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i have just moved into a 4 bed house with a 100amp main isolator in the consumer unit, PME supply with mcbs. The house has 2 showers of 8.5 kw each, electric oven 2.3kw, immersion heater (assumed to be 3.0kw), 3 lighting circuits, plus 3 ring mains for 13 amp sockets. Even after allowing for diversity is not the main isolator switch overloaded? It is quite possible that the oven and both showers could all be on at the same time (i.e. 84 amps), if the immersion was on as well this would be 97 amps, leaving only 3 amps for other things like kettle, tvs(x3), freezers(x2), lights, etc. One side of board has RCD , but no RCD protection to the showers (!), only to the 3 ring mains. Opinions and advice please.
 
The oven and immersion will have thermostats so will cycle on and off. The showers will only be on for relatively short periods of time so I think you'll be alright. If you're worried, perhaps you could set the immersion to come on at times the showers are not likely to be used?

I would definitely get the lack of RCD protection on the showers sorted out though!
 

SJD

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Mentor
Arms
Esteemed
As mentioned, the lack of RCDs for the showers is a priority.

The service fuse on the incoming supply will be a maximum of 100A, and it might well have a lower value fitted, e.g. 80A. It will withstand a significant overload for the time it takes some to have a shower (well, perhaps my daughter excepted).
 

mhar

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Arms
Why not clamp (or get somebody to clamp) your meter live tail so that you can see what the actual demand is when you turn everything on. It is usually significantly less than you expect.

You can also get energy monitors quite cheaply which display your energy usage in real time, I came accross an 'owl' one Friday.
 
O

Octopus

Quite the informative video on max demand / possible overload

Some interesting opinions that chap has ...... about 15 mins in a reference to non compliance of 314 for more than 1 cable in an mcb ........ hope he didn’t C2 that

On a reality level there are so many installs like this around ....... be interesting to see what happened next !
 
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