I have just replaced a light switch following decorating and the circuit breaker will not reset. The switch is correctly wired as i have checked. Even put the old switch back to check the new switch wasn't faulty. After about an hour of doing other things i returned to the problem and the mcb would reset. The circuit has never tripped therefore is it likely to be a faulty mcb? Apart from swapping it with the other light circuit is there some way i can check? don't want to have this issue again if it trips for real....candles anyone
faulty mcb -light circuit
- Thread starter dd2005
- Start date
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I take it you didn't try resetting the MCB with the main switch off? This is the easiest way to tell if the MCB is faulty.
Wondering if you have caught any wires with the back box screws in the switch, only an issue when it is in place.
Wondering if you have caught any wires with the back box screws in the switch, only an issue when it is in place.
how many wires are there at the switch, and what colours are they?
it is very unlikely to be the MCB. Consider the sequence:
1) MCB does not trip
2) Changes made
3) MCB trips.
how many lamps does it turn on, and what sort?
is the new switch metal, and was the old one plastic?
it is very unlikely to be the MCB. Consider the sequence:
1) MCB does not trip
2) Changes made
3) MCB trips.
how many lamps does it turn on, and what sort?
is the new switch metal, and was the old one plastic?
The switch was plastic as the old one, just new. The wires were both red and connected correctly. There was no trip before the switch was replaced and now the MCB has let me reset it (after an hours wait), the system has not tripped since. All lights on the ground floor have been used and it has not tripped, it is not overloaded (I have checked the lamp ratings).
The next thing I will try is to switch off the mains and try turning the circuit breaker on and off. Will get a spare MCB before I try it in case it is faulty.
The next thing I will try is to switch off the mains and try turning the circuit breaker on and off. Will get a spare MCB before I try it in case it is faulty.
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If the MCB has been functioning without tripping prior to replacement of switch, then tripped and locked once new switch was fitted. You then replaced back to original/old switch, it worked fine and then put new switch back on and worked fine.
I assume when you originally replaced old for new, you introduced a fault to the circuit, have you snagged the perm live or switched live to a metal back box that had been earthed?
Look for damage to the red insulation on the cables, it does not need to be much, may be hardly noticeable if your not looking for it!
I assume when you originally replaced old for new, you introduced a fault to the circuit, have you snagged the perm live or switched live to a metal back box that had been earthed?
Look for damage to the red insulation on the cables, it does not need to be much, may be hardly noticeable if your not looking for it!
Sorry, misunderstanding....sequence as follows:
1) Circuit worked fine, hadnt tripped
2) Circuit switched off at breaker to change light switch;
3) New light switch installed;
4) Breaker wont reset;
5) Refitted old switch;
6) Breaker still wont reset;
7) Waited an hour whilst doing other things;
8 ) Breaker could then be reset.
9) Did 1 to 3 again;
10) Breaker wouldnt reset;
11) Waited an hour and then the breaker would reset again.
Basically it hasnt tripped but for some reason wouldnt reset, with either the new or old configuration unless you wait an hour or so! Frustrating! As Spark123 said, will try switching the breaker with the main isolation switch off to narrow it down. Last night had to walk round the house with a torch whilst waiting for the breaker to let me reset it!
1) Circuit worked fine, hadnt tripped
2) Circuit switched off at breaker to change light switch;
3) New light switch installed;
4) Breaker wont reset;
5) Refitted old switch;
6) Breaker still wont reset;
7) Waited an hour whilst doing other things;
8 ) Breaker could then be reset.
9) Did 1 to 3 again;
10) Breaker wouldnt reset;
11) Waited an hour and then the breaker would reset again.
Basically it hasnt tripped but for some reason wouldnt reset, with either the new or old configuration unless you wait an hour or so! Frustrating! As Spark123 said, will try switching the breaker with the main isolation switch off to narrow it down. Last night had to walk round the house with a torch whilst waiting for the breaker to let me reset it!
Not quite, if I understand what we're being told. I don't think that the MCB has ever 'tripped' - rather, it could not be switched back on after having been switched off whilst the work was done. That could have been a (temporary) problem with the MCB ('sticking'/'not latching') - particularly since it appears that the circuit is now functioning normally and the MCB not tripping.
Kind Regards, John
And prey tell how did you solve the problem?
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The smaller buttons on the old Wylex breakers are prone to sticking in the in position. This means that the larger button will not stay latched.
Sometimes the buttons get worn and faulty and the MCB can trip not because there's an electrical fault, but a mechanical one.
Sometimes the buttons get worn and faulty and the MCB can trip not because there's an electrical fault, but a mechanical one.
Thanks for all the replies, going to get a new breaker and fit that. If that doesnt solve the problem then diagnostics will have to start!
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