S-Plan

A central heating control architecture using two motorised zone valves to independently control space heating and hot water from a system or heat-only boiler.

S-Plan is the modern UK central heating control architecture, used since the 1980s with system and heat-only boilers. Two two-port motorised zone valves (typically Honeywell V4043H or Drayton ZV3) split the boiler flow between the radiator circuit and the hot water cylinder coil, each controlled independently by its own thermostat or programmer channel.

S-Plan is the spec we install on every Cornwall boiler retrofit because it allows full Time-and-Temperature-Zoning (compliant with Building Regulations Part L) and works seamlessly with smart thermostats and OpenTherm. It also makes maintenance easier: one zone valve fails and only that zone goes down.

S-Plan Plus extends the same idea to multiple radiator zones (e.g. upstairs and downstairs separately controlled). See our boiler installation page.