OP
hightower
Why should they be different though?They are for earthing not bonding.
Discuss Bit quick advice please in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net
Why should they be different though?They are for earthing not bonding.
Because for a cpc the Adiabatic equation can also be used.Thanks but why are they different. Why is a steel to copper equivalency that's good for a CPC not good enough for bonding?
544.1.1 and the * under table 54.8 both say about the bonding conductor being copper or a cross-sectional area affording equivilant conductance in other metals. GN8 has a section on it but I don't have it around me ATM. Probably to do with limiting touch voltages under fault conditions etc.Why should they be different though?
Man did I struggle with this one ... The SWA table gives k numbers suitable for use in the adiabatic equation. I haven't got it open, but I recall the factor is about 2.2. For bonding it's about voltage rise so it's the resistivity that's important and as LSK has said the factor is about 8.5. So armour is normally ok for CPC but rarely enough for bonding.Why should they be different though?
So what are the copper equivalent columns in that link referring to then? Reason we've used 4-core is because it's what the factory owner had lying around and he's on a cost saving exercise. Will have to have a look at pulling in a separate conductor.
Reply to Bit quick advice please in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net
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