Not necessarily. The kit includes a C-Wire Adapter for exactly this situation. First, let's see if you have a hidden option.
Look at the bundle of wires coming from your wall. You may need to gently pull it out. Look for an extra, unused wire tucked back in the wall. It could be any color. If you find one, you can connect it as your C-wire at both ends, which is the best solution.
If there's no unused wire, you'll use the included C-Wire Adapter. The installation is more involved:
- You must turn off power at the breaker.
- The adapter installs at your furnace control board, not at the thermostat.
- You'll need to follow the separate instruction guide included in the adapter's box.
If that didn't work / seems too complex: There are two cases where you should call a pro:
- If you have a zoning panel (multiple thermostats controlling one furnace), adapter installation is complicated. Call 1-855-733-5465 to find an installer.
- If you have a line voltage system (thick black wires with wire nuts, or labeled 120V+), the T9 is not compatible. Do not attempt installation.
Heads up: A C-wire or the adapter is required. The thermostat will not power on reliably without it.