Very High PSC

[Greyprof]

I have just been wiring a new conservatory and when I checked the Ze it came out as 0.02 ohms and the psc as 7.2kA. The existing MCB's are only rated as 6kA so I assume that they need changing to 10kA. A new MCB which feeds a small additional CU is already rated as 10kA so I assume that the MCB's in the additional CU will need to be rated at 10kA as well. What about the main switch in main CU and RCDs are they rated as well (nothing written on Eaton main switch, but 6000 written on RCD). hELP!!

 

[peteludman]

good question made me think but you are testing the main isolator what is the psc of that ?

 

[Greyprof]

good question made me think but you are testing the main isolator what is the psc of that ?

This was the main isolator.

 

[peteludman]

not 6kva for main isolator

 

[Greyprof]

not 6kva for main isolator

Do you mean the main isolator needs to be 10kA or do you mean it will not be 6kA anyway? Thanks by the way for the interest.

 

[andyb]

If the board is to bs 5486-13 or bs en 60439-3 and supplied through a fuse to bs 1361 or bs 88 at no more than 100 amps, then you are ok up to fault currents up to 16ka with your mcb rated at 6k. (provided they are the correct mcb for thet board)