In article ,
Chris French writes:

Unlikley I'd have thought.

how many people consider the rating of their main fuse when using their
electrical devices, and when was the last time you heard of someone
blowing their main fuse?

Old Wylex rewirable fuse box - metal clad version.
If you leave the plastic fuse cover off, there is only a short path
between the supply side of the fuse and the front metal case opening.
When one of the rewirable fuses blows, the arc will often end up
contacting the front metal case opening, causing a much bigger arc
which is protected only by the main fuse. The plastic fuse cover
actually sits inside the front metal case opening, preventing this
when it's fitted.

In a block of flats which all originally had these Wylex units, and
many had long-since lost the plastic front covers, blown mains fuses
were a regular occurance.

In another case, I have seen a main cutout operating close to its
max rating, which caused all the pitch to melt and run out of the
head-end connection and make a mess. It's possible a poor connection
might have contributed to this too.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]