Powering Your Thermostat

You must provide external power to your thermostat in order for it to function properly. This power can come from the HVAC unit in your home, or from an external transformer. If your Thermostat is properly setup to control your HVAC system, but you cannot access it from the website, it likely that the thermostat is not powered properly. To verify the thermostat has power, please remove the batteries while your thermostat is still connected. If the screen on your thermostat is blank when you remove the batteries, then you don't have power to the thermostat. This page will give you a number of examples on how you can power your thermostat.

Method 1: Connect your "C" Wire with Existing Cabling

Often times there are extra wires in the wall, and you can use one of those wires to power your Thermostat. Follow the directions below:

  • Turn off power to your HVAC unit
  • Find your thermostat terminal block inside of your HVAC unit (you most likely have to remove a protective panel)
  • Connect one of the extra wires to the "C" terminal on your HVAC unit (this likely has a "C" label, and possibly has another wire connected to it)
  • Connect the other end of the same wire to the "C" terminal on the thermostat
  • Replace protective panels on the thermostat and power back on your HVAC
  • Test that the thermostat has power by removing the batteries. If the screen stays on when the batteries have been removed, then you have successfully applied power to the thermostat.

Method 2: Power your thermostat with an External Transformer

If you don't have an extra wire in the wall, you can power your thermostat with an external transformer. If you don't already have one, you can purchase one from our online store at http://store.radiothermsotat.com. Once you have a 24VAC transformer, follow the steps below to apply power to your thermostat:

  • Connect one wires from the external transformer to the "C" terminal on the thermostat.
  • Connect the other wire to the "Rh" terminal
  • Plug in your external transformer
  • Verify your thermostat has power by removing the batteries

Videos to Help Power Your Thermostat

The video below shows how to connect an extra wire to your thermostat.

The video below shows how to connect an external transformer to your thermostat.

Images of an HVAC "C" terminal
Click on image for higher resolution

cTerminal         Wiring
Left is a picture of a wiring terminal bock in the furnace, right is an open furnace.