Controls
Room Thermostat
In short
Room Thermostat: Temperature-based heating control. It has 3 terminals: L (Live), N (Neutral), SL (Switched Live).
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 |
|---|---|---|---|
| L | Live | Wiring centre terminal 4 (CH demand from the programmer's CH ON) | Wiring centre terminal 4 (CH demand from the programmer's CH ON) |
| N | Neutral | Wiring centre terminal 2 (neutral) | Wiring centre terminal 2 (neutral) |
| SL | Switched Live | Wiring centre terminal 5 (room stat call, on to the heating valve brown) | Wiring centre terminal 5 (room stat call, on to the valve white) |
How it fails
- Room thermostat not switching
230 V arrives at the stat, the stat is calling, nothing leaves it: failed thermostat.
- Programmer: heating channel failed
The display says CH ON but terminal 4 never goes live: the heating relay inside the programmer 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.
Where it connects
Lessons that use it
- What is Switched Live?
Electrical Fundamentals
- Permanent Live vs Switched Live
Electrical Fundamentals
- The Wiring Centre
Electrical Fundamentals
- The Room Thermostat
Component Library
- The Zone Valve (2-Port)
Component Library
- The 3-Port Valve (Mid-Position)
Component Library
- Room Thermostat Wiring
S-Plan Wiring
- Room Thermostat Wiring
Y-Plan Wiring
Systems it is part of
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