volt stick conundrum

[Tim+]

I’m helping out at newly establishing Mensshed. We’ve got and old industrial unit and when we arrived all the lights were working.

Alas, now half of them aren’t working. I’ve been looking for any obvious faults like loose connections in light fittings but they all seem good. A poke around with a volt meter establishes that no power is getting to any of the internal connections of any of the affected lights.

Oddly (or perhaps not) my volt stick is adamant that every wire is live. I just curious how this can be.

The lights are all connected by either one or two 1mm T&E cables apart from one that has three cables, one of which is 2.5mm T&E. Would it be reasonable to assume that this should be the main power supply for these lights?

Next puzzle is that most of the lighting is controlled by switches in the main fuse cupboard, there are no light switches in the “warehouse” part of the unit.

There’s a gang of three switches that work all the office lights and another gang of two switches that have power, but do nothing. We’re pretty certain that these are the switches for the lights that aren’t working.

I’m struggling to get my head around how the switches have power (and do actually work) but there’s no power in the connection blocks in any of the lights. Only one of the lights has three cables but we have two switches which suggest two lighting circuits.

As a short term workaround until such time as we can get an electrician in I was wondering about disconnecting the 2.5 cable (and making it safe) and running a new power supply to that point.

Switching the lights on and off isn’t an issue at the moment as everything is switched off at the main fusebox whenever we leave the building.

Does this sound safe/reasonable/ludicrous?

Tim

[Andy Burns]

voltstick picking up capacitive coupling to other live wires?

is it a digital multimeter or an old-school analogue one (high vs low impedance)

[Tim+]

Analogue meter. I dare say it must be down to capacitative coupling. Just makes me wonder what use is a volt stick? Are they useful for anything?

Tim

[Paul Herber]

The switch is in the neutral wire.

[Andy Burns]

Aren't they more for finding if something is dead?

That said, mine has a button to lower the sensitivity.

[Tim+]

My problem is that I can’t really visualise the wiring. It’s not like domestic wiring where a ceiling rose would have a live circuit but the live (or neutral if done incorrectly) to the lamp then interrupted by a switch as there’s only a three-terminal Live/Neutral/Earth chocolate block type connector in each light fitting and no switch wiring that I can see.

Tim

[Robin]

Is the route of the cable from switch to lights (and if different fusebox to lights) visible? I ask as I'd suspect something done since you arrived - e.g. someone finding (possibly without realising it) there is a switch in the "warehouse" :)

[Tim+]

Alas the wiring is all under floorboards upstairs and I’ve lifted a few boards to try and trace it but I’m a long way from knowing where it all goes. We keep looking for an overlooked switch but there aren’t any.

I’m beginning to think that something may have been buggered up when someone removed an armoured supply cable to a non-existent outside shed. There was a bare cable dangling around in the area behind our unit and probably not unreasonably this wasn’t considered safe. As it’s gone now I can’t see where the internal connection was but I did find a redundant fused connection box today (with no fuse). On removing the front plate there were no wires at all, in or out.

That said, I can’t imagine that the lights would have been on the same circuit as a fairly heavy armoured cable feeding an outside shed.

I’m beginning to think that it must be two long radial circuits from the consumer unit, quite possibly switched on the neutral. There is definitely power at the switches but nowt at any light.

More head scratching and maybe floorboard lifting done.

Dunno if this is relevant but it used to be an electrical factors. Maybe like the cobblers children being the worst shod, an electrical factors wiring is gonna be dodgy. ;-)

Tim

[David]

What brand of Volt stick? I have two, one of which works well and the other detects phantom current.

Cheers

Dave R

[Chris Green]

Simple, the neutral connection has failed! :-)

However volts sticks will light up on capacitive feed between cables so are not very useful for this sort of thing anyway.

[alan_m]

Domestic wiring is changing to bringing permanent live and neutral to the switch and then the fitting only has switched live and neutral, plus earth.

2 plate method

[Tim+]

I think this must be how they’ve done it. With the the switches a long way from the lights and only two light circuits it would be relatively wasteful of wire to run switch loops all the way back to the fuse cupboard.

Tim

[Tim+]

Spent two hours with a qualified sparky today and he couldn’t find the fault! Annoying but at least I don’t feel so bad about not being able to track it down. ;-)

Tim

[Brian Gaff]

Well you would need to start somewhere to find out where its broken, and if your suggestion works, then it has to be in the unit you cannot work out. The question is, why did it fail, is there some hidden circuit breaker or trip you are anaware of?

Often when taking on problems in work done by others, ignore logic completely!

Brian

[Brian Gaff]

Well they do tell you that a live cable is somewhere running closely with your wire I guess. I used to be a bit perplexed when a double insulated bit of hi if with no earth would light those sticks quite often when switched on or off, indeed if there was a satin finish to the case metal, merely running a light finger along you could feel the 50 hz. Brian