hum from CU

[orbital]

Been installing some lighting to a property.

Noticed that a slight hum was coming from the CU. Its a Wylex board with MCBs (60898) No RCD

Its a recently renovated house, and all electrical work seems to be of a good standard, done about 7 years ago

Worked out that it comes from two sources. The intruder alarm and a lighting circuit that also has smokes attached. switch one off the hum changes tone, switch both off it stops

Removing the line conductors from the MCBs stops the noise.

Any ideas what can cause this. All connections are tight. MCB is sitting correctly

Its not a very loud hum but is noticeable when the cupboard door is open

 

[bluetobits]

Dodgy breakers? Have you any you could swap them with to eliminate possibility?

 

[Lee321]

i know exactly what it is

 

[m4tty]

[quote name='Lee

 

[Robojin]

What tune was it humming :coat

 

[kme]

"Flight of the wasp bumble bee"

 

[Lee321]

its forgot the words ROTFWL :run

 

[green-hornet]

There can be a number of reasons, mcb working close to its maximum, mixed lighting with dimmers, transformers etc,faulty mcb.

I had a 6amp behaving in just the same way, tried a 10amp and the hum went. Although I did change it for another 6amp later and the hum was not there.

 

[Evans Electric]

If its Wylex perhaps you should check the date codes in case its one of those that melts and causes a fire.

 

[orbital]

Replaced the mcb's hum stopped.

 

[Evans Electric]

Interesting .