Hello all!

I started thinking about this with residential wiring: The UK uses 32A ring mains, rest of Europe 10, 13, 16 or even 20A radials. (What is the norm down under?)

I came up with this concept:

20A radials for general purpose sockets. 20A @ 230V gives 4600 W, which is more heat than can dissipate from most rooms. Therefore very few appliances will use the full capacity of the circuit.

The IEE regulations allow a 32A ring main to serve a maximum of 100 sqm, i.e. 70W per sqm. If we assume a power need of 100W per sqm. the 20A circuit would be sufficent for 46 sqm. Let's say 50 sqm just to keep things simple.

The cable would be 2.5 sqmm (13 AWG) or in some cases 4 sqmm. Maximum length with 2.5 sq.mm at 4% voltage drop is 32 metres (100 feet). 4 sqmm allows for 50 m. This is sufficient for most homes, I think. A 30x30 m house is 900 sqm, i.e. 10000 sqft. Double that if it is a two story house... (I'd sure like to own that house!)

20A type B MCB:s should be sufficient to protect the 0.75 sqmm (18 AWG) cords used for small appliances. (I have done a few calculations on this)

Separate lighting circuits would be optional.

A few appliances like washing machines, tumble dryers, storage heater etc. will have dedicated 20A circuits.

Now for the RCD:s. With 20A circuits the number of grounded appliances per circuit will be rather limited. This means little current leaking back through the earth conductor. I think (without knowing) that this will allow 10 mA RCD:s to be used. One RCD per circuit, not one or two for the whole house.

This arrangement has two benefits:
10 mA is low enough to save children.
And a fault on one circuit will not turn the whole house black.

Unlike the US where the GFI/RCD is mounted in the receptables, RCD:s in the consumer unit will also protect people from faults in the wiring. The drawback is of course the high price of a combined MCB/RCD:s (RCBO).

Here's another good thing: 20A is enough for any appliance used in a home, except for the cooker. This means that the same appliance could be sold and used in entire Europe, without having to make different versions for the single phase and the 3-phase countries.

Ideas, suggestions, opinions?