James H wrote:

As part of the planning for my new kitchen, I looked at the current layout
today. I would have helped my dad to rewire it but Part P seems to have put
paid to that. I would still like to know what to ask the electrician and

Why? Part P does not stop you DIYing it. The only difference from before
is you need to either a) submit a building notice to the council prior
to starting work, or b) ignore part P ;-)

The kitchen has two single sockets above the worktop on the ring, one each
side of the hob. From one, a spur cable runs diagonally unshielded under
the plaster to the cooker hood, with no form of isolation! The other single
socket has a spur cable going to a socket under the worktop, itself having a
spur cable along the floor to a small CU with RCD under the sink for
powering the garden circuit. The cooker outlet (with socket) supplies the
electric oven and igniter for the gas hob.

Hmmm nice ;-)

What does the garden circuit feed?

Obviously the diagonal hood cable is a no-no but I was wondering how the
cable(s) to the hood could be run. Dropping from the ceiling, as the two
sockets above the worktop are wired, would be feasible but where could an
isolation switch go? I wouldn't want it behind the chimney. How is it done

Is there a cupboard adjacent to the hood? If so you could have a single
socket in the cupboard and simply plug the cooker hood into that.

from below? Keeping to the vertical/horizontal from an accessory rule, a
cable dropped vertically from the hood could necessitate an accessory behind
the hob? I won't be having units on either side of the extractor. Is
putting the cable in metal conduit, a switched FCU to one side of the hob
and unswitched outlet behind the hood the best method?

If you mechanically protect the cable than you can run it in non
standard places (or bury it 2" deep if the walls are thick enough).

Under Part P, must the approved person do absolutely everything? If I left

Nope you can do it all yourself (with building notice, and allowing the
council to have it inspected at the stages they want). Councils in
general don't seem to have got their act together with this, so you will
need to speak to yours to find out how they play it.

some nicely chased walls in the (to be) gutted kitchen, where the
electrician would want them, I gather he could use them? To save on
expensive electrician's time and cost, it would make sense to do as much
prep work as possible. Where does Part P draw the line on what is
electrical? Could I put back-boxes in?

Yes you can...

I expect a new ring main to supply the kitchen would be desirable. The

Yup. Possibly a non RCD protected radial to feed the fridge and boiler
as well.

kitchen items on the ring would take a dishwasher, fridge freezer, combi
microwave, gas hob, extractor and kettle. The washing machine and tumble
drier are in the downstairs loo - but that's another wiring issue.

I expect an electrician would route the cable along the wall in the adjacent
integral garage containing the consumer unit. Since the cable would not be
coming from the ceiling, would it be acceptable to run cables on the surface
(in trunking if necessary) in the void behind base units? This would be on
the right level for the hob and dishwasher outlets (accessed from units to
the side of these).

Yup probably.

Even if the wall was chased horizontally on the line of the above-worktop
sockets, how would the dishwasher cable be dropped? The dishwasher will be
midway between the cooker and sink-drainer, with the outlet under the
drainer. Could the cable do a right angle above the drainer, in the
horizontal plane of the above-worktop sockets and vertical plane of
dishwasher outlet, even though there is no visible accessory at the point of
the right-angle?

Not quite sure I am am visualising this correctly, but it sounds like
you are saying you want to come straight up from the under worktop
socket to a cable chase that runs horizontally between two other
accessories (one possibly being the isolating switch for said socket),
turn 90 degrees and carry on to the switch? If so then it complies with
the requirement that the cable runs are in direct line of the visible
accessories so sounds ok to me.

Would the following be a valid new ring layout, with S being a switched
socket, the bottom two being for the dishwasher (right) and hob (left)
mounted under the worktop in accessible cupboards. Everything else is
above. The rough location of the appliances is shown, the cooker outlet for
the oven is not. Hopefully the ASCII art is readable.


Hood---|
(m/w) (kettle) |
|
---SS------SS------SS--------FCU----SS-------|
-| (Hob) |
| (f/f) (Oven} (D/W) |
| |
|-----------------S-------------------------S



Layout looks mostly ok (depending on how to solve the extractor issues).
You want to design the cable layout so that you don't end up
concentrating all the big loads at one end of the circuit - you want
them spread out around the ring, or toward the middle of it. Things like
kettles/toasters you can largely ignore since they are short duration
loads.

This suggestion ignores adding RCD protection. Is it especially necessary?
Is the electrician likely to suggest it?

Is there any possibility that someone may in future plug in an appliance
that they may use outside? If so then the answer is a definite yes. You
have also not mentioned what type of earthing system you have (i.e. TN
or TN-C-S with an earth provided along with the supply, or a TT setup
with local earth rod). If your earthing is TT then *all*circuits need
RCD protection.

Lastly, I need to move the garden electrics, as the CU is mounted in the
sink unit that is being replaced, and the spur socket from which it is
unsuitably wired will no longer be there. As garden wiring is notifiable,
even though it is already there, I presume I cannot do the rewiring for
that? Would the electrician consider spurring from the bottom-right S above
if he did it?

Again it depends on what we are talking about. If it is just a single
exterior socket for example, then it would not be uncommon to provide
that from the ring or a spur from it. Perhaps with the addition of a
dedicated RCD if the main supply circuit is not already protected by it.
If on the other hand you are talking about a 30m cable run to a
collection of out buildings which have power and light circuits then you
would be looking for a dedicated submain run from the main CU or even
taken as a split feed before it.

Sorry there's lots here, but thanks in advance for any helpful answers.

Hope that helps...


--
Cheers,

John.

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