When I first received an ecobee3 smart thermostat for review, I wrote a guide to installing an ecobee3 for first-time ecobee users. This post, by contrast, is for ecobee old-timers. I’ll walk through how to replace your original ecobee “Smart” unit and upgrade to the ecobee3, while re-using your existing in-wall wiring (if you’re replacing a regular thermostat, I recommend reading my standard install guide instead).
The instructions in this guide are based on the two (so far) ecobee Smart to ecobee3 upgrades I’ve done at our main Seattle house and our vacation place in Utah. I’ll be using photos from both upgrades throughout.
Before You Start
This is a bit of a repeat of what I said in my main install guide, but the only two thing you’ll probably need are:
- A Phillips screwdriver to mount your ecobee3 to the wall
- A small flat head screwdriver to remove the existing wires from your ecobee Smart wall unit and the Equipment Interface (EI)
- You might also need a drill to make some holes to install the included drywall anchors when securing your ecobee3 to the wall
Important tip: I highly recommend that before doing anything, you login to your account on ecobee.com, open up the web interface for your existing ecobee Smart thermostat, and take a screen shot of your existing programming schedule. It will come in very handy when re-creating your schedule on the ecobee3. You could also take some screen shots of any settings accessible via the web interface. But it’s also important to take some photos (using your mobile phone is easiest) of all the configuration screens in your ecobee Smart, so that you can set up your ecobee3 with the same settings (such as window efficiency, or AUX temperature cut-off, etc.)
Finally, make sure you’re aware of the limitations of the ecobee3 vs. the older ecobee Smart that might affect your system. The ecobee3 is an upgrade in nearly every way, and for most homeowners, there won’t be any issue. However, the ecobee3 only allows you to control one external accessory (such as a humidifier, de-humidifier, or ventilator), so if you have more than one of these currently being controlled by your EI, you’ll have to choose which one you want the ecobee3 to manage.
Step 1: Kill the Power to your HVAC
The first step in any DIY project that involves any sort of power (even a “relatively” low voltage such as 24V), is to kill the power. If your furnace has a light switch nearby that doesn’t actually turn off any lights, that’s probably the power switch for your furnace. If you don’t have a switch, just throw the breaker (or breakers, if there’s more than one) that power your system.
Step 2: Photograph your Existing Installation
You’re going to be swapping around your existing wiring, and probably even simplifying it a bit, so before you start, it’s a great idea to snap some photos of where all the existing wires go… just in case something goes wrong and you have to put everything back. If you have to go back to your original setup, you’ll want to be able to do so quickly enough that your spouse doesn’t notice the temperature drop (or spike) in the house. 🙂
Step 3: Unwire the Existing Equipment Interface (EI)
The ecobee3 doesn’t use an Equipment Interface (EI) like the older Smart, so let’s start by disconnecting all its wiring. Locate your EI:
Original ecobee Smart Equipment Interface
then gently remove the top cover by pulling from the sides:
Inside the Equipment Interface
In the above photo, you can see three sets of wires connecting to the EI:
- On the far left, there’s a dark brown 6-strand wire bundle with White, Blue, Red, and Green wires (the other two are clipped) connecting to a wiring block on the lower left portion of the circuit board. This wire bundle runs from your EI to your wall-mounted thermostat location.
- To the right of that first wire is a lighter brown 8-strand wire bundle that connects from your EI to your furnace’s terminal block. The Orange (24V) and Black (COM) ones are powering the EI, the Yellow (Y), White (W O/B), Green (G), Blue (W2 AUX), and Red (R/H) ones connect to the corresponding terminals in your furnace, and the final Brown wire (COM) is wire-nutted to the White wire in the grey-covered bundle.
- The grey-covered bundle on the right has only two wires hooked up: the Red one’s getting 24V power from the ACC1 terminal on the EI and delivering it to one side of a 24V solenoid on a humidifier, and the White one connects the COM from the furnace to the other side of the humidifier’s solenoid (if you don’t have a humidifier or other external accessory, you won’t have to worry about this).
Unwire everything, remove any screws used to mount your EI, and set it aside.
Step 4: Check How Many Wires You Need, and How Many You Have
Remove whatever panels you need to from your furnace to expose the control board. My Bryant furnace at the Utah house has a main panel I can pop off without tools:
Main panel removed
and a smaller panel below with two screws holding it in place. Removing the smaller panel reveals the location of my control board:
My furnace’s control board
Take note of which terminals are in use on your control board — which will depend on how many heating stages your furnace supports, whether you have an external A/C unit, whether you have a heat pump, etc. Mine is a standard two-stage gas furnace with an external A/C condenser, meaning the following terminals were in use for my setup:
- W2
- G
- COM/24V (also called a “C” wire)
- W/W1
- Y/Y2
- R
That means I needed 6 wires from my furnace to the wall location of my thermostat. The good news is that in most setups, you probably replaced your older original thermostat with your ecobee Smart (like I did), and probably already have the correct number of wires in the wall from your original thermostat (like I do). Here’s a photo of the original wall-mounted wiring harness before I replaced it with my ecobee Smart — with all six of those wires connected to the appropriate terminals:
The bottom line is that if you have at least as many wires at your wall location as you have terminals connected at your furnace, your ecobee3 can be wired to control everything you’ve got. If that’s the case for you, go ahead and skip down to the next step.
