02-09-2015, 04:43 PM
(02-09-2015, 04:34 PM)ppppenguin Wrote:Some boaters have run earth to the battery negative and then to an earth point on the hull - not a good idea but still done. I always endorse a floating DC circuit and a hull ground for the mains earth.Quote:My understanding of RCD's is that under normal conditions the voltages between live and neutral cancel and the vector sum is zero. If there is some leak between live and neutral, the vector sum isn't zero. In the device is a toroidal transformer that will detect and trip the circuit.
RCDs, as their name suggests, measure currents, not voltages. The toroid is a current transformer that has bothe live and neutral as its primary. If the difference between the L and N currents exceed the rating then the current in the secondary will cause a trip. I'd need to think about whether a vector or scalar difference is involved.
As for "leak between live and neutral" this is normal current consumption! I think you meant between live or neutral and earth.
If you're working with an independent supply such as an inverter and the output is floating (ie not referenced to earth) an RCD is completely useless.
