Relax
Well-known member
Ouch. Was looking at smart thermostat as enbridge rebate plus black friday takes a bunch off the price. House was only wired with four wire thermostat wire. The plan is to install a heat pump next year so I would like at least 8 wires, preferably a few more for spares or humidifier/erv control. No good route for adding a wire with finished ceiling in basement. I might be able to run up into attic, around soffit to garage, down garage wall, through wall into furnace room. That will need a bunch of wire. Being an idiot I was thinking thermostat wire would be cheap as it's thin copper. Nope. Five wire thermostat cable is $1/ft when you buy it by the spool. That may be enough to re-evaluate the project.
Such a stupid system. I don't know why nest or ecobee haven't gone to communicating units. Install a breakout box in the furnace room, use three wires up to thermostat for power, common and data. Done. Even if that was an add-on that doubled the price, it's still cheaper than installing more wire. As breakout box has some brains (to decode data), it would be easy enough for it to be the master device and could function without the input device Obviously sensing temp in the furnace room not the living area but better than nothing in a pinch. If they were smart, if it lost connection to input device it would run the fan for a few minutes an hour and check temp in the return air to decide whether to fire the furnace.
It can't be that hard to make my own communicating thermostat from scratch. Or maybe I can get away with just the breakout box. It grabs dumb signals from the existing thermostat (heat, cool or fan) and modifies them appropriately (which stage of heating, which stage of cooling, engage reversing valve, etc.). Have a second dumb thermostat in the basement wired in parallel set at 50F as a failsafe in case the smart box takes a dump. That's easier than making my own hardware input device and having to make communication work. Something like a raspberry pi connected to wifi with an IO board, relay board and a 24V transformer gets me most of the way there wrt hardware.
EDIT:
FWIW, given my expected use, Nest is the clear favorite at this time. In the past, ecobee was slightly ahead imo.
When they installed my Ecobee, I only had 4 thermostat wires, so they had to install an additional included module that converts the 4 wires to 5 on the furnace. I notice sometimes that the Ecobee says the fan and heat are running, but nothing is happening, and sometimes when I tell it to turn the fan off (when I change the filter) it doesn't stop immediately like my old thermostat used to. Not sure if that's an issue with the converter, or if it's just a delay in what the Ecobee is telling the furnace what to do. In any case, I plan on installing more wires so I can remove that converter, as well as tie everything together (HRV, humidifier, and future dehumidifier) with a real Indoor Air Quality controller to replace the Ecobee so they all work together based on interior and exterior conditions.