Why is this light dimmer buzzing?

[Pipps]

Why is this light dimmer buzzing?

There is a BG NBN82 dual dimmer switch pictured below. Each dimmer controls a separate lighting zone. Zone A has 8 and Zone B has 5 spotlights. All identical 500lm LED GU10 dimmable spotlights throughout.

The dimmer controls work equally fine for both circuits. But for Zone B only, a loud buzzing is emitted from the dimmer switch and the LED bulbs themselves immediately upon switching on. This happens regardless of the level of dimming; it is equally intrusive at both full and minimum light settings. Zone A is always silent.

The technical data (PDF) mentions seemingly nothing of relevance. While the product details (screenshot below) (PDF) states that: "There can be issues with dimming CFL and LED lamps at a low lighting level. The Nexus dimmer products have an adjustable minimum level feature which can be used to adjust the lighting output at a low level, to stabilise the load."

Adjusting either of the tiny rear flathead adjuster controls (pictured below) readily alter the sensitivity of the front dimmer switch on the light level of the circuit. But the buzzing noise remains equally loud from Zone B and the switch itself regardless of the level set or the combined configuration.

What could be causing this issue?

 

[winston1]

It is not uncommon and due to the fact that it is switching 50 Hz. If it is new I would reject and get a replacement.

 

[ericmark]

Zone A has 8 and Zone B has 5 spotlights

At say 6 watt each that's 48 watt and 30 watt and dimming switch designed for 60 to 400 watt, so neither circuit has enough load for those switches.

There is a problem using LED lamps with wall dimmers, the way LED's are driven varies make to make of lamp, a LED is current dependent, so some thing is needed to limit the current, it could be a simple capacitor or a complex integrated circuit. There may be a large smoothing capacitor or it may use some other method to stop flicker.

I don't use dimmers, but do use electronic switches with no neutral, most lamps worked A1, but the G9 bulbs small ones always flickered, the large one worked A1, but can't fit cover.

So when I wanted landing lights with high and low level output I used a duel relay I can select centre only, outers only, or all 5 so three levels of lighting, well actually a lot more, as centre bulb is colour changing, and dimmable, but there are some wall switches which are claimed to work with LED lights, but if you want ambiance, you also need to change colour temperature, even if not actual colour, so way to go is smart bulbs, however there are it seems some dimming switches which have less problems, but that does not change the colour temperature.

Quartz lamps should not be dimmed, (reduces bulb life) and CFL could not be dimmed, so lost all my dimming switches well before LED's came in.

 

[Pipps]

Would the buzzing disappear if we put all 13 lamps on just one circuit?

 

[Pipps]

At say 6 watt each that's 48 watt and 30 watt and dimming switch designed for 60 to 400 watt, so neither circuit has enough load for those switches.

Why is Zone A with 48 watts not emitting any buzzing at all?

 

[winston1]

Would the buzzing disappear if we put all 13 lamps on just one circuit?

Maybe, maybe not. Try it.

 

[flameport]

Reasons - different loading, slightly different component values in each dimmer, minor variations to the components in each lamp, different capacitance due to the wiring lengths and so on.
Endless possibilities and would take endless time to resolve.

Solution - replace the dimmers with Zano or Varilight.
You can keep the same plate, just change the modules.

 

[Rodders53]

Quartz lamps should not be dimmed, (reduces bulb life)

What is your source of technical reference for that one, please? TV studio lighting in the 80s was mainly a mix of quartz tungsten halogen and/or hard glass tungsten halogen. I'm sure I'd have been made aware of any life issues that quartz glass lamps had.


OP swap the A and B circuits over. Does the noise stay with B or move to A? {Dimmer module causing the noise and, maybe, faulty}?
The BG spec for those dimmers (from the link supplied) is min 5W and max 50W for LED so it may be unwise to try to drive all lamps from one module.