rewiring a light circuit

[Stephen]

That's why I thought it might be better to rewire and have peace of mind, rather than try to fix what is already there. Thanks.

[Stephen]

Yes, that's what I was thinking. Who knows what other junction boxes are hidden that I have not found yet.

[Stephen]

Usually bathroom lights don't seem to have the loop in/out. I was thinking of putting the bathroom light at the end of the radial for that reason.

[Stephen]

That's what I was thinking ;(

Thanks.

[Stephen]

Already have both of these :)

Thanks.

[Stephen]

I think Dave was right when he said that it is wiring that has been added to over the years, which explains all the different styles of cable I am finding. It was more the way the sockets are wired that concerned me than the lights but my worry was that if the sockets are wrong the lights will be too! There's definitely the shared neutral on the stair's light, so who knows what else I may find.

I have removed or rewired the unearthed sockets and like George said, I am trying to trace the layout to see what else needs to be done.

I suppose my only unanswered question is, if I did a complete rewire, what should I do with the lights on the stairs? Would you put them on the same circuit as the floor they are on, or a circuit all of there own, or something else?

Thanks, Stephen.

[Dave Plowman (News)]

If there are spare ways on the CU and easy to do, on its own. So that if another lighting circuit trips, you still have lights in the hall.

[Muddymike]

Hello,

Did the vendors complete a pre sale questionnaire? If so what did they answer about the electrics?

Mike

[John Rumm]

One option there is a long slim (say 6mm) drill bit - poke it up through the ceiling through the ceiling rose, and drill through the chipboard floor. Once through, take the drill out of the chock and leave the bit there, then go find the end upstairs - if its just carpet upstairs you probably won't even see the hole its left later!

(although you can pull that up first if you are feeling energetic)

Alternatively, if you have a board access holesaw:

(see the Chipboard sheet section)

Then you can stick in an exploratory hole, and use it to work out where the real one needs to be (as was the case in that picture - the left hand plated hole was the first "best guess" - turned out to be one joist over)

Yup, its hard to ignite, and if nothing else serves to insulate the floor above from the heat of the fire for a bit longer. (the wire mesh ensures that if the ceiling below fails, it does not fall with it)

True - but if they were not like that, you would have to drill through them all anyway. (rods will go along the joists easily enough[1], but across them is never easy regardless of the construction)

[1] Alas you will sometimes have a nogging, or bit of herringbone that can block a rod even when going along the joist. One of those egg whisk like balloons on the end of the rods can help them skip over things like that.

Yup, not desirable, but alas quite common.

nope, that was fine.

[John Rumm]

With many light fittings there is insufficient termination space to take in three cables. In these cases, just make the terminations in a junction box (say something like a wago box with wago push fit terminals), and then connect that via a flying cable to the light. The JB can be pushed up into the ceiling void.

e.g.

[John Rumm]

I normally do upstairs on the upstairs circuit, and downstairs on the downstairs, then two way switch both of them. That means that isolating any one circuit will isolate all the lights notionally on the circuit / floor.

The only thing to watch then, is that the switch positions will have lives from both upstairs and downstairs circuits in them, but the light positions won't

Like that:

[tabbypurr]

Then if you change the MCB to 20A it should be compliant

normally easily fixed

I can't help thinking you're making an awful lot of unneecssary work for yourself by considering a rewire. It sounds like a fairly easy repair job. Testing circuit resistances would also be best practice.

NT

[Robin]

I've met problems if the ceiling rose is fitted with the cables alongside (or through) a joist. Then a hole big enough for a junction box (even one of the slimline Wagobox light junction boxes) sometimes won't be covered by a light fitting with a footprint about the same size as the rose. Where redecorating the ceiling is not an option I've felt the need for something even slimmer - eg a tube which takes 3 Wago terminals in "series" rather than "parallel". But I can't quite persaude myself that stuffing them in a bit of conduit is OK - even with silicone applied as "strain relief".

Would a pro just man up and cut a large hole in the joist?

[Andrew Gabriel]

Well, they were often installed at first fix in retirement flats, so residents didn't need the volume knob on max. Probably been replaced with bluetooth nowadays.

The singles were much thicker than needed for a 60W LPS, can't recall if 2.5mm or 4mm - I presumed this is because they are self-supporting up the column, although not as tall as yours.

What, no apprentice?

[John Rumm]

Enough of them seem to go with the "cocoon some chock block in insulating tape" approach ;-)

To be fair a bit of conduit will make for reasonably decent protection.

[ARW]

Afraid not and those posts are pretty high IMHO:-(

These car park LEDs were a doddle to fit.

as they can be lowered down using a special tool [1]. A couple of them would of course need a few car parking spaces to be coned off to allow them to be lowered down.

I used 1.5mm 3 core flex for the drop to the fuse.

[1] And with the help of a spade as the gardeners have very kindly built the soil up around some of the posts and planted nice plants around them! I fitted them on a hot summers day and guessed the angle of them, I then had to return in the dark with a lux meter and make some adjustments to a couple of them.

[Vir Campestris]

That seems odd. Either 2.5mm cable is happy with 32A (a double can supply 26A, even without one of the things being faulty) - in which case the ring's 4mm is grossly overspecced - or it can't, in which case obscure circumstances could overload the cable.

A quick google suggests 2.5mm^2 is only good for 20A!

Andy

[ARW]

2.5mm when not installed in insulation is good for 27A.

A double socket will soon fail if it is used for supplying 26A for a prolonged period.

[John Rumm]

It depends on the installation method.

To be used in a ring circuit then it needs to be 21A "as installed" or higher. If you can't meet that, with the actual installation (say too much insulation or circuit grouping) then you will need to use a larger CSA cable.

It is also important to clearly differentiate between overload currents and fault currents[1]. With a general purpose circuit you need to provide protection against both types of over current. Normally this protection is provided by the fuse or MCB at the origin of the circuit.

In the case of fault currents, this is the only place you can do it.

With overloads however you can split the responsibility and provide the protection via some other means. This is the design principle that a spur uses for overload protection. The fuse/MCB can't do it, since the rating is higher than the maximum capacity of the 2.5mm^2 cable even in the "clipped direct" mode giving the full 27A, but by controlling the load that can be applied to the end of it[2], you can achieve the same result. Normally a double socket is rated at 20A continuous maximum load (not 26A), and that will be less than the installed capacity of the single piece of cable in the spur.

(I am sure there will be someone along shortly to come up with a scheme involving a pair of 4 way extension leads, 6kW of static load, a length of rubber tubing, and a yak, to highlight why this is not true, and hence why we so commonly see properties burst into flames daily!)

[1] from

Fault Current

This is the current that flows when a short circuit fault occurs in a circuit between either the live and neutral conductors, or the live and earth conductors. The magnitude of fault currents can be huge (100s or

1000s of Amps) since they are limited only by the resistance of the wires in the circuit between the consumer unit and the fault, and the impedance of your power supply and earth connection as delivered to the property.

Overload Current

This occurs when the total current demand made by the appliances connected to the circuit exceed its design capacity. This significance of an overload will depend on its magnitude and its duration. Small overloads may be tolerable for long durations, while big ones can only be tolerated for short durations, before any damage to the circuit wiring occurs.

[2] Hence the rule about no more than one single or double socket on an unfused spur.

[The Natural Philosopher]