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BillyTheSparks

Hello All.

I have recently rewired a house, and fitted a TD-Line CU (main switch and all RCBO's).

All has been fine until now, 1x 6a RCBO for the kitchen and TV room lights has started making a sort of buzzing/humming noise. I haven't heard it myself but the client says that it isn't very loud, but can be heard from about 3m away.

I have checked ALL the terminals are tight on both the load side of all RCBO's and the busbar, and also the main switch.

This circuit has 1x outside light which is a ES CFL lamp, a total of 4x under unit lights (SELV 20w each), and a total of 16x LED downlights.
The LED downlights are on dimmer switches, 1 leading edge for 4x lights - 1 trailing edge for 12x lights.

I'm assuming that the LEDs are causing some kind of interference with the RCBO but I'm not too sure.
I'm going there tomorrow to hopefully listen for myself, but would like any information that might help, if you have had experience of this in the past or know of any underlying factors that I haven't thought of or know about in relation to TD-Line or RCBOs??

Thank you in advance
 
TD-line is from a local wholesalers (not sure if I can name them) I believe they are made by CED/Europa.

The LEDs are GU10 cap and therefore have no seperate drivers.
 
What is the current through it with all the lights on. Maybe it's noisy because it's very close to the tripping threshold.

Does it still buzz if you bypass the dimmers?
 
I haven't as yet taken off the dimmers off, going there tomorrow to have a proper look. So will post back with what I have found. I just wanted any opinions or advice before going hammer and tongs at it.

The total load with no diversity would be 171w/0.75a with all lights on so it's nowhere near the tripping threshold.
 
Hit it hard with the end of a screwdriver, large PZ2 whilst shouting "Flaming piece of poo"......Job done!

Works with wylex RCBO's
 
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Had a similar problem in the spring with an RCD. Customer complained of 'fizzing noise from fusebox'. Tried everything obvious then noticed the lights were very slightly dimming when the fizzing noise was heard???
Turned out to be a poor joint on the DNO's incoming property connection which they fixed. Managed to see the voltage momentarily dip down on my meter, so knew it was the supply.
 
Installed about 8 of the TD Line RCBO's recently with no problem, all tested within tolerance etc, even ramp tested them just to be safe !

Have no dimmers on the RFC's so can't comment at that problem.
 
Ok, a quick update.

The noise only occurs whilst either set of 4x5w LED lights are on (there are 2 sets of 4x5w LEDs).
Its not the RCBO being a problem, just the dimmer switches which I thought was bizzare as 1 is a leading edge the other a trailing edge.

So I changed both dimmers to a different make and so far no noise!

Many thanks for all the posts.
Billy. :8:
 
MCBs and RCBOs contain mechanical parts. Normally the supply is a nice smooth 50 or 60Hz sine wave and the designer of the MCB/RCBO has ensured that the mechanical parts are not resonant at multiple and sub-multiples of the basic supply frequency. However, when fast switching electronics (e.g. dimmers) are introduced the supply waveform is distorted far from a sine wave and harmonics are generated on the fast rising/falling edges that are not related to the basic supply frequency, this can in some unfortunate cases resonate the MCB/RCBO mechanical mechanism causing an intense buzzing noise.
 

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