boilerfurnacethermostat-c-wirewire
The new thermostat I purchased doesn't run on batteries, and needs 24 volt power. I have only a red and a white wire connected between the boiler and the thermostat, but there is also a third, unused wire. The instructions from the thermostat say to hook that third wire to the C terminal on thermostat and to the furnace's C, but I have a boiler with no C. Where do I put it on here? Please help I'm desperate.
After glancing through the White-Rodgers 1361 zone valve Installation Instructions, I'd say the C wire should be attached to terminal 1. While R should attach to 5, and W should attach to 4.
From the pic, I'm guessing the transformer is the black device under the junction box. Looks yellow and purple coming off of that, you're connecting to the yellow, so the purple would be the common. To be sure, you'd want to connect a multimeter and verify the voltages to ground. It would also be helpful to find the wiring diagram for your boiler to be sure you're interpreting these wires correctly.
Assuming purple is the common, you'd run your wire to that, preferably through that wiring block where the other thermostat wires are connected on the left. There's no issue connecting the common to multiple places.
Best Answer
Unfortunately, the Aquastat you're using does not expose a
Cterminal. The transformer is likely soldered directly to the board; so unless you're good with a solder gun, you're going to have to buy a different thermostat.The red wire attached to the
Tterminal, should be connected to theRterminal of the thermostat. The white wire attached to theTterminal, should be connected to theWterminal of the thermostat. When the thermostat calls for heat, it will connect theRterminal to theWterminal. This will cause the coil to pull a switch closed (relay), which tells the boiler that the thermostat is cold.If you're not afraid to potentially break things, and you really want to try to get the new thermostat working. You could try to add your own
Cwire. You'll simply have to connect the newCwire, to the other lead of the secondary coil of the transformer.Left image shows original wiring. Right image shows where the
Cterminal should be added.WARNING:
Modifying the wiring of the Aquastat will likely void the warranty, and could potentially damage the equipment. Proceed at your own risk.