MCB tripping

[Durksy]

Hi.
A friend has recently started experiencing the 16a mcb feeding outside lights and sockets tripping out.
These lights and sockets have been installed for years with no problems.they are switched from an ip rated 3 gang switch(each switch being individually fused with a 2.5a quick blow fuse)
9 months ago I connected a pump and filter into the spare switch,9 months have passed with no problems however last week the breaker started tripping.we have both reset and it holds on for five to ten minutes before tripping again.
I am a bit stumped as have one by one disconnected each outgoing cable from each switch and each time mcb still trips.
Has anyone experienced anything like this and possibly shed some light on what the fault maybe?

 

[Chri5]

What happens when you disconnect all the loads from the circuit and re energise?

If it holds then simply add one device at a time and re test, maybe you can isolate the fault down to one device on the load.

It might be a bunch of items all being a bit mA leaky that builds up and then falls over what over the rating of the rcd is
Externally the suspects are everything, have you an ir tester?

Have you done a visual at all loads including checking seals, looking for condensation, rush, rot, bugs?

Cable wear, uv or rodent damage etc?

 

[Durksy]

Havnt n ir tester no,how does that work?
I have disconnected all loads and added one at once and there are no visibly apparent visual faults.
Also not fed by rcd/rcbo as he will not pay for one despite my best efforts!!so would that rule out the mA leaky scenario?

 

[JohnW2]

It might be a bunch of items all being a bit mA leaky that builds up and then falls over what over the rating of the rcd is

The OP appears to be talking about a 16A MCB, not an RCD.

Kind Regards, John

 

[Chri5]

It might be a bunch of items all being a bit mA leaky that builds up and then falls over what over the rating of the rcd is

The OP appears to be talking about a 16A MCB, not an RCD.

Kind Regards, John

My error

Op have you tried changing the mcb, even temporarily for another in the board, and proved the mcb as ok?

 

[JohnW2]

My error

Fret not - we all do it

Op have you tried changing the mcb, even temporarily for another in the board, and proved the mcb as ok?

Good idea. Intermittent tripping of an MCB such as described is, I would have thought, a fairly unusual phenomenon (much less common than with RCDs) - and I rather doubt that the usual outdoor culprits for RCD tripping (moisture, frank water, dead spiders/rodents/whatever, or just general muck) would be enough to trip a 16A MCB.

Kind Regards, John