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Powering a WIFI thermostat from a Burnham Steammax boiler

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DaveEvans
DaveEvans Posts: 5
in Thermostats and Controls

The C-wire should be the wire from the transformer that becomes yellow.

My problem is that the TT wires are a dry loop, so that they are there only to be closed and there is no clear distinction between the R and W thermostat wires. One goes to the relay and the other connects to a blue wire, based on the wiring diagram. The latter would be the R, to my mind. But the voltage reading to it to a C is a phantom 4.7 VAC; to the former is 0.

How to get 24 VAC to the R wire? Should already be 28 VAC from the blue wire side. Puzzled. Sorry if this has been answered, but couldn't find same.

Thx.

Comments

  • Jamie Hall
    Jamie Hall Posts: 27,866

    Electricity is colourblind. It is quite likely that the wire you are calling R isn't the 24 VAC feed — but that the one you are calling W is. If you have a multimeter this should be easy to determine…

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • DaveEvans
    DaveEvans Posts: 5

    I'm really speaking of what the wires go to, Rh or W. A non-powered thermostat has no need for voltage in the R wire; all that matters is making the connection with the W. One of the TT-labelled wires shows 4.7 VAC to the common ground, the other 0 VAC.

  • EBEBRATT-Ed
    EBEBRATT-Ed Posts: 21,107

    Burnham's wiring diagram SUCKS because they change colors all over the place which makes it confusing.

    The BLUE low voltage wire coming off the transformer changes to Yellow and goes to the thermostat that is the HOT -RED ® terminal on the stat.

    The other YELLOW coming from the thermostat pulls in the relay coil that is the "W" wire to the thermostat.

    The "COMMON" wire "C" on the thermostat connects to the "YELLOW" low voltage wire coming off the transformer. This wire goes to the other yellow wire on the relay coil.

    Trace these wires out to make sure they are correct as the changing wire colors makes it a mess to figure out.

  • HVACNUT
    HVACNUT Posts: 7,720
    Screenshot_20261013_171026_Samsung Notes.jpg

    You need to pay attention to the yellows. The Common coming off the transformer is Yellow (2). Thats the C at the thermostat. Splice it in where you can.

    Rh and W are both Yellow at the boiler wire tails. You need to make sure the yellow wire thats connected to the Blue wire (1) from the transformer is connected to Rh. The other Yellow wire at the tail is W at the thermostat.

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