Power Supply
Fused Spur
In short
Fused Spur: 3A Fused Spur - Main power isolator for heating system. It has 3 terminals: L (Live), N (Neutral), E (Earth).
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 1 (permanent live) | Wiring centre terminal 1 (permanent live) |
| N | Neutral | Wiring centre terminal 2 (neutral) | Wiring centre terminal 2 (neutral) |
| E | Earth | Wiring centre terminal 3 (earth) | Wiring centre terminal 3 (earth) |
How it fails
- Blown 3 A fuse in the fused spur
The spur is on and its neon is lit, but there is no output: the 3 A fuse has blown. (On site: find out WHY before you replace it.)
- Supply live open circuit between spur and wiring centre
230 V leaves the spur but never arrives at the other end of the conductor: open circuit.
- Boiler switched live landed on permanent live
The boiler's SL is landed on the permanent-live terminal, so it fires with no demand at all - no boiler interlock.
Where it connects
Lessons that use it
- Welcome to Draw Warm
Getting Started
- Using the Tools
Getting Started
- Connecting Wires
Getting Started
- Using the Multimeter
Getting Started
- Introduction to Mains Electricity
Electrical Fundamentals
- Spot the Dangerous Wiring
Electrical Fundamentals
- What is Switched Live?
Electrical Fundamentals
- Permanent Live vs Switched Live
Electrical Fundamentals
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