Hi People

I am currently working on a new flat block. I have a electricity board supply for each flat which has a main 100A fuse. This then feeds a electricity meter which then feeds a 100A double pole isolator. From the isolator i have a 16mm 3-core SWA feeding each flat.
Do i need a switch fuse or mcb before i connect my SWA to the isolator?
My current plan is to connect my SWA in to a 60A switch fuse then conect this to the isolator with double insulated tails but is this necessary?

DB is more than 3mtrs away from the supply intake by a long shot so yes you will need fused isolation. You dont want an MCB there, if it trips how are the tenants going to know why they have no electric? Think if the inconvienice for the residents at the top of the flats. The 100A DP iso is presumably what the DNO has put there?

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Yes you will need a switchfuse for each flat after the meter. Use the switchfuse, why have an isolator as well?
You MUST contact the electricity supplier to get their ok for your arrangement otherwise you can be made to rip it all out and start again.

If your in UKPN land, you can achieve all this will a ryefield board, but everywhere has their own take on it.

16mm? how long are the runs?

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Lack of planning on your part doesn't make it an emergency on mine....

Every man has to know his limitations- Dirty Harry

The electricity supplier has installed the 100A DP isolator. Seams a little pointless as I could have conected my switch fuse straight to the meter. The longes run is about 30M maximum so on a 60A switch fuse 16mm will be fine.

Jason
The Isolator fitted by the Electricity board gives the facility that you don't have to connect to their meter and means that for all intense and purposes they have finished putting the liability on you making the system live. Connect your switch fuse to the isolator as you state with your SWA glanded into your switch fuse
I more than suspect that the armouring on the SWA 16mm submain will be OK as your protective conductor to your consumer unit
I presume that the electricity board have supplied an earth terminal, do all your bonding from the origin to the services with no bonding in the apartments, bonding conductor size based on the electricity board incoming neutral
good luck with your project make sure you get paid
MrP

LoL - I'm going to disagree witha that Mr P - you have a collection of installations - how does each installation comply with BS 7671 if you have no bonding in place. Equally, the sub main armouring is almost certainly inadequate to act as both a CPC and a bonding conductor.

The main incoming services need bonding to the suppliers MET - you need an appropriately sized copper or equivalent size non copper conductor to the earth marshalling terminal in each flat and then bonding to the services as they enter each flat (assuming the flat has extraneous services of course - water may well be plastic and heating may be electric).

If it's PME then we have to up the game further

Regards

OMS

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Failure is always an option

The words twenty pound and origin come to mind
I think we will agree to disagree

MrP Its a tage hot at the mo

for sure Mr P - we always do on this one

Keep out of the sun, yes - too much of it ain't good, trust me

regards

OMS

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Failure is always an option

Hi Jason,
A 100A fuse is too large for a 16mm SWA!
Fuse it down as you have planned (25mm tails in free air).

@ Dave
He will be fusing it down to comply with regs re DB being more then 3 mtrs from intake.
He wouldn't be putting the same sized fuse in his fused iso. The 100a fuse he talks about is the DNO fuse.

-------------------------
www.icertifi.co.uk
BS 7671 electrical certificates on your iPhone/iPod

www.tapengines.com
Electrical apps for electricians and engineers on iPhone & iPad

yet again, cockburn shows total ignorance...

--with a 100amp fuse (BS1361) in the ryefield, we feed and protect the
tails, meter, isolator and then consumers tails and steel M/SW/F.
then, with a 3 core 16sq mm or 25sq mm SWA (depending on load) glanded into the steel M/SW/F, we connect in the same fashion to the distribution board in the flat.
as regards equipotential bonding, normally this would be marshalled
at the meter position, but in this case the DNO allow the 10sq mm
wires to the services, to be fitted in the distribution board in the flat.
these bonds are fitted at the point of entry into the flat and irrespective
of plastic or copper at that point.
the consumers tails of course, are conventional, ie 16sq mm/25sq mm
double insulated + 16sq mm earth lead from the M/SW/F to the isolator.
the PSCC max in this situation of 16KA is at the DNO position M/F

Regards.

given we don't know the supply arrangements, may be not so ukpn..
I'm going to have a cup uo tea from my leaky kettle on my green and yellow filing cabinet.....

Wear wellies and marigold gloves - just in case you fill up with leaking electrons -

OMS

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Failure is always an option

...thinking that a good bit of scotch broth might be better than tea, followed by a good port...not cockburns, possibly taylors...