Circuit breaker tripped off, Would not reset!!

[Anil.ks]

Hi,
On fine early morning all the lights in home went off whilst sockets and all electric appliances work. On checking main switch, the Wylex Consumer Unit (of the 2) one had tripped, I thought it was a spike and circuit breaker tripped. Tried to reset to on but lights wouldnt turn on. Checked the MCBs(it has 3 X 15A blue MCBs) from the same switch box and replaced all fuses still lights wouldn't turn on.
I remember there was no activity to trigger circuit breaker nor other electric appliances running but just the lights on! What could be probable reason, I can not figure out.

Thanking in advance
--A

 

[industryspark]

Your post has a few things in which arent clear.

what size is the mcb for the lighting circuit (the one which wont reset)?

what are the fuses you replaced?

it sounds like you have a fault on the circuit which you need to sort out before it will allow you to reset it.

 

[Anil.ks]

Hi, Industryspark,

Apologies am novice to electrics!! Thanks for your reply.
There are 2 consumer units in my flat and I replaced the 15A fuses from tripped box! but it turned out that, that consumer unit is no longer used and is redundant! I had to replace a fuse from the other consumer unit, an MCB that is of rating 5A(white) and lights were back. It was a bulb that blew and caused problem.

thanks again for your reply
--A