Determining if their is a potential difference.

magnoliafan89 · Jun 28, 2018

Hi guys

I asked this question on a recent thread abd was referred to some earlier posted videos but this didnt give me the answer i was looking for.

My question is this. If you have something metallic in a property that isnt plugged in...say for arguement sake a metal pole that came out the wall so was part of the fabric of the building, is there a way of finding out if u were touching say a cooker under fault that was live and also touching this pole if their was any potential difference to get 240 run through you?

People were mentioning insulation resistance and continuity tests but i was wondering what tests you would do and what results you'd be looking for?

Cheers guys

Marvo · Jun 28, 2018

Maybe have a read of this and shout if there's something you're not sure about A guide to the determination of extraneous-conductive-parts - https://www.voltimum.co.uk/articles/guide-determination-extraneous

static zap · Jun 29, 2018

Bear in mind that during any IR tests part could potentially be a hazard ,if part reappears any where else in home ! and others are present.
(and is not grounded )

Deleted member 26818 · Jun 29, 2018

As usual, there are a few different schools of thought regarding this.
In any event the resistance between the extraneous-conductive part and the installation earth has to be measured.
There are two methods to measure resistance, one is to use a low ohm multimeter and the other is to use an Insulation Resistance meter.
The IR meter is usful for higher values.

A measurement of 23 kohms taken between the extraneous part and the MET is generally taken by just about everyone as an indication that the extraneous part is not connected to earth and therefore there is no difference in potential.
Some will say 22 kohms is acceptable as the resistance of the body of an average health person is 1 kohm.
Then again others will say that 7.67 kohms is acceptable as we allow up to 30mA to pass across a human body.

To check whether an extraneous-conductive part is bonded, a measurement of no greater than 0.05 ohms is generally accepted by just about everyone as an indication that the extraneous part is reliably connected to earth and that there would again be no difference in potential.