Lyle,
The service fuse here is similar to what you'd find in Northern Ireland or elsewhere in the UK (although the physical design of the fuse may, in some installations be quite different)
Typically it's either 63, 80 or 100Amps
Regardless of the type of fuse, it's installed and sealed by the ESB (poco)
In recent years the ESB has started installing isolators after their meter, in some cases actually built into the meter itself. This is the demarkation point between the network and the consumer's equipment.
The consumer unit still carries a main switch and main fuse (or breaker in recent years). This would usually be the same rating as the service fuse.
The logic is to protect the consumer unit and wiring against fire should it become accidently overloaded... e.g. if a consumer somehow manages to connect >80Amps of equipment across several final circuits.
The tripping / blowing characteristics of the main fuse / breaker would be similar to any normal diazed fuse or MCB ... so, it would tend to blow more rapidly than a service fuse.
If you have more than one panel / consumer unit. Each one would have an appropriately rated main fuse. E.g in apartment blocks, garage services etc etc..
It's probabally not 100% necessary in a standard domestic installation, but it has remained the normal practice here and is required by the wiring rules.
[This message has been edited by djk (edited 02-19-2005).]
