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" ? Simon.
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. Simon.
Yup, sounds ok. Spur can be in 2.5mm^2 T&E, and you probably need the SFCU fused at 3A - but follow the cooker hood instructions on that.
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.
I have misplaced my "clue by four", so I can't give him a smack with it...
Indeed - at a socket (FCU etc) would be best (assuming its a socket circuit!)
Why would it be better, you both claimed that the spurs are perfectly safe.
Do you ever read what you have written before pressing the send button?
Too thick to understand what I say are you?
Non sequitur...
Ah, found it! Come 'ere you dozy twonk...
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.
OK, since the main radial circuit wiring will all be surface wired with socket boxes in the back of cupboards, I can just run the radial branch to the nearest socket instead of to a junction box. I sort of didn't quite think of that for some reason. I was imagining having to run vertically from a yet-to-be positioned socket. Are three 4mm2 cables connected in a socket box likely to be crowded ? Thanks, Simon.
I tried to say that in the OP, but used the wrong terminology. I said "inaccessible-type junction box". I should have said "maintenance free". 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 boxes ;-) Simon.
Yup that sounds better.
Yes very, however it varies with the brand of the accessory - some have more terminal space than others. However you actually only need 2 x 4mm and 1 x 2.5mm, which should be a bit easier.
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 did.
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.
A 4-way plug block is fused, and so is an extension lead. Simon.
As your comment was not relevant to John's point then I suggest that you are the thick one.
You are Jerry AICMFP. You will recall the difference between overload and fault being explained to you, Jerry, a few weeks ago.
MBQ
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.
So you are too thick.
It is possible to get them in. A deeper backbox is recommended. I wired a kitchen up last week using 4mm and it was no hardship getting the cables into a BG socket.
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