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Testing if supplementary bonding is required.

MrJack96
I have read some bits stating we can measure between the two metallic parts in question and referring to the formula 


50/ia will give you the resistance needed to keep touch voltage to less than 50v 


my questions can we do the same test to determine if the part has a high enough resistance to not require bonding and what sort of figures we should look for?
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    Well, we are not theoretical physicists, so some tolerance is allowed. Even then, it's relative potential rather than absolute. +/- 25 V?

    It's a bit more than a minor tolerance - with a TN system, low Ze and reduced c.p.c.s you can easily get a p.d. of half mains voltage even within the equipotential zone - and the effect of main bonding is at best "undefined" as there are no actual requirements to achieve (just c.s.a. for the bonding conductors - the length is uncontrolled and thus so is their impedance). It's all really a matter of best efforts than anything guaranteed.

       - Andy.
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  • 0
    Well, we are not theoretical physicists, so some tolerance is allowed. Even then, it's relative potential rather than absolute. +/- 25 V?

    It's a bit more than a minor tolerance - with a TN system, low Ze and reduced c.p.c.s you can easily get a p.d. of half mains voltage even within the equipotential zone - and the effect of main bonding is at best "undefined" as there are no actual requirements to achieve (just c.s.a. for the bonding conductors - the length is uncontrolled and thus so is their impedance). It's all really a matter of best efforts than anything guaranteed.

       - Andy.
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