Split-load Switch / RCD flipping down repeatedly

I've just eyeballed and felt around the external 2-way socket. It's in a plastic box attached to the wall, there's a bead of silicone around it, no water collecting inside, it has a plastic drop-down door in well place. Nothing to see there I think. Well, I doubt that I can check any further.

I've not checked the external light fittings yet. I did manage to just test them... they work and nothing tripped. Not an answer, I know, but just writing it down. I'll do some firing-up of the boiler later - over lunch - and report back.
 
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If the boiler is on a fused spur, hopefully that is also a full isolator - which includes the neutral and live
if you can turn that off at the isolator and it still trips that may eliminate the boiler - but i would pull the switch off just to check its wired up for both
 
Diffrence line neutral 8 Feb 24 reduced.jpg
I use a clamp on ammeter to measure the earth leakage, seen here showing 8 mA, the accepted limit for a RCD is 1/3 of the RCD rating, so 9 mA is the limit. I actually have 14 RCBO's so well within the limit, but the problem in the past has been when RCD's were fitted often no one tested back ground leakage.

So standard test for RCD is it will trip at rated current and will not trip at ½ rated current which is far enough if latter tested with all circuits turned on, as with a 30 mA RCD that means one has a 15 mA leeway, so likely the same as testing leakage below 9 mA, however often they were tested with all MCB's off, so all a bit hit and miss as to how much extra leakage will cause a trip.

Today we would normally use RCBO's which is a MCB and RCD combined, main reason is so less will trip with a fault, one could replace the RCD with an isolator then fit RCBO's on everything supplied by that isolator, or one can hunt for the fault.

The meter normally used to find the fault VC60B.jpg used DC at 500 volt. This will locate faults, but because it uses DC it will not show back ground leakage, the inductive and capacitive linking in the cables means there is always some leakage. And this will vary home to home, so one person may find the two RCD's are fine, others they trip all too frequent.

My old house had two very old RCD's fitted in the 90's when son decided to become a radio amateur, and I found over the years I would get a bout of tripping, it may trip 4 times in a week, then no change made and go for 2 years before next trip. I blamed spikes on the supply, but no way of proving this, however resetting one, could cause the other one to trip, in theroy that should not happen, so it seems reasonable to consider spikes can cause the old units to trip.

New units use electronics, but spikes can damage electronics, so a surge protection device (SPD) is really required to protect the RCD's.

So we start to reach the point where it seems prudent to swap whole consumer unit (CU) and go steel with all RCBO's.

The old idea was to split the house side to side, this reduced the loop impedance, and spread out the load better, and reduced the need to run extension leads up/down stairs, which is a temptation when one has a unknown fault tripping one RCD, however there was a problem, the idea is not to have lights and sockets on same RCD as if you do some thing to give you a shock and trip the RCD last thing you want is to also be plunged into darkness, and to split lights side to side was not easy, so there was a move to splitting up/down for sockets as well. Today with RCBO's we can return to side to side split.

As to the fault in question it has already been dealt with however the comment
I've just eyeballed and felt around the external 2-way socket. It's in a plastic box attached to the wall, there's a bead of silicone around it,
is flawed, as it means any water which does get in, can't get out again, often better to have a small hole in the bottom, often the sealing bead has a small space at bottom so any water can leave. The problem is when the weather is warm air inside the box expands, and then when it rains it cools so effectively sucking in water. It is the vary fact that some one has tried to seal it, that causes the problem.

Outside lights are the worst, as there is a tendency to mount the PIR under the lamp, so any water which does get in, drains down into the PIR and causes problems, rare to find drain holes in PIR's.
 
So... if I was minded to (and I might) then I should have someone come in and swap out all the existing MCBs with new RCBOs and this would then pinpoint my issue once it ever re-occurred (assuming it would - hasn't today after sometime last night, so far)?

And the RCDs currently sat in there would become redundant, so they could be removed?
 
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So... if I was minded to (and I might) then I should have someone come in and swap out all the existing MCBs with new RCBOs and this would then pinpoint my issue once it ever re-occurred (assuming it would - hasn't today after sometime last night, so far)?

And the RCDs currently sat in there would become redundant, so they could be removed?


