Confused

[Pete999]

I'm going to ask what might sound dumb coming from someone of my age and experience, I don't do much now and have done very little in the way of domestic installations, having spent much of my time on commercial or industrial work, thats not to say I don't know how to install domestic electrical installations. The confusion lies with junction boxes under the floors of houses during a rewire, many moons ago on a social housing project we wired everything lighting wise, back to a central point on the first floor, and connecting the lighting points and switches in a large junction box, likewise if we needed to add a 13a socket we would sometime break into the RFC with a 30a JB fitted to a noggin under the floor. My question is, is this still allowed? I mean fitting a JB under the flooring and forming a trap, where possible in the floor boards.

 

[imago]

The holes are typically in all the wrong places. The majority of them are drilled too close to the top or bottom of the joist so would be well within range for a screw or nail.

Cable could be routed through some of them but it'd end up a right rats nest and use way more cable than required.

There were plenty of cowboys about, working on price, to silly deadlines, not too bothered because "it's only" etc. Not just in the electrical trade either. We mostly do refurbs, and the cr4p we find from the 1970s and earlier would make your hair curl.

 

[Engineer54]

The holes are typically in all the wrong places. The majority of them are drilled too close to the top or bottom of the joist so would be well within range for a screw or nail.

Cable could be routed through some of them but it'd end up a right rats nest and use way more cable than required.

There were plenty of cowboys about, working on price, to silly deadlines, not too bothered because "it's only" etc. Not just in the electrical trade either. We mostly do refurbs, and the cr4p we find from the 1970s and earlier would make your hair curl.

You wouldn't have found many cowboys about before the 70's (which is what imeant by ''relatively recently'')!! As i say, that property probably had a 100 years with very little being touched, especially by cowboys....

 

[shanky887614]

I like wiring lights in single core, makes life hell when someone has lost the sw feed though going to the light

 

[davesparks]

Eh? Like 99% on here - loop in and out at switch or light point. Preference for light point for a number of reasons

Well I guess I was just taught different to anyone else. A central joint box makes alterations and fault finding a doddle.

I don't like looping at switches due to the number of cables that end up behind the switch. But some situations require it.
I don't like looping at lights anymore as all these ridiculous lights fittings people but don't have the space for one cable in them, let alone 3.

 

[imago]

You wouldn't have found many cowboys about before the 70's (which is what imeant by ''relatively recently'')!! As i say, that property probably had a 100 years with very little being touched, especially by cowboys....

Most of the work we do is on properties Victorian through to mid seventies and I would say without fear of error that 25 - 30% of all the original construction/installation work we uncover on refurbs and restorations is poor to awful.

That covers structural work such as the much vaunted 6" by 3" joists which everyone says are so much stronger than the 'modern rubbish'. But that doesn't take into account the fact that they are installed so that an inch and a half at each end is all that's holding everything up. Done because the persons installing them were either bad at their job or didn't care. Which makes the construction considerably weaker than the supposedly poorer construction methods used today. Lime mortar using next to no lime, sand and cement mortar using next to no cement, because they were trying to cut costs. Results in very weak and unstable walls and supports. Low grade inferior concrete used in social housing throughout the '50s '60s and '70s. Electrical installs from new in '60 and '70s houses where cables run across walls at 45 degrees, or run down one wall then go through it to an outlet so that there's no indication of a cable being present. And lets not forget the much despised (apparently) junction box. When were they at their peak for use? Oh yes, the decades of the perfect tradesmen in the '60s and '70s.

Rose tinted spectacles aside, there were just as many cowboys cutting just as many corners in the '50s '60s and '70s and before as there are now. It's just that some people have selective memories and like to pretend that everything old was fantastically constructed and everything new is poorly constructed. Both of which are demonstrably incorrect.

Edited to add:-
I would say that the main difference between trades now and forty plus years ago is at the top end, not the bottom. The worst from then and the worst from now are about on a par. However, the best work from that era is better than the best from now. I think there are a few reasons, but the main one being the time and budgets allowed on the high end jobs covered the construction phase as well as accessories and finish. I also think that some jobs that were inspected to a higher standard.

 

[imago]

I don't like looping at lights anymore as all these ridiculous lights fittings people but don't have the space for one cable in them, let alone 3.

