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?
Most electric showers are retrofitted and involves getting a cable from the front of the house or flat from the cupboard under the stairs, the cellar, the hallway, kitchen or cloakroom it’s rare that Method C can be achieved throughout its circuit length.
The installation method for the whole circuit is going to be that at the point where it is most stressed. So if there’s a section of cable in mini trunking it Method B, even if it’s only a small part of the whole circuit and the rest would be Method C.
If there is one metre or less running under insulation in the loft the whole circuit could be Method 101, so I often end up in the loft trying to pull the cable out of the installation, even if there’s only 75 mm of loft insulation it still makes the cable rating borderline.
Most electric showers are retrofitted and involves getting a cable from the front of the house or flat from the cupboard under the stairs, the cellar, the hallway, kitchen or cloakroom it’s rare that Method C can be achieved throughout its circuit length.
The installation method for the whole circuit is going to be that at the point where it is most stressed. So if there’s a section of cable in mini trunking it Method B, even if it’s only a small part of the whole circuit and the rest would be Method C.
If there is one metre or less running under insulation in the loft the whole circuit could be Method 101, so I often end up in the loft trying to pull the cable out of the installation, even if there’s only 75 mm of loft insulation it still makes the cable rating borderline.
