Hi All - thanks for the replies.  I've started on the inspection and the first thing is just to document "as built".  I am still puzzled by their use of 3 phase in a domestic installation.  It must be more expensive, for no apparent advantage.   There is a hob running of 2 phases of 16 A.  Why not 1 phase of 32 A?  I'm wondering if there's a historical or legacy factor here.  I live in rural Norfolk and there are a lot of strange quirks here eg 2 phase supplies to remote farms.

Stephen

I am still puzzled by their use of 3 phase in a domestic installation.  It must be more expensive, for no apparent advantage.   There is a hob running of 2 phases of 16 A.  Why not 1 phase of 32 A?  I'm wondering if there's a historical or legacy factor here. 

I think generally their domestic supplies are 3∅ at 32A/phase rather than say 100A single phase - but that does mean that 32A on a single phase isn't really available for any one load. It has certain advantages - less voltage drop in the N, possibly slightly cheaper wiring (say 3x 2.5mm² (total 7.5mm²) rather than 2x6mm² (total 12mm²) for the live conductors to the hob), and no parts need carry the large currents that seem to start a lot of CU fires over here. The smaller c.s.a. supply cables also mean fewer problems with high PFCs - no 16kA fudge factors for them.

   - Andy.

Thanks Andy - that's a very insightful answer.  I'll try to fit in with the locals.  There are many ways to achieve the same result.  In the end safety is the most important factor and that is achieved by a combination of physics and convention.  They all drive on the wrong side of the road here, but don't crash into each other.

Stephen

My experience is more Swiss than German however it seems that a large amount of Europe uses three phase to the house or apartment which is probably a historic thing. The typical British ‘small house’ does not tend to exist on the mainland. A large house or apartment block will be fed with 3 phase from the cable in the street (or from overhead wires) and it would then seem logical to take the three phases to each apartment.

The cost of components may be a bit higher, I would think a 3 phase main fuse and meter  would cost more than single phase but there is also less copper which may offset the difference. As Andy says will 3 x 32A be cheaper than 1 x 100A?

Another different logic is the use of a circuit per room rather than splitting lights and power per floor and the use of ring final circuits. I asked the local inspector if I could install UK 13A sockets in my house in Switzerland. His response was yes, as long as there is one Swiss socket per room. Ring final circuits and reduced CSA cpcs were not allowed.

My experience is more Swiss than German however it seems that a large amount of Europe uses three phase to the house or apartment which is probably a historic thing. The typical British ‘small house’ does not tend to exist on the mainland. A large house or apartment block will be fed with 3 phase from the cable in the street (or from overhead wires) and it would then seem logical to take the three phases to each apartment.

The cost of components may be a bit higher, I would think a 3 phase main fuse and meter  would cost more than single phase but there is also less copper which may offset the difference. As Andy says will 3 x 32A be cheaper than 1 x 100A?

Another different logic is the use of a circuit per room rather than splitting lights and power per floor and the use of ring final circuits. I asked the local inspector if I could install UK 13A sockets in my house in Switzerland. His response was yes, as long as there is one Swiss socket per room. Ring final circuits and reduced CSA cpcs were not allowed.

Thanks Roger - I think I'm going down a rabbit hole here.  Why not reduced CSA cpcs?  All the breakers in this house are rated type B, which implies the use of the adiabatic equation. Another "shot in the dark" I've brought my Fluke 1651, can I get a European mains plug adaptor?  If it's not polarised, how will it work?  Should I just use crock clips and duct tape, like Apollo 13? Should I call Tom Hanks?

Stephen

Why not reduced CSA cpcs?

Primarily it's down to the 0.4s disconnection time calculation being based on a touch voltage of half mains voltage, no more - reduced c.p.c. break that assumption. In the UK we sort of presume that main bonding will reduce touch voltages to compensate, but there are a number of situations where that doesn't entirely work. They don't use UK style T&E (mostly c.p.c.s have to be insulated) - so using full sized c.p.c.s isn't that much of an issue. Full sized c.p.c.s also avoid some of the nastier problems with N-PE faults and c.p.c.s ending up carrying N currents.

   - Andy.