I've started using those Wago 'two in one out' lighting connectors. You can then push the main body of connectors up into the ceiling and only have L N and E coming down to the fitting. Everything is still accessible, but life is made much easier.

 

[Sparkie30]

In T&E, that's the very LAST way i'd ever wire a house!! Switch looping can lead to backboxes being well an truly packed, and for no good reason either!!

Also opens the door to allow DIY'ers to easily get up to all sorts of unmentionables on a lighting circuit!!!

Thats why we are all different it's works for me but not for you. I think as long you fix a 35mm back you have plenty of space.

As for DIY'ers it's the opposite, when they open the box it will scare them off hopefully anyway.

 

[davesparks]

I've started using those Wago 'two in one out' lighting connectors. You can then push the main body of connectors up into the ceiling and only have L N and E coming down to the fitting. Everything is still accessible, but life is made much easier.

Are you putting them in enclosure before pushing them through the ceiling and into the void above?

 

[wozz]

3x1.5mm in a 35mm backbox causes a problem? I must say I can't remember there ever being a problem with this. That said there isn't a will always do method, depends on the fittings, construction to name but a few considerations. I've used centeral jbs when wiring houses that are very old, having one cable at a wall light is a lot easier, also older houses have nice places to tuck them away.

 

[davesparks]

No it doesn't, but once you have multiple switches in one back box you get a lot of cables.
Especially when people insist on using 1.5 for a 6A cct instead of 1.0

 

[Richard3009]

On the subject of drilling joists how many sparks and plumbers follow the guidlines of what is acceptable.

 

[davesparks]

I do, they aren't really guidelines though as they are the rules laid out in the building regs (I think its part A or part B) and the building regs are law.
If you don't then the building inspectors can require that cables are removed from the holes and that the joists be reinforced where the holes are in the wrong place.
I have seen it happen when plumbers have drilled in the wrong place.

 

[wozz]

No it doesn't, but once you have multiple switches in one back box you get a lot of cables.
Especially when people insist on using 1.5 for a 6A cct instead of 1.0

Would that also depend on derating factors, rather than just breaker size??

 

[davesparks]

Of course it depends on good installation design.

But as a general rule the most onerous factor is for cables buried completely in insulation which can be a factor of 0.5.
The basic CCC of 1.0 from the tables is over 12A.

So as a rule of thumb 1.0 is going to be fine for the vast majority of domestic work.

 

[wozz]

Unless you include any grouping at the same time.

I used 1.5 as a worse case sinario that's all.

Loop at switch, loop at light, centeral jb they all have their place.

 

[richy3333]

Sounds a bit like the old central point ''Octopus'' wiring system of the 70's.... Didn't really catch on, and many got ripped out, not that many years after they were installed. Weren't too readily adaptable for additions etc, and often ended up with needing additional JB's to get over the central Octopus systems restrictions, which basically nullified any perceived or otherwise advantages of the system...

I still see these a lot as an old spark used this in my area. Even now when he's called out of retirement he still does it! Some JB's are a bugger to find!

 

[davesparks]

I think you are referring to an RB4 type system as opposed to the octopus.
As I understand it the octopus system was a prefab setup. It arrived on site as a load of pre made cables you just dropped into place.

 

[davesparks]

Unless you include any grouping at the same time.

I used 1.5 as a worse case sinario that's all.

Loop at switch, loop at light, centeral jb they all have their place.

That would be a badly designed installation in my opinion. Cables totally buried in thermal insulation and bunched together at the same time!

 

[imago]

Are you putting them in enclosure before pushing them through the ceiling and into the void above?

No, but most of the time I sleeve the earth so they should be fine.

 

[Hawkmoon]

No, but most of the time I sleeve the earth so they should be fine.

Guessing you are joking here, no? :confused5:

 

[dazza1981]

No, but most of the time I sleeve the earth so they should be fine.

Do you not normally sleeve the earth wire when using T+E then mate ???

 

[imago]

Yes lads, I'm joking. I use either the small wago boxes, line light JBs or the slim choc box type depending on what's best at the time.

