MCBs tripping randomly?

[Lewis Curle]

Hi all,

So I’ve been having a strange fault in my house which has just appeared over the past few days. About a month ago I moved my pc set up into the sun house to make space for my second kid.

Inside the sun house/garage I have a DB that is fed of a 40A type B breaker fed by a 6mm core cable.( it’s not a SWA it’s a wierd cable with loads of little cables as a neutral) but I have insulation resistance tested that feed cable and it’s all good. On the garage DB I have a 32A ring main and a 6a lighting circuit. I have had my pc setup in there for a few weeks now and it’s been totally fine up until a few days ago when the 40A MCB is tripping of at random times. It can go off when I’m there and gaming or off through the day when I’m at work.

The circuits in the garage have all tested out totally fine and the feed cable going to the garage DB has tested out fine as well. But for some reason the 40A MCB in my board keeps tripping off. I have changed the MCB as of yesterday and it has went off again today whilst I was at work. There is nothing on in the sun house when the MCB trips. 40A is huge MCB for a house and I can’t get my head round what is causing it because there isn’t even anything above 10A going through that circuit.

Now this would be fine if it was just this circuit going off. As I could slowly work my way through what is wrong with it. But over the past 4 days as well as my garage MCB tripping I’ve had both upstairs and downstairs rings trip off, and as of today the upstairs lights have also tripped off.

They sometimes trip at the same time as the garage but they have tripped off just by themselves. I have tested all the rings and they appear to have no issues with the cables.

What makes it even more confusing is I have a split RCD DB, not once has the RCDs ever tripped on either side. But I have had the garage MCB trip on the left RCD and lights on the right RCD trip at the same time. This has also happened with the ring mains in the house.

I can’t get my head around how a single circuit on its own like the garage can appear to have an effect on another single circuit that are on separate RCDs.

Could it be an issue with the DB itself? Because as far as I can tell after testing each cable they haven’t got any issues. The MCBs can stay on for hours and just trip off.

Any help into this would be great as I’ve been pulling my hair out for days now.

Thanks, Lewis

 

[timhoward]

It might help to stick a photo up of your main house consumer unit and the consumer unit in the sun house.
Before going any further please also press the test button on both RCD's and check they actually work.
(By the way the weird cable is called split concentric)

 

[Lewis Curle]

It might help to stick a photo up of your main house consumer unit and the consumer unit in the sun house.
Before going any further please also press the test button on both RCD's and check they actually work.
(By the way the weird cable is called split concentric)

Thanks for the info on the cable, I’ll get some photos when I get home

 

[pc1966]

Very strange indeed.

When you say you have tested the insulation resistance was that using an electrician's style of meter that applies 250V or 500V DC during the test, or a multi-meter that applies a couple of volts at most?

Several circuits having similar faults is worrying as it suggests some common problem and if they are unrelated circuits that could be mice/rats chewing cables.

If you can do as suggested, try the test-buttons on the RCD to verify they are able to trip on a simulated fault, and get some photos it would help. Also if you can get a photo of the inside of your CU safely that would be good. So only if you can totally power it off at the main switch and are OK to remove it, photo it, and replace cover again without touching anything or disturbing the main 'tails' feeding it (large cables from the supply meter, etc).

 

[Lewis Curle]

Very strange indeed.

When you say you have tested the insulation resistance was that using an electrician's style of meter that applies 250V or 500V DC during the test, or a multi-meter that applies a couple of volts at most?

Several circuits having similar faults is worrying as it suggests some common problem and if they are unrelated circuits that could be mice/rats chewing cables.

If you can do as suggested, try the test-buttons on the RCD to verify they are able to trip on a simulated fault, and get some photos it would help. Also if you can get a photo of the inside of your CU safely that would be good. So only if you can totally power it off at the main switch and are OK to remove it, photo it, and replace cover again without touching anything or disturbing the main 'tails' feeding it (large cables from the supply meter, etc).

So the RCDs are working fine but just tonight the garage has went off twice and the down stairs ring has went off just now. What do you mean by CU?

For the record also my house is 7 years old and there isn’t many places rats or anything could get at the cables,

I tested the cables on all the circuits that were tripping and they have all passed a 500v insulation resistance test.