However, that wasn’t the case for me. Because a few months after installing my ecobee Smart at the Utah house, I purchased a humidifier. Wiring it to the ecobee Smart wasn’t a big deal, because I could just wire it directly to the ecobee EI, and didn’t need any additional wires in the wall.
But ecobee3 doesn’t have an EI, and since I’d need all six wires in the wall to connect from the ecobee3 to the six terminals on my furnace, I’d be two wires short: the two wires that connect to the 24V solenoid on my humidifier.
But that wasn’t going to stop me. In actuality, I could wire one side of my humidifier’s solenoid directly to the COM terminal of my furnace, which is where I already had it wired when using the ecobee EI. So now I was only one wire short.
I solved the second half of my problem using a nifty little device called the Power Extender Kit (PEK), which is included free with every ecobee3. Because the ecobee3 requires a C wire to operate, the PEK is designed to be used in installations where the wall-mounted thermostat location has no C (COM) wire, and essentially creates a “virtual” C wire using the R, G, Y, and W wires (check Step 4 of my ecobee3 install guide to see more about how the PEK works). The PEK has five wires coming out one side (that connect to the furnace board) and four terminals on the other side (for connecting four wires to your wall-mounted thermostat location).
Inside the ecobee PEK
Standard 4 wire thermostat connections go in this side
So my plan was to use four of the six existing in-wall wires with the PEK to take care of my R, G, Y, W, and C wires, leaving one wire for my W2 terminal and the last wire for the 24V+ side of my humidifier’s solenoid. That’s six wires for the price of four!
When I was done wiring it up on the furnace side, it looked like this (don’t worry – I prettied it up before I was finished):
ecobee’s PEK turning four wires into five
As promised, here it is all prettied up:
Cleaned up install of PEK and wiring
Step 5: Remove the ecobee Smart Wall Unit and Install the ecobee3 Wiring Harness
With everything finished down in the furnace room, you’re now ready to focus on the wall-mounted location for your ecobee3.
Gently remove the main portion of your ecobee Smart thermostat (a small screwdriver in the side indentations can help), and set it aside. Then disconnect the four wires from the wiring harness, unscrew the wiring harness from the wall and set it aside, too. You should now just have your thermostat wire bundle sticking out of the wall, like this:
Six-strand bundle of thermostat wire
You can see where I put some drywall filler putty in the two outside holes (created by my ecobee Smart), but I didn’t need to fill any of the others because they’d be covered by the ecobee3. I also discovered a full Cat5e cable in the wall behind my thermostat location. That might be interesting for future reference, but the other end of that Cat5e actually went to my network punch-down block, and not to my furnace.
Now you’re ready to mounted your ecobee3 wiring harness to the wall (I got super lucky – the mounting holes lined up with the holes from the old original thermostat I’d removed when installing the ecobee Smart) and connect all the wires to their appropriate terminals:
ecobee3 wiring harness mounted
Note that if you’re using the PEK, you have to install your R wire to the Rc location on the wiring harness. If you’re not using the PEK, then you can use either the Rc or the Rh.
Use the built-in level to make sure it’s mounted properly before tightening the screws, then press the main ecobee3 unit gently into place. It should make a quiet “click.” when it seats properly.
ecobee3 wired up and installed on the wall
Step 6: Power It Up… and Cross Your Fingers
Go back down to your furnace location, power it up, and then run back upstairs or inside to the ecobee3’s wall location. If all went well, you’ll be greeted with the ecobee logo on your screen as the unit boots up.
If you see nothing, don’t worry — go back through and re-check all your connections. It’s possible a wire came loose, or maybe you accidentally swapped a couple of wires. There’s also a troubleshooting section in the ecobee3’s installation guide, and you can always call ecobee’s tech support and they’ll help you out. I don’t get paid by ecobee, however, so posting install problems in the comments below won’t help you much. 🙂 I do, however, recommend you stop by the SmartHomeHub discussion forums and check out the ecobee3 Install Help thread for community-based support from other ecobee3 users.
Step 7: Configure and Tinker
At this point, you’re ready to walk through the start-up configuration wizard on the ecobee3 and set everything up — including your remote sensors, which is probably what convinced you to ditch your ecobee Smart for an ecobee3. For configuration tips, you can jump directly to Step 8 of my regular install guide and follow along from there!
Step 8: Join the ecobee Conversation at SmartHomeHub.net
Congratulations on a successful upgrade!
If you’re already an ecobee user, then there’s a good chance you’re already participating in the ecobee user discussions over on SmartHomeHub.net. If you’re not, consider yourself invited! It’s a user-driven discussion forum (founded by yours truly) focused on all things home automation, with a lot of ecobee owners taking part. Though not an official ecobee company resource, you’ll also find that a number of prominent ecobee staffers hang out there, and they are always happy to hear user feedback and suggestions for tweaks, fixes, and new features.
As always, I welcome your comments and feedback below. But remember: as I mentioned earlier, I won’t be answering any ecobee3 tech support questions here. I’ll answer general questions, but for support I recommend contacting ecobee support directly, or asking your questions at SmartHomeHub.net for unofficial community-based support (where I do take part in the support conversations).
