Sale! Honeywell 5-2 Day Programmable Thermostat with Backlight RTH2300B1038

★★★★☆ 7 day programming with 4 set time/temp combinations per day. Works much better than the 1950s mechanical thermostat that it's replacing. Doesn't look as cool, but works much better. Initial programming is a bit tedious but not difficult. I'm only using it for heating. The manual doesn't cover the wiring for a simple system like mine so hopefully the following information will help anybody else out who needs to use it. To connect a 2-wire millivolt system, just connect the wires to the W and R terminals. I believe the same applies for a 24V system but I didn't test. None of the other connections are used for anything. It doesn't matter which of the 2 wires goes to W or R but if you have one that is red or has a red stripe you may as well put it on the red one.. You can find a youtube video by searching for "Honeywell programmable thermostat 2 wire install"

★★★☆☆ For a heating thermostat, back in the day you had the choice between a 2-wire round mechanical or a 3-wire digital unit. The extra wire needed for powering the digital unit of course. Now the 3-wire units are pretty fancy and some are ridiculously expensive. For a simple heating circuit, the Honeywell RTH2300B connects like a 2-wire thermostat and it uses 2 AAA batteries to power the unit. Why not power the unit on 24 VAC with a 3-wire connection? Cost. Profit. It's OK with me. While you now have to worry about batteries going bad, you'll also not have to worry about losing your settings/programming due to power outages. You still keep your settings when you change the batteries - just follow directions and switch it to OFF first. Anyways there seems to be plenty of used/open-box sales of this unit online. I'm guessing folks didn't like the battery-operation thing. It's also pretty tiny. If you're willing to risk it, you should be able to get this online for less than $10 (open-box). I'd say that's a good value. I got 3 and all work fine. Not a scratch on them.

★★★★☆ Works perfectly and easy to set up. It came with a printed user manual, but was missing installation instructions (easy to look up online) and the mounting screws (instructons said they were included. I just re-used the old ones). One tricky thing: mine was VERY difficult to snap apart for mounting. I had to pull so hard I was sure it would break, and I have been a service tech for 30 years, so I know all the tricks. In the end I just had to trust the instructions and pull like hell.