I've decided the best way to connect my cooker hood is via a "spur"
off the 32A 4mm radial for fixed appliances. Is it OK to create a spur
using an inaccessible-type junction box (not plastered in, just behind
some units) rather than at a socket ? Can't think why not, but y'know
best to check.
Any limit to the length of "spur" ?
Sorry, forgot to say, the wiring at that point is behind units, but
all surface wired.
The wiring will go from surface wired to buried in a horizontal line
with an FSU that will be just above the wall units, so not visible
from most positions.
Well that advice (although sound) is just the sort of thing that will give
Dennis a heart attack.
I would not actually be happy with a junction box behind kitchen units if it
is only a few feet to the nearest socket.
<rummage> Ah, found it!
Come 'ere you dozy twonk...
<fx whoosh, whack, Owwww>
It would be better to originate your spur from an existing accessory
that is to remain visible such as a socket or a FCU etc, rather than
originate it from a concealed junction box. This is assuming the JB is a
screw connection type that should remain available for inspection. If
using a maintenance free JB then that is a different matter. The issue
at hand is whether the junction box remains accessible, and has
absolutely nothing to do with spurs.
The spur would obviously be perfectly safe (yes even to you denis),
since it would not be feasible to overload a 2.5mm^2 cable via a single
fused connection unit (and certainly not with a cooker hood), and the
cable would be more than adequately fault protected by a B32 MCB at the
origin of the circuit.
I tried to say that in the OP, but used the wrong terminology.
I said "inaccessible-type junction box". I should have said
Which kind of shifts the argument.
The debate is then between a maintenance free junction box when the
spur could reasonably be taked from a nearby socket (even if you have
to run horizontally a bit further to reach the socket).
This makes the argument about spurs, and not about accessible junction
Indeed. However if you already have a close by accessory, then there is
not much to be gained from adding an extra JB other than cost.
(Although wago push wire terminals in an empty box may be easier to use
with a larger number of stiff wires - so probably easier to wire a
branch (i.e. 4mm^2) rather than at a socket).
Well there is nothing to argue about when the spur is feeding a single
FCU and nothing else - even in dennis land ;-)
Well at least you realise that you have to qualify what the load is to
"know" its safe, that's progress I suppose.
Unlike the situation where somebody can plug in a four way and overload the
circuit without you having any control over the load on the installation you
Ah those words again, "adequately fault protected" but not against overload
(strange that that isn't a fault?) should someone put a 13A socket on a 2.5
mm spur and then plug in a four way.
I do like the words electricians use when they blame the user for
overloading their "perfectly protected" installations, they are usually
something like "well they shouldn't do that", "f'ing idiots", "everybody
knows that you can overload a socket without the fuse ever blowing", "they
deserve to have killed their family by doing that".
All to save a bit of copper.
Have a look at what current it takes to blow the fuse and note that it is
frequently higher than the current rating of 2.5 mm2 T&E and that is before
someone has replaced it with a nail because it keeps blowing or has been
unfortunate enough to fit a duff fuse like the ones that have been around
every few years that don't actually work.
I would never rely on a user supplied protection device to protect something
I installed as I know the bloody user will screw it up.
Some will and argue that they are correct while saying I am wrong even
though everything I said to do complies with the same regs they are using to
claim they are correct.
You can choose to do either or even do something not in the regs, after all
the regs are there to help those that don't actually know what they are
doing and provided you do the sums "anything" goes as long as you can prove
its safe. Just don't expect the average electrician to have a clue if its
not to the regs.
I know the bit of the regs you think I don't. I just don't agree with it. I
am not alone in thinking this.
What's more, I don't have to prove its right as I am not using it.
However its easy to prove the alternative I said is true as in all cases it
exceeds the regs.
There are no circumstances where it would be wrong to use 4 mm2 cable in
place of 2.5 mm2 cable.
There are no occasions where it is unsafe to fit a smaller breaker on a 2.5
You could even use 2.5 mm2 radials as per the later editions of the regs.
These BTW are there to replace rings so even the IEE thinks you are onto a
Give it a few more editions of the regs and you wont be doing what you are
Are we going to have the same argument as last time or have you come up with
something new and worth listening to?
I expect not.
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