An electrician wiring a two-point dimmed lighting circuit in a Leeds new-build fitted two master touch dimmers instead of one master and one secondary. Both units powered up fine. Neither would actually control the light level correctly.

What's Actually Different Between Master and Secondary?

A master touch dimmer is the unit doing the real work: it contains the electronic dimming circuit, typically an intelligent trailing-edge design, and it's the one physically wired into the live lighting circuit. A secondary touch dimmer is essentially a remote control wired to the master, with no dimming electronics of its own. Touch either unit and the light responds the same way, but only because the secondary is signalling the master to act, not dimming anything itself.

This matters when something goes wrong. If a light won't dim at all, the fault is almost always in the master unit or its wiring back to the circuit. If one specific touch point stops responding but the others still work, check that particular secondary and its link back to the master, rather than assuming the whole circuit has failed.

How Many Secondaries Can One Master Actually Control?

This depends on the specific BG module's rated load and how many bulbs the dimmer is driving, not just the number of secondary switches wired in. Dimmer modules on the BG Evolve and Nexus ranges are commonly rated to handle up to 10 bulbs or 100W of LED load per module, and that ceiling applies regardless of how many secondary touch points are added to the circuit. Adding secondaries doesn't increase what the master can drive; it only adds more places to control it from.

BG Touch Dimmer Options: Master and Secondary Pairing

This is a genuine trade opinion rather than a spec note: always order master and secondary units in matching finish and gang configuration at the same time, from the same range. Mixing an Evolve master with a Nexus secondary on the same circuit isn't a wiring problem, since they're electrically compatible within BG's system, but it's a finish mismatch that shows up immediately to anyone standing between the two switches.

Does This Replace Two-Way or Intermediate Switching?

No, it's a different system entirely, not a dimmer version of two-way switching. Standard two-way and intermediate switches physically route the live conductor through strapping wires between switch positions. Touch dimmer master and secondary units use a signalling connection between the units instead. The two systems aren't interchangeable components, and a job needing multi-point dimming should be specified as a master-and-secondary touch dimmer set from the outset, not patched together from standard two-way switch parts. We've covered the strapping-wire alternative separately in Intermediate Switching Explained: Wiring Three Points, if a straightforward toggle switch is actually what the job needs instead of dimming.

A master and secondary pair in a mid-range BG finish typically runs to somewhere in the region of £25 to £40 for the two units combined, against roughly £12 to £18 for a single non-dimming two-way switch pair doing the equivalent job without dimming. That premium buys genuine multi-point light-level control rather than just on/off, which is usually the point of specifying it in the first place. All of this remains ordinary lighting circuit work under Building Regulations Part P, assessed the same way as any other new or altered lighting circuit. Browse the wider dimmer switches range if standard rotary or push dimmers are a better fit for a single-point room.

Frequently Asked Questions