It’s just confusing me that if something in the garage was causing an issue on the sockets it would trip the now 16A MCB that I changed today from the 32A in an attempt to get it to trip. So as far as I can see there isn’t an issue in the garage circuits. They have all been tested as well and showing no issues.

But to trip a 40A MCB instead of a 16A is the most baffeling part to me. It’s also not consistent at all when it decides to trip

 

[Lewis Curle]

So the RCDs are working fine but just tonight the garage has went off twice and the down stairs ring has went off just now. What do you mean by CU?

For the record also my house is 7 years old and there isn’t many places rats or anything could get at the cables,

I tested the cables on all the circuits that were tripping and they have all passed a 500v insulation resistance test.

It’s just confusing me that if something in the garage was causing an issue on the sockets it would trip the now 16A MCB that I changed today from the 32A in an attempt to get it to trip. So as far as I can see there isn’t an issue in the garage circuits. They have all been tested as well and showing no issues.

But to trip a 40A MCB instead of a 16A is the most baffeling part to me. It’s also not consistent at all when it decides to trip

 

[UNG]

Do you have a fridge or freezer in the garage

 

[Lewis Curle]

Do you have a fridge or freezer in the garage

Only thing plugged in right now is my pc set up mate!

 

[timhoward]

It’s just confusing me that if something in the garage was causing an issue on the sockets it would trip the now 16A MCB that I changed today from the 32A in an attempt to get it to trip. So as far as I can see there isn’t an issue in the garage circuits. They have all been tested as well and showing no issues.

But to trip a 40A MCB instead of a 16A is the most baffeling part to me. It’s also not consistent at all when it decides to trip

It's hard to follow what you are saying. But exchanging breakers is definitely not going to help add clarity.

So we are looking for something that
a) is not leaking current to earth (the RCDs are functional)
b) is either 4 independent faults on different circuits or is somehow causing sufficient current to flow to cause any permutation of 4 different breakers to trip.

A similar photo of the inside of the smaller CU (consumer unit) might be worth doing.

(The neutrals from the SplitCon cable to the smaller CU are a right mess and possibly dangerous as it looks like the screw is biting on insulation. They need improving.)

@pc1966 - a very random thought - I don't suppose a broken supply neutral and very unbalanced phases between neighbouring properties could cause enough of a current hike to have this scatter gun effect?!

 

[davesparks]

I tested the cables on all the circuits that were tripping and they have all passed a 500v insulation resistance test.

When you say passed an IR test do you mean they had a perfect >999megohm or a just scraped through at 1megohm?

ut to trip a 40A MCB instead of a 16A is the most baffeling part to me. It’s also not consistent at all when it decides to trip

A 40A MCB and a 16A MCB will not discriminate on a fault, it is pretty much pot luck which one will trip first.

 

[pc1966]

@pc1966 - a very random thought - I don't suppose a broken supply neutral and very unbalanced phases between neighbouring properties could cause enough of a current hike to have this scatter gun effect?!

I would be surprised if you would see that happen a couple of times and not have blown some equipment up in the process!

To throw enough current to trip a 40A MCB is not going to go well with a PC, etc.

 

[pc1966]

I tested the cables on all the circuits that were tripping and they have all passed a 500v insulation resistance test.

When you did the IR testing of the cables did you do it more or less in the following way:

• The CPC (earth) of the cable remains connected to the installations main earth terminal at all times (basically you leave them in place as normally connected).
• After isolating both ends of the cable L and N (maybe just open the garage CU main switch as it should be double-pole to isolate those) connect N to E and then IR test L to N+E
• Then connect N to L and IR test L+N to E

I'm asking as it is common to do a quick and safe test of L+N to E since it avoids the risk of over-voltage on low power electronics like LED lights, dimmer switches, etc, and it usually picks up faults on T&E cable as that has the E (CPC) between L & N. However, in the case of SWA or split-concentric cable that has been crushed you might get a L-N fault and that would trip the over-current MCB protection without tripping the RCD protection for faults to E.

The reason for keeping the CPC connected is in case there is damage like a nail, etc, to true Earth but not to the CPC. With the CPC earthed then it shows up on the same test.

