Ohm sweet ohm
As with all the work we are taking on, we are attempting to do it using the knowledge and experience we have gained in the UK and trying to apply this to French materials and other information we pick up over internet discussions boards, translated instructions on the material packaging and other bits of info and advice we collect along the way. We accept that our methods may not be “right” and anticipate having to correct some of the work we are carrying out. Our philosophy is that “the best way to learn is just to get on and do it”, so we are not suggesting or advising here, merely stating what worked for us!
We managed to get a measured earth rod impedance to just over 300 ohms. Although this is sufficient to trip the 30 mA RCD and is within the recommended regulatory UK limit, we also plan to utilise the steel reinforcing grid that will be laid when the floor is concreted to suppliment this.
We noticed that all electrical accessories in France are plastic. All the earth conductors are insulated. It would appear that getting anything like a decent earth is something of a problem and it would seem that plastic is used to reduce the risk of contact with floating earth voltages almost attempting to make the installation ‘double insulated’ or ‘class 2’. Obviously any metal appliances or fittings must have an effective earth and from what I had seen when I examined our neighbour’s installation, this is not always observed. There doesn’t seem to be much concern about this which in English standards is quite horrendous.
It appears that in areas susceptible to lightning strikes, an extra lightning protective device is required to be fitted in the fuseboard. I have not seen these before and they seem to be a quite expensive ‘one shot’ device which has to be replaced after every lightning strike (I suppose that this is not so bad as lightning never strikes twice in the same place (:) All devices in the fuseboard are double pole. We bought a 7way board with additional 32 Amp breaker for the cooker. In English terms this would be more than adequate for the size of the house but the exclusive use of radial circuits for power sockets may mean that this might be a bit on the small side. Our total incoming power is 7Kw (30 Amp) and even if we upgraded this to 40 Amp – the maximum our supply will allow us – there would seem little point in having much more than 4 16 Amp socket circuits on top of the water heater and cooker.
Cable: Twin and earth is not allowed in France and they use a round solid multi-core cable in 1.5 and 2.5 sizes. The 1.5 cable comes in 3, 4 and 5 cores including an insulated earth conductor. This stuff on the face of it, seems really good and in a lot of ways, I think I prefer it to twin and earth, however it is not as flexible and this makes it very awkward to connect accessories into the round plastic boxes as there is not much room inside the box. A liberal amount of swearing was found to solve the problem!!