RCDs for fault protection in adibatic equasion

[oscar21]

I has this discussion the other week, someone was saying an RCD will save someones life because it limits the shock to 30mA. I said you still get the maximum current the body can pass due to its resistance which may be way more than 30mA, the saving grace is it wont be for very long.

I think it was something to do with the difference in time between an MCB tripping and an RCD tripping on a shower circuit, I said there was hardly any difference between the two if an earth fault occurred on the circuit.

 

[Pretty Mouth]

32a rcbo starbraker

For starbreaker MCBs I only have limited I²t data unfortunately:

For a B32, fault current of 6kA, the I²t is 31760 A²s. Gives you a CPC of 1.5mm² once you've run it through the adiabatic.

I expect the Ipf at the CU is lower than 6kA, which would probably allow a smaller CPC, if we had the I²t data to prove it. But we don't. That is frustrating.

 

[pc1966]

I expect the Ipf at the CU is lower than 6kA, which would probably allow a smaller CPC, if we had the I²t data to prove it. But we don't. That is frustrating.

Most likely it would be fine, as it is fairly certain the I2t drops with PFC (at least until thermal region) and 6kA is quite high for a domestic CU.

Also for a RFC you ought to have two CPC in parallel, though near the ends (close to CU) it will mostly be current in one leg, and higher PFC as well, so not a good basis for such an argument!