 

[Lewis Curle]

When you did the IR testing of the cables did you do it more or less in the following way:

• The CPC (earth) of the cable remains connected to the installations main earth terminal at all times (basically you leave them in place as normally connected).
• After isolating both ends of the cable L and N (maybe just open the garage CU main switch as it should be double-pole to isolate those) connect N to E and then IR test L to N+E
• Then connect N to L and IR test L+N to E

I'm asking as it is common to do a quick and safe test of L+N to E since it avoids the risk of over-voltage on low power electronics like LED lights, dimmer switches, etc, and it usually picks up faults on T&E cable as that has the E (CPC) between L & N. However, in the case of SWA or split-concentric cable that has been crushed you might get a L-N fault and that would trip the over-current MCB protection without tripping the RCD protection for faults to E.

The reason for keeping the CPC connected is in case there is damage like a nail, etc, to true Earth but not to the CPC. With the CPC earthed then it shows up on the same test.

I have more or less already done what you have described sir, but I’ll double check it again tonight just to be sure.

Something I noticed last night was when my partner started using the downstairs ring circuit to watch TV, turn lamps on and turn in the dishwasher. The downstairs ring tripped then the garage a few minutes later.

I’m unsure on how these circuits could be effecting each other but when my partner went to bed last night I have about an hour and half of no tripping on the pc. So I’m pretty sure there’s not an L-E fault anywhere like a dead short as it would trip instantly.

But I will double check the insulation resistance tonight,

Thanks all for your replies so far.

 

[Lewis Curle]

When you say passed an IR test do you mean they had a perfect >999megohm or a just scraped through at 1megohm?



A 40A MCB and a 16A MCB will not discriminate on a fault, it is pretty much pot luck which one will trip first.

They passed with the max reading off the tester. So when you say it will not discriminate on a fault what do you mean? The MCBs in the garage board have never tripped it’s always the 40A MCB one. So if there was an overload somehow being caused it would trip the 16A one first no?

Thanks for your reply though mate

 

[pc1966]

So when you say it will not discriminate on a fault what do you mean? The MCBs in the garage board have never tripped it’s always the 40A MCB one. So if there was an overload somehow being caused it would trip the 16A one first no?

Fault discrimination, now known as selectivity, is the ability of a cascade of protective devices to only trip the closest to the fault.

In the case of MCB they are selective on overloads that take time on the thermal trip side (so up to x3 or so from the rated value of the upstream device) but if you get a big fault, such as a short-circuit, then both devices would have the "instant" magnetic trip underway before the downstream device has actually opened and isolated the fault. Basically in many case both devices trip.

When cascading breakers when it matters, you need to add a short delay on the upstream device to give the downstream one time to act, but if it does not (or the fault is before it) then the upstream will go. Usually that means using a MCCB (at high cost) or a fuse (cheap, effective, but a pain to replace and typically means electrically-skilled staff).

If you look at commercial/industrial catalogues of electrical devices they often will have tables in the back giving you the selectivity limits for various combinations of fuse/MCB, MCCB/MCB, MCB/MCB and so on.

 

[davesparks]

They passed with the max reading off the tester. So when you say it will not discriminate on a fault what do you mean? The MCBs in the garage board have never tripped it’s always the 40A MCB one. So if there was an overload somehow being caused it would trip the 16A one first no?

Thanks for your reply though mate

By not discriminate I mean if there is a fault then there is no guarantee that the 16A MCB will operate before the 40A MCB.
If it is an overload then the 16A will operate first yes.

 

[pc1966]

Example table from Hager. Not quite your case, but if you had a 40A B-curve MCB feeding a 16A B-curve RCBO then any prospective fault above 0.19kA = 190A is likely to trip both devices:

 

[Lewis Curle]

Fault discrimination, now known as selectivity, is the ability of a cascade of protective devices to only trip the closest to the fault.

In the case of MCB they are selective on overloads that take time on the thermal trip side (so up to x3 or so from the rated value of the upstream device) but if you get a big fault, such as a short-circuit, then both devices would have the "instant" magnetic trip underway before the downstream device has actually opened and isolated the fault. Basically in many case both devices trip.

When cascading breakers when it matters, you need to add a short delay on the upstream device to give the downstream one time to act, but if it does not (or the fault is before it) then the upstream will go. Usually that means using a MCCB (at high cost) or a fuse (cheap, effective, but a pain to replace and typically means electrically-skilled staff).

