Honeywell TH1110D2009/U T1 Pro non-programmable thermostat for 24 Vac systems, single stage heat and cool systems. Single stage heat pumps without aux heat.

Only on a single stage heat pump with no auxiliary or backup heat. The T1 Pro TH1110D2009/U handles up to 1 heat / 1 cool on heat pumps and up to 1 heat / 1 cool on conventional systems, and changeover is manual, so you switch between heating and cooling at the stat rather than the system doing it automatically. If the heat pump has electric strip backup, this is the wrong stat.

It is a 24 Vac low voltage stat, so it runs gas, oil or electric warm air, a hot water coil, gas/oil/electric hydronic, and steam or gravity systems, plus single stage cooling. Supply voltage is 20 to 30 Vac at 50 or 60 Hz. It will not work on line voltage baseboard or millivolt systems.

No, it can run either way. Power method is battery or hardwired, so if the opening has no common wire you can run it on batteries and still get the backlit display. Where a C wire is present, hardwire it and skip battery changes across a portfolio of units.

The stat measures 4-1/16 x 4-1/16 x 1-3/32 inches, so it covers a square footprint just over four inches. It mounts on the Honeywell UWP mounting system, which is included in the box along with a J-box adaptor for openings where the wiring lands in an electrical box. On a large older stat footprint you may still see paint edges past the four inch square, and a cover plate is the fix.

Box includes the thermostat itself, the UWP mounting system, and an installation (J-box) adaptor. Terminations are made at the UWP, so nothing extra is required for a standard 24 Vac hookup. Batteries are the only consumable to think about if you are not landing a common wire.

Non-programmable is the right call where you do not want tenants or staff fighting a schedule, or where you are standardizing a lot of units on one simple stat. The TH1110D2009/U has a small display with soft key controls and a HEAT-OFF-COOL system switch plus AUTO-ON fan switch, so there is nothing to set beyond a setpoint. If you need setback schedules to cut runtime in a vacant or off-hours space, this is not the model to buy.

Heat sets from 32 F to 90 F and cool from 50 F to 99 F (0 to 32 C heat, 10 to 37 C cool). That top and bottom matter for freeze protection setpoints in a vacant unit and for a warehouse or shop space you only want tempered, not conditioned to comfort.

Accuracy is 1 F (0.5 C) with a differential of plus or minus 1 F (plus or minus 0.5 C), so equipment cycles around the setpoint within about a degree. It reads ambient air temperature only, with no remote or return air sensor input.

Operating range is 32 F to 102 F (0 to 39 C) with humidity from 5 to 90 percent RH non-condensing. That covers a garage or mechanical room in most climates, but a space that swings below freezing or condenses on the wall is outside what the stat is rated to operate in. Storage and shipping range runs 20 F to 120 F, so cold stock sitting in a truck is fine.

Relay type switching, rated 0.02 to 1.0 A running on both heat and cool, and 0.02 to 0.05 A on fan. Standard 24 Vac gas valves, contactors and fan relays sit inside that. If you are driving something heavier than a typical control circuit load, put a pilot relay between the stat and the load.

Honeywell TH1110D2009/U, T1 Pro series, white, non-programmable, single stage heat and cool. The display is 2.37 square inches with soft keys and a backlight. That MPN is what to put on the order so you do not get a programmable or multi-stage T-series stat by mistake.