Connectors
Wiring Centre 25 (lever connectors)
In short
A DrawWarm wiring centre with 25 lever-connector blocks round three sides. Its terminals: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25.
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.
What it is
A WIRING CENTRE is the box where the wires of a heating system meet and are joined. This DrawWarm one has 25 blocks of LEVER CONNECTORS round three sides of the box:
- 1 to 7 along the top.
- 8 to 16 down the right side.
- 17 to 25 down the left side.
Each block is one connector. Lift a lever, push the stripped core into the hole, then press the lever down. Every wire on a block is joined to every other wire on that block. No block is joined to any other.
The holes face the middle, where the cables come in through the GROMMETS.
Blocks 1, 2 and 3 have five levers, and the others fewer. The numbers are a habit that helps, not a rule the box knows.
Terminals
| Terminal | What it is for |
|---|---|
| 1 | Block 1. |
| 2 | Block 2. |
| 3 | Block 3. |
| 4 | Block 4. |
| 5 | Block 5. |
| 6 | Block 6. |
| 7 | Block 7. |
| 8 | Block 8. |
| 9 | Block 9. |
| 10 | Block 10. |
| 11 | Block 11. |
| 12 | Block 12. |
| 13 | Block 13. |
| 14 | Block 14. |
| 15 | Block 15. |
| 16 | Block 16. |
| 17 | Block 17. |
| 18 | Block 18. |
| 19 | Block 19. |
| 20 | Block 20. |
| 21 | Block 21. |
| 22 | Block 22. |
| 23 | Block 23. |
| 24 | Block 24. |
| 25 | Block 25. |
What the meter reads
Live tests. On site, any reading taken with the supply on is work on or near live parts. Regulation 14 of the Electricity at Work Regulations 1989 allows it only when working dead is unreasonable, as when a fault shows only while the controls work, and only with suitable precautions: test leads made to the HSE’s guidance note GS38, fingers behind the guards. Regulation 16 allows it only for a competent person, or a learner under the supervision of one. Wiring and repairs are always done dead. In the simulator, nothing is live.
The Draw Warm Method numbers the blocks:
- 1: the live (L).
- 2: the neutral (N).
- 3: the earth (E).
- 4: the central heating (CH) demand, to the room thermostat (stat).
- 5: the call of the room thermostat.
- 6: the hot water (HW) demand, to the cylinder thermostat.
- 7: the Y-Plan's grey.
- 8: the call of the cylinder thermostat. A Y-Plan's orange is on 8 too.
- 10: the S-Plan's oranges, to the boiler's switched live (SL).
DrawWarm's lessons use block 9 for a second heating zone's call.
The numbering is a habit: read the schedule, never assume.
Where it connects
Also in connectors
Practise it in the simulator.
Runs in the browser on a laptop or desktop. Cancel any time.