Suggest you get advice from a local competent spark. What you think may be possible but eyes on site always trumps random advice over the internet
 
Today I've had the MCB the boiler was on made redundant and the boiler has been moved to a new and separate RCBO.

The RCD tripping has continued since last I posted, only intermittently.

My hope is that if the RCD keeps on tripping and taking out multiple MCBs without providing a clue, then at least the boiler remains operating.

If the boiler MCBO now starts tripping then the issue has been pin-pointed, although that may open up a whole new can of worms.

If the former, the next step is to start unplugging things in the house, and to only plug them in when using them. That may help identify it.

Strange things we noted...

1) As I was taking a picture of the consumer board for him, I had to move various stuff in the understairs cupboard - as I did that, the RCD tripped and I couldn't put it back up again. I flipped all other circuits, and it came back up fine... then I started bringing up others one by one and it did trip again several times in quick succession - not always when the same set of MCBs was in the up position. Interesting nevertheless.

2) As the Electrician was putting the cover back on again... the RCD tripped and we both went "whoa! and he said he had "brushed" the MCB for the outside sockets.

Today there has been no further RCD tripping.

I don't think I'm really any further along, not really... but I like the boiler being separated-out onto the new RCBO.

Oh, while I was at it I did ask about going full RCBO with a new full metal jacket consumer board - and he recommended FuseBox. I'd not heard of this brand before but they seem reasonably priced - and it says they're made in Scotland.
 
Oh, while I was at it I did ask about going full RCBO with a new full metal jacket consumer board - and he recommended FuseBox. I'd not heard of this brand before but they seem reasonably priced - and it says they're made in Scotland.

Not sure this is correct BUT I swapped to Fusebox a few years back and they are decent units and as yet not had any issues with the ones I've installed for customers
 
Have any measurements been taken to determine the level of earth leakage and the actual earth leakage value (ramp test) at which the RCD trips?
 
Sounds like you need to keep a diary of when it trips and what you were using. Also what were the RCD test results?
 
No; but he wasn't there for that... he just did what I asked him to today... now there's a chance it's not boiler-related and, if so, it tripping becomes significantly less of a problem if the heating is still on. I do know what he charges for open-ended fault-finding though and I may end up going down this route.
 
Sounds like you need to keep a diary of when it trips and what you were using. Also what were the RCD test results?
Yes, been doing that... I think I mentioned before - sometimes it's overnight. Today it seemed linked to when I moved an unplugged vacuum cleaner in the understairs cupboard (obviously not, but that's what I was doing at the time)... so far it has seemed random, but we have had a lot of rain in the last couple of days, so if it starts tripping tomorrow, could be back to my original thinking of it being, somehow, a delayed effect from weather.

As of now I'm at a loss. There were no RCD test results I'm aware of from today? But I did press the T button a while back and it worked (I suspect that isn't what you mean as a result). Apologies, I'm just a home owner.
 
The RCD is tripping due to current flowing to Earth from either the Live and/or Neutral.

Turning OFF the MCB on the faulty circuit will not stop the fault tripping the RCD.
It will more often than not, you basically need a dead short N-E to trip a RCD with the live disconnected in most casesr.
 
Oh, while I was at it I did ask about going full RCBO with a new full metal jacket consumer board - and he recommended FuseBox. I'd not heard of this brand before but they seem reasonably priced - and it says they're made in Scotland.
Fusebox are based in scotland but I'm pretty sure at least the actual protective devices are made in China.

When I first looked at them a few years back, they looked a bit shady but they seem to be trying to move up in the world.
 
So the RCD did trip, without any MCB tripping, but the boiler was - obviously - OK now it's on its RCBO and I'm (everyone is!) glad it's ruled-out.

That leaves External Sockets, Ground Floor Lights (inc. the external lights - which could be a suspect), First Floor Lights, First Floor Sockets and Oven on the tripping RCD.

I've removed every plug I could find from the First Floor Sockets to monitor and I've turned off External Sockets, First Floor Sockets and Oven too. Let's see if that does anything at all... I discern some conflicting advice on the benefit of doing this. I'll give it a few days like this if there's no incident to report back quickly.
 
Sometimes completely disconnecting things logically can throw up some possible clues but also it can often leave you chasing a Red Haddock
 

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