6A MCB Tripping

[Andy Crisbaenpeef]

Hi
A friend has a problem with his security light. i have not visited his house as yet but I,m intrigued by his problem.

He was replacing fuse wire in his consumer unit every time it blew, I suggested he replace rewirable (semi enclosed ?)fuse with 6A MCB.

His MCB trips within a time range of Mil sec's to 5 Hrs after he has switched on the feed to the Pir Security light outside. The light does not need to illuminate to trip the MCB but need only a live feed to it.

I suggested he 1. replace the OLD Light completely, (he did to no avail). 2 check ceiling rose in Kitchen as he thinks light was fed from it (his father inl-aw checked it out and gave the ok??), 3 look at switch and make sure all connections secure etc (he did and says all ok). He has also assured me that any visible cable to the light looks ok.

I have now suggested he replace the switch (old switch) to eliminate the final accessory, (Unless junction boxed somewhere).

My question is this, given the above, what trips an mcb after 5 hrs one day and trips it immediately on another day?

My thoughts are , as it is intermittent then water may be involved somewhere?.

Any help appreciated with poss causes.

I have offered to take a look at it if his light switch replacement is unsuccessful.

Andy

 

[Spark123]

Water is a likely culprit, it would be advisable to have an electrician carry out an Insulation Resistance test on the circuit. What is the total wattage of lighting on the circuit?

 

[Andy Crisbaenpeef]

Not sure on wattage though he does have a seperate circuit for upstairs and down. Nothing added to circuit in years but tripping started a few weeks ago without any work having been done (not even a pic put on well with a nail).

 

[333rocky333]

Look at the cable between where it leaves the building and the outside light , it may be perished.

 

[The Yellow Transit]

As all the accessories have been changed it would appear to be cable damage poss a nail through the cable or chaffed against a pipe, water or gas ,each time the mcb trips it may be burning through whatever has caused the damage, this may cause a fire , get it sorted as soon as poss

 

[Andy Crisbaenpeef]

Will take on board the replies and post once solution is achieved. Thanks

 

[Andy Crisbaenpeef]

Was informed today that they have ran a flex to the light now and plugged into conservatory. I asked do they want me to look at it but was informed that they were happy to live with the setup as it is.

No conclusion I'm afraid.