Solar panel supply

Is the circuit breaker rating relevant for a solar panel supply.  I have seen ratings as low as 6 amps and up tp 16 or 20.

Indeed it is - very relevant. The current the PV inverter produces flows through cables in just the same way as any load (if in the opposite direction) - so ratings & cable sizes need to be calculated in the same way.


Shock protection generally works a little differently though - because PV inverter can continue to generate a voltage after the protective device at the CU has opened. Usually the inverter spots the lack of mains and shuts down but the total time taken can be considerable - certainly longer than the 40ms disconnection time required for additional protection. The upshot of that is if the PV a.c. circuit needs additional protection by 30mA RCD (say because the cable is concealed in a wall) then you need a double pole switching RCD so that the PV circuit becomes a separated from earth once the RCD trips - so preventing shocks to earth even in the inverter is still generating. (See reg 551.7.1 (ii)). Single pole switching RCBOs are unlikely to be suitable in such cases.


  -  Andy.

Is the circuit breaker rating relevant for a solar panel supply.  I have seen ratings as low as 6 amps and up tp 16 or 20.

Indeed it is - very relevant. The current the PV inverter produces flows through cables in just the same way as any load (if in the opposite direction) - so ratings & cable sizes need to be calculated in the same way.


Shock protection generally works a little differently though - because PV inverter can continue to generate a voltage after the protective device at the CU has opened. Usually the inverter spots the lack of mains and shuts down but the total time taken can be considerable - certainly longer than the 40ms disconnection time required for additional protection. The upshot of that is if the PV a.c. circuit needs additional protection by 30mA RCD (say because the cable is concealed in a wall) then you need a double pole switching RCD so that the PV circuit becomes a separated from earth once the RCD trips - so preventing shocks to earth even in the inverter is still generating. (See reg 551.7.1 (ii)). Single pole switching RCBOs are unlikely to be suitable in such cases.


  -  Andy.