More Hidden Junction Boxes

[ICTRich]

Would appreciate some advice...
I’ve not been a big one for getting involved with electrics, its always been my philosophy to ‘get someone in’ for anything more than running a spur.
I’ve been doing some decorating and as per a previous post, are putting a new tv on the wall. I’m running a cat5e and a telephone cable to where the tv is from the bedroom above. However, when I got the floorboards up, I have found 2 hidden junction boxes. They seem to be connected to the ring main, one cable from the JB runs down to a socket in the lounge and the other runs to a socket in the next bedroom.
After reading a few posts on here, I’m guessing its not correct to have hidden JB’s. What should I do and are they safe? Any advice would be appreciated.
Also, the cable that runs to the down stairs socket is no longer needed. I just want to get rid of the socket as its obviously where a tv used to be on the wall and is surface mounted half way up the wall. Can I just disconnect from JB leaving just two wires connected and remove all?
Thanks for any help.

 

[ericmark]

For many years the round Bakelite junction box was the norm and they were fitted in many unlikely places without too much of a problem. However it was noted that in some situations the terminals did become loose caused but vibration (people walking on the floor) and heat (expansion and contraction) so where junction boxes are fitted where they can not be checked on the 10 yearly inspection and test then a type which does not suffer from the problems are now used.

You use the word "Hidden" and there is nothing to say you can't hide them only that they must be where one can maintain them. So as long as there is a scheduled maintenance document saying where they are then being hidden is OK.

Many years ago I tended to leave wires in so I could use them in the future but over the years I have been caught out too many times where they have been damaged while not energised and re-energising them has caused problems. So since I will no longer use existing cables which have been left de-energised I see no point leaving them in. In fact tracing de-energised cables to find if truly de-energised is a problem so I actively remove un-used cables in most cases.

Junction boxes under floor boards are a problem as likely when fitted we did not have fitted carpet and if screwed rather than nailed down floorboards are used technically if a lose rug is used it's not against the regulations.

In theroy where the electrician writes on the floorboard junction box below then the carpet fitter should not nail down carpets over it and there is no reason why Velcro could not fix a carpet so it can be lifted for maintenance.

I have in the past when finding a junction box used crimps to join cable but still used the box to house the crimps as tape can be removed without a tool so not permitted but there is a screw holding on lid of box so a tool is required. So are you sure the box has screws or could it contain some other method of joining cables?

 

[ICTRich]

Thanks for the reply,

The JB has 3 cables going in all screwed in. One thing I have noticed are the cables are very tight with hardly any movement in them and the JB is just floating and not attached to anything. It is also near a hot central heating pipe...

Heres a pic, the cable I want to remove is the 2.5 T&E that dissapears into the wall with a lighting cable.

Untitled

• ICTRich
• 14 Apr 2012
• 1

 

[rebuke]

If you're removing a spur and so just have the two cables that are part of the ring, you could replace the junction box with crimps, which would then be a permanent connection.

To do this you'd need some correctly sized crimps, a proper ratcheting crimp tool (not one of the cheap automotive things), and some way of ensuring the cables remain double insulated (either something like heatshrink or put them inside an enclosure of some sort).

 

[ICTRich]

Are these what I need?

http://www.screwfix.com/p/ratchet-crimping-tool-1-5-10mm/49092

http://www.screwfix.com/p/crimp-insulated-red-butt-pack-of-100/86908

Thanks again.

 

[rebuke]

The crimp tool looks to me like it's one for uninsulated crimps, not the insulated ones you need, so I think that's the wrong thing, however it seems Screwfix don't list any others, which is a bit odd. What you want is one described as working with insulated crimps such as http://www.tlc-direct.co.uk/Products/DVDHCR15.html (they also normally have red blue and yellow coloured dots on the jaws as you can see in the pic so you know which bit to put the relevant crimp into).

You'll also need the blue crimps to use with the live + neutral connections (assuming this is a standard 2.5mm ring main), the red crimps are the right size for the CPC (aka earth).

A few tips if you've not crimped cables before:
* If you've got enough slack in the cables, try to strip a reasonable amount of outer insulation back so you can stagger the crimps, i.e. you'd end up with something like this:

--[crimp]--------------------
-----------[crimp]-----------
--------------------[crimp]--

* Always test that a crimp has worked properly by giving the cable a little tug to check it doesn't just fall back out, as sometimes things can misalign etc.

 

[adamr7747]

You could replace the junction boxes with "maintenance free" ones.

Can I just disconnect from JB leaving just two wires connected and remove all?

Yes, if you're sure that it's just a spur from the ring main and goes nowhere else.

Adam