MCBs tripping randomly?

[timhoward]

In spite of the anticipated reaction and assurances I think a little experiment is due to disprove human interaction before wasting more time on this .

Buy another Wylex B32 MCB (3 or 4 quid)
Swap the B40 for a B32. Don't say a word to anyone but move the sockets on the right to the new B32 on the left (along with the respective neutrals) and connect the summer house to the empty B32 on the right (and move the neutral too). This is all temporary.
See if the the same breaker keeps tripping.

If the problem moves to the right without anyone else knowing then it's an electrical problem that is foxing the finest electricians I know.
If the problem stays on the left I'm afraid it's most likely to be a human interaction issue.

 

[Lewis Curle]

Just to confirm.

the original summer house was experiencing random trips
it was fed from a normal mcb

the board has been changed and the same thing is happening with the new equipment

the outgoing live cable has been removed from the circuit breaker and the breaker still trips at random times.

if all the above is correct, i would be looking for a mechanical reason for tripping as mentioned above by @DPG

I would be considering a covert ip camera watching the board with the cover off and seeing what is going on.

edit,
A video of a breaker tripping on its own with no outgoing cable attached would really amaze me.
if that happens, i would be recommending posting on a forum that follows ley lines, ghosts, spirits, extra-terrestrials, EMF and grounding, etc.

I’ll try and get a video on Saturday when I have time, speak to you all then and thanks for your time!

 

[Lewis Curle]

In spite of the anticipated reaction and assurances I think a little experiment is due to disprove human interaction before wasting more time on this .

Buy another Wylex B32 MCB (3 or 4 quid)
Swap the B40 for a B32. Don't say a word to anyone but move the sockets on the right to the new B32 on the left (along with the respective neutrals) and connect the summer house to the empty B32 on the right (and move the neutral too). This is all temporary.
See if the the same breaker keeps tripping.

If the problem moves to the right without anyone else knowing then it's an electrical problem that is foxing the finest electricians I know.
If the problem stays on the left I'm afraid it's most likely to be a human interaction issue.

I’ll also try this

 

[James]

I’ll try and get a video on Saturday when I have time, speak to you all then and thanks for your time!

You have such an unusual fault, there are a dozen highly trained and experienced electricians here that are invested in your problem and would love to find out what the problem is.
Mystery hunters should be a new member tag for all that have posted there ideas here!!
Our time is given freely but thankyou for recognising it.

 

[mainline]

Remove the mcb and lock it away for a few days, bet it hasn't tripped in that time.

 

[domsta72]

A few questions.
Did you not carry out a full eicr before the board change?
All new colour cables in your photo - a full rewire at some stage, extended circuits or a newish property?
Knowing you have had on going issues, you chose to fit a dual rcd board rather than an rcbo board (and no spd).

 

[marconi]

I am minded - not yet decided since Carlise is half a day's travel each way - to take a look myself so intrigued am I with this problem.

My suspicions have turned to the smart meter. it contains a contactor which isolates the incoming mains in the event of tampering, end of credit, remote supplied command or loss of incoming mains power. The working hypothesis is that there are very brief complete interruptions in mains power to the output terminals of this smart meter caused by some sort of fault associated with this relay or its control including the meter enclosures anti-tamper circuitry. When there is a a very brief interruption in 240Vac when some non-trivial current is being supplied as would be the case when you and /or your wife are using electrical equipment or indeed when fridges and freezers start or run - then the transient currents which flow briefly after power returns to normal causes very high but short duration pulses of magnetic flux in the short circuit solenoid of the mcbs. These pulses of high current high magnetic flux are interpreted by those circuit breakers passing current as short circuits and thus they trip. Oddly but not physically impossible the sunhouse mcb trips even when it is only connected to the busbar but nothing to its output because the high pulse of magnetic flux(es) from adjacent mcbs link its own short circuit solenoid causing it to trip.

These events are initiated and noticeable only when non-trivial currents are flowing thus during gaming, cooking and the use of high power white appliances.

It is still not certain even though the dno have been and tested(? ) that there is no external fault with the distribution network your home connects to noting it is a PME supply. If it was a street long problem others would be complaining - and they are not - so if there was a supply defect then more probably it would be in the feed to your home. Is your street fed by overhead lines?

Would you please load up the ring circuits and your sunhouse too (so reconnect the fed to it to the B40A mcb) and then take a rolling pin or hammer and tap the smart meter in a number of places a number of times. Obviously don't beat the living daylights out of it as much as most of us would quire understandably want to at 50p a kWh!

