Quick Summary The Ecobee Power Extender Kit (PEK) is a small adapter that comes in the box with most Ecobee thermostats. It installs at the furnace control boa…
Quick Summary
The Ecobee Power Extender Kit (PEK) is a small adapter that comes in the box with most Ecobee thermostats. It installs at the furnace control board and converts your existing wiring to provide the C-wire power the Ecobee needs — without running a new wire. This guide walks through the full installation.
What You Need Ecobee Power Extender Kit (included in the box, or order from ecobee.com) Screwdriver (flathead and Phillips) Phone to photograph existing wiring before disconnecting 15–30 minutes
Before You Start: Photograph Your Existing Wiring
Before touching anything: Remove your old thermostat from the wall. Take a clear photo of all the wires and which terminal each one is connected to. Label each wire with tape if needed (R, G, Y, W, etc.). This is your reference if anything goes wrong.
Step 1: Turn Off Power to the HVAC System Go to your electrical panel. Turn off the breaker labeled "Furnace," "HVAC," or "Air Handler." Confirm power is off by checking that the furnace control board lights are off.
Step 2: Locate the Furnace Control Board Open the furnace panel (usually a removable front cover). Find the control board — the circuit board with all the thermostat wires connected. Locate the thermostat wire terminals: R, C, G, Y, W (and possibly others).
Step 3: Install the PEK at the Furnace
The PEK replaces the direct connection between the thermostat wires and the furnace control board. Disconnect the thermostat wires from the furnace control board terminals. Connect the thermostat wires to the corresponding terminals on the PEK (match wire colors to labels). Connect the PEK's output wires to the furnace control board terminals (the PEK has labeled wires for R, C, G, Y, W). The PEK uses the G-wire (fan) to create a virtual C-wire — this means independent fan control will be disabled (fan only runs with heating/cooling).
Step 4: Connect Wires at the Thermostat Base At the wall, connect the thermostat wires to the Ecobee base terminals. The Ecobee base has terminals labeled R, C, G, Y, W, and others. Connect each wire to its matching terminal. Important: The C terminal on the Ecobee base must have a wire connected — the PEK provides this via the G-wire conversion.
Step 5: Turn Power Back On Turn the furnace breaker back on. Wait 2 minutes for the furnace control board to initialize. The Ecobee should power on and display the setup screen.
Step 6: Complete Ecobee Setup Follow the on-screen setup wizard. When asked about wiring, select your system type. The Ecobee will detect the connected wires automatically. Complete Wi-Fi setup and account connection. Test heating and cooling to confirm the system responds correctly.
Common PEK Installation Mistakes