Metal steps secured to concrete (bonding)

[newfutile]

We have had 2 metal steps installed to cover main supply cables (out to flats) from a Ryefield .
when measured IR from MET to steps i got 0.091 MegOhms.

The usual calculations are for when a 30 ma RCD is protecting (which is not the case here)

91 Kohm is above the usual value of 23 Kohm I usually use (10ma).

Should these be bonded to earth?

 

[Aaron b]

I wouldn't earth it. As you say using the equations the maximum current that flows through the body is < than 10mA.

Using the formula from GN8:


rearranged to:


I get 2.5mA when taking ZT as 1000ohms as suggested in the guidance.

Are there any other earthed parts within touching distance? GN 8 states "Consequently, for a conductive part to be able to introduce a potential to a person (or livestock) in contact with the potential of any of the conductive parts, that part should be accessible to such a person (or livestock)." I assume this would also apply to your situation.

(I am referencing the 17th ed amd 2 of guidance note 8)

 

[newfutile]

Yes there is a metal ryefield on the PME earth and a 3 phase DB easily touchable