After this, please take some small plastic clear freezer bags and aluminium foil. Using an mcb as a template cut out two pieces of ally foil shaped to both sides of the mcb. Place these each in a small plastic freezer bag. Interposed these insulated ally sheets between the sides of the mcbs which usually trip. Wait and see what transpires. Obviously take great care that the ally is inside the plastic and does not touch the busbar. No shame if you think this is too risky for you to do. You really do have to be very careful. I only suggest it because you are a qualified electrician. You are making a Faraday shield. See

Faraday cage - Wikipedia - https://en.wikipedia.org/wiki/Faraday_cage

Also wiggle the meter tails to see if their movement causes the trip.

I recall a smart problem in Birmingham when its radio transmissions interfered with the electronics of the rcd causing it to trip - but your rcd does not trip so we will keep that on the back burner for now.

Is the meter cupboard metal or plastic including the door? Is the mobile phone signal strong where you live? How old is the smart meter in the cabinet?

 

[mainline]

I am minded - not yet decided since Carlise is half a day's travel each way - to take a look myself so intrigued am I with this problem.

My suspicions have turned to the smart meter. it contains a contactor which isolates the incoming mains in the event of tampering, end of credit, remote supplied command or loss of incoming mains power. The working hypothesis is that there are very brief complete interruptions in mains power to the output terminals of this smart meter caused by some sort of fault associated with this relay or its control including the meter enclosures anti-tamper circuitry. When there is a a very brief interruption in 240Vac when some non-trivial current is being supplied as would be the case when you and /or your wife are using electrical equipment or indeed when fridges and freezers start or run - then the transient currents which flow briefly after power returns to normal causes very high but short duration pulses of magnetic flux in the short circuit solenoid of the mcbs. These pulses of high current high magnetic flux are interpreted by those circuit breakers passing current as short circuits and thus they trip. Oddly but not physically impossible the sunhouse mcb trips even when it is only connected to the busbar but nothing to its output because the high pulse of magnetic flux(es) from adjacent mcbs link its own short circuit solenoid causing it to trip.

These events are initiated and noticeable only when non-trivial currents are flowing thus during gaming, cooking and the use of high power white appliances.

It is still not certain even though the dno have been and tested(? ) that there is no external fault with the distribution network your home connects to noting it is a PME supply. If it was a street long problem others would be complaining - and they are not - so if there was a supply defect then more probably it would be in the feed to your home. Is your street fed by overhead lines?

Would you please load up the ring circuits and your sunhouse too (so reconnect the fed to it to the B40A mcb) and then take a rolling pin or hammer and tap the smart meter in a number of places a number of times. Obviously don't beat the living daylights out of it as much as most of us would quire understandably want to at 50p a kWh!

Also wiggle the meter tails to see if their movement causes the trip.

I recall a smart problem in Birmingham when its radio transmissions interfered with the electronics of the rcd causing it to trip - but your rcd does not trip so we will keep that on the back burner for now.

Is the meter cupboard metal or plastic including the door? Is the mobile phone signal strong where you live? How old is the smart meter in the cabinet?

Does the theory still stand when there is no connection to the outgoing side of the mcb ?

Hope it’s not caused by a ham radio station next door

 

[marconi]

Does the theory still stand when there is no connection to the outgoing side of the mcb ?

I wrote - albeit I have edited the text a few times so maybe you did not see it -

Oddly but not physically impossible the sunhouse mcb trips even when it is only connected to the busbar but nothing to its output because the high pulse of magnetic flux(es) from adjacent mcbs link its own short circuit solenoid causing it to trip.

 

[Lewis Curle]

A few questions.
Did you not carry out a full eicr before the board change?
All new colour cables in your photo - a full rewire at some stage, extended circuits or a newish property?
Knowing you have had on going issues, you chose to fit a dual rcd board rather than an rcbo board (and no spd).

My house is 7 years old mate and the sun house is just an extension of the old garage, but the cable feeding the garage is the original cable.
It didn’t even cross my mind to fit an rcbo board to be honest mate.

 

[Lewis Curle]

I am minded - not yet decided since Carlise is half a day's travel each way - to take a look myself so intrigued am I with this problem.

My suspicions have turned to the smart meter. it contains a contactor which isolates the incoming mains in the event of tampering, end of credit, remote supplied command or loss of incoming mains power. The working hypothesis is that there are very brief complete interruptions in mains power to the output terminals of this smart meter caused by some sort of fault associated with this relay or its control including the meter enclosures anti-tamper circuitry. When there is a a very brief interruption in 240Vac when some non-trivial current is being supplied as would be the case when you and /or your wife are using electrical equipment or indeed when fridges and freezers start or run - then the transient currents which flow briefly after power returns to normal causes very high but short duration pulses of magnetic flux in the short circuit solenoid of the mcbs. These pulses of high current high magnetic flux are interpreted by those circuit breakers passing current as short circuits and thus they trip. Oddly but not physically impossible the sunhouse mcb trips even when it is only connected to the busbar but nothing to its output because the high pulse of magnetic flux(es) from adjacent mcbs link its own short circuit solenoid causing it to trip.

These events are initiated and noticeable only when non-trivial currents are flowing thus during gaming, cooking and the use of high power white appliances.

It is still not certain even though the dno have been and tested(? ) that there is no external fault with the distribution network your home connects to noting it is a PME supply. If it was a street long problem others would be complaining - and they are not - so if there was a supply defect then more probably it would be in the feed to your home. Is your street fed by overhead lines?

Would you please load up the ring circuits and your sunhouse too (so reconnect the fed to it to the B40A mcb) and then take a rolling pin or hammer and tap the smart meter in a number of places a number of times. Obviously don't beat the living daylights out of it as much as most of us would quire understandably want to at 50p a kWh!

After this, please take some small plastic clear freezer bags and aluminium foil. Using an mcb as a template cut out two pieces of ally foil shaped to both sides of the mcb. Place these each in a small plastic freezer bag. Interposed these insulated ally sheets between the sides of the mcbs which usually trip. Wait and see what transpires. Obviously take great care that the ally is inside the plastic and does not touch the busbar. No shame if you think this is too risky for you to do. You really do have to be very careful. I only suggest it because you are a qualified electrician. You are making a Faraday shield. See

Faraday cage - Wikipedia - https://en.wikipedia.org/wiki/Faraday_cage

Also wiggle the meter tails to see if their movement causes the trip.

I recall a smart problem in Birmingham when its radio transmissions interfered with the electronics of the rcd causing it to trip - but your rcd does not trip so we will keep that on the back burner for now.

Is the meter cupboard metal or plastic including the door? Is the mobile phone signal strong where you live? How old is the smart meter in the cabinet?

Feel free to come to Carlisle mate you’re most welcome to. I’m currently at work and I have tomorrow planned in for trying things. So I will do as you have asked! I will get the info you have asked for tonight though.

Again thanks for your time in this

 

[marconi]

If I were to travel what's best - weekday or weekend?

 

[pc1966]

When there is a a very brief interruption in 240Vac when some non-trivial current is being supplied as would be the case when you and /or your wife are using electrical equipment or indeed when fridges and freezers start or run - then the transient currents which flow briefly after power returns to normal causes very high but short duration pulses of magnetic flux in the short circuit solenoid of the mcbs.

While that sounds plausible in theory, I really doubt any home system is going to produce that big a magnetic field. Indeed if it did, I would expect to see bent steel enclosures!

 

[marconi]

While that sounds plausible in theory, I really doubt any home system is going to produce that big a magnetic field. Indeed if it did, I would expect to see bent steel enclosures!

Noted.

To fathom this problem I am being creative in generating the hypothesis to inspire the next line of diagnosis. I can see myself visiting.............

I am more open minded about extraordinary current waveforms of several hundreds of Amperes and short duration with their associated magnetic field/flux. Quirky circumstances causing resonance perhaps and not necessarily at 50Hz but a harmonic or several of them?

I don't care if I am wrong.

 

[Lucien Nunes]

Even short-circuit currents of many kA do not trip adjacent MCBs. I could ask a friend who has a large magnet-charger (i.e. huge electromagnet) to try tripping an MCB with it.

 

[brianmoooore]

In spite of the anticipated reaction and assurances I think a little experiment is due to disprove human interaction before wasting more time on this .

Buy another Wylex B32 MCB (3 or 4 quid)
Swap the B40 for a B32. Don't say a word to anyone but move the sockets on the right to the new B32 on the left (along with the respective neutrals) and connect the summer house to the empty B32 on the right (and move the neutral too). This is all temporary.
See if the the same breaker keeps tripping.

If the problem moves to the right without anyone else knowing then it's an electrical problem that is foxing the finest electricians I know.
If the problem stays on the left I'm afraid it's most likely to be a human interaction issue.

This is the next thing that should be done. See if the fault stays with the MCB or moves with the circuit.
Same technique is often used to sort a misfire on an engine. Move the ignition coil or the injector, and see if the fault follows the component or stays with the cylinder.