It was tongue in cheek because a lot of people get wound up by what they call Electrical Trainee. Then they seem to go round the forum playing Billy big balls assuming that they are the only ones with a clue.

 

[specs]

All of my rewires are neutrals at switches, you can't go wrong, multiple cables! use a deeper box/ box extension+ wago /line connectors + line/wago j'boxes dependant on application. One light to install no problem, multiple lights, no problem, multiple switching, no problem, I use 1.5 t&e for line into box from cu and 1.0 t&e for supply to lights from sw, ( easily identifiable) and loop from sw to sw in 1.5 t&e, , 3 plate from rose is dead to me now that connectors have improved to such a level. I look forward to further forward thinking in the world of electrical connectors. I also look forward to a time when 9kw boilers and 6/7 kw hobs can be connected using bell wire as a supply cable. Probably not in my lifetime but the rate at which LED technology is improving, I feel sure it will come.

 

[davesparks]

No matter how much technology improves 9KW will still be 9KW!

Do you include a fuse at each reduction from 1.5 to 1.0? Only there's this regulation that requires a fuse at each reduction in cable current carrying capacity.

Mixing cable sizes throughout a circuit like that is bad practice in my opinion. Ok if you've got a long run of lights and you've upped the cable at the start for volt drop and then drop the size as you go along the circuit that makes sense.

 

[SJD]

... I use 1.5 t&e for line into box from cu and 1.0 t&e for supply to lights from sw, ( easily identifiable) and loop from sw to sw in 1.5 t&e, ...

Given that so many decorative lights nowadays have minimal room in the housing for connections, I can see this perhaps makes sense.

For example, I just installed for someone a couple of B&Q bathroom lights which came with the L, N and E exiting the top as singles with some heat-resistant sleeving around each. They were supplied with a 4-way choc bloc and instructions "to wrap a few turns of insulation tape around it" before pushing it into the ceiling!

I have to say I try to avoid mixing cable sizes in a screw terminal, the thinner cable tends not to be gripped so tightly, but maybe 1.0 and 1.5mm2 is OK.

 

[Guest111]

IIRC the octopus was a preformed wiring system, there was another which used a box about 10" square for wiring the lights,this was basically an overgrown jb with plenty of terminals in,they were used a lot in our area on 1970's council houses and the downstairs lights one was always located at the top of the stairs and the upstairs was just inside the loft hatch.I cant for the life of me remember but I think they were made by henley or BICC.

 

[specs]

Given that so many decorative lights nowadays have minimal room in the housing for connections, I can see this perhaps makes sense.



I have to say I try to avoid mixing cable sizes in a screw terminal, the thinner cable tends not to be gripped so tightly, but maybe 1.0 and 1.5mm2 is OK.

cable sizes in switch are not mixed in same screw terminal. 1.5 in, 1.0 out.

 

[specs]

No matter how much technology improves 9KW will still be 9KW!

Do you include a fuse at each reduction from 1.5 to 1.0? Only there's this regulation that requires a fuse at each reduction in cable current carrying capacity.

Mixing cable sizes throughout a circuit like that is bad practice in my opinion. Ok if you've got a long run of lights and you've upped the cable at the start for volt drop and then drop the size as you go along the circuit that makes sense.

I wil get bck to this when I get hme keybod not respodig.

 

[specs]

No matter how much technology improves 9KW will still be 9KW!


Mixing cable sizes throughout a circuit like that is bad practice in my opinion. Ok if you've got a long run of lights and you've upped the cable at the start for volt drop and then drop the size as you go along the circuit that makes sense.

I run 1.5 to each sw in a room from the cu (mcb 6amp) I then run a max of 20 down lighters on that circuit, ie 6 lamps in 1 room 6 in the next and 8 in the last room ( these are all LEDs ) ( we don't fit anything else).Total load 100 watts. I could run each circuit in bell wire (well near enough ) but i don't, because that would be what I consider bad practice.

 

[specs]

No matter how much technology improves 9KW will still be 9KW!

Do you include a fuse at each reduction from 1.5 to 1.0? Only there's this regulation that requires a fuse at each reduction in cable current carrying capacity.
.

Do you include a fuse at every rose that you install or do you run your l/holders in 1.00mm or 1.5 flex ( inc down lighters ) I think not