I had a phone call from my son yesterday, the shower in his house had broken and not being a plumber/electrician got a couple of quotes. The old one was 6.5 kW with 6mm cable. The plumbers all seemed to think that the cable and MCB should be replaced as the current rating was inadequate for a replacement, the MCB is 40A. I had a quick check what could be fitted as there are many more powerful ones available and this weather the water is not wonderfully warm! I have not really thought about shower cables for a long time as they are almost always in good condition. Table 4D2 6mm clipped direct says 46A, continuous rating. A 10.5kW shower takes 45.65A on 230V so is quite satisfactory on the 6mm cable. In fact, the model I was looking at (Mira fancy thermostatic, expensive) would only take this power at full flow and temperature rise as it has electronic thermostatic proportional control and normal running current would be modulated and somewhat less. I consider this to be perfectly satisfactory, but the plumbers obviously haven't read the regulations. I often find the same with cookers, various sellers suggest 10mm cable, which may well not be the existing size. Should any change be made, and why do would you do this?
Clipped direct includes cables installed on brick walls with or without capping covered in plaster
Indeed. On the other hand most shower cables run through a floor void at some point - that's method B - now what does a 6mm² look like?
- Andy.
Will 'cable installed in a ceiling' in section 7.2 of Apdx 4 also apply if there's no junction box, just the cable in the ceiling, that refers to RM A?
I believe that the junction box heat concerns apply to heat created by a luminaire, such as a tungsten filament lamp. Sometimes a junction box was situated close to or by a hot luminaire.
Table 4D5 is for use with cables at 30 degrees C ambient temp. and conductor operating temp. of 70 degrees C. You could warm your hands on a winter's day at 70 degrees C. The old fashioned big brown circular junction boxes that I use won't be adversely affected by a warm environment or catch fire.
Clipped direct includes cables installed on brick walls with or without capping covered in plaster
Indeed. On the other hand most shower cables run through a floor void at some point - that's method B - now what does a 6mm² look like?
- Andy.
Will 'cable installed in a ceiling' in section 7.2 of Apdx 4 also apply if there's no junction box, just the cable in the ceiling, that refers to RM A?
I believe that the junction box heat concerns apply to heat created by a luminaire, such as a tungsten filament lamp. Sometimes a junction box was situated close to or by a hot luminaire.
Table 4D5 is for use with cables at 30 degrees C ambient temp. and conductor operating temp. of 70 degrees C. You could warm your hands on a winter's day at 70 degrees C. The old fashioned big brown circular junction boxes that I use won't be adversely affected by a warm environment or catch fire.
