I'm looking at fitting a commercial garage out.
I plan to put a 4 pole 300MA S TYPE rcd as main switch on a 12 way 3 phase board providing I can get the Ra down low enough, should be fine though, otherwise it'll be a 100ma s type. Socket circuits and maybe lighting circuits will go on 30ma DP RCBO. There are a few circuits that don't need to be 30ma additionally protected. These circuits will have fault protection by the 300ma s type. And the ones on the 30ma will be fault protected with the 30ma rcbos. The final circuits that are non rcd protected, if a fault develops on them they will trip the 300ma rcd knocking the rest of the building off.
Two questions, the first;
I might be massively overlooking something here. But is there anyway I can design it better so that a fault of the non additionally protected circuits won't knock the 300ma s type out on a fault and cutting power to all other circuits?
I just can't think, forgive me.
The second question, and one I've not fully known for a long time, shamefully!
TT, use a 4 pole isolator and isolate the neutral, got it. TN don't have to isolate the neutral. Why?
Is it because the Neutral in a TN system is effectively tied down with earth either via the pme or at the substation so the potential difference would be much lower than between a neutral and earth fault on a TT system?
If the above is just boll***s, I'm sorry ?.
Cheers..
I plan to put a 4 pole 300MA S TYPE rcd as main switch on a 12 way 3 phase board providing I can get the Ra down low enough, should be fine though, otherwise it'll be a 100ma s type. Socket circuits and maybe lighting circuits will go on 30ma DP RCBO. There are a few circuits that don't need to be 30ma additionally protected. These circuits will have fault protection by the 300ma s type. And the ones on the 30ma will be fault protected with the 30ma rcbos. The final circuits that are non rcd protected, if a fault develops on them they will trip the 300ma rcd knocking the rest of the building off.
Two questions, the first;
I might be massively overlooking something here. But is there anyway I can design it better so that a fault of the non additionally protected circuits won't knock the 300ma s type out on a fault and cutting power to all other circuits?
I just can't think, forgive me.
The second question, and one I've not fully known for a long time, shamefully!
TT, use a 4 pole isolator and isolate the neutral, got it. TN don't have to isolate the neutral. Why?
Is it because the Neutral in a TN system is effectively tied down with earth either via the pme or at the substation so the potential difference would be much lower than between a neutral and earth fault on a TT system?
If the above is just boll***s, I'm sorry ?.
Cheers..
