An S Plan heating system uses zone valves. Usually this plan uses 2 of these together. It is designed to provide independent time and temperature control for both heating and hot water in a fully pumped system.
The following devices are commonly found in this system on the electrical side.
- Dual channel programmer (heating and hot water timing)
- 2 Port Zone valves Qty 2
- Room thermostat
- Cylinder Thermostat
How it works:
Heating: Your programmer is scheduled to switch on. When it actually switches on, it sends a voltage to the room thermostat. If the room thermostat says the zone / home is colder than the target temperature (ie room thermostat says 21 degrees, but the zone / home says it 16 degrees inside) then it sends signal to the zone valve to open up the water pathway so the boiler can switch on and start sending heated water by the pump to the heating system / radiators. This then start warming up the home.
Hot Water: Your programmer is scheduled to switch on. When it actually switches on, it sends a voltage to the cylinder thermostat. If the cylinder thermostat says the cylinder is colder than the target temperature (ie thermostat says 60 degrees degrees, but the water is at 40 degrees) then it sends signal to the zone valve to open up the water pathway so the boiler can switch on and start sending heated water by the pump to the hot water cylinder coil. This then warms up the hot water indirectly.
Please note in both cases it takes approx 10 secs from once the voltage is sent to the zone valve, for it to then send a signal for the boiler to actually fire up and switch on.
S Plan Plus is simply an additional or 3rd zone valve added to control another heating circuit. ie a zone valve for downstairs, a zone valve for upstairs and a zone valve for the hot water. You could equally have a zone valve for underfloor, and one for radiators etc. Simply its 2 heating zones and a hot water zone.
Common fault finding videos: