Its a metal (stainless steel) casing with a mirror door, has a canopy
over the door with 2 low voltage downlighters recessed into it. The
lights are operated via a rocker switch at the top rh side covered in
a rubber membrane. The whole thing is shiny mirror like metal finish
inside and out. I have an isolator switch mounted on the wall in the
room behind it. It's above a wash hand basin in my downstairs shower
room- where I shave.
With the door open, as I put my hand in to get my shaving foam, I get
a small electrical shock, on the back of my arm, just below my elbow,
where it touches the corner of the open door! It's a constant 'buzz' -
not painful, but uncomfortable and obviously worrying!
How can I go about finding the fault? It happens when the isolator
switch is on or off! I'm wondering if the unit is faulty or has a
fixing nicked a cable in the wall? It's been up for a couple of Years
and only when the missus mentioned getting the same shock have I
thought I'd better get it resolved :)
I'll leave the electricians in the group to answer your query - but on the
issue of the 'buzz'... When my wife's iPod is on charge (using a non-Apple
compatible charger), if you pick it up and run your finger lightly over the
metal surface, there is also this 'buzz' sensation. I wouldn't describe it
as an electric shock - just a very very mild 'tingling' sensation.
As the output of the charger is low, I am assuming that there is no danger
Yep... 'A mild tingling sensation' also is a
better way of describing what I'm getting.
Btw: using google groups on my iPhone is very
Frustrating- is there an app available that would
make using this ng any easier?
We don't know what's causing the problem, but there is a chance it could be
something that could fail into becoming extremely dangerous.
Risk assessment mental exercise:
1) Dangerous condition not proven but suspected: outcome potentially
2) Inconvenience of isolating suspect circuit - sod all.
Makes it a no brainer - turn it off and check it out.
Most unlikely to have anything to do with Usenet. The term 'NewsReader'
is mostly associated with RSS these days.
NewsTap (Usenet Newsreader) is in the iTunes App Store.
In iTunes - Beware,
"You must be at least 17 years old to download this application"
* Infrequent/Mild Sexual Content or Nudity
* Infrequent/Mild Cartoon or Fantasy Violence
* Infrequent/Mild Simulated Gambling
* Infrequent/Mild Profanity or Crude Humour
* Infrequent/Mild Horror/Fear Themes
* Frequent/Intense Mature/Suggestive Themes
* Infrequent/Mild Alcohol, Tobacco, Drug Use or References to these"
Must be good then....
On the newsgroup front: the google app now has some integration with the Safari app on an iPhone but it's a bit clunky AFAICT: if you go to the normal group web page in Safari and find the thread your interested in, there is a link in the right sidebar that says 'try the new google groups experience' this reconfigures the display to suit mobile viewing and is much better with the posts laid out in tabs one atop the other. It could do with a link to your star marked threads though, so one can easily navigate to a current/favourite thread!
Try it and see what you think.
These 'tingles' are usually the result of capacitive leakage between the
mains and the case of a Class 2 ('double insulated') appliance. The
relevant safety standards usually allow up to to 0.5 mA leakage at 50 Hz
(more at higher frequencies). It's completely harmless [*] but can be
annoying and/or worrying. (The 'return' path for the current is via the
body's natural capacitance to earth, typically a few hundred
picofarads.) It's becoming more common with the move away from
iron-cored transformers to switch-mode circuits in wall-wart PSUs - a
consequence of the WEEE and EuP directives.
With a high impedance voltmeter (any DMM these days) you'll typically
measure 100 volts or more between the case and earth. The source
impedance of these errant volts is very high though, and just touching
the case will lower the touch voltage considerably. Temporarily earth
the case via (say) a 10k ohm resistor and measure the voltage across the
resistor if you want to get an idea of the available touch current.
Unless there is a fault, no.
[*] One case to be aware of is where several items of Class 2 AV
equipment are interconnected by the signal wiring. Here the available
leakage touch current will add up and can reach dangerous levels (>3.5
mA is considered dangerous, >10-15 mA can be lethal). Earthing the
system (either directly or via a resistor) is advised in such cases.
I've experienced similar 'tingles' with a couple of modern appliances at customers homes during my work and have always wondered what's behind the cause. It seems that construction of the appliances would explain the occurrence in most cases from what I have read posted here, but the potential for it to be lethal is of concern, especially to those with no knowledge of how these things work! I'm going to isolate the whole circuit and see if the buzz persists and will report back with further findings. My belief is that it's harmless but I am going to check all the wiring to see if it's sound. I put the unit up myself and the stud wall it's on including first fix cabling, so I'm sure it's not cable damage. I can bring in a friend to check for leakages but would also like to know how I can remove the buzz using bonding if the fault is capacitor leakage.
Thanks to all for the great and useful info.
It was the comment that "It happens when the isolator switch is on or off!"
in your first post that would suggest that it is not harmless!
Hopefully you will not be using your arm to conduct further tests.
Now it doesn't occur with the fused spur 'off'!
Could it be residual static that gave this result before? Also, I only ever felt
this buzz on the back of my arm where I have more hairs! With no other part of
my arm, hand, fingers or Tongue :)
Have you got a DVM? If so, set it to 240v AC and measure between the
cabinet metal and a nearby tap - assuming it is connected with copper
pipe. Or a mains earth from somewhere if not.
DVMs have a very high input impedance and should show anything you feel.
You could even try holding one lead while probing the cabinet case with
*Failure is not an option. It's bundled with your software.
Dave Plowman firstname.lastname@example.org London SW
Right... I have my Rapitest MAS830L
Can I use that? Not sure about all of the settings on it as I only use the
audible buzzer on
it for continuity :)
I have been looking for a manual / user guide for it!
Ok. Had some time to really think about this now.
Narrowed it down to the tingling caused when touching cabinet and tap, or with
bare feet on the tiled floor, it doesn't happen with shoes on, just touching the
So, I have set my DMM to 200VAC and probed the cabinet door and the mixer tap
result gives varied readings, starting as high as 10.4 and dropping always to
00.1VAC (is this dissipating through merely touching/probing?)
I also probed from the cabinet to a nearby towel rail...
and get similar results
And between the cabinet and a fly lead connected to the earth block in the
The reading seem to be all over the place on all these test points, but always
quickly drop to 00.1
I also get readings by moding over to 2VDC
What can I deduce from these figures?
I'm no expert when it come to mains wiring but heres my interpretation
Tiled floor (assuming glazed ceramic) would be a good insulator and no
route to earth, so attempting readings between floor and anything else
wouldn't be meaningfull
readings on the 2VDC would also be fairly meaningless , try holding on
to the probes, you'll prob see a similar readings. Your body will be
acting as an aerial of picking up electrical noise, the digital meters
are very sensitive
If the readings drop off quickly that would suggest to me some kind of
filtering capacitor which you are discharging. possibly an input
capacitor on the transformer
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