Found live wires - help with advice

[diynotLD]

The problem:
While renovating a cupboard I have found unconnected wires hidden behind a simple wooden panel. The thinner wires all have labels like ‘hallway’, 'window contact' and ‘PIR’ so it was an old alarm system that was either removed or never connected - there are no traces of any previous PIR or other connectors having been installed anywhere. So we thought these are likely to be dead and that's why someone tucked them away 13 + yrs ago before I bought it. See attached pics!

I ran my Stanley S300 cable/stud detector over the wall and it showed a live wire in that area I bought a voltage tester pen to double check exactly where, and it shows AC in the thinner wires but not the thick one (which I had assumed could have been connected to a main alarm box so why no power?). Confusing.

This cupboard is where the consumer unit is located (as seen in photo). The electrics were all checked last year when I had a new kitchen installed and they needed to update the consumer unit. Electrician went round and checked all the circuits and was happy with everything - sadly we hadn’t discovered this mystery panel back then! But there is nothing labelled 'alarm' or anything in the unit this seems to lead to so I can't just switch off that circuit. I've read here about alarm fitters adding them to a lighting circuit, but we switched off the Lighting one and it was still showing power so I have no idea (it may be on the Sockets circuit but haven't been able to switch that off just yet).

Plan?
My idea was to shorten and cap these off, under a blanking plate/something so it's obvious something is there for future safety - but when I looked online I see terminal blocks and junction boxes & Wago 221 connectors for joining things and I'm not entirely sure what I should do to just terminate this. Ideally I want the neatest finish possible for the wall finish as this is in my living room so please point me in the right direction

Normally I would call an electrician to sort out things like this (I’m an experienced DIYer, happy to change sockets and lights etc but I leave further electrical work to the pros) but obviously it’s not easy to find someone to visit right now! I don't want to leave this uncovered (or back behind a piece of wood!).

1. The thicker one - do I strip this back and connect each wire separately to terminal/junction box along with the thinner wires individually? What box and amp rating do I need?

2. My plan is to paint this cupboard, and shelve it out with brackets installed left and right. It did have a previous shelf in there under the consumer unit, but I will be opening the wall a little to double check what's in there now!

Thanks in advance for advice

 

[terryplumb]

All the cables run into the wall ,what is the other side of the wall ? Can't you follow the cables to establish where they go ? They really need to be traced to where they terminate ,and be stripped out / disconnected .

 

[flameport]

I bought a voltage tester pen

Unreliable and capable of indicating live wires where there are none. Bonus feature - not working when there are live wires present.

The thinner wires are alarm cable, normally used at 12 volts. They won't be connected to 230V AC.
The larger one probably was, and isn't now.

99% that all of those wires were disconnected long ago, and what the pen and the other detector is finding is just capacitive coupling between those wires and others that happen to be run near them.

Why do you have a new Hager consumer unit, with a 30 year old Crabtree effort next to it?

 

[diynotLD]

Why do you have a new Hager consumer unit, with a 30 year old Crabtree effort next to it?

I'm not entirely sure - when I had the new kitchen fitted last year they said the kitchen stuff needed to be on its own circuit and the consumer unit needed to be upgraded, so the old one was taken out and the new Hager one replaced it. One peculiarity of my flat is we have 2 electricity connections or MPANS (had old Economy 7 tariff for storage heaters, and it occasionally causes confusion for energy supplier but it's not unheard of) - perhaps this has something to do with the other unit? I wasn't here to ask questions of the electrician at the time so not sure.

 

[diynotLD]

All the cables run into the wall ,what is the other side of the wall ? Can't you follow the cables to establish where they go ? They really need to be traced to where they terminate ,and be stripped out / disconnected .

That wall where the wires come out is a void under the staircase, at the side of my living room. I was going to open up the wall a little bit to check what's there before I screw any shelf brackets in, but I can't strip out the cabling completely (not confident doing it myself) until I can get an electrician. If I can trace where it comes from it might help though.

 

[diynotLD]

Unreliable and capable of indicating live wires where there are none. Bonus feature - not working when there are live wires present.

Well that's annoying. Product had some pretty good reviews (Screwfix). I did test it on a few known wires before I checked that one. What do you use as a professional for properly reliable checks?

 

[flameport]

This:


however even a cheap £5 multimeter will be far better than any magic wand device.
To measure voltage properly, it's necessary to connect two probes onto the conductors themselves.

Otherwise it could be picking up anything - stray voltages from other nearby cables, EM fields from the consumer unit, Radio 4, the list is endless.

 

[John D v2.0]

The only failsafe check is to have a proper two pole voltage tester and put one end on a known earth eg the metal screw of the consumer unit and the other end on each wire in turn.
A multi meter might do, but can indicate voltage when non is present, bit not usually the other way round.
Those pens are pretty good but can produce confusing results which is not ideal.

 

[delmel]

Alarm / Data / Cat 5 cables were often installed on new builds with the view to try and upsell options either alarm system or door entry some other gadgetry that they thought they may be able to upsell the buyer on which were not necessarily taken. So it may never actually have ever been connected.

 

[yorkspark]

As a test, rub your magic wand on the clothes your wearing and they will 99% of the time light up.

The alarm cables, if not required can simply be chopped off and forgotten about, likewise the same with the twin and earth if you can see the other end and after proving that its dead