 

[timhoward]

@marconi I've driven from Eastbourne to Carlisle several times having lived in both places. Granted once was in an LDV Pilot with a cat and a 2 year old for company which is a combination of vehicular technology and company I never want to do again. Whether the differential or the cat made more noise is open to debate. But my point is that if it were me I'd want to rule out human intervention before travelling.
(But if you do go to Carlisle - I'd suggest you'd enjoy a visit to Bookcase on Castle Street which is the best 2nd hand bookshop spread over many floors I've ever found, all properly organised like a library)

 

[nicebutdim]

@marconi I've driven from Eastbourne to Carlisle several times having lived in both places. Granted once was in an LDV Pilot with a cat and a 2 year old for company which is a combination of vehicular technology and company I never want to do again. Whether the differential or the cat made more noise is open to debate. But my point is that if it were me I'd want to rule out human intervention before travelling.
(But if you do go to Carlisle - I'd suggest you'd enjoy a visit to Bookcase on Castle Street which is the best 2nd hand bookshop spread over many floors I've ever found, all properly organised like a library)

I'd wager the cat was significantly more responsive than the steering in that LDV.

 

[mainline]

I think we all need to get our heads together on this one.
So what I propose is all chip in and hire a coach, we can all meet up and go together a few pub stops on the way.

 

[mainline]

I think we all need to get our heads together on this one.
So what I propose is all chip in and hire a coach, we can all meet up and go together a few pub stops on the way.

Tim can bring his self calibrated Megger and I'll bring some southern comfort.

 

[James]

If there is beer involved, count me in!
maybe even some cheesecake?

 

[timhoward]

Tim can bring his self calibrated Megger and I'll bring some southern comfort.

If you start drinking it in Cornwall you'd better get your creative theories down on paper around the Bristol area, leaving it any later could be risky!

If there is beer involved, count me in!
maybe even some cheesecake?

If I'm allowed to take over navigation then I propose a detour at J40 of the M6 - Venison Burgers at the Mill in Mungrisdale, a couple of pints of Old Peculiar at the Dog and Gun in Keswick, en-route back to the coach we pass the Castle and the Oddfellows Arms, then take the scenic route via A595 to Carlisle with a few nice village pubs on the way.
We just need a designated safe-isolation person....

 

[marconi]

Lewis Curle: One of the photos you sent me on my phone has the isolator switch-fuse and above it a grey plastic box. Could you open up the grey box and take a photo please and post it?

 

[marconi]

To save me re-reading everything you have written - once there has been an mcb trip event do you ever have further trips the same day? Or is the earliest next event sometime during the following day? Does it only happen once the street lights start to come on or are on?

What kind of street lights in your road?

Is the consumer unit in a hot room or cupboard which gets hot ie airing cupboard, above a cooker or built in oven

When the mcbs trip could you feel them shortly afterwards to see if they are getting warm/hot through prolonged overcurrent due to overloading of the circuit.

In regard to overloading, could you list what is connected to each final ring circuit and post so I/we can consider the likelihood of overloading them?

Have any plug fuses ruptured during the period of this problem?

What type of space and water heating do you normally use?

How many fridges and freezers are plugged in and switched on?

Do you have a microwave? Is it a combination microwave?

An air fryer?

What type of oven do you have? Radiant rings, IR halogen, induction?

Would anyone in your street be using an electric arc welder, air compressor or car lift powered by the mains?

Are their many EV chargers in use in your road?

A bit left field and please don't be offended but would you suspect anyone in your street has a cannabis farm with its heavy heating, lighting and fan load?

Are their many solar panels to be seen along your road?

How far away in metres is the supply transformer for your overhead lines?

 

[marconi]

The query about cu location and ambient temperature and loading on your final circuits is a line of thinking to do with derating the current handling capacity of mcbs dependent on temperature inside the consumer unit and grouping of mcbs side by side. See:

http://www.hagerelectro.com.au/files/download/0/32587_1/0/TECHINFO_MCBS.PDF

Note the power dissipation per pole table. Power dissipation per pole also applies to RCDs and the Main Switch. I just wonder if the way you consume electricity is such you have episodes of several high amperage and reasonably long duration current flows which are causing your consumer unit interior to warm up so much that derating of mcbs for temp and grouping becomes significant, thence they eventually trip on overcurrent overload.

A simple way to test this would be to run the consumer unit with the cover off for a week if of course this can be done safely.

 

[davesparks]

A simple way to test this would be to run the consumer unit with the cover off for a week if of course this can be done safely.

