Several times in the last month, we have experienced small power surges that cause the circuit breakers to trip. Most of the time this has been the "sockets" circuit breaker, however 15 minutes ago the RCCB "protected circuits" tripped, while the other circuit breakers remained on. During this the "sockets" lost power, but lights, and the rest of the electrical system did not go off. Is this unusual behaviour? From what I've read, if the RCCB trips, the entire electrical system is supposed to stop working.
Electrical – RCCB trips and causes sockets to lose power, but lights, etc. don’t lose power
circuit breakerelectricaluk
Related Solutions
Some surge protectors work by "redirecting" surges to the equipment ground, which is pretty much the definition of a ground fault. In this case, it's definitely possible that surge suppressors could be tripping GFCI receptacles/breakers (given a large enough surge).
As for the AFCIs... When electrical contacts separate, they often create an arc between the contacts. This arc spans the gap until the contacts are too far apart, and the arc can no longer be sustained. It's possible (in theory) that the GFCI tripping could create a large enough arc, for long enough to cause the AFCI to trip. It's not likely that a properly functioning GFCI would do this, but if the GFCI was old and worn it could be opening the contacts slow enough that a detectable arc is being produced.
Determining if the GFCI tripping is causing the AFCI to trip, is a simple test. Simply press the test button on the GFCI. If the AFCI trips, you'll have figured out half the problem. If the ACFI does not trip, you could repeat the test using a receptacle tester with a GFCI test function.
If it's determined that the GFCI is causing the AFCI breaker to trip, replacing the GFCI receptacle may resolve that part of the issue.
Figuring out if the surge suppressor is tripping the GFCI, is a more difficult proposition. It will likely require you to monitor the supply voltage over some time, to identify and document possible surges.
That main breaker appears to be an RCD (Residual Current Device, also known as a GFCI or Ground Fault Circuit Interrupter).
So, apparently you have a ground fault somewhere in one or both of the circuits that are tripping the RCD. Since those circuits are both outside, they might travel through a common junction box or conduit that's suffered from water intrusion (and perhaps the nighttime temperatures lead to condensation that trips the breaker).
Some electrical equipment can lead to nuisance tripping of RCD/GFCI devices (such as electrical motors or fluorescent lights), though since you say that the breaker trips even when the circuits are not in use, this is likely not the problem.
I'd trace out the wires that lead out to those outside outlets and perimeter lights and see if you can find any damage or water problems.
There are a number of stack exchange questions on gfci tripping, which might help you isolate the problem.
If you can't find the problem, I'd call out an electrician to evaluate the circuits and if he can't find the problem, maybe try switching out the main breaker to see if that main RCD is faulty.
Providing your location would be useful, you're apparently not in the USA since that breaker does not seem to be common here.
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Best Answer
Yes this is normal.
Under the 16th edition IEEE wiring regulations (introduced in 1991, superseeded in 2008, there were amendments, but I don't think any of them are relavent here) in TN installations* RCD protection in normal domestic situations was only required for sockets that could be reasonably expected to supply equipment outside the equipotential zone**. Interpretations of this varied, but in practice it meant that at least all downstairs sockets and frequently all sockets ended up being RCD protected.
Some houses were wired with a RCD covering everything but this was frowned upon because a single fault could leave the whole house in darkness.
It therefore became common practice to fit "Split load" boards where some of the circuits were on RCD and others were not. Exactly what got put on the RCD side was quite variable with some electricians putting everything except lights on the RCD and others only putting sockets and showers (I don't think an explicit requirement to put showers on the RCD but it was widely seen as a bloody good idea) on the RCD side. This appears to be the situation you have.
Since the 17th edition practically all domestic wiring needs to be on a RCD. On cheaper installations it was/is common practice to use a consumer unit with two RCDs so you only lost half the stuff when a RCD went out. Higher-end installations would often use "RCBOs" which combine the functionality of a RCD and a MCB and allow each circuit to be individually RCD protected. Until recently these were pretty expensive though.
There is no compulsion however to upgrade your existing installation to the 17th or 18th edition regs. Heck there isn't actually an explicit legal requirement to follow the IEEE wiring regulations (aka BS7671) at all, just a requirement that “Reasonable provision shall be made in the design and installation of electrical installations in order to protect persons operating, maintaining or altering the installations from fire or injury.”. Most electricians however will insist (and may be bound by industry schemes they are a member of to insist) that any new work is done to the current edition. In practice this means they will want to RCD protect any new wiring when modifying an installation.
* in a TT installation everything needs to be RCD protected, but sometimes with RCDs that have a higher trip current.
** I think there may have been some requirements for RCDs related to swimming pools and marinas as well, but those wouldn't apply in the vast majority of domestic installations.