Can the Ecobee3 be installed without the dreaded C wire? edit: Nope. You lose fan control.
The Nest cannot, well it CAN, but you lose fan control in the process making it worthless. I never understood why no thermostat supports alternative power, considering tons of property would be an easy installation without the rarely available C wire.
Quick shout out for the Honeywell Wi-Fi Smart Touchscreen Thermostat. It too requires the C wire, costs the same as Nest, but has a much better touch interface than the Nest while providing the same-ish automatic functionality.
You don't lose fan control with the ecobee3 Power Extender Kit. Also, the C wire is not rarely available, basically any house since the early 90s will have one already wired up, and any house that has upgraded hvac unit in say the last 15 years will have the capacity to install one by running a wire to the mainboard.
> You don't lose fan control with the ecobee3 Power Extender Kit.
Read page 12 of their guide. The PEK requires additional connectors that not all systems even have. A lot of people will lose fan control, just like the Nest.
> Also, the C wire is not rarely available, basically any house since the early 90s will have one already wired up
Our house was built in 1998, doesn't have it, a coworker's house was built in 2005 and had to get it installed for their Nest ($120 callout + $120 in time), the in-laws returned a Nest because their home from roughly 2001-02 lacked it. Where are you getting this information? There's nothing in building codes that requires running the C wire, so builders will only run it if the thermostat requires it and most included ones do not.
> any house that has upgraded hvac unit in say the last 15 years will have the capacity to install one by running a wire to the mainboard.
Running wires behind walls isn't trivial in an already built home. Least of all if you're going up two to three floors.
My house and all houses in my development were built in 1995 and have one. Most programmable thermostats recommend using a C wire(or batteries, but if they're being put in a new development they generally put the C wire in), and programmable thermostats have been "strongly recommended"/mandatory in many states for new developments for quite a while.
Also have a relative in an older development that used the PEK and he can control his fan independently of the hvac just fine... I've actually more commonly heard of some control boards that mess with the fan if you use the C wire rather than the power extension kit, since the control board basically fakes the C wire using the G wire as the Nest does if you don't have a C wire. The PEK works differently.
It has nothing at all to do with programmable Vs. non-programmable. All of the homes I mentioned above, including ours, have a programmable thermostat.
You don't need a C wire for a programmable thermostat. The other channels provide power, the C wire just provides more. It is useful if you want to run a color LCD screen or WiFi. If you have a thermostat with a black & white calculator-like LCD, it likely doesn't have a C wire running to it.
> I've actually more commonly heard of some control boards that mess with the fan if you use the C wire rather than the power extension kit, since the control board basically fakes the C wire using the G wire as the Nest does if you don't have a C wire.
What? That would burn out thermostats. How would the control board know to pass 24Vac through a low voltage line? Can you link anything to this "common thing" that control boards do? Sorry but I'm extremely skeptical of that, it doesn't even make sense from a thermostat signal point of view, since they'd just assume you would run C if C was required during installation rather than doing the hack you're suggesting here.
The reality is that C isn't required on almost any included thermostat, programmable or simple. Good installers run the C but terminate it, bad installers just don't run the unneeded C. I've never heard or read about a first party control board which acts like a bypass kit out of the box, and I don't even understand the point.
House built in '99/00 by a large builder: No C wire.
With that said, the Ecobee that I bought off eBay included the PEK. It required a few hours up in the attic but was easier than I thought it was going to be.
"so builders will only run it if the thermostat requires it and most included ones do not."
From what i can tell, this is wrong. I asked 30 builders in 3 states (a mailing list), and every single one of them basically agreed with the statement that they have put them in all homes they've built since 1990.
The truth is, AFAIK, the largest homebuilders in the US do it as a matter of policy.
The building code does not require running low voltage wiring (including RG6) anywhere, either, but most do it nowadays.
A lot of houses have the thermostat wire run for it but the installer just cut it off to hide it.
In my old house from 1950s the furnace had the terminal so I just ran a new wire. Easy if you have some fishtape or something similar. Kind of depends how far your thermostat is from your furnace though.
I had two Honeywell Smart thermostats get fried by power surges. Because the design of these 'smart' thermostats is just stupid.
It's wrong for any of these thermostats to be using these wires for power. That is not the purpose of those wires. For that matter, it's shit engineering to require the thermostat be mounted on the wall hooked up to those wires like your old thermostat. The purpose of those wires, with their 24V AC, is to toggle relays. They could just as easily be done directly _at the furnace_, or just have a low-power battery powered radio module on the relay wires, with a WiFi or other wireless receptor talking to your sensors elsewhere, and with an app on your phone or tablet to control it.
Nest is an absolutely terrible design that everyone else copied. Its terrible design is crap for installation, customer support, and maintenance. It's needlessly complex.
What relay does a C wire toggle? From what I've read its only purpose is to provide a continuous stream of power. There's nothing in the spec that forbids using the R and C wires for power, in fact that is their stated purpose.
Now, these bypass kits or similar, are a little hacky. But you're talking about the C wire itself being so, which just isn't the case. IF you have one available that is exactly what it is design to do.
Wifi is really hard to run constantly on battery. Honeywell makes the Lyric which has power stealing (charges when the equipment runs) so it doesn't require a C-wire.
The Nest cannot, well it CAN, but you lose fan control in the process making it worthless. I never understood why no thermostat supports alternative power, considering tons of property would be an easy installation without the rarely available C wire.
Quick shout out for the Honeywell Wi-Fi Smart Touchscreen Thermostat. It too requires the C wire, costs the same as Nest, but has a much better touch interface than the Nest while providing the same-ish automatic functionality.