If you look at commercial/industrial catalogues of electrical devices they often will have tables in the back giving you the selectivity limits for various combinations of fuse/MCB, MCCB/MCB, MCB/MCB and so on.

So after reading all that and thanks for the information, it looks like the fault is happening from the main DB in my house to the little one in the garage? Since the garage ones never trip it just be occurring before those MCBs are involved?

Another question is it even possible for a single circuit such as the garage one, to have an effect on other circuits in the DB. The most confusing part to me is other MCBs have been going off as well.

Thanks for you time again

 

[pc1966]

So after reading all that and thanks for the information, it looks like the fault is happening from the main DB in my house to the little one in the garage? Since the garage ones never trip it just be occurring before those MCBs are involved?

It looks that way.

Another question is it even possible for a single circuit such as the garage one, to have an effect on other circuits in the DB. The most confusing part to me is other MCBs have been going off as well.

It is just possible that a big fault on one circuit causes enough of a surge on another that it also trips.

But they would go simultaneously to all intents and purposes, and it is odd to have that without some evidence of poor IR readings.

 

[Lewis Curle]

It looks that way.


It is just possible that a big fault on one circuit causes enough of a surge on another that it also trips.

But they would go simultaneously to all intents and purposes, and it is odd to have that without some evidence of poor IR readings.

Alright mate well I’ll do another IR test tonight on the circuit, just to be sure. I’ll keep you informed on my findings!

 

[UNG]

So the last time I saw a fault like / similar to this was around 35 or so years ago and the memory is a little bit hazy about it but I do recall the problem ended up as a DNO distribution issue

Now to get a bit more background where is this property located is it urban, semi rural or rural, how is the supply delivered is it underground or overhead,

Does this random tripping occur more or only during episodes of wet weather

What connected loads does the garage have, are there any PIR controlled outdoor lights supplied from the garage

While trying to identify the fault have you done any random voltage checks of the main supply at different times to see if there are any large variations that may suggest an external mains issue

 

[Lewis Curle]

So the last time I saw a fault like / similar to this was around 35 or so years ago and the memory is a little bit hazy about it but I do recall the problem ended up as a DNO distribution issue

Now to get a bit more background where is this property located is it urban, semi rural or rural, how is the supply delivered is it underground or overhead,

Does this random tripping occur more or only during episodes of wet weather

What connected loads does the garage have, are there any PIR controlled outdoor lights supplied from the garage

While trying to identify the fault have you done any random voltage checks of the main supply at different times to see if there are any large variations that may suggest an external mains issue

Hello mate thanks for your message.
I live in an semi urban set of new builds on the outside of town. I’m pretty sure all the cables are ran underground because there’s a subby not 100ft from my house.

I do have an outside light that hasn’t work for some time now that is on a pir, I didn’t think to look at that since the 6A MCB baby ever tripped that controls it. I will diss connect it tonight to test!

As far as the voltage checks I seem to get a level 240V when I’ve checked, but I will double check again to be sure!

Cheers, Lewis

 

[marconi]

Hello. Please would you tell me:

1. The make, model and power of your gaming PSU. Do you have more than one?
2. Do you plug them directly into a socket or via a surge suppression socket strip?
3. When you say nothing is on do you mean the PC, IT and gaming equipment including PSU is switched off on the equipment or at the socket?
4. Co-incident with moving the equipment to the sunhouse have you added any equipment or changed any of it?
5. Have you tried leaving the 40A mcb off for a few days to isolate power to the sunhouse and the equipment in there?
6. What white goods do you have ie washer, dryer, dishwasher and microwave? Have these changed recently?
7. Do you have an induction hob?
8. Have you had a smart meter fitted recently or at all?
9. Do your lights ever flicker? Do your neighbours ever?
10. Has any digging been done in the garden near the cable to the sunhouse?
11. Have you had any water leaks or rain water ingress to your home of sunhouse?
12. Who did the electricity supply to the sunhouse? Do you have a test certificate if it was done after the main house? How long is the cable run?
13. Would you say the problem never happened until the shift of equipment to the sunhouse?
14. Do you have an electric vehicle charger?
15. What exactly is fed by each circuit breaker - a labelled picture would be helpful.
16. Do you have air conditioning units or heat pumps?
17. Please post a picture of your supply intake and meter.

