OT what is that vibrating sensation you get when you lightly touch the metal on a mains appliance?

[me]

In message , Lobster writes

Maybe it only affects people called David?

[me]

In message , MBQ writes

See other response - I will check out the wiring and then the actual earth-status of the (Ikea :) lamp asaic.

It appears to be lacquered metal.

nowt.

well, I did suggest that's what I kinda thought it must be

[me]

And when I wrote 'lightly touch' I referring to touch with my forearms, which are quite hairy and thus sensitive to something like that?

I see. :)

[Dave]

...snipped

As others have, said it's leakage current; what you're feeling is mild nerve stimulation as you form a path to earth. The cause is almost certainly capacitive coupling to an ungrounded conductor. If the equipment is double insulated it's absolutely normal to get this effect, if it's not double insulated (i.e. it's supposed to have a ground wire) then check the earthing and treat it with care.

Dave S

[Ian Stirling]

New meters (digital) are only around a fiver, but if not abused, it should be fine.

If it's two appliances, it's less likely to be a fault with the appliance. As a basic check, take the plug out, and measure on a low-ohms range the resistance between the earth pin (the long one) and the metal of the appliance. It should measure under an ohm or two.

If this is so, then it's likely that the appliance is not at fault.

[Pete C]

Hi,

Sound like the appliance needs an insulation test, to check there is no leakage to earth and that the earth is connected (AFIAK).

If this passes then it could be an earthing fault with the supply.

cheers, Pete,

[Lobster]

Several people have suggested something along the above lines - assuming the appliance checks out OK, then what tests should be carried out to check house earthing in general and/or isolate any fault?

Thanks David (who has the same problem has the OP - see other post)

[Dave Plowman]

The correct way is with a purpose made meter. It dumps a large voltage pulse to earth and measures the resistance by checking what current flows in that split second. But they're expensive, so not really worth it for a DIY toolbox. So most would get an electrician in to do it for them.

[Lurch]

On 19 May 2004 23:55:54 -0700, in uk.d-i-y [e-mail] (Lobster) strung together this:

Basically, a full periodic installation test. Then you'll have all earth paths, external and internal, tested and verified. You could just check the Ze, the Zs on the affected circuit and the R1\R2 and an insulation test. I'd have a full test though, for what they cost.

[Pete C]

First it would be worth checking if their is a connection between the metal case of the appliance and the earth pin on the plug, this can be done with a continuity test on a cheap DMM.

If that's OK, check the connection between the earth on the socket and the earth on another socket and a metal water pipe that goes down to ground level.

A full insulation test is not really a DIY job unless you have the right equipment, but insulation failure is pretty rare AFAIK.

cheers, Pete.

[Richard Savage]

Is it a slightly 'furry' feeling that you can just detect with finger tips? All my HiFi - which is connected to the mains via two core cable, i.e. no earth - exhibits this characteristic, and has done in three different houses and one Hall of Residence. Having said that, there is an intrigingly large voltage difference between the screen of my UHF aerial and the case of my tuner, i.e. finger detectible!

[N. Thornton]

Re a little ac on all your earthed bits:

Have come across buildings like this. The mains earth isnt always at earth potential. On a ground-rod earthed system, persistent leakage can set up an ac potential on the earth wiring. If there is no RCD, as is the case with a lot of such installs, particularly older ones, generally nothing will trip, and you may notice that earth isnt quite earth. There are plenty of installs like this around. Most are protected by v-ELCBs, which will not trip on these kind of minor faults.

Is it dangerous? No, although it has to be a risk factor to more than a zero extent, since it indicates there is leakage to earth somewhere, plus less than perfect earthing, plus no RCD. Nonetheless the risk factor would normally be very small.

OTOH it could be something more problematic, which might indicate a greater risk. We cant know from here.

You could work out what your installation setup is by looking at the CU and asking, maybe you could locate leaky appliances with a very simple homemade tester, applying mains live to appliance L and N, earthing E, and a meter in the live to measure i flow. However you should only use mains voltage appliance tests if youre competent to do so safely: one must appreciate and manage the risks.

Some qs to get you started: Do you have wire fuses or switchable trips? Do you live in town or country? Do you know when the house was last rewired? Do you know if you ahve an earth rod?

It might be necessary to take matters further, though usually not. Calling an electrician for a whole house install and appliance test seems rushing it to me, but for all we know it could possibly be very necessary. Only you can decide which course of action to take.

Regards, NT

[me]

In message , Dave writes

Ok, that's the explanation then - thanks all.

[me]

In message , Ian Stirling writes

It works fine - except that the high Ohms range doesn't work any more since the 15V battery it requires is no longer available. I still find it more satisfying to see a swinging needle rather just an LCD readout. :)

[me]

In message , Pete C writes

Except that as Richard S wrote, I have experienced this in numerous homes (and also including a HoR where I guess the wiring was checked annually by a pro).

[me]

In message , N. Thornton writes

trips here

town

hmmm, 50's ?

don't have

[N. Thornton]

In that case something may be wrong. You shouldnt get this on a town no earth rod install.

Regards, NT

[N. Thornton]

Now the OP has told us its a 1950s install, with MCBs (retrofitted??). If it really is 50s it will inevitably fail on a wide range of counts.

Regards, NT

[Dave Plowman]

Check out Ebay for a spare battery. What type is it?

Trouble is most measurements given these days assume a high impedance meter, so you might have a problem there.

DVMs are now available with a bar graph extra readout which gives some semblance of a swinging needle.

[Lurch]

On 23 May 2004 02:45:47 -0700, [e-mail] (N. Thornton) strung together this:

Yes, I've just noticed that. I can see it either being a PITA to find the actual fault that's causing this problem, in a sort the wheat from the chaff stylee. Either that or just go straight for a rewire! Either way, I'm glad he doesn't live near me!