Is this a switch in the neutral instead of the live?

[Davisonp]

I had an odd one today.

I was investigating a problem with a light that was not working. As it turns out, it was multiple loose connections causing the problem.

The circuit is wired in old unearthed two core cables making the contact voltage tester a waste of time.

At the light fitting there is a single two core black and red cable appearing and connecting into the ceiling rose, however, a non contact voltage detector indicates that there is constant voltage on the black cable regardless of the switch position. This black cable is connected to the pendent neutral.

The light switch is a double switch and both switches have a two core cable to each switch. The non contact voltage detector does not detect any voltage at the switch unless the light controlled by that switch is turned on and working.

I was surprised that the non contact voltage detector only detects voltage at the switches when the light controlled by that switch is illuminated. The switch controlling a compact florescent lamp does not surprise me too much, but the second switch controls halogen bulbs, so I would expect there to be voltage potential at the light switch even if the switch is in the neutral cable and the switch has the lights off.


I am pretty sure both lights have the switch in the neutral. Can anyone confirm my theory, and why there appears to be no voltage at the switch when the halogen lights are turned off.

 

[Pete999]

Don#t use a Non contact voltage indicator to trace faults or problems.

 

[telectrix]

as pete says, these voltsticks can pick up stray voltages all over the place and cannot be relied on except as a rough guide. test circuits as per taught using approved testers.

 

[hightower]

as pete says, these voltsticks can pick up stray voltages all over the place and cannot be relied on except as a rough guide. test circuits as per taught using approved testers.

Difficult to test using two probe type when all you have is a line and a switch line at the box. Time to invest in a single probe voltage tester?

 

[Rosco]

Rub a Voltstick on your fleece and you could be fault finding for years lol

 

[buzzlightyear]

voltsticks to inducate magnetic force.

 

[Pete999]

voltsticks to inducate magnetic force.

voltsticks to inducate magnetic force.

Inducate WTF is inducate

 

[Dave OCD]

If the switch was connected across neutrals surely you'd have mains potential on one side of the switch when off -an open neutral ?

 

[Davisonp]

Don#t use a Non contact voltage indicator to trace faults or problems.

Initial investigation was with a contact voltage tester, that confirmed there was no voltage whatsoever at the switch, and when testing the ceiling rose, no voltage between live and neutral regardless of the switch position.

My contact voltage tester beeps a warning if you touch anything with live potential, but will only display the voltage when you touch the other prong to an earth or neutral, somewhere creating a potential, and the tester also has a constant tone to indicate continuity. So, no power detected anywhere by the touch voltage tester.

So, on the working light switch, the contact detector gives no voltage or potential between the two cables with the switch in the open position, then the tester reports continuity when the switch is closed and the light is on and power must be running through the switch, so why does the touch tester not beep to tell me there is AC?, unless the continuity test overrides the AC warning in this situation, and yes, the tester is working correctly as confirmed with both the test box I carry and self the internal self testing.

So, I moved to the contactless tester as a tool.

Nothing identified at either switch until the working light turned on then power detected on both the switch cables for that light, but nothing detected on the other switch wires, it was then that one of the leads popped out of the non working light switch and I found all four connectors were loose.

Tightening the switch connectors and the light still did not work.

So, back to the ceiling rose, and the non contact voltage detector could not detect anything in the red cable, but it did indicate voltage on the black cable, regardless of the switch position.

So, why does the contact voltage detector not find voltage in the neutral area of the ceiling rose, It is because the black cable was also loose, and not connecting with the neutral bar of the ceiling rose, but visually appeared to be fine. The non contact tester could detect the voltage.

Reconnecting the black cable and tightening the connections on the ceiling rose, and the light works again.

So, the question is why is there no voltage at the switch? Is my suspicion of a switch in the neutral correct?

 

[Davisonp]

as pete says, these voltsticks can pick up stray voltages all over the place and cannot be relied on except as a rough guide. test circuits as per taught using approved testers.

See answer to pete.

 

[Davisonp]

If the switch was connected across neutrals surely you'd have mains potential on one side of the switch when off -an open neutral ?

That is what I would expect, but the contact voltage tester says there is nothing, and that is what is confusing me.

 

[Davisonp]

I could have wired my megger MFT up to the earth of a socket and used that for a voltage identifier, but with a mum trying to keep three under 10 kids away from me while I investigate I did not want to go back to the van for extra equipment or have extra trailing wires around the house and I wanted to get sorted and safe as quickly as I could.

 

[sparksburnout]

Inducate WTF is inducate

That is what I would expect, but the contact voltage tester says there is nothing, and that is what is confusing me.

If all else fails, you could always chuck this non contact carp in the bin and do some good old dead testing?

 

[westward10]

This really is rudimentary fault finding, assuming there is a fault.

 

[Davisonp]

This really is rudimentary fault finding, assuming there is a fault.

I have found the fault, and am asking if my interpretation is correct.

 

[westward10]

So what was the fault, in a few sentences.

 

[Des 56]

I have found the fault, and am asking if my interpretation is correct.

Sorry Dave I don't want to come over as "holier than thou" but, Have you found this fault?

Reverse polarity is a fault,unless this is definitely proven one way or the other,this potential fault remains

 

[sparksburnout]

I have found the fault, and am asking if my interpretation is correct.

The question is, did you use the procedures you were taught during your training? I can't remember the bit about using a non-contact voltage tester? You should be doing basic dead tests to identify this type of well, basic, fault? It does rather sound a bit chaotic.

 

[buzzlightyear]

with a mum trying to keep three under 10 kids away

never work with dogs or children in house.

 

[PEG]

You cannot make an assessment of what voltages are present,using the method stated,regardless of the number and age of any kids running about.

Please do not take this the wrong way,but a customers arrangements can never,usurp the correct method of either proving or testing. It just creates a potential risk,and can slow down finding any fault.

 

[Davisonp]

Thank you to all who have tried to help. I am not going to justify my actions anymore. I was there and know the circumstances.

If anyone has any experience of the symptoms experienced with switches in neutral cables on lighting circuits that do not have an earth please share your thoughts and experience.

Thank you.

 

[buzzlightyear]

we have all been their. fault finding is hard when you have little tikes running round under you feet .next time you go to a job with kids in the house tell the parent to lock them under the stairs.

 

[davesparks]

Don't start the job if there are children running amok, it makes it dangerous for them and you.
Politely talk to the parents and arrange for the children to be removed whilst you are working.

 

[The Ghost]

From what you say, sounds like it is switched on the neutral. I had a problem, light not working. Used a non touch voltage tester got a voltage, switched on-voltage disappeared! Magic! Thought about it, got my two pole voltage tester which showed <12v. So switch on light and it just soaks up the apparent voltage (cat II fitting) Just saying as to how non contact voltage detectors can confuse, luckily I had an earth to test to. Where are the switch and supply junctioned and terminated under the floorboards I suppose?

 

[Davisonp]

Don't start the job if there are children running amok, it makes it dangerous for them and you.
Politely talk to the parents and arrange for the children to be removed whilst you are working.

Hi Dave,
This is the difference between being onsite assessing the situation moment by moment and trying to describe the situation to others after.
I put my hopup up across a kitchen entrance to create a physical barrier and the initial investigation is to check the bulb and light fitting for any obvious problem. The light fitting is an easy reach for me, but out of reach to the kids, so that gives a chance to assess if the children will say behind the barrier or ignore it without creating any danger to them or me.
Actually, the kids stayed behind the hopup, and by the time I had had eliminated the bulb as the problem and had a look at the fitting, the kids had got bored watching me and went back to the TV.
Mum was around but could not stay with the kids all the time.
Now I have to decide whether to proceed or not, and since the problem is likely to be:
1) Faulty switch
2) Damaged cable in voids
3) Loose connection (most likely).
Since loose connections create heat and there is a fire risk, and the kids have not crossed the barrier and now wandered off, I began investigation.
The kids did not cross the barrier at any time and were never close to me while I was working.
Had the situation been a fault in the living room light, that would have been a completely different matter and required different actions to keep the kids and me safe.

 

[Davisonp]

From what you say, sounds like it is switched on the neutral. I had a problem, light not working. Used a non touch voltage tester got a voltage, switched on-voltage disappeared! Magic! Thought about it, got my two pole voltage tester which showed <12v. So switch on light and it just soaks up the apparent voltage (cat II fitting) Just saying as to how non contact voltage detectors can confuse, luckily I had an earth to test to. Where are the switch and supply junctioned and terminated under the floorboards I suppose?

Yes, it can’t be a switch in the permanent live as there is no permanent live at the switch, so the switch has to be in the neutral.

Also, the GS38 voltage detector indicates the permanent live is not on the red cable in the ceiling rose, so the permanent live for this circuit is down the black cable, so, for this circuit, live and neutral are reversed.

 

[DPG]

But I thought you said you had found the fault? I'm confused.
Daz43

 

[westward10]

Either stare at kids long enough to scare them away or give them an IR test.

 

[Davisonp]

Either stare at kids long enough to scare them away or give them an IR test.

One of the students gave himself an IR test back when I was in training. Someone else had the croc clips and he did not understand what he was meant to be doing, so he decided to hold one end of the wire being tested to the tester lead with one hand, and the other end of the wire to the other tester lead with his other hand and pressed the test button with his elbow. It hurt.

 

[Davisonp]

But I thought you said you had found the fault? I'm confused.
Daz43

The fault I was there to fix was the light not working. That was down to loose connections and is solved.

The fact that some of the lighting have the switch in the neutral cable, and the permanent live to the light I was working on is coming in on the black cable is something to be notified to the landlord for them to address. So, there is an installation fault, but that is going to require further work to address it.

I was confused about readings I was getting during investigation but I am now clear on what is going on.

 

[KennyKen]

Unsleeved Switch line?

 

[KennyKen]

You should have a permanent feed at the switch. Whether it's 2 or 3 plate wiring.

 

[buzzlightyear]

how is down under Kennyken .

 

[KennyKen]

Very warm at the moment

 

[buzzlightyear]

where's about in Oz are you in Kennyken.

 

[KennyKen]

I live on the Gold Coast and work in Darwin

 

[buzzlightyear]

lucky man.

 

[KennyKen]

anyone can do it. Little bit of perseverance.

 

[sparksburnout]

The fault I was there to fix was the light not working. That was down to loose connections and is solved.

The fact that some of the lighting have the switch in the neutral cable, and the permanent live to the light I was working on is coming in on the black cable is something to be notified to the landlord for them to address. So, there is an installation fault, but that is going to require further work to address it.

I was confused about readings I was getting during investigation but I am now clear on what is going on.

So you are going to waltz off leaving the live and neutral reversed then??

 

[DPG]

To be fair he said he's going to report it to the landlord and advise further investigation. He can't force the landlord to have the work done.