We have hydro radiant floor heating in our basement that came with the house that uses our propane boiler to heat the water. It requires 3x 2-wire heat only thermostats for 3 zones: bar/gym, office/2nd living room, and guest bedrooms. This thing takes a full day to get to temperature, so likely we will turn it on and it stays on for the entire season.
The only use case I can think of for smart controls is when we go out of town and to turn it on/off remotely. Can you think of others? Temperature adjustment based on zone temps probably isn’t that helpful if it takes a full day to feel the difference.
Also, looking for smart 2-wire heat only thermostat suggestions if you think the benefits are worth it. Didn’t realize this was going to be harder to find than a regular thermostat…
I have some nice, but older, Ecobee Wi-Fi thermostats, but yesterday I ordered a couple of Honeywell T-6 Pro Z-wave thermostats. They were used, 75 bucks for both. We'll see. They might do what you want; not sure how long the batteries would last, although Honeywell seems to have given it some thought (excerpt from manual below).
For me, (I've got baseboard hydronic), I'd be concerned about a power and/or heating outage when on vacation in the winter. What a potential mess.
• If a C wire is not used or present, the thermostat must be powered by batteries.
The thermostat will operate in LSS mode (power-save, sleep mode) to help
conserve battery life after it has been included in a Z-Wave network. The Z-Wave
radio supports beaming. It allows other devices in the network to wake up the
Z-Wave thermostat, accept commands, and then go back to sleep.
It just occurred to me, maybe there's something special about those thermostats, with regards to hysteresis. I have no idea how it's controlled, as in, it takes a mile to stop a freight train..something along those lines. I have no idea if those T-6 could handle it, there's another controller, etc, etc. This'd be a job for a radiant heat forum.
Take a look at the Sinope Zigbee TH1400ZB thermostat for low voltage systems (hydronic, forced air, etc.), using the advanced community driver will unlock a bunch of other features that are usually reserved to there own hub. Their line of thermostats are way above any other on the market.
ok sorry did not notice (or register in my brain) 2-wire in the title. hmmm maybe time to upgrade and add the C-Wire to the setup. Since this was a hydronic system, I assumed that all had multiple wires ,never saw a system with only 2 wires except for fan forced furnaces with old mercury ball thermostats.
So the Sinope thermostat might be overkill for your application since it won't be able to use all it's features like pump anti-seize, floor heat monitoring with an external temp probe, etc.)
Search Amazon or ebay for Zigbee Centralite Xfinity 3156105.
If it's a 24VAC control circuit, this is one should work. Battery powered, 2-wire compatible, adjustable hysteresis. It's not the prettiest option, but they work well and the price is right.
I use three Zen Zigbee thermostats on my old 2-wire hydronic baseboard system and they work great. There are many setup options for different types of systems. Run for year(s?) on 4 AA batteries. I think I got them on eBay for half this price on Amazon ($75-ish). I have since added a C-wire to them by simply installing a 24v DC transformer and doing a run to them (obvs need to be able to run a wire), but if you can accomplish this, the battery backup is nice to be able to monitor temperatures if the power goes out.
