Strange issue - Who can solve my 'tripping' challenge?

[gingerrubix]

Hey all, I'm looking for some advice to help me troubleshoot my strange issue with my consumer unit/fuse board on which my RCD keeps tripping.

Disclaimer - I'm a DIYer. I have an electrician involved and I'm 100% planning on leaving the work to the pro(s). However, He's not had time to do any real testing just yet, so I thought I'd get the ball rolling as he's said it might be a nightmare to solve.

So, I have an empty property that my recent tenants have moved out of. Near the end of their tenancy, they were reporting that the electricity was tripping throughout the night.

The consumer unit only has one RCD which protects breakers for downstairs sockets, upstairs sockets, the cooker and a single socket that sits next to the unit.

When they moved out I thought it'd be a simple process to isolate the issue (how wrong I was ha ha)

I thought it would be an appliance/device plugged in somewhere but even with EVERYTHING unplugged including the cooker, extractor fan, fridge-freezer, even the boiler, but it still trips… even if ALL the MCBs are switched to OFF.

But, it doesn't trip immediately, it doesn't trip during the day either.

This is where it gets weird…..

It seems to be tripping at the exact time each night, at 00:53 (or at least 3 out of the 4 times I've accurately timed it - the other time was close at 00:15). It doesn't make sense!

I believe that this type of tripping issue could be down to water ingress, I thought I may have found a candidate in a socket that was in a chimney breast that was always getting soaked/prone to leaking, but the electrician, removed that socket and made it safe (connecting the wires) but it still tripping and besides…..if it was water ingress, why would it trip at exactly the same time of night 3 times in a row?

One thing I haven't been able to test so far (because I'm not living at the property) is if it would continue to trip later in the evening, if I reset it. At the moment, I'm going round to the property every morning and finding it tripped.

Could it be a problem with the consumer unit itself?

This seems like a proper head-scratcher to me so hoping the combined brain of all you helpful/experienced lot may be able to point us in the right direction.

Happy to share pics if you need them.

Thanks in advance

Ginge

Extra info - that may or may not be related.
Bit of background on the things the tenant did.

• Running cat5 around the house (meaning getting under the floorboards where electric wires run quite loosely)#
• Changing light fittings (some not fitted to the ceiling properly/safely)
• Changing light switches (swapping for touch sensors etc)
• Disconnected the alarm panel - to replace with a touchscreen system that I think controlled the heating/lights, etc. I think this would have triggered the tamper on the alarm so they pulled a fuse from the main alarm panel to disconnect.
• He was also charging his electric car by feeding a cable from inside the house through the letterbox, out onto the road.
• He has changed a double socket in the hallway - not sure why but this would be the closest socket for him to charge his car.

Also, I have an old boiler that's just turned a fault after they moved out but it still powers up fine (being replaced in the next few days)
During the tenancy they have had the meter changed. But based on the label from the energy company EON, this was back in January 2023 - so over a year ago.
There have been recent reports of rats being seen on the street - I did consider that could have been a cause but again…. Why is it tripping at the same time each night?

 

[SJD]

Tripping at a specific time suggests something switching at that time, and the one thing I immediately think of is an off-peak supply. Do you have that, or used to, or does the meter support it (for something now removed, like storage heaters)?

There are occaisional reports of smart meters causing issues with tripping RCDs, and I assume the new-ish meter is a smart meter. Might help to post a photo of the meter & consumer unit, someone here might say yes I've seen issues with that combination.

I'd not normally install a consumer unit nowadays having one RCD protecting several circuits, for the very reason that if something trips it, you don't know which circuit to blame, and it trips several or all circuits. Depending on the age of the unit, you might consider changing it anyway to an all-RCBO unit, so that if one RCBO trips, it only affects the one circuit, and likely it is something on that circuit that caused the issue.

 

[R-fur]

Mysterious tripping is often due to a N-E fault which you electrician can test for. As SJD said it could tie in with off peak heating.

