Dimmer buzzing

[Delboy247]

Hi all quick question I recently installed 8 downlights 50w lamps low voltage. The problem is i'm getting a slight buzz at the fusebox when the dimmer is dimmed (400w dimmer) the breaker is a 10a wylex breaker tnc-s any suggestions would be great.

 

[ezzzekiel]

poor quality dimmer or maybe too much load for it , try removing some dimmers and see if it goes away

 

[Colin Integrale]

Actually at the fuseboard and not at the switch?

 

[Delboy247]

Actually at the fuseboard and not at the switch?

Yes at the fuse box and the switch.

 

[Colin Integrale]

Like ezzzekeil said... try changing the switch. I changed some for my brother in law a while back for MK and they were surprisingly noisy, then I put some cheaper GET ones in our living room and they're quiet as anything..

As for the buzzing at the fuseboard.... hmmmm

 

[GrannySmiff]

Buzzing at the CU, thats not good, the dimmer buzzes because it has some sort of variable resistor, well some electronic component anyway and its usuall for them to give of a slight buzz and better quality ones will buzz less, also would you want a slighty higer rated dimmer? if you are pulling 400w and it is a 400w or is that fine?.

But as for the CU what is there that can buzz apart from things that shouldn't buzz?

 

[i=p/u]

take 2 bulbs out and try, happened in my sisters had 4x60w bulbs for 240w dimmer, changed them to 40w bulbs and was quieter

 

[IQ Electrical]

Hi all quick question I recently installed 8 downlights 50w lamps low voltage. The problem is i'm getting a slight buzz at the fusebox when the dimmer is dimmed (400w dimmer) the breaker is a 10a wylex breaker tnc-s any suggestions would be great.

Does the 400W rating apply to low-voltage lighting?

Also, are you using dimmable transformers and if so, how many?

Some dimmers state a maximum of 4 transformers (for example)

Have a read of this: Dimmer Guide

 

[telectrix]

i would first change the dimmer. at minimum you need a 700watt dimmer for a 400 watt load halogen, and as previously stated, make sure the trasnsformers are the dimmable type.

 

[WDMDL]

It's to be expected to some extent.
The dimming element is not a variable resistor, it is a semiconductor device (triac) that switches the load on at a certain point through each half cycle. You choose the point by adjusting the variable resistor.
So instead of that lovely sinewave, the current waveform has horrible square edges.
The filtering in the dimmer removes most of the higher-frequency components for EMC compliance, but the filter inductor can buzz if it's not a "potted" type.
You will also be hearing the result of this distorted current waveform at the MCB, as they contain a solenoid element for rapid disconnection in the event of a short circuit. It will be causing the components to move, hence the noise.

Have a look at this:http://www.ilight.co.uk/downloads/iLIGHT%20Binder-HowDimmers.pdf

Simon.

 

[IQ Electrical]

That's a good answer, the TRIAC chops the waveform to create a dimming effect.

 

[Merl]

Check out this HowStuffWorks "How Dimmer Switches Work" to understand how a dimmer switch works.

Check out this Circuit breaker - Wikipedia, the free encyclopedia to understand how an MCB works.

The buzzing at the Consumer Unit may be from the MCB which has an electromagnetic coil inside as part of the overload protection. It may be poor filtration in the dimmer switch causing an induced harmonic into the circuit and causing the mcb buzz.

 

[Merl]

Beaten to it by Simon there!

Good answer Simon.

I'll have to learn to type faster!!

 

[Marvo]

Buzzing at the CU....are any of the MCB's running warm, like above body temperature? If so then measure the current through the warm one to make sure it's not on the tripping threshold. If the current is low try remaking the terminations top and bottom. If that doesn't help then replace it.
If there's no warm MCB's try swapping the one that's buzzing for another identical rated one. If oanother MCB doesn't buzz on the same circuit then replace the one that did buzz.

 

[GrannySmiff]

Its the buzz at the CU that should be talked about.

 

[Marvo]

Yes buzzing at the CU isn't a good sign.

The buzzing at the Consumer Unit may be from the MCB which has an electromagnetic coil inside as part of the overload protection. It may be poor filtration in the dimmer switch causing an induced harmonic into the circuit and causing the mcb buzz.

Nice idea and could be possible but maybe a long shot. I've never encountered MCB's buzzing because of poor PF or harmonics, even in the triplen range which would cause the highest heating effects. I would check for more obvious causes first.

 

[egginyourface]

have u measured how many amps the mcb is drawing when all the lights are on?

 

[Delboy247]

It Has nothing to do what the mcb is drawing as it only happens when this dimmer is operated I will look more in to on Tuesday thanks for everyones oppinions.