Hacking the Ecobee3 for Wiring Success
I recently purchase an Ecobee3 thermostat. This is a brief story about why I went with it, and the issues I had wiring it up.
Why not Nest?
So this is the question everyone asked me. Honestly, I’ve wanted a Nest thermostat for a long time. It’s a good question because the Nest looks cool, its designed by a cool guy, and they really were the first easily accessible tool for anyone interested in home automation.
When it came down to entering my credit card numbers, I first decided to do some homework. Reading reviews of the Nest thermostat it was becoming clear that while I had wanted for so long, it was possibly not the best choice. When I hunted for alternatives, Ecobee3 was only $30 more and featured much better ratings, so I went for it.
Installation
I expected this to be fairly straightforward. I found the user guide to be rather extensive, covering a large array of wiring possibilities and while I wasn’t 100% which diagram my heating / cooling system aligned with, I could only imagine it was one of the common options as my apartment building is fairly modern (2006).
It turns out that my WaterFurnace Heat Pump system while very similar to many of the wiring options, is in fact not one of the wiring options.
A bit of background first
In a conventional heating / cooling system in Canada or the USA you have an outdoor compressor (for cooling) and an indoor furnace (for heating). In these systems you normally have 4 or 5 wires attached to your internal thermostat. These do have designated coloured wires that should be used for each input, but the installation teams regularly mix things up so I would suggest not trusting the wire colours when you install a new thermostat, rather trusting the inputs that they were in on your old system:
- R —Normally red — 24V+
- G — Normally green — Fan relay
- W — Normally white — Cooling relay
- Y — Normally yellow — Heating relay
- C —Normally black — Low voltage accessories*
*Some systems do not have this 5th “C” wire, but that is another problem (that I did not have to worry about) and it’s fairly easily solved.
Heat pump systems are different and contain one extra wire, the O wire (Normally orange). This is because Heat pumps only consist of a compressor (not a separate furnace / cooling system) that you can choose to produce heat or cold by reversing its operation (in other areas of the world these might be referred to as “Reverse Cycle Air Conditioners”).The O wire is what tells the compressor if it should be running in heating or cooling mode.
Getting it to work
Based on the fact that I believed I had a heat pump (although I’m no expert in this field and assumed I could be wrong) and upon initial review of the existing wiring, it appeared my wiring matched the “Air or Geothermal Heat Pump” option. Unfortunatly I only had 5 wires coming out of the wall and that diagram required 6 inputs.
I connected everything as if I had a conventional system. This implementation produced a rather disturbing problem in that the system only operated the fan in cool mode, but heat mode worked fine. I resorted to the Internet again but found that while most of the forums talking about installing the Ecobee3 were interesting, they did not actually help.
Studying the old wiring setup, eventually the solution jumped out. I needed to bridge W1 and the Y1 inputs just like my old thermostat had, this was the 6th input I’m missing to match the diagram. As s00n as I did this, everything worked. The only catch is you need to reconfigure the Ecobee3 and tell it if a positive or negative polarity on the O/B wire should indicate heating or cooling mode (I just guessed it. If you guess wrong try again — there are only 2 options)
In conclusion
The Ecobee3 is a good thermostat, its wiring diagrams are not as good. Sadly the user guide never suggests creating jumpers in any of its diagrams, in fact as you can see in the wiring diagram, they often mention how smart the Ecobee3 is in that it will jumper some connections internally for you and this discouraged me from considering jumpers as an option (for a few hours).
The installation process would have been very simple if the jumper between W1 and Y1 were in fact done internally or listed on the diagram. At one point I had the wiring without the jumper, the result was that the compressor would click (I assume the valve changing position for cooling mode) but never actually turn on, so the jumper is pretty important.
So this was my experience, I wanted to write this in the hope that it saves someone else out there a few hours of their life. It took me around 4 hours to get this wiring sorted, but since that time the Ecobee3 has run perfectly and I’m very happy with the purchase. Good luck!