 

[gingerrubix]

I did think about that off-peak heating, could that be like a surge directly at the service cable (if that's the right term)?
I'll be honest, I don't know what a smart meter looks like (as I don't have one at my home property) but it wouldn't surprise me if they had one fitted.
I'll post some pictures of both that and the consumer unit (which is pretty old)

 

[gingerrubix]

Here's the meter and the consumer unit

 

[davesparks]

You need to get some basic tests carried out following a logical process, anything else at this stage is just guesswork.

A test of the RCD to make sure it is working as expected and thorough IR testing of all circuits would be my starting point.

Also the next test due sticker shows that the last person to inspect and test the installation recommended that it be done again within 12 months, this is unusual for a domestic installation and suggests that the previous test report will have identified some issues.

 

[snowhead]

Yes, that's the MEM RCD most often associated with tripping by "Smart" Meter.

 

[gingerrubix]

Yes, that's the MEM RCD most often associated with tripping by "Smart" Meter.

Really? I feel like we may be onto something. If it turns out to be that combo causing the trip, what type of action would I take? Is it a fix from the energy supplier side or do I need a new board that's not susceptible to this smart meter triggering?

 

[littlespark]

There are thoughts on how a smart meter can trip an rcd, and although I’ve never come across it myself, there are some solutions I’ve learned from this forum.

Distance seems to be an issue. If the rcd is within a foot or so of the meter, it can trip.

A metallic shield… (bit of cardboard wrapped in tinfoil) between the meter and the rcd creates a barrier. The communication signal can’t get through.


Just my thoughts.

 

[gingerrubix]

Well, the RCD and meter are very close together. I'll run some tests this evening. After a Google, I can see people suggesting trying to make a phone call on a phone held close to the RCD to see if that trips it.

I'll give the cardboard & tinfoil shield a try too. At least if it stops the tripping I know 'what' the problem is. It's then finding the solution.

I read that the more modern metal consumer units are all metal construction and earthed which apparently acts as a shield to RF. Fixed it for someone on another forum

 

[mainline]

Really? I feel like we may be onto something. If it turns out to be that combo causing the trip, what type of action would I take? Is it a fix from the energy supplier side or do I need a new board that's not susceptible to this smart meter triggering?

As @davesparks
You really need to do some testing first it could be there's a fault and without that fault being there it may not trip.

It this meter recent ?

 

[gingerrubix]

As @davesparks
You really need to do some testing first it could be there's a fault and without that fault being there it may not trip.

I appreciate that @mainline, but as it's been consistently tripping at exactly the same time each evening, if shoving an RF barrier between the two devices prevents it tripping then surely it points towards that theory of the smart meter triggering it.
Of course, from there we'd then redirect the focus to the suitability of the RCD/Consumer unit/smart meter.

 

[littlespark]

Its a dated MEM consumer unit... so likely the RCD has become more sensitive over the years. The electrician can perform a "ramp" test to find the threshold... ie, a 30mA RCD should not trip at half that... (15mA) but many of them are in the 20's

 

[Rockingit]

Its a dated MEM consumer unit... so likely the RCD has become more sensitive over the years. The electrician can perform a "ramp" test to find the threshold... ie, a 30mA RCD should not trip at half that... (15mA) but many of them are in the 20's

I had some weird thing years ago with two RCD's on the same rail where a fault on the one would also trip the other. I finally put it down to them not having great internal shielding and as the field was collapsing in the coil of one the hysteresis was inducting into the other next to it. Something about how all those electrons gotta go somewhere...... But I find it hard to imagine that the regular cellular system would able to do that otherwise it'd be widespread and very much a known thing.

 

[James]

If you have an electric cooker / hob it is worth turning it off at the big isolator switch next to the cooker, see if the fault goes away.
it is one of the common causes of faults like yours.
as above, some testing really needs to be done but you might get lucky on that one.