How Ecobee Power Extender Kit Works: A Helpful Illustrated Guide


What is The Power Extender Kit?

If you have Ecobee thermostat and only have two wires, a red and white one, with no C wire, then this is the article you have been waiting for.

Ecobee Power extender kit is a kit that gets installed on your furnace control board if you have only two wires, and it is wired with the thermostat wires you have to create a C.

The work of the power extender kit is  to connect  the Gwire from the PEK to the C terminal on the thermostat, and the Y wire from the PEK to another special PEK terminal on your thermostat.

The thermostats use the power extender kit to signal a change to its behaviour, and instead of it using the Y, W AND G wires for their normal purposes, it now uses them to control the power extender kit. At idle, one of the wires gets connected to the PEK terminal and then functions like the C wire, and that leaves two wires which can either be on or off.

How Does The Power Extender Kit Work?

What I suspect, that the PEK toggles a switch between the Y and the C wires depending on whether you need the fan or not. So when it is in its idle state, the Y wire is open and the power circuit of the Ecobee is completed by C to your furnace via the Y wire at the thermostat. 

And when the fan needs to be on, the C wire closes, the Y is closed, and the Ecobee power circuit is completed in series with the fan coil through the Y wire at the thermostat. I have no idea how it gets to communicate this switching action though I am not an EE. 

What could be happening is that the Ecobee Power Extender Kit uses the power stealing technology? This means that it tries to steal as much energy as it can from the HVAC control lines so that it can recharge its batteries. This means that the thermostat gets more energy when the system is off and gets less energy when it is running. Thus the chances of failure are even higher when your AC is almost ever running.

Do I Need a C Wire?

Yes! You should ensure you install a C wire if you are upgrading your thermostat. Almost all modern thermostats, whether smart or not require a power source. This doesn’t seem likely to change anytime soon. Though there are smart thermostats that do not need to have a C wire.

Can I Use Ecobee Without C Wire?

Ecobee thermostats are few of the smart thermostats that do not require a common wire. Even though they do not need to have one when you are installing them, you need to have the 4 wire thermostat cable because you will have to use the power extender kit.

You will have to connect the wires from your furnace to the power extender kit and then connect them to your thermostat. Ecobee includes the power extender kit to their Ecobee 3 Lite and the Ecobee4 smart thermostats so that you have to make separate purchases.

Do I Need The Power Extender Kit?

If you don’t have a C wire and have atleast some four wires for your thermostat to work with, then you need to have the solution. This is what I did with my thermostats. The Power Extender Kit (PEK) is to be installed at the furnace control board and is wired in with the thermostat wires to create a C.

What should I do if I don’t have C wire?

These are a few things that I would recommend you do if you don’t have C wire.

You can hire a pro who will run new wires between your furnace and the thermostat you have. (You may also do this yourself). Then grab a Venstar Add-a-Wire, that adds a 5th wire to the four wire setup you have.

You can also get a smart thermostat that’s designed to work with a system that lacks a C wire, like the ecobee3 (which has an adapter for C wireless system) or the Emerson Sensi (which doesn’t need a C wire in most systems).

How I Used My Power Extender Kit

I personally used the 24 Volt C-Wire power adapter for Installation Of my New Thermostat. This helped me to install my Ecobee-thermostat with no-c-wire.

You will need to buy a 24 Volt C-Wire Power adapter from Amazon (I haven’t found them in local stores personally). Check the current price on the ones that I personally purchased over here on Amazon. They are relatively inexpensive and typically can be purchased for under $30. Many of these come with a rather long power cord, some are 25 feet or more!

Home Guide Report

SMART HOME GADGETS ARE MY THING! I’ve been building my smart home for a few years. I recently started thinking of everything that I’ve learned over these years and everything I wish I knew when I got started. I created this site to share with you all of the helpful tips I’ve come across. Hopefully, you will enjoy my posts and be a regular around here!

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