Buzzing RCBO

[Deleted member 9648]

Staff accommodation in a large hotel, was asked by maintenance guy to look at a DB. MK board with 3x RCBO's serving rings, and the rest lighting MCB's. One of the RCBO's was making a very noticeable buzzing noise,but otherwise worked fine. Disconnected cables and the buzzing stopped, IR circuit...nothing untoward. Reconnect cables and the buzzing starts again...with or without load. Was going to go and pick up a replacement straight away, but maintenance guy insisted on leaving it to the morning as he was already overtime.... 'and anyway,it's been like it for weeks'!

Any suggestions as to the cause of the buzzing?

 

[Pete999]

overload????? near the limit on the over current side

 

[telectrix]

try switching the circuits from the buzzing RCBO with another. if the buzzing stays with the original RCBO, replace. if it follows the circuit, then it's a circuit problem. one other possibility is to move the RCDO position so as to be next to a different device than the one it's next to at present (harmonics).

 

[Dave OCD]

It's more than likely the RCBO itself, had this on the older 'plug in' Wylex type MCBs before as well.

 

[Deleted member 9648]

Thanks fella's.....didn't have a lot of time as I said....it was last knockings after an afternoon repairing hot cupboards in the hotel, but definitely not overload as it did it with no load at all. I suspect faulty RCBO, will find out in the morning.....just seems odd that as soon as cables disconnected it stops,and clamp meter showing zero amps on the circuit

 

[telectrix]

maybe the letters "MK" are a clue.

 

[ruston]

maybe the letters "MK" are a clue.

Remember the ad they used to use "You can tell a good electrician by what they throw away."
Times have changed since then.

 

[Darkwood]

Is this buzzing RCBO for a lighting circuit and are the lights dimmed ??? - swap the dimmer out with a normal switch and see if it stops.

 

[Dave OCD]

Is this buzzing RCBO for a lighting circuit and are the lights dimmed ??? - swap the dimmer out with a normal switch and see if it stops.

No he said it's for a ring.

 

[Darkwood]

My Bad - read it too quickly :13:

 

[richy3333]

I reckon twill be bees or wasps!?

 

[telectrix]

or a happy RCBO.

 

[Dave OCD]

Staff accommodation- could be a rogue Rampant rabbit.:laugh3:

 

[Marvo]

As already mentioned, high load current and some kind of PWM electronics such as dimmers or maybe a fan speed controller etc are the causes I've come across. As per Tel's suggestion swap the circuits or even RCBO's around and see if the buzzing follows one in particular. I had a similar problem with an MCB once and two new replacements did exactly the same, I had to use a replacement from a different manufacturer eventually. There was obviously a compatibility issue with something on the load side that caused resonance with that particular MCB design.

 

[PEG]

Staff accommodation- could be a rogue Rampant rabbit.:laugh3:

He said it was a ring...which means the pleasure aid you speak of,is corded...

I make it a rule,not to use a mains powered device of this type...caused a right mess last time...:wings: