(Low) Voltage remains when circuit switched OFF!

[NoddingDonkey]

HI,
(excuse the layman's explanation - I suspect someone will point out my big error before too long!)
Measured at the hallway ceiling rose;
Phase to earth = 231v
Phase to neutral = 231v
(and to check closer, neutral to earth = 0.14v)

The switched line is 231v when the hall light is selected ON, but sticks at 27volts when selected OFF. This 27v is fairly consistent too. Other lights (measured from bulb sockets only) had up to 45v yesterday, but some were found to be zero today. Nothing I can think of had changed overnight. I could understand fluctations and variations but not steady readings changing overnight to steady zero.
Mathew

 

[pdcelec]

since it changed overnight (more likely that it happened when you switched the landing light off upstairs when you went to bed). This sounds like a fault on the strappers or maybe even that the landing light live is fed from the downstairs circuit and the neutral is fed from the upstairs circuit. Could you confirm this?

 

[NoddingDonkey]

Er, I can confirm I don't have a landing - it's a bungalow , so only one loop for the lighting, though I have fed the spotlights off from it. 'Strappers' isn't a term I have come across before, so unfortunately I don't follow that bit, though I can see what you mean about switches having been switched as I moved about last night.
Pardon my lack of knowledge here, are you thinking that I may have one of the spotlight spurs 'back-to-front' or mis-wired?
Thanks in advance,
Mathew

 

[Spark123]

I'm thinking it is just capacitive coupling, what voltage do you get with a filament lamp installed?
Strappers are the connecting wires between light switches.

 

[Big_Spark]

ND said that everything was switched off. That means there's no current. If there's no current, there's no induced voltage. I.e. inductance cannot cause the observed voltage.

It's caused by capacitance.

This is fundamental electricity theory and I would have thought that any electrician would have appreciated the distinction between inductance and capacitance.

Stoday, he did not say the ****ing electricity was turned off..just the light switch. As such inductance due to damaged insulation can and does happen...as such an Insulation test should be done in order ot rule this out..

 

[Big_Spark]

Noddingdonkey..Great name by the way...how old is the wiring in your bungalow?

Can you tell if the cable is PVC or something else? What type of light switches do you have, how old are they and your cieling roses?

 

[Stoday]

Stoday, he did not say the **** electricity was turned off..just the light switch. As such inductance due to damaged insulation can and does happen...as such an Insulation test should be done in order ot rule this out..

ND said, in his first post, "I have checked this with ALL other circuits OFF at the main box and the problem is the same, ".

BS - if you don't read what someone writes, it's unreasonable to expect anyone to regard your advice as other than nonsense.

 

[Big_Spark]

Stoday..your misreading the post..he said "All OTHER circuits"...but the lighting circuit was on..

So to quote you fella..

if you don't read what someone writes, it's unreasonable to expect anyone to regard your advice as other than nonsense.

 

[Stoday]

When lights are switched OFF, the positive line shows a consistent, but different voltage for each room...
...I have checked this with ALL other circuits OFF at the main box and the problem is the same,

This is like banging your head against a brick wall.

 

[DDoyle]

Stoday, I think it's that we are reading this differently, and perhaps we need NoddingDonkey to clarify it..

Yes he is saying the lights are OFF..but then he says that.

I have checked this with ALL other circuits OFF at the main box and the problem is the same,

Now perhaps I have read this as he means the light switches are off and the POWER is off to the other circuits..or perhaps he actually means what you take it to mean which is ALL POWER OFFF.

To be honest if he is getting voltage readings when there is no power to the property then he is in a unique situation, I have certainly never heard of this in the past as what is left to "create" this potential difference, whether it is capacitive inductance or simple run of the mill inductance..you need something there to create the process..Do you see my point?

The reason I asked when his Bungalow was last rewired and the age of the accessories is that this type of problem is reasonably common in installations that are wired in VIR and with older accessories.

Perhaps NoddingDonkey can reply and clarify if the SWITCHES were off or it was the POWER which was OFF to the Lighting Circuit as well as the others so that you and I can stop going around in circles over it..

 

[NoddingDonkey]

Hi,
Powering EVERYTHING OFF at the main box, = all voltages ZERO ( )
Lighting circuit OFF at box, everything else ON = all (light) voltages ZERO ( )
Lighting circuit ON at main box, everything else OFF = problem voltages ( )
As mentioned earlier, when the lights are switched ON, the voltages are always as should be (234ish), but when switched OFF, some room light sockets have voltages up to about 45v. Steady, as in not fluctuating, but not consistent though, as the lounge DID have a problem (48hrs ago) but now does not, likewise the kitchen. Need to check now with bulbs in place as suggested. Get back to you later.

Having checked the basics as above, it looks like influence from non-lighting circuits can be eliminated. My apologies for lack of clarity in earlier posts.

 

[pdcelec]

INSULATION RESISTANCE TEST IS STILL REQUIRED

 

[NoddingDonkey]

Point duly noted about the insulation test.
A hint of progress;
Prompted by Spark123's comments, I have found that the cause of the voltages 'changing' from one day to the next is BULBS (or lack of). The ones that measured upto 45v one day and nothing the next was because they were all multi-bulb fitments, and it appears I measured with NO bulbs in each room on day one, but with one bulb in place of the pair/trio since. Trying again just now has proven that without bulbs, there is a voltage when switched OFF, but with bulbs IN, the voltage is ZERO when switched off.

I can now report that there is a residual voltage in the light sockets in each room with the relevant light 'switched off', but NOT if there is a bulb in place in that room. If this is the capacitve aspect(?), I figure (as a layman), that as the problem is coming from within the lighting circuit only, it may be caused by the only two 'objects' in the lighting loop that are not plain filaments (there are no compacts/flourescents etc). These being the transformer for the kitchen LV spots and the LV light/fan combination in the bathroom. How is my logic on this?

 

[Qedelec]

Sounds to me like the filament bulbs are 'grounding' the voltage, whereas the transformers (which are using semiconductors), don't.

I suspect the prodlem is induced voltages.

Insulation tests will not reveal this but are a good idea.

1. try to map out the sequence of the lights.
2. halve the circuit and separate the feed fom the remain part of the circuit.
3. keep halving till you discover what part of the circuit is causing your symptoms.

I'm inclined to suspect the problem will be a wrongly connected additional accessory

 

[NoddingDonkey]

Afternoon folks,
Well, after disconnecting the fan/light in the bathroom (no joy) and then the transformer for the LV spots in the kitchen (no joy either), then changed a couple of switches that were the only non-new ones in the place, it appears the problem is solved.

It was the ******* multimeter!!

My pal came over and pondered things and was as baffled as myself, with only induced voltage from the switch cabling his last thoughts. And then, as I checked the voltage in one room, he checked another with his meter, and lo, no problem voltage. Same with EVERY light socket. No volts, no current available when switched off, NONE. (I had been using the meter correctly, by the way ). Not even gonna contemplate HOW the meter is doing this, as there doesn't seem to be a problem to worry about now (it wasn't the battery, as that was changed mid-problem). It does seem weird that the indications were so 'steady', ieven though puzzling.

So, unless someone informs me otherwise, it just remains for me to say a big thank you to everyone who offered their thoughts, opinions and time. I might add this seems to be a very 'lively' forum. Wonder if the plumbing forum is a bit 'soggy' by comparison?
Cheers Gents,
Mathew