Honeywell Home X8S Smart Thermostat X8VMC8B (Black, no sensor)

What this listing is: the black X8S, US version

The X8S is Honeywell Home's Wi-Fi thermostat with a 5-inch display, controlled through the First Alert app and set up for Matter from the thermostat's menu. This listing is the black version without a room sensor, model X8VMC8B/W. Resideo's installation manual lists X8VMC8B as the X8S black thermostat for the US, and Honeywell's product page shows SKU X8VMC8B/U.

The manual's package list is the thermostat, the UWP wall plate, screws and anchors, and literature, and it notes that kits may include other accessories. Resideo gives the thermostat's size as 90 x 133 x 24 mm, which corresponds to the listing's 3.54 by 5.24 by 0.96 inches. Honeywell's page lists XRSENSOR room sensors as optional; none comes with this version.

How many stages it runs: the maker page disagrees with the manual

The installation manual says the X8S works with up to 3 heat/2 cool heat pump systems with electric backup heat and up to 2 heat/2 cool gas or oil forced air with air conditioning, plus radiant hot water. Its specification page repeats up to 3H/2C heat pump and 2H/2C conventional, and the Amazon listing uses the same numbers.

Honeywell's product page specification table instead lists up to 4 heat/2 cool for heat pumps and up to 3 heat/4 cool for conventional systems. None of the three sources explains the difference. If your system needs more than 3 heat/2 cool on a heat pump or 2 heat/2 cool on a conventional system, confirm with Honeywell before buying.

Heat pump backup and the equipment it will not run

The manual's installer settings let you choose a heat pump's backup heat type, but state that the thermostat only supports electric backup. If a non-electric backup type is chosen, the manual says the thermostat will warn that it is not compatible and recommends contacting an HVAC professional.

The manual also says it does not work with electric baseboard heat at 120-240 V, does not support S terminals, and is for indoor use only. It lists humidification, dehumidification and ventilation among the equipment it can control, though Honeywell's page and the listing note that additional HVAC equipment may be required for that.

C wire: required, with a free adapter voucher in the box

The manual lists 24 VAC power by C wire as required, and Honeywell's page lists the power source as hardwired with a C wire. The manual says a spare wire in the bundle can serve as the C wire; if there is none and your old thermostat had both Y and G connected, the optional THP9045A C-wire adapter can be used.

The manual and the listing both say a voucher for a free C-wire adapter is included in the box. Wi-Fi is dual band, 2.4 and 5 GHz, and the manual lists power consumption of 3.0 VA maximum. The manual gives an operating ambient range of 37°F to 102°F, and it covers wiring in detail; we do not reproduce those steps here.

Features: doorbell view, sensors, radar and scheduling

The manual's list of doorbell-capable models includes X8VMC8B, and the user guide says First Alert VX1 or Ring doorbells, which are not included, are linked through the First Alert app. The manual also has a section on how linked doorbells behave when several doorbells or several thermostats are involved; read it if you have more than one of either.

The manual lists up to 20 XRSENSOR room sensors per thermostat, a built-in radar sensor that can wake the screen, Auto Away location-based control, smart alerts, automatic changeover and Adaptive Recovery. Heating setpoints run from 40°F to 90°F and cooling from 50°F to 99°F, and humidification can be set from 0 to 90 percent RH.

Humidity sensor accuracy is listed as plus or minus 5 percent RH from 30 to 50 percent at 75°F. The user guide adds seven idle-screen styles and colors, and Matter setup from the thermostat's menu.

Warranty

The X8S user guide states a 2-year limited warranty and points to resideo.info/US-Warranty-THERMOSTAT for terms, adding that Resideo Customer Care at 1-800-633-3991 will mail a printed copy free of charge. Honeywell's product page lists the warranty as 2 years limited.

We did not read the written warranty itself, so check it before relying on details such as coverage of add-on room sensors or reinstallation costs. The warranty length is the one figure the user guide and Honeywell's product page both state, and both give two years.