S-Plan · wiring diagram
S-Plan Plus wiring diagram
In short
An S-Plan is a fully pumped heating system with two 2-port motorised zone valves, one for central heating and one for hot water, driven by a programmer, a room thermostat and a cylinder thermostat. Each valve’s end switch feeds the boiler’s switched live, so the boiler fires only while a valve is open: the boiler interlock.
Two heating zones and hot water: three 2-port valves, and two room stats sharing the programmer's one heating channel, on DrawWarm's own heat-only boiler pumping through its own PUMP OUT. The second zone's call is on block 9. The wiring centre is fed from the boiler's 230 V OUT: one supply for the boiler and its controls.
An S-Plan wired in the simulator; this page’s circuit is listed wire by wire below. Wire colours as the lessons teach them. The meter reads what the circuit is doing.
The wiring centre, block by block
A block is a plain conductor: every wire landed on it is joined to every other, and to nothing else. The numbers are the habit the DrawWarm Method teaches, so the next engineer can read your work.
| Block | As the lessons teach it | Wired here |
|---|---|---|
| 1 | Permanent live from the fused spur, and both valves’ greys | DrawWarm Heat Only OUT_L, 2-Port Valve (heating) G, 2-Port Valve (hot water) G, Dual Channel Programmer L, 2-Port Valve (second heating zone) G |
| 2 | Neutral | DrawWarm Heat Only OUT_N, Room Thermostat #1 N, 2-Port Valve (heating) N, 2-Port Valve (second heating zone) N, Room Thermostat #2 N, 2-Port Valve (hot water) N, Dual Channel Programmer N |
| 3 | Earth | DrawWarm Heat Only OUT_E, 2-Port Valve (heating) E, 2-Port Valve (second heating zone) E, 2-Port Valve (hot water) E, Dual Channel Programmer E |
| 4 | Heating demand from the programmer, out to the room thermostat | Room Thermostat #1 L, Room Thermostat #2 L, Dual Channel Programmer 4 |
| 5 | The room thermostat’s call, out to the heating valve’s brown | Room Thermostat #1 SL, 2-Port Valve (heating) B |
| 6 | Hot water demand from the programmer, out to the cylinder thermostat | Cylinder Thermostat C, Dual Channel Programmer 3 |
| 8 | The cylinder thermostat’s call, out to the hot water valve’s brown | 2-Port Valve (hot water) B, Cylinder Thermostat 1 |
| 9 | A second heating zone’s call, where there is one | 2-Port Valve (second heating zone) B, Room Thermostat #2 SL |
| 10 | The valves’ oranges in, the boiler’s switched live out | DrawWarm Heat Only SL, 2-Port Valve (heating) O, 2-Port Valve (second heating zone) O, 2-Port Valve (hot water) O |
Every wire, terminal by terminal
| From | Terminal | To | Terminal | Colour |
|---|---|---|---|---|
| Fused Spur | E | DrawWarm Heat Only | E | Green/yellow (earth) |
| Fused Spur | N | DrawWarm Heat Only | N | Blue (neutral) |
| Fused Spur | L | DrawWarm Heat Only | L | Brown (live) |
| DrawWarm Heat Only | PL | Circulation Pump | L | Brown (live) |
| DrawWarm Heat Only | PN | Circulation Pump | N | Blue (neutral) |
| DrawWarm Heat Only | PE | Circulation Pump | E | Green/yellow (earth) |
| DrawWarm Heat Only | OUT_L | Wiring Centre | 1 | Brown (live) |
| Room Thermostat #1 | L | Wiring Centre | 4 | Black |
| DrawWarm Heat Only | OUT_N | Wiring Centre | 2 | Blue (neutral) |
| DrawWarm Heat Only | OUT_E | Wiring Centre | 3 | Green/yellow (earth) |
| DrawWarm Heat Only | SL | Wiring Centre | 10 | Orange |
| Room Thermostat #1 | N | Wiring Centre | 2 | Blue (neutral) |
| Room Thermostat #1 | SL | Wiring Centre | 5 | Brown (live) |
| 2-Port Valve (heating) | E | Wiring Centre | 3 | Green/yellow (earth) |
| 2-Port Valve (heating) | N | Wiring Centre | 2 | Blue (neutral) |
| 2-Port Valve (heating) | B | Wiring Centre | 5 | Brown (live) |
| 2-Port Valve (heating) | G | Wiring Centre | 1 | Grey |
| 2-Port Valve (heating) | O | Wiring Centre | 10 | Orange |
| 2-Port Valve (second heating zone) | E | Wiring Centre | 3 | Green/yellow (earth) |
| 2-Port Valve (second heating zone) | N | Wiring Centre | 2 | Blue (neutral) |
| 2-Port Valve (second heating zone) | B | Wiring Centre | 9 | Brown (live) |
| 2-Port Valve (second heating zone) | O | Wiring Centre | 10 | Orange |
| 2-Port Valve (hot water) | B | Wiring Centre | 8 | Brown (live) |
| 2-Port Valve (hot water) | O | Wiring Centre | 10 | Orange |
| Cylinder Thermostat | 1 | Wiring Centre | 8 | Brown (live) |
| Cylinder Thermostat | C | Wiring Centre | 6 | Grey |
| Room Thermostat #2 | SL | Wiring Centre | 9 | Brown (live) |
| Room Thermostat #2 | N | Wiring Centre | 2 | Blue (neutral) |
| Room Thermostat #2 | L | Wiring Centre | 4 | Black |
| Dual Channel Programmer | 4 | Wiring Centre | 4 | Black |
| Dual Channel Programmer | 3 | Wiring Centre | 6 | Grey |
| 2-Port Valve (hot water) | G | Wiring Centre | 1 | Grey |
| 2-Port Valve (hot water) | N | Wiring Centre | 2 | Blue (neutral) |
| 2-Port Valve (hot water) | E | Wiring Centre | 3 | Green/yellow (earth) |
| Dual Channel Programmer | N | Wiring Centre | 2 | Blue (neutral) |
| Dual Channel Programmer | L | Wiring Centre | 1 | Brown (live) |
| Dual Channel Programmer | E | Wiring Centre | 3 | Green/yellow (earth) |
| 2-Port Valve (second heating zone) | G | Wiring Centre | 1 | Grey |
Where it connects
Lessons that start from it
- More zones
Intermediate · Unit 3
- Commissioning
Intermediate · Unit 9
Other systems
Back to every wiring diagram.
If this is your home: this page is written for heating engineers, and for learners under the supervision of one. It explains how the wiring works; it is not training to do the work. In England and Wales, electrical work in a home must meet the Building Regulations (Part P), and some of it must be notified to building control or done by a registered electrician; Scotland and Northern Ireland have their own rules. For the wiring, call a registered electrician or a heating engineer competent in controls. Work inside a gas boiler is for a Gas Safe registered engineer only. If you smell gas, leave the building and call the gas emergency number: 0800 111 999 in Great Britain, 0800 002 001 in Northern Ireland.
Practise it in the simulator.
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