Hi everyone
Recently I have come across an advert of someone selling Afdds C type and the person mentioned the need to sell because Zs was too high so he was considering changing the circuit breaker back to B type as it allows enough Zs to meet the regulations.
As Afdds is also combination of Rcds so Zs would be 1667 ohms which someone mentioned to which he replied for earth fault loop yes but for L-N loop doesnt meet regulations hence the replacement.
Furthermore he says for L-N doesnt meet reg for short circuit thats why we do PSCC. If TNC-S arrangement then because of Neutral and earth are connected so we do not need to do PSCC and Prospect earth fault current would be same as short circuit.
As I am also in a learning stage so always mess up some concepts when I come across these questions so some questions emerged in my mind which if someone could answer and correct me if I am wrong .
My understanding was we carry out Ipf at origin to check if there is enough fault current generated if Supply side L-E comes in contact to disconnect Main cutout fuse or Circuit breakers hence we also consider short circuit capacity of MCBS.
By checking PSCC at origin we ensure that if L-N at supply side comes in contact it would disconnect main cutout fuse or MCBS.
on the load side afcourse as fault current depends upon the MCBs such as 32type B MCB would have minimum of 160A of fault current hence 230/160*0.95 would make 1.37 ohms resistance max to meet disconnection times.
Since the person mentioned he checked PSCC and it did not meet Zs so he is considering it back to type B, does he mean that, he carried out PSCC at supply side or towards load side on final circuits?
As on load side we usually carry out Zs to ensure it meets reg and since the Afdds contains RCD so it would meet regs.
Do you guys carry out PSCC on final circuits to see it circuit breakers would trip if short circuit were to happen like he did ? as my understanding was to only check Zs to meet regs and he said Zs was ok but PSCC was not met.
Straight after the post he took it off and I could not question him but the question is bugging me .
Recently I have come across an advert of someone selling Afdds C type and the person mentioned the need to sell because Zs was too high so he was considering changing the circuit breaker back to B type as it allows enough Zs to meet the regulations.
As Afdds is also combination of Rcds so Zs would be 1667 ohms which someone mentioned to which he replied for earth fault loop yes but for L-N loop doesnt meet regulations hence the replacement.
Furthermore he says for L-N doesnt meet reg for short circuit thats why we do PSCC. If TNC-S arrangement then because of Neutral and earth are connected so we do not need to do PSCC and Prospect earth fault current would be same as short circuit.
As I am also in a learning stage so always mess up some concepts when I come across these questions so some questions emerged in my mind which if someone could answer and correct me if I am wrong .
My understanding was we carry out Ipf at origin to check if there is enough fault current generated if Supply side L-E comes in contact to disconnect Main cutout fuse or Circuit breakers hence we also consider short circuit capacity of MCBS.
By checking PSCC at origin we ensure that if L-N at supply side comes in contact it would disconnect main cutout fuse or MCBS.
on the load side afcourse as fault current depends upon the MCBs such as 32type B MCB would have minimum of 160A of fault current hence 230/160*0.95 would make 1.37 ohms resistance max to meet disconnection times.
Since the person mentioned he checked PSCC and it did not meet Zs so he is considering it back to type B, does he mean that, he carried out PSCC at supply side or towards load side on final circuits?
As on load side we usually carry out Zs to ensure it meets reg and since the Afdds contains RCD so it would meet regs.
Do you guys carry out PSCC on final circuits to see it circuit breakers would trip if short circuit were to happen like he did ? as my understanding was to only check Zs to meet regs and he said Zs was ok but PSCC was not met.
Straight after the post he took it off and I could not question him but the question is bugging me .
