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showers per unit

Postby jackdor » Tue Dec 11, 2007 1:40 am

Hi if a 5 bedroomed house want to have 4 8.5kv showers in and the existing c unit mains sw is rated at 100amp. could you install another c unit and put 2 on each. what would be the safe way and the legal way to do this, b4 i get a quote. my brother in law said he had a split board put in when he had his shower fitted. Any advise is welcome. Thanx.
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Postby sparx » Tue Dec 11, 2007 5:12 pm

each shower would take 37Amps, potentially if all on together could draw 148A except that the largest single phase domestic supply is fused in cut-out at 100A!
The fact that your main sw. is rated at 100A is irrelevant to the problem, as if sufficient spare 'ways' in board are available then you can't overload board as company fuse will blow first.
Showers should be RCD protected so maybe a second C.U. may be an answer with an RCD as main sw. the 'tails' will still go to same supply via a 'Henley Block' connector so still only got 100A to play with, however you can allow for some diversity ie not all will be in use at same time, which is what supply authority allow for eg when calculating for a new housing estate they work on an average load per house of around 20A i'm told, otherwise the cable sizes, transformers ect. would be huge.
see what the 'part p' leckies have to say and maybe repost their solutions before commiting.
must you use electric showers? no pumpable hot water?
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Postby ericmark » Tue Dec 11, 2007 10:25 pm

As sparx says 147.8 amps is over the total supply to house and if you all wanted to go out together and all tried to shower there would be a problem plus electric is expensive way to heat water and you only get a dribble out of 8.5Kw showers so some form of storage for the hot water is required even a combo boiler is only about 30Kw so storage is only answer. There are electric water heating units and main pressure storage tanks which because mains pressure can be mounted nearly anywhere and give better showers with some pressure I would prefer one good shower than 4 drip units mine direct from gas boiler is 27Kw and I feel clean in mins I hate visiting my sister with electric shower.


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