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MCB type for shower in old CU


 
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Brad77

from United Kingdom

Joined: 31 Mar 2011
Posts: 4
Location: Nottingham,
United Kingdom

PostPosted: Tue May 31, 2011 2:21 pm Reply with quote

I've just got a shower, its 8.5KW.

Our consumer unit is very old, its a MEM Memera21.

Currently its got 2x 5A MCBs for lights, 16A for Immersion Heater, 32A for power sockets and 32A for the cooker.
The cooker wire goes into a big switch on the wall behind the cooker and inside this theres another wire that goes off in the wall up to the airing cupboard upstairs which is behind where the shower will go, here there is another switch like you'd have for a cooker.

So I know the shower should ideally be on a seperate MCB and wire, but I'm wondering if it'd be safe to use this existing wire. It obviously used to be for a shower before we bought the house but no idea what power rating that was.

I've seen the maths of 8500W/230v = 36.96A
So I think I'll need to change the MCB from 32A to a 40A (or rather I'll be getting an electrician in to swap this).

The MCBs already in use are Type1,
I've found a Type3 (http://www.reconelectrical.co.uk/index.php?act=viewProd&productId=27527)
and I found a TypeB (http://www.neweysonline.co.uk/mem-mcb-memshield-type-b-40a-single-pole-230v-ac/1050072404/ProductInformation.raction)
Are these any good for this CU?
The only place I've found a Type1 MCB is on ebay for 30+postage, I'm trying to do this a cheaply as possible.

Thanks,
Brad.
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Taylortwocities

from United Kingdom

Joined: 27 Jul 2006
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Location: Oxfordshire,
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PostPosted: Tue May 31, 2011 3:05 pm Reply with quote

Brad77 wrote:


So I know the shower should ideally be on a seperate MCB and wire, but I'm wondering if it'd be safe to use this existing wire.


It is not a matter of "ideally" - it is essential. You cannot share the circuit for the cooker with the shower. Period.
You will need a omplete new circuit from the CU to the shower.


Also, you will need to protect the shower circuit with an RCD and provide an isolation switch in/near the bathroom.
Also this is notifiable work. So, unless you are competent with electrical work, you need a registered electrician to do this work for you.

See http://www.diynot.com/wiki/electrics:part_p:diy_electrical_work_and_the_law for details
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Brad77 (1 Jun 2011)
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holmslaw

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PostPosted: Tue May 31, 2011 3:39 pm Reply with quote

..


Last edited by holmslaw on Tue Apr 10, 2012 9:06 am, edited 1 time in total
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Brad77 (1 Jun 2011)
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bernardgreen

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PostPosted: Tue May 31, 2011 4:09 pm Reply with quote

Brad77 wrote:
I'm trying to do this a cheaply as possible.


Money can be replaced, a life lost cannot be replaced.
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Brad77 (1 Jun 2011)
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ban-all-sheds

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PostPosted: Tue May 31, 2011 5:02 pm Reply with quote

Brad77 wrote:
I'll be getting an electrician in to swap this

Use him to get a proper job done, with a new circuit, a new MCB, testing and certifications regarding electrical and building regulations compliance.

You won't find anybody competent who is prepared to do what you want anyway.
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Brad77 (1 Jun 2011)
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Brad77

from United Kingdom

Joined: 31 Mar 2011
Posts: 4
Location: Nottingham,
United Kingdom

PostPosted: Wed Jun 01, 2011 9:57 am Reply with quote

Thanks for all the replies guys.

I was hoping for an answer like: "it's not ideal but will probably be ok", i.e. the cheapest answer.
But honestly I was expecting answers like you've all given.

My CU has a black piece of plastic to the left of the MCBs, I'm hoping this can be removed to allow another MCB to be installed.

If I buy an MCB, pull up carpets and floorboards and lay a 10mm cable. Then disconnect the wire in the airing cupboard switch, and also disconnect it in the cooker switch.
Then get an electrician in to wire it all up, is that something they'd do?
Or would they insist on laying the cable themselves and buying all the parts themselves?

oh and I forgot I need an RCD, not sure where that goes, another task for an electrician.
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holmslaw

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PostPosted: Wed Jun 01, 2011 10:26 am Reply with quote

..
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