K
knasher
The boards i tested were none RCD protected, with 60A sub main protective device. Is the easiest way to solve the problem to install a main RCD incomer, eg 63A, 30mA at each DB? any advise?
Discuss Zs too high at distribution boards in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net
its TN-C-S supply
sorry just picked up all other responses to my query. Ze at origin is 0.08,(should be 0.35 shouldnt it for TN-C-S?
Not certain if the Ze of 0.08 is the measured value, or reference to the given value of 0.8 for TN-S systems?
I wasn't thinking about the sinks, more along the lines of crittle windows.I want to know the reason for the high Zs before he starts stringing green/yellow to the nearest sink!
Found a bit more info from PIR guys and it includes: absence of supplementary bonding in places (been given code 1, which seems a bit bit extreme - wouldn't it be code 2?). Also, mentions poor connections on some ring final circuit patresses in certain offices. Another point mentioned is main bonding being terminated at sub distribution boards and not MET. All of these things could affect Zs couldn't they? Excuse my ignorance.
One final question for IQ electrical, can you tell me how you got your Zs figures - i've looked in GN3, OS guide and BS7671, applied rule of thumb etc but am none the wiser. Can you enlighten me. Cheers again everyone!
If you let me know the distribution circuit cable details (CSA, approximate length, is the swa alone being used as the cpc) then I can calculate the R1+R2 and we can then see if there is a fault.
The R1+R2 added to your Ze of 0.08 Ohms will give us a worst case scenario, with actual parallel paths, your measured Zs should be lower than my calculated figure.
Reply to Zs too high at distribution boards in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net
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