Wired Thermostat: The ENGO E901 runs on 2 x AA batteries and connects to your boiler with a simple two-wire, voltage-free (COM/NO) connection. A straightforward upgrade from an old two-wire dial room thermostat Set Your Week Once: 3 ready-made programmes plus 6 you can write yourself, with up to 6 time and temperature changes a day. Party mode holds a temperature for up to 9 hours, holiday mode covers days away, frost protection at 7°C Accurate Control: Choose TPI or hysteresis (±0.25 or ±0.5°C) control and set anywhere from 5 to 35°C, in heating or cooling mode. Every setting sits behind a hidden button panel, leaving a clean front and clear display Works With Your Heating: The voltage-free relay (max load 5(3)A) switches gas or oil boilers, combi boilers, heat pumps, pumps, actuators and ENGO wiring centres. Needs a cable run from the thermostat to the boiler; fitting by a qualified installer Slim and Neat: 150 x 84 x 22 mm, surface-mounted on the wall. Instruction included and available online, with installation and setup videos and dedicated telephone and email support In the Box: E901 thermostat, short instruction, 2 x AA batteries and mounting screws