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?
Problem is that even if those plumbers have heard of diversity, they probably think that it means that you have to genuflect at the start of a game or race. ?
I don't think that I would apply diversity to a normal basic fixed load shower. It can probably be set at half load or full load with two sets of heating elements. I would rate it at full load Amps. for cable sizing. The previously mentioned all singing all dancing electronic shower automatically adjusts the load current I believe, according to the incoming water temperature and the water temperature set by the user for comfort. So in that case things may be different in practice, but I would still chose a supply cable based on full load current.
Problem is that even if those plumbers have heard of diversity, they probably think that it means that you have to genuflect at the start of a game or race. ?
I don't think that I would apply diversity to a normal basic fixed load shower. It can probably be set at half load or full load with two sets of heating elements. I would rate it at full load Amps. for cable sizing. The previously mentioned all singing all dancing electronic shower automatically adjusts the load current I believe, according to the incoming water temperature and the water temperature set by the user for comfort. So in that case things may be different in practice, but I would still chose a supply cable based on full load current.
