Lights blowing mcb

[WELLSIANA]

So whats is your ideas...5 amp mcb with main switch 30ma rcd....nice house , dry etc ...put any combination of lights on and after around 4-5 minutes mcb blows.....the lambs are varied but i can not see any overload and it will do it with only a handful on...if you leave say 1 or 2 lights on it will not blow...and any selected but add load in any are even light it blows...so far my views is could be mcb fault but then why would it not blow with less lights...small fault...but why would that not take out rcd ?..and this has been doing it for years not short term...a mcb blowing seems overload but i can not see that as it does it well in on loading...any views ?

 

[Knobhead]

After 35 years, to be honest I’d be too ashamed to ask for random ideas when I couldn’t be bothered to do initial any testing.

 

[Paul.M]

I'm guessing that the 'condescending' line that was removed was aimed at me,if so, am I bothered....no, skins far too thick and besides I grew a pair a long time ago!

It was not aimed at any individual member so dont take any personal offence. It was a rant on a thread from a new-ish member that has been removed so not to inflame the thread. No big deal really, dont worry about it.

 

[Paul.M]

After 35 years, to be honest I’d be too ashamed to ask for random ideas when I couldn’t be bothered to do initial any testing.

In his defense he only looked at the job, so he only flicked on a few switches and saw the problem that the customer has told him. Says he is going to do the job and we can only assume that a time served spark will take test equipment with him.

The OP has been given some great advice but if this was me I would check the terminations in the CU, then the ceiling roses, then the switches, clamp test before and after the visual checks. After all of thesr trips, the mcb will be knackered so change it. Simple fault find and rectification in my mind.

 

[Knobhead]

Paul, there’s many ways to approach a job, asking on the net for wild ideas certainly wouldn’t be my approach.

Would you ask before doing some basic tests?
I’d do the tests and then think about them.
Yes, there has been some good advice, but they are guesses.

I worked with a guy, “the last time this happened it was xxxx”. He could add hours to a shutdown by diving off hither and yon.
The same guy confidently told me the main fuses to a drive were OK, they were sat on a steel bench, the bench tested at 0Ω across the fuse.

Our trade was founded on physics and logical thinking, what happened?

 

[Farmelectrics]

Let's hope he comes back and shares his findings with us

 

[telectrix]

my money's on a tired/stressed MCB, having had too many cheap lamps blow over a period of time, but , pending the OP doing some testing, it's a shot in the dark. ( pun intended ).