No that can't be done safely, and I'm surprised to see anyone suggesting that a CU could be left without its cover fitted for a week.

Moving the MCB to the end of the row would be a far safer way to prove this.


However I doubt that the cause of this problem is electrical. The MCB apparently trips with no outgoing conductor connected. I have seen protective devices trip with no outgoing conductor connected a few times and the causes have been faulty/damaged devices, vibration or mechanical impact.


In situations like this it is easy to get distracted by very interesting, vaguely plausible, technical explanations for the problem when in reality an over-tightened terminal screw may have caused the mechanism to twist slightly.

 

[marconi]

No that can't be done safely, and I'm surprised to see anyone suggesting that a CU could be left without its cover fitted for a week.

Moving the MCB to the end of the row would be a far safer way to prove this.


However I doubt that the cause of this problem is electrical. The MCB apparently trips with no outgoing conductor connected. I have seen protective devices trip with no outgoing conductor connected a few times and the causes have been faulty/damaged devices, vibration or mechanical impact.


In situations like this it is easy to get distracted by very interesting, vaguely plausible, technical explanations for the problem when in reality an over-tightened terminal screw may have caused the mechanism to twist slightly.

Sensible advice. Forgive me for I will not say any more in response.

 

[mainline]

No that can't be done safely, and I'm surprised to see anyone suggesting that a CU could be left without its cover fitted for a week.

Marconi did say IF it can be done safely.
That would depend on the circumstances.
The O/p is an electrician, and he maybe the only one with access to it.
It also could be in a lockable cupboard.

In situations like this it is easy to get distracted by very interesting, vaguely plausible, technical explanations for the problem when in reality an over-tightened terminal screw may have caused the mechanism to twist slightly.

The MCB has been replaced with a new one.


Maybe the Op lives in a train station or on a building site.

 

[LastManOnline]

Sensible advice. Forgive me for I will not say any more in response.

I am not inclined to add any more comment to this thread as in my first post (post 67).Having hastily read the thread,I suggested that the issue likely lay with the OP who I assumed (wrongly) was an amateur.I should have read the previous 66 posts more thoroughly.I want to offer my sincere apologies to the OP.
Now that I have read the thread thoroughly ,my initial impression of this being an unconventional and unique problem remains the same.
For that reason I do hope that "Marconi" stays on the case as I believe he has a unique skill set that facillitates "thinking outside the box"
in ways that most conventionally trained sparks dont.It would be marvellous to find out the cause of this problem.

 

[mainline]

Wondering if the O/P has tried it with the lid off, and then put a decent load on it.

 

[OnlQQker]

( it’s not a SWA it’s a wierd cable with loads of little cables as a neutral)

Got a pic of this cable Op?

 

[brianmoooore]

Don't recall the post quoted above, but that will be split concentric cable. The insulation on the individual neutrals in this cable is thin and fragile, making it more susceptible to neutral - earth faults than other cables.

 

[OnlQQker]

Don't recall the post quoted above, but that will be split concentric cable. The insulation on the individual neutrals in this cable is thin and fragile, making it more susceptible to neutral - earth faults than other cables.

Op's first post (page 1)

I will look up spilt concentric cable as never seen it before!

 

[OnlQQker]

I'm guessing it's this stuff but 6mm

25mm² Split Concentric Cable (Cut Length Sold By The Mtr)

Single-phase split concentric cable

www.cef.co.uk

So does that bundle of neutrals connect into the consumer unit? cuz on the pics the OP posted I couldn't see them?

 

[davesparks]

I'm guessing it's this stuff but 6mm

25mm² Split Concentric Cable (Cut Length Sold By The Mtr)

Single-phase split concentric cable

www.cef.co.uk

So does that bundle of neutrals connect into the consumer unit? cuz on the pics the OP posted I couldn't see them?

Yes that's the cable, if you look at the picture in post #94 you can see the bundle of neutrals connected into the Neutral bar and also another one in the top of the main switch.
Presumably this board is fed via a split-con submain.

 

[davesparks]

Don't recall the post quoted above, but that will be split concentric cable. The insulation on the individual neutrals in this cable is thin and fragile, making it more susceptible to neutral - earth faults than other cables.

Interesting, is it a particular brand of cable that you've had this problem with?

 

[brianmoooore]

Interesting, is it a particular brand of cable that you've had this problem with?

No particular brand. It's a characteristic of the cable - the insulation on the neutrals is thin and easily damaged, especially inside the CU.
I normally twist the neutrals tightly together and wrap the bunch with a few layers of PVC tape.