My hypothesis is you have a loose line, neutral or earth connection(s) - within or without your property - which is causing high dV/dt of the supply voltage; a or several connected loads have mains filters within them which are reacting to the high dV/dt with a high albeit brief current as their capacitors change their state of charge. I suspect the circuit for the sunhouse since it has used unusually split concentric cable which needs care terminating well. The reliable conduction of a connection or joint can vary with current density.

 

[Lewis Curle]

Hello. Please would you tell me:

1. The make, model and power of your gaming PSU. Do you have more than one?
2. Do you plug them directly into a socket or via a surge suppression socket strip?
3. When you say nothing is on do you mean the PC, IT and gaming equipment including PSU is switched off on the equipment or at the socket?
4. Co-incident with moving the equipment to the sunhouse have you added any equipment or changed any of it?
5. Have you tried leaving the 40A mcb off for a few days to isolate power to the sunhouse and the equipment in there?
6. What white goods do you have ie washer, dryer, dishwasher and microwave? Have these changed recently?
7. Do you have an induction hob?
8. Have you had a smart meter fitted recently or at all?
9. Do your lights ever flicker? Do your neighbours ever?
10. Has any digging been done in the garden near the cable to the sunhouse?
11. Have you had any water leaks or rain water ingress to your home of sunhouse?
12. Who did the electricity supply to the sunhouse? Do you have a test certificate if it was done after the main house? How long is the cable run?
13. Would you say the problem never happened until the shift of equipment to the sunhouse?
14. Do you have an electric vehicle charger?
15. What exactly is fed by each circuit breaker - a labelled picture would be helpful.
16. Do you have air conditioning units or heat pumps?
17. Please post a picture of your supply intake and meter.

My hypothesis is you have a loose line, neutral or earth connection(s) - within or without your property - which is causing high dV/dt of the supply voltage; a or several connected loads have mains filters within them which are reacting to the high dV/dt with a high albeit brief current as their capacitors change their state of charge. I suspect the circuit for the sunhouse since it has used unusually split concentric cable which needs care terminating well.

Wow thanks for taking the time to write all that.

Hello. Please would you tell me:

1. The make, model and power of your gaming PSU. Do you have more than one?
2. Do you plug them directly into a socket or via a surge suppression socket strip?
3. When you say nothing is on do you mean the PC, IT and gaming equipment including PSU is switched off on the equipment or at the socket?
4. Co-incident with moving the equipment to the sunhouse have you added any equipment or changed any of it?
5. Have you tried leaving the 40A mcb off for a few days to isolate power to the sunhouse and the equipment in there?
6. What white goods do you have ie washer, dryer, dishwasher and microwave? Have these changed recently?
7. Do you have an induction hob?
8. Have you had a smart meter fitted recently or at all?
9. Do your lights ever flicker? Do your neighbours ever?
10. Has any digging been done in the garden near the cable to the sunhouse?
11. Have you had any water leaks or rain water ingress to your home of sunhouse?
12. Who did the electricity supply to the sunhouse? Do you have a test certificate if it was done after the main house? How long is the cable run?
13. Would you say the problem never happened until the shift of equipment to the sunhouse?
14. Do you have an electric vehicle charger?
15. What exactly is fed by each circuit breaker - a labelled picture would be helpful.
16. Do you have air conditioning units or heat pumps?
17. Please post a picture of your supply intake and meter.

My hypothesis is you have a loose line, neutral or earth connection(s) - within or without your property - which is causing high dV/dt of the supply voltage; a or several connected loads have mains filters within them which are reacting to the high dV/dt with a high albeit brief current as their capacitors change their state of charge. I suspect the circuit for the sunhouse since it has used unusually split concentric cable which needs care terminating well. The reliable conduction of a connection or joint can vary with current density

Hello. Please would you tell me:

