I have a 60A no fuse Mitsi breaker switch between the supply and my consumer unit. I noticed that when the shower is used (4.5 KW) the breaker makes a buzzing noise. Its only when the shower is used. Main CU Switch is also 63A which remains silent. Is this normal / cause for concern ?

Thanks.

Is this something new? Is the buzz loud?

If not, and nothing is getting warm or making funny smells it's likely just fine.

If it's worrying you get the unit replaced, but remember that the incoming side is live all the time, get your local sparks to do the work.

Not too loud. It's been in place for a year but the buzzing came recently. No smells.

Thanks.

Try turning it off and back on.

Breaker/Switch manufacturers advise that the device be turn off and on several times every 6 months.

In our hot and humid conditions this is very important as oxidation of internal components build up over time.

The same is true for the wire connections at the panel and breakers, they also should be checked for "tightness" every 6 months.

If you don't know what you are doing get a Qualified Electrician to do this. I also would like to warn everyone be careful of the Neutral wires,, tighten in place. More Electricians are injured or killed by the Neutral wire. Remember all the power that goes into a circuit must come back out (ON The Neutral). Safety first in all cases, wear shoes! if you are using a tester to check voltage, test it on a circuit that you know has voltage to ensure it is working.

Again, Safety First, if in doubt have a Qualified Electrician check things, there are several good check lists available on line as a guide. this check done 2 X a year well save you a lot of problems down the road and allow you to find problems when they are just starting.

Remember "BE SAFE"

Can you see the wire connections? Maybe take the cover off. The buzzing might be sparking due to loose wire connection and will eventually burn and/or melt things which could result in fire. These things should not be making noise so something is wrong.