Valves
3-Port Valve
In short
3-Port Valve: Ultra-realistic 3-port Y-Plan valve with position-dependent switching. It has 5 terminals: E (Earth), N (Neutral), W (White), G (Grey), O (Orange).
If this is your home: this page is written for heating engineers. Mains wiring and gas appliances are not DIY jobs; call a Gas Safe registered engineer. If you smell gas, leave the building and call the National Gas Emergency Service on 0800 111 999.
Terminals
| Terminal | What it is | On an S-Plan | On a Y-Plan |
|---|---|---|---|
| E | Earth | — | Wiring centre terminal 3 (earth) |
| N | Neutral | — | Wiring centre terminal 2 (neutral) |
| W | White | — | Wiring centre terminal 5 (room stat call) |
| G | Grey | — | Wiring centre terminal 7 (programmer HW OFF and cylinder stat satisfied) |
| O | Orange | — | Wiring centre terminal 8 (with the cylinder stat call, on to the boiler SL) |
How it fails
- 3-port valve: motor failed (stuck at rest)
White is live (and grey too, with hot water off) but the valve stays at B: the actuator has failed.
- 3-port valve: white wire open circuit
The room stat's call leaves the stat but never reaches the valve's white: open circuit conductor.
- Y-Plan: cylinder stat call wire open circuit
For hot water alone the boiler is fired by the cylinder stat's call. That conductor is broken, so the boiler only runs when the heating drives the valve's orange.
Where it connects
Lessons that use it
- The 3-Port Valve (Mid-Position)
Component Library
- 3-Port Mid-Position Valve
Y-Plan Wiring
Systems it is part of
Also in valves
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