Installing DOOR Thermostat

This guide covers installing a DOOR Thermostat on a compatible 24 VAC HVAC system. It assumes you are replacing an existing thermostat — for a new install, ignore the references to the old thermostat. This involves working with line-adjacent HVAC wiring; if you are not comfortable doing so, use a qualified installer.

Important: Before touching any wiring, turn off the HVAC equipment at the circuit breaker panel. Working on a live thermostat can cause injury and equipment damage.

About this device

The Thermostat controls the HVAC over its wired terminals and reports to the DOOR App through the DOOR Hub (it does not join WiFi). It requires a C (Common) wire — it will not function without one. Schedules run locally on the device, so heating and cooling continue even if the Hub or internet is down.

Requirements

A compatible 24 VAC system: forced air, hydronic, heat pump, oil, gas, or electric. Not compatible with millivolt systems (e.g., gas fireplace) or 120/240 V systems (e.g., baseboard electric).
A C (Common) wire at the thermostat location, or a C wire adapter.
A DOOR Hub installed and online (for app control and activation).
The DOOR App, signed in with Device Management permissions.

In the kit

Thermostat
Mounting plate ("back plate")
Wire labels
Wall screws (4) and drywall anchors (4)
C wire
Quick Start Guide

Tools

Drill with bits
Multimeter
Medium Phillips screwdriver and small slotted screwdriver
Level and pencil
Alternative mounting hardware as needed

Steps

Turn off power to the HVAC equipment at the breaker panel. Confirm there are no energized wires at the thermostat with a multimeter.
Label the existing wires with the supplied labels (C, R, Y1, etc.) before disconnecting, and photograph the old wiring as a backup.
Remove the old thermostat and back plate. Don't let the cable fall into the wall.
Mount the new back plate, covering the hole and leveling it. Do not overtighten — overtightening warps the plate and affects operation.
Terminate each wire on its matching screw terminal using the wiring table below. Loosen each terminal first, then gently tug each wire to confirm a solid connection.
Set the HP/GAS switch on the back of the thermostat: HP for heat-pump systems, GAS otherwise.
Set the O/B switch (heat pumps only): O to energize the reversing valve on cooling (warm climates) or B to energize it on heating (cold climates). On GAS, the valve energizes for heating only.
Snap the thermostat onto the back plate until it clicks, with no gaps. Tug gently to confirm it's seated.
Turn power back on. The display should light immediately. If not, power off and recheck the terminations — especially the C wire.

Wiring table

Terminal	Typical wire	Function
R	R, RC, RH (red)	24 VAC power
C	C, COM (cyan)	24 VAC common — required
G	G (green)	Fan relay
Y1	Y1 (yellow)	Stage 1 cool / heat-pump stage 1 compressor
Y2	Y2 (yellow/light blue)	Stage 2 cool / heat-pump stage 2 compressor
W1	W1, W, O/B (white/brown)	Stage 1 heat / heat-pump stage 1
W2	W2 (white/brown)	Stage 2 heat / heat-pump stage 2
AUX	AUX	Auxiliary heat

Activate in the DOOR App

After the display powers on, add the Thermostat to the DOOR App: tap Devices → Add a device → scan the QR code (or enter the serial number) → follow the on-screen steps, and assign it to the correct Unit.

Verification

The display lights up and shows the current temperature and a white connection indicator.
The Thermostat shows Online in the DOOR App, assigned to the correct Unit.
Test each mode (HEAT, COOL, fan) and confirm the HVAC responds.

Troubleshooting

Display stays dark after power-on — recheck the C wire and all terminations; the Thermostat won't run without a C wire. Confirm 24 VAC at R–C with a multimeter.
Heat pump runs backwards (heats when set to cool) — flip the O/B switch.
No app control — confirm the DOOR Hub is online; HVAC control is wired, but the app depends on the Hub.
For more, see DOOR Thermostat troubleshooting.

Diagrams

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