Found two cables floor to ceiling

[Richard Cull]

Hi, box room project - discovered two electrical cables on first floor (one fairly small and one fairly large - see pic). Not enough slack to reroute, so planning to add a length to both using connector boxes in the loft.

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I don't know what the cables are for. The circuit board is not far below the cables, so assume it's the lighting circuit? But then confused why two different thicknesses? On first floor there is wired fire alarm, extractor fan, heating tank, lights - may be one of those (circuit board has its own circuit for heating tank as also smoke alarms).

If needed to, I could suss out what the cables feed into by using a multimeter against the cable and switching on/off each of the fuses until I know which is delivering the current.
However, to save time, I also thought of just switching off all the electrics and cracking on with adding the lengths in the loft, irrelevant of what they might be feeding. The only thing I expect to be a problem is ensuring I use the regulatory extender boxes (and cabling of course). Is there something that I could just use for both cables (connector that satisfies high load and loft moisture).

Cheers everybody

 

[sparkwright]

At a guess, one cable for lighting, one cable for smoke detector - but who knows, could be anything.

Can't you just go up in the loft, find them, and trace where they go?

There MAY be some slack up there.

You don't really want any joints in the wall, so a jb (junction box) under the floor and a jb in the loft, with a new piece of cable in between, may be the answer.

However, you can not install cables just anywhere in a wall - they need to be in safe zones, so they can't be drilled into easily.

Send a close up of the cables, or work out where they go, then we can tell you what cable and junction boxes you need to get.

 

[Richard Cull]

Hi thanks for all the info.

Attached are a couple of photos with dimensions. There are no markings on the wires. I can't really get to the wires and further. The floorboards are thick and glued, so would be quite a disaster I think to trace them that way. Upstairs, I can trace but there will need to be a lot of board lifting, which will be pretty time consuming I think.

I did check for slack at a few different points and didn't seem to be.

My friend suggested a multimeter that can check currents through the wire sheathing ie not cutting the wire to test. I can check through trial and error flicking on/off the circuit board switches to test with the multimeter which it links to?

Thanks again

 

[sparkwright]

Yes, don't waste your time unnecessarily lifting floorboards.

This is a rare example of where a 'voltstick' would come in handy, to give some indication as to what circuits these cables are on.

Of course, an electrician would come in and see those cables, and know exactly what size conductor, and the number of conductors, in each cable - and would also know instantly which rated junction boxes to use.

That's just experience.

The measurements don't mean much to me, as I don't have any bits of cable or a ruler to hand - they could be anything AFAIAC.

Someone here might be able to work that out for you.

Another option is once you have worked out where your junction boxes are going to go, turn the power completely off and snip the cables with insulated wire cutters, strip some sheath back, and send another photo.

Work safely.

Also, did you take on board the business about wiring safe zones in walls?

 

[SFK]

Note that the cables have their wire rating stamped into them. You can see it just below the ruler.
Often hard to see, a bit of dirt/pencil wiped into it and use phone camera at angle can make easier to see.
Will also tell you if it is 3+E (4 core) wire normally used for interconnected mains smoke alarms.

 

[Richard Cull]

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[Richard Cull]

Thanks - very well observed!

Yes, so the thicker one is:

BS6004 (H) BASEC HANNI

Thinner:

BS6004 BASEC 102/001

Hopefully that helps.

Yes, I'll look into the safe zones absolutely - not worried getting my head around that.

I was planning on putting the extension junction boxes in the loft. Hopefully that is fine - it also means if I works backwards up the loft, I can create enough slack and keep the junction boxes accessible for future checking etc. I hope that sounds right.

With the wires on mind, what junction boxes would be needed? I assume on the outset one that complies to BS6004 as they both seem to be stamped with that

 

[Richard Cull]

Just noticed the smaller one has H2005 stamped on it.

Judging by the thickness and some of the contortions on the larger wire, in thinking it may be 4 core as mentioned above. The wire is secondary thicker than a standard two plug socket.

 

[Richard Cull]

Ok got a voltstick and have now deduced that the thicker is the wired smoke alarm and the thinner is upstairs lighting circuit.
So, considering extending the wire length of these in the loft with junction boxes, am I fine to do this and what ones would be best suited? Any help is most appreciated. Thanks

 

[Taylortwocities]

Where the cables are is not in a “Safe zone”.

You are permitted to run cables within 150mm of the wall, so move the cables over to near the wall and you are sorted.

you may need to extend the cables. An accessible junction box in the loft will be easiest.

 

[Richard Cull]

Hi thanks. The cables are just left where they were found, but will be rerouted with safe zone in mind. Tbh, I was surprised to find them there - wouldn't have a clue if I had drilled into the wall before I remove it (I was lucky to get away without cutting the wires when removing the plasterboard!).

The cables with definitely need to be extended for how I want to reroute them. Any ideas on the appropriate junction box that I can put in the loft to do this?

Thanks for your help

 

[sparkwright]

Ok got a voltstick and have now deduced that the thicker is the wired smoke alarm and the thinner is upstairs lighting circuit.
So, considering extending the wire length of these in the loft with junction boxes, am I fine to do this and what ones would be best suited? Any help is most appreciated. Thanks

You need either 1.0mm2 or 1.5mm2 T+E and two 3 terminal maintenance free junction boxes for the thinner cable.
and
either 1.0mm2 or 1.5mm2 3 core+earth cable and two 4 terminal mainrenance free junction boxes for the thicker cable.

Where are you running these cables, and how do they relate to safe cable zones?

 

[Taylortwocities]

@Richard Cull i may have missed it, but is the stud wall staying where it is?

 

[Richard Cull]

Hi thanks for the info on that info, very useful. Based on your advice, it looks like this connector would suit both types of cable:




I'm ever so slightly concerned about the loft moisture levels in the winter, but I assume once clamped and the lid screwed down on the junction box, this isn't a problem?

The stud wall is going, yes. I'm building over the stairwell to extend the box room. It will essentially be a new bulk head (for stair height regulations) and two partition walls that will create a built in wardrobe on top of the bulk head. So, the rerouting of the cables will go through the new bulk head and then up one of the new stud walls that will be built above up to the ceiling.

I haven't looked into safe zones yet but when rerouting I'll check online for this! I don't know if you have a quick round up of that?

Thanks for all your help
Rich

 

[Taylortwocities]

Ok. So ignore my suggestion to move the cables near the wall. That doesn’t apply if you don’t have a corner!
Great explanation of cable zones provided by the fabulous @flameport here:
https://flameport.com/wiring_regulations/BS7671_selected_subjects/zones_concealed_cables.cs4

edit. No picture of your proposed junction box.