When undertaking an EICR on a distribution board loaded with RCDs at first glance how do you know if the RCD is providing fault, additional or fire protection or all of the aforementioned, and consequently which disconnection time test to apply?
When undertaking an EICR on a distribution board loaded with RCDs at first glance how do you know if the RCD is providing fault, additional or fire protection or all of the aforementioned, and consequently which disconnection time test to apply?
Distribution to final circuits? or further distribution boards?
RCDs or RCBOs.?
If RCDs then I suspect they will be providing both fault and additional protection depending on the RCD ratings but no short circuit or overload protection.
If RCBOs then protection as above plus overload and short circuit protection.
You may prefer to go the other way - the RCD will either be an instant trip sort or selective, with the time delay specified -
"Is it meeting its own spec ?" may be a good first question.
Generally it will be doing all 3, unless something else is doing one or the other.
The Zs of the circuits it supplies and their MCB/fuse rating will be the next consideration. If the Zs is high enough that the MCB or fuse may not operate promptly then the RCD is doing the earth fault detection, as the fuse or MCB is not.
IF the circuit is the kind that requires additional protection, (sockets, or shallow T and E cables or bathroom wiring or...) then it is doing the additional protection too.
If however the Zs (at the far end of the circuit) is low enough that the fuse or MCB provides the main ADS, then the RCD is doing additional protection only
If you like it or not it will always provide some fire protection, but that may not be its main purpose, but if neither additional prod nor ADS apply then than that may be all it is for in that location.
how do you know if the RCD is providing fault, additional or fire protection or all of the aforementioned, and consequently which disconnection time test to apply?
Probably look at it the other way around - consider the installation served first and see what requirements it would have - then see whether the RCDs meet those.
(That's presuming you don't have the original design documentation available....? )
