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Hi everyone!

Sorry for what might be useless questions, but I'm just starting out with my electrician courses.

My mum lives in a flat and wants to add a 10.5 kW electric shower which would draw about 44 amps. She already has underfloor heating that uses a maximum of 44 amps (10,590 W) as well as all the other stuff (including sockets, lights, immersion heater and cooker) which, at worst, might draw up to a further 50 amps.

At the moment, the underfloor heating is supplied from the meter by a 10mm cable. The rest of the house is supplied by another 10mm cable.

An electrician has advised that a third 10mm cable from the meter would be needed for the electric shower. However, he has also said that she would need to get in touch with her supplier (EDF) to increase the supply current upwards from the current 100 amps.

Mum has asked me for advice but, as I'm just starting out, I really couldn't say much for sure.

My questions are:
(1) Will the supplier agree to swap out the 100 amp fuse (and any inadequate cable) to increase the supply to 150 amp or more? Will this cost a lot?
(2) After the meter, will she need to have three separate 60 amp switch fuses (one for each of the three 10mm cable feeds)?
(3) Will she need three consumer units in her flat? (1 split load unit for the general lighting and power, 1 rcd-protected unit for the underfloor heating, and 1 rcd-protected unit for the electric shower.)

My guess is that the answer should probably be "yes" to all three of the questions above but I'd be very grateful for any advice or extra information you might be able to give me.

Thanks a million!

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  • Thread Starter Thread Starter
  • #2
hmmmmmm your supplier will charge you a fortune,
this heated floor seems a lot for a flat, how do you arrive at the rated wattage? have you measured actual current draw?, is it off peak ie economy 7 ? do you have a split rate meter? do you have a 100a fuse in the main incommer to start with, (you say its a flat sometimes will only have 60A )
Have you allowed for diversity ie, not everything can be used at the same time ( if you add up all the mcb values on most consumer units quite often the all add up to more than 100a anyway) this may be your answer ie, can youe biggest load (heated floor) be timed so as it is not on when you are using the shower.
are you all electric? you mentioned immersion heater if this is your only form of hot water (no gas) and you are paying for a tank of hot water per day you may be better with a power shower- one that is electrically pumper and not heated- will only need a very low amperage feed but will require a hot water supply, get this right and it will out perform any 10kw electric shower
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