S-Plan Systems: Two Motorised Valves
S-Plan uses two separate two-port valves — one for heating, one for hot water — so each service is controlled independently.
S-Plan uses two separate two-port valves — one for heating, one for hot water — so each service is controlled independently. It is the layout we most often install because faults are easy to isolate.
How the calls work
A thermostat or cylinder stat opens its valve, the valve's end switch fires the boiler, and each service runs without borrowing from the other.
Failure behaviour
A single stuck valve takes out one service and leaves the other working, which makes diagnosis quicker than on shared-valve layouts.
Extending it
Adding a third zone is straightforward: another two-port valve and another stat into the wiring centre.
Diagnostic clues on S-Plan
- Heating works but hot water does not, or the reverse
- Valve motor humming with no movement
- Boiler firing with no valve calling
Who does the work
- Gas Safe registered engineers — registration 554328
- Worcester Bosch accredited installer
- John The Plumb Ltd, company registration 10026483
S-Plan fault or upgrade
Describe which service has stopped and we can usually narrow it to the valve, the stat or the wiring centre before arriving.
Questions we get asked
How do I know I have S-Plan?
Look for two separate valve heads on separate pipes near the cylinder, rather than one three-port valve.
Can a valve head be replaced without draining?
Usually the head alone can be changed in place; the body needs the system drained down.
Is S-Plan better than Y-Plan?
For fault isolation and zoning, generally yes. Y-Plan is not wrong, it is just less flexible.