After some advice: Mild tingle from shower when in use

[TheGovernor]

Having watched your video, if wonder if there used to be a pumped shower there. It may have been supplied by the lighting circuit and when removed the cable was left in the wall.mnow when you wet the wall the plasterboard is getting damp and causing a high resistance path to the live cable in the wall. If you go in the loft can you see any cables dropping down the wall above the shower location?

Sorry flyingsparks, almost missed your question.

I am 99% certain there wasn't a pump there, we've had the house for 14 years, the previous owners had it form new for about two and a half. There's no evidence anywhere in the loft (or anywhere else) of anything being installed, no orphaned screws or junction boxes in odd places etc.

Plus, all of the other showers are exactly the same type and install...

 

[bernardgreen]

Can you measure the voltage between the "pip work and a genuine ground reference from a short metal rod pushed into wet ground outside the house ?

When doing this be extremely careful and consider the possibility that the voltage difference could be 230 volts if there is a polarity reversal on the incoming supply cable. It is ( should be ) very un-likely that the supply polarity is reversed but it has to allowed for when considering your safety.

Using a short rod will limit any current should there be a large voltage difference and the lead from the reference rod comes in contact with pipe work.

 

[JohnW2]

I was holding it in a pair of 1000V insulated grips; can it go through them?

I presume you're talking about metal grips with insulation over the metal. In that case, the answer might well be 'yes' (with capacitive coupling through the {thin} insulation to your hand)

I note the article said if you rest the detector on a pile of books while 'touching' a live wire it does not light.

Does that not 'prove' my point - that these devices rely on capacitive coupling to earth through something like a human body?

Kind Regards, John

 

[JohnW2]

Referring back to last night when I was showing you all reading of 1.9v between the waste and the shower assembly, I took readings today after a shower and the voltage was 5.9v. ... After about 5 minutes the voltage dropped to 4.5v. ... I then got my (now groaning) wife to switch off the upstairs light circuit at the CU and the voltage dropped to about 1.3v immediately. ... Got her to put it back on, straight back to 4.5v.

Measurements with modern multimeters can be just as problematic as the issues of voltage detection devices we have been discussing, since the high impedance of these meters allows them to 'measure' what are simply 'induced voltages' picked up in one cable (or bit of metal) from another.. Although these induced voltages are 'real', their nature is such that that they are capable of resulting in virtually no current - hence no danger and, often, can't be even felt. If that's the case, then connecting some load (like an ordinary light bulb, or a medium-value resistor if you have one) between the probes of your multimeter would be expected to make these small measured voltages 'disappear'.

Kind Regards, John

 

[Jackrae]

On a positive vein, getting your kids involved in an engineering investigation problem is great and hopefully entices them into a future career.

 

[EFLImpudence]

I was holding it in a pair of 1000V insulated grips; can it go through them?

I presume you're talking about metal grips with insulation over the metal. In that case, the answer might well be 'yes' (with capacitive coupling through the {thin} insulation to your hand)

Well, proper VDE insulation, not just a plastic cover.

I note the article said if you rest the detector on a pile of books while 'touching' a live wire it does not light.

Does that not 'prove' my point - that these devices rely on capacitive coupling to earth through something like a human body?

Yes.
So, does that mean a person just has to be nearby (how near?) and not actually touching the pen?



Back to problem.

I am getting confused.
If, as above, the voltages are <5V and may only be induced why is the detector lighting?
The one I have states 50 - 1000Vac and Fluke's is 200 - 1000Vac.

 

[JohnW2]

I presume you're talking about metal grips with insulation over the metal. In that case, the answer might well be 'yes' (with capacitive coupling through the {thin} insulation to your hand)

Well, proper VDE insulation, not just a plastic cover.

Sure, but with a whole pile of metal inside. Had you held the device with some sort of plastic tool, the resuly may well have been different.

]Does that not 'prove' my point - that these devices rely on capacitive coupling to earth through something like a human body?

Yes. So, does that mean a person just has to be nearby (how near?) and not actually touching the pen?

It presumably means that they have to be 'near enough' for there to be an adequate capacitive coupling to their body - it sounds as if through the thickness of VDE insulation is enough.

Back to problem. ... I am getting confused. ... If, as above, the voltages are <5V and may only be induced why is the detector lighting? ... The one I have states 50 - 1000Vac and Fluke's is 200 - 1000Vac.

Aren't we quite probably back to these 'measurement issues' again? If we are talking about induced voltages, they might be >50V (or whatever) 'when left alone' (e.g. when detected by a non-contact device) but, when measured by a multimeter, although the meter's impedance will be high, it may well be low enough to drop the voltage right down to the small figures (<6V) that the multimeter has been displaying. ... but, as with everything in this saga, who knows?!

Kind Regards, John

 

[Jackrae]

For what it's worth :-

I occasionally do derusting of steel components by electrolysis, whereby a bucket of mild washing soda solution and a 12 volt DC supply are used to remove rust from steel components. With uncut skin lifting parts out of the solution, using bare hands, causes no sensation; but if the skin has any form of cut in it, the current flowing through the fluid causes quite an exciting tingle - and that's without me touching any of the the circuit electrodes.

viz :electrically safe but low voltages/currents can cause quite a sensation if the skin is punctured.

 

[ban-all-sheds]

Have you tried cut hands in the liquid when no electricity is present?

 

[Jackrae]

Yep
totally different sensation

 

[JohnW2]

For what it's worth :- 12 volt DC supply ...With uncut skin lifting parts out of the solution, using bare hands, causes no sensation; but if the skin has any form of cut in it, the current flowing through the fluid causes quite an exciting tingle. ...

Indeed - as I said, exposed bodily tissues are very sensitive to electricity, particularly when wet (skin is a pretty good protector) - it only takes 50mV or so to activate a nerve cell or fibre. If you applied 12V via a couple of electrodes on your tongue, you'd probably experience more than just a 'tingle'!

Kind Regards, John

 

[TheGovernor]

Can you measure the voltage between the "pip work and a genuine ground reference from a short metal rod pushed into wet ground outside the house ?

When doing this be extremely careful and consider the possibility that the voltage difference could be 230 volts if there is a polarity reversal on the incoming supply cable. It is ( should be ) very un-likely that the supply polarity is reversed but it has to allowed for when considering your safety.

Using a short rod will limit any current should there be a large voltage difference and the lead from the reference rod comes in contact with pipe work.

I will have a think about how I do that bernardgreen, are you thinking that I measure between a radiator and true ground?

I'll go and see if I can find a short metal rod and dig my willies out too

 

[JohnW2]

... and dig my willies out too

Some typos are more of an issue than others

Kind Regards, John

 

[ban-all-sheds]

I told you not to try that, and my advice still holds.

Even if you do have more than 1.

 

[TheGovernor]

I told you not to try that, and my advice still holds.

Even if you do have more than 1.

Do you mean don't do the pipework to true earth test ban-all-sheds?