Eph Controls B322P 3-port motorised valve

Central heating valves direct and control the flow of hot water from the boiler to the radiators and the hot water cylinder. This category covers motorised two-port zone valves, three-port mid-position and diverter valves, automatic bypass valves, replacement actuators and powerheads, and control packs that pair a valve with a thermostat or timer.

Motorised valves

• Two-port zone valves: open or close one circuit, such as the heating or the hot water, so each zone can have its own time and temperature control.
• Three-port mid-position valves: direct water to the heating, the hot water or, resting midway, both at once.
• Three-port diverter valves: direct water to one circuit or the other, not both together.

Sizes include 22mm and 28mm compression, BSP threads and some 15mm versions. On many valves the actuator or powerhead can be changed without draining the system, and a manual lever opens the valve for filling and draining. Check the flow arrow on the body, and match a replacement head to the valve body.

Bypass valves

An automatic bypass valve opens as radiator and zone valves close, keeping a minimum flow through the boiler and limiting pressure build-up. Bypass valves fitted inside a boiler are boiler parts: work inside a gas boiler must only be carried out by a Gas Safe registered engineer.

Regulations and wiring

In England, Approved Document L expects controls wired so the boiler and pump switch off when neither heating nor hot water is needed; TRVs alone do not do this. A new heating system in a home of 150 square metres or more should have at least two heating zones. Wiring should be done by a competent person to the current wiring regulations.

For thermostats and programmers, see heating controls; for radiator valves, see thermostatic radiator valves.