying to fast charge it's battery. Try leaving it connected for a few hours. If that doesn't help, I guess a call to Nest support might be in order. The yellow & the blue are the correct wire colors. Any chance the xfrmr's been replaced or that schematic isn't the correct one?
Sign In or Register to comment.


It looks like you're new here. If you want to get involved, click one of these buttons!