testing an MCB

while I am on an electricity role I would like to know how to test an mcb. A mate switched his on and off a few times and it kept tripping. It had not been turned in 30 years. It came about that it had failed and new one was needed. He thought his circuits were dodgy.

This can waste a lot of time, so who do you first test the mcb to see if that is OK?

Reply to
Bay Man
Loading thread data ...

Depends on what sort of test you want to do. Checking it actually switches on and off when expected (i.e. when manually switched) is easy enough to do with a voltmeter or voltstick on the output live wires(s) for the circuit. If its tripping unexpectedly, then a clamp meter around the live wires will verify if the current load is adequate to cause the trip. Note that adequate current to cause an "instant" trip is significantly higher than the device rating - typically 5x the rating for a type B device. Actually checking that it trips at the expected current is somewhat more difficult in a domestic environment - especially with the higher current devices, but may be possible if you have a high rated load such as an electric shower that can be used.

Reply to
John Rumm

First of all test the MCB with no load on it. If it trips then it is shagged.

The second test is usually to try the circuit on another MCB in the CU. Preferably one with the same rating, but a lower rating will do for some circuits. eg you can try the sockets out on a 16A or 20A MCB for a while. Providing that you do not then switch the washer, dishwasher and kettle on at the same time it should give some indication that the circuit is fine and that the sockets MCB was faulty.

Reply to
ARWadsworth

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.