Noisy RCD. - BG brand

[1Justin]

I thought I'd try a BG CU.

The RCD's are noisy under load. Perhaps 2KW sets them off, a buzz which is quite audible from a few feet away. I swapped the noisy RCD for the second (since that side was still unused when I worked this out), the other one is also noisy, but less so.

Both switch fine, measure up (disconnect) fine, Zs fine, and no signs of anything wrong, no smell, heat etc. - Just the noise.

Is this normal for a BG brand RCD? Does anyone have anything to offer, or should I take them back?

 

[GLENNSPARK]

It may be it's close to the tripping threshold or it may be there's something wrong with them. To be honest if there's no problems with the circuits I'd return them to the wholesaler for a warranty and get them to investigate the issue, bottom line is they shouldn't make a noise and the customer will probably complain sooner or later.

well this was my initial thoughts here marv...

i will say this though Justin....a while back one of the counter staff at a screwfix up here in Leeds mentioned they`d had a lot of these british general boards back with issues about this n that....

 

[GLENNSPARK]

Hi Glenn, Hmm leakage. Firstly might a standing leak show up as significant offset in the break time between positive and negative cycles? (I see no big difference).

& Insulation resistance is very high.

I also don't have a current clamp - maybe I should have one, would be handy from time to time. Thanks.

a requirement really when RCDs are about...the alternative is to ramp it off load...then again on load...the difference will be leakage....

 

[1Justin]

Yep, I've just been looking up clamp meters on line, need one with good resolution down to mA and AC DC also.

I was unsure of the BG board in general, maybe not again..

Mechanically it's nice, better than MK. The front goes on really well and doesn't bend. (- Perhaps removing it is a tad too easy though with two quarter turn locks). The switches run right to left, but the earth bar is numbered left to right. - RCD is right to left so to speak, which means I couldn't try it out this evening in my own MK board since the busbar on wrong side.

 

[Marvo]

Yep, I've just been looking up clamp meters on line, need one with good resolution down to mA and AC DC also.

I don't know how you're going to test the actual leakage without one. I would look at the Dilog earth leakage clamp, it's very reasonably priced and gets good reports but I'm not sure about it's DC capabilities.

 

[GLENNSPARK]

here you go Justin...£39 off fleabay...
now, i`v got one of these....and their OK...

Mini AC Leakage Current Tester ST-9810 (AMECaL) | eBay

 

[GLENNSPARK]

Yep, I've just been looking up clamp meters on line, need one with good resolution down to mA and AC DC also.

I was unsure of the BG board in general, maybe not again..

Mechanically it's nice, better than MK. The front goes on really well and doesn't bend. (- Perhaps removing it is a tad too easy though with two quarter turn locks). The switches run right to left, but the earth bar is numbered left to right. - RCD is right to left so to speak, which means I couldn't try it out this evening in my own MK board since the busbar on wrong side.

the BG enclosure is a bit better than the MK/electrium stuff...but its the devices that count here as well.....
it isn`t just a pretty picture....

 

[GLENNSPARK]

Yep, I've just been looking up clamp meters on line, need one with good resolution down to mA and AC DC also.

I was unsure of the BG board in general, maybe not again..

Mechanically it's nice, better than MK. The front goes on really well and doesn't bend. (- Perhaps removing it is a tad too easy though with two quarter turn locks). The switches run right to left, but the earth bar is numbered left to right. - RCD is right to left so to speak, which means I couldn't try it out this evening in my own MK board since the busbar on wrong side.

this is why i`d say it was so important with boards utilising these quarter locks that any protective covers to internal exposed conductive parts (busbars etc) must be in place...as in my eyes these boards are accessable without the use of a tool (a yale key will open em)....

 

[Knobhead]

Hi Glenn,

Well I don't know, but a kettle is heated with a ceramic wire coil. Not exactly a motor winding I know, but it's not going to be a pure resistor. Anyhow, clutching at straws here since Chopper posed the question.

"Clamping all the tails together?" I'm not with you on that one.

Please, please, don't tell me you're a qualified electrician.

You've just dragged my opinion of modern electricians to an all time low.

 

[1Justin]

Please, please, don't tell me you're a qualified electrician.

You've just dragged my opinion of modern electricians to an all time low.

Hi Tony, Thate's quite a strong statement.
Any wire coil will be inductive. - (In fact any piece of wire at all is inductive). - It's just a question of degree. A thin straight wire in air is about 1nH (ie 1 billionth Henry) per mm length. I used to work on circuits up to 2GHz where every 1mm of straight wire could have a significant reactive effect on a circuit. At 50 Hz this is admittedly fairly academic, - but I didn't mention it to raise an argument.

It is possible to wind a coil "non inductively" whereby some of the turns go one way and some in reverse so the magnetic fields almost cancel. Maybe kettle elements are wound such. If the kettle element was just a bulk resistor it would have very low inductance - but most heating elements are wound coil (nichrome wire typically) on a ceramic former.

I think this discussion is somethat superfluous though, and I am quite happy to accept somnething like a kettle - to all common standards in electrical circuits at 50Hz doesn't represent much of an inductance.

What I wanted to get at was the noisy RCD's which still are doing so. I must replace one, and (as very usefully advised here, thanks guys) also buy a earth clamp.

Rgds

 

[Marvo]

A standard tube element can be considered as a linear load to all intents and purposes. It certainly won't cause harmonics that could remotely effect the operation of an RCD or cause it to become noisy. Switched mode supplies in computers, laptops, phones, battery chargers etc often have terrible power factor and are far more likely to cause harmonics plus they often have MOS type surge arrestors that have standing leakage to earth. I'd concentrate on this type of equipment rather than heating element loads.

 

[1Justin]

Thanks Marvo, point well made.

Rgds

 

[not clever]

The only time I've had a BG rcd give any buzzing noise, was when there was a dimmer on the lighting circuit. bypassed the dimmer = no buzzing swapped the dimmer for a new one sorted no more buzzing from the rcd.