Lighting with a Dimmer
A dimmer replaces the 1-way switch in the switch line.
● Line● Neutral● Earth
Tap any wire, switch or device to see what it is.
Useful Information
Wired exactly like a 1-way switch; the dimmer sits in the switch line.
Some smart dimmers need a neutral at the switch — run 3-core or twin & earth plus neutral.
Important to know
- Check the dimmer's minimum load — many LEDs flicker below it.
- Dimmers must be de-rated when ganged together (manufacturer).
- Remove or bypass electronic dimmers before insulation resistance testing (643.3.3).
BS 7671:2018+A4:2026 references
512.1.5559.5.1643.3.3
Study notes paraphrased — check against your copy of BS 7671.