Y plan link

S plan link

W plan link

C plan link

full honeywell wiring guides, including fault finding

Y plan is most common using a 3 port mid position valve, with both hot water & heating pumped & temperture controlled.

S plan is most common using 2 port zone valves, with both hot water & heating pumped & temperture controlled.

W plan is using a 3 port diverting valve to give hot water priority, over heating, with both hot water & heating pumped & temperture controlled.

C plan is to control the water tempeture on a gravity hot water system with pumped heating, using a room thermostat.


Changing a 6 wire Switchmaster 3 port valve to a 5 wire standard 3 port mid position valve

old switchmaster > function > new standard

old Blue > Neutral > new Blue
old Green/yellow > Earth> new Green/Yellow
old Yellow > CH on > new White
old White > HW off > new Grey

old Red > Hw on > newOrange LINK TO
old Orange > boiler on > newOrange LINK

some new 3 port mid postition valves dont have an earth.