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3 way Junction box into two Fused Spurs for Outside Shop Lights

Postby helpmeplz » Wed Apr 03, 2019 9:40 pm

Hi guys, currently got 3 shop lights outside powered directly from the CU through a fused spur.
With the three lights outside , I need to isolate 2 lights together and the other light into 2 separate fused spurs so I can control them separately.

Currently, before the cable reaches the fused spur I plan on using a three way junction box and from there adding the other fused spur.

Is this allowed?

Help appreciated.
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Simply Build It

Postby Mr White » Wed Apr 03, 2019 9:58 pm

If anything was done incorrectly who ever carried out the work would be liable. As it's for a shop (Commercial premises) I would suggest that you would be better off getting a qualified electrician to do the job for you. Just because something works, does not mean its correct or safe.
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Postby helpmeplz » Wed Apr 03, 2019 10:03 pm

Hi Mr White, thanks for your reply, but it's my shop and my premises and yes you are correct. But the method I mentioned, is that ok?
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Postby ericmark » Wed Apr 03, 2019 11:20 pm

It would depend on size of cable and size of MCB/Fuse/RCBO in the consumer unit.

It is permitted to have a fuse at the destination rather than at origin if less than three meters of cable and there are no branches. So there is not single answer to your question.

For any alteration there must be covering paperwork, be it minor works or full installation certificate there needs to be the paper work which shows you have tested and inspected the work.

If the work looks suspect then one would need to be very careful, and when you say direct from CU and has a FCU the first question that comes to mind is why have a FCU why is the MCB not small enough without having a FCU?

There may be many reasons, for example it may be a RCD FCU because there was no RCD in the consumer unit. However assuming already RCD protected then I would be looking at grid switches, so I can have one fuse at three switches all in a double socket back box.

The problem with commercial is if anything goes wrong you have HSE crawling all over the place and when it goes to court often it's not the person one considers as guilty who ends up being found guilty.

In the case of Emma Shaw for example the electrician left a little too much slack, the plaster hit the cable and this resulted in line being connected to metal within the wall, then a plumber missed putting glue on a tun dish, and a thermostat became faulty causing water to be ejected into the tun dish which because left without glue came apart letting water onto the floor and the lady got hold of the stop tap while in the water and was killed.

It seems an electricians mate when testing instead of writing down actual reading talked in canteen and made up a result, so looking at 4 people all in some way involved in the death.

However it was the electrical foreman who was found guilty for using an electricians mate rather than a fully qualified electrician.
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