"Ro" wrote
| I live in a 20 year old appartment building.

In Ireland I surmise from your posting address, so things might be a bit
different there but

| The main fuse blew the other day, and when I replaced it,

in UK customers are not supposed to replace the supplier's main fuse.

| I noticed that the fuse was a 50A fuse, ...
| since there's very little difference between the appearance of the
| 50A and 63A fuse.

If they were British Standard fuses shouldn't they be different sizes and
colours? Don't know about Irish fuses.

| (I should mention that everything in the appartment is electric, even the
| central heating boiler!)

A 50A supply is woefully inadequate for all-electric. I live in a
refurbished-twenty-years-ago flat and my supply is 100A - with gas heating.

Owain