1. The make, model and power of your gaming PSU. Do you have more than one?
2. Do you plug them directly into a socket or via a surge suppression socket strip?
3. When you say nothing is on do you mean the PC, IT and gaming equipment including PSU is switched off on the equipment or at the socket?
4. Co-incident with moving the equipment to the sunhouse have you added any equipment or changed any of it?
5. Have you tried leaving the 40A mcb off for a few days to isolate power to the sunhouse and the equipment in there?
6. What white goods do you have ie washer, dryer, dishwasher and microwave? Have these changed recently?
7. Do you have an induction hob?
8. Have you had a smart meter fitted recently or at all?
9. Do your lights ever flicker? Do your neighbours ever?
10. Has any digging been done in the garden near the cable to the sunhouse?
11. Have you had any water leaks or rain water ingress to your home of sunhouse?
12. Who did the electricity supply to the sunhouse? Do you have a test certificate if it was done after the main house? How long is the cable run?
13. Would you say the problem never happened until the shift of equipment to the sunhouse?
14. Do you have an electric vehicle charger?
15. What exactly is fed by each circuit breaker - a labelled picture would be helpful.
16. Do you have air conditioning units or heat pumps?
17. Please post a picture of your supply intake and meter.

My hypothesis is you have a loose line, neutral or earth connection(s) - within or without your property - which is causing high dV/dt of the supply voltage; a or several connected loads have mains filters within them which are reacting to the high dV/dt with a high albeit brief current as their capacitors change their state of charge. I suspect the circuit for the sunhouse since it has used unusually split concentric cable which needs care terminating well. The reliable conduction of a connection or joint can vary with current density.

Hello mate first of all thanks for taking the time to write all that!

So I’m unsure on my PSU model I will find out tonight
2.

Hello. Please would you tell me:

1. The make, model and power of your gaming PSU. Do you have more than one?
2. Do you plug them directly into a socket or via a surge suppression socket strip?
3. When you say nothing is on do you mean the PC, IT and gaming equipment including PSU is switched off on the equipment or at the socket?
4. Co-incident with moving the equipment to the sunhouse have you added any equipment or changed any of it?
5. Have you tried leaving the 40A mcb off for a few days to isolate power to the sunhouse and the equipment in there?
6. What white goods do you have ie washer, dryer, dishwasher and microwave? Have these changed recently?
7. Do you have an induction hob?
8. Have you had a smart meter fitted recently or at all?
9. Do your lights ever flicker? Do your neighbours ever?
10. Has any digging been done in the garden near the cable to the sunhouse?
11. Have you had any water leaks or rain water ingress to your home of sunhouse?
12. Who did the electricity supply to the sunhouse? Do you have a test certificate if it was done after the main house? How long is the cable run?
13. Would you say the problem never happened until the shift of equipment to the sunhouse?
14. Do you have an electric vehicle charger?
15. What exactly is fed by each circuit breaker - a labelled picture would be helpful.
16. Do you have air conditioning units or heat pumps?
17. Please post a picture of your supply intake and meter.

My hypothesis is you have a loose line, neutral or earth connection(s) - within or without your property - which is causing high dV/dt of the supply voltage; a or several connected loads have mains filters within them which are reacting to the high dV/dt with a high albeit brief current as their capacitors change their state of charge. I suspect the circuit for the sunhouse since it has used unusually split concentric cable which needs care terminating well. The reliable conduction of a connection or joint can vary with current density.

I will put my pc details in the chat for you to see sir! First of all thanks for taking the time to write all that.
1. See picture
2. It is all plugged in via a surge suppression strip, i have only changed that as of a couple of days ago and the issue is still happening.
3.I leave my PC and everything plugged in and turned on at the socket.
4. My PC has never tripped the inside circuits of my house before, The garage in the past has been found with the MCB off but never this much.
5. I havent left it off for more than a day no.
6. Yeah we have all of the above but no they have not been touched since we moved in.
7. We have a Gas hob
8. We have a smart meter just plugged into the sockets in the kitchen, we have recently plugged it back in a few weeks ago, however i unplugged it again to see if it was causing the issue and it appears to not have had any effect as its still tripping.
9.Not that i know off.
10. No digging has been done since we moved in,
11.No water that i can tell.
12.Its definitely gotten worse since the equipment was moved in, But we have used the sun house a lot in the past and i must say it was rarely off but it has happened.
13.Not never happened just happening a lot more now.
14. NO
15. The 40A one in the picture is the garage one but ill get a laballed pictuire.
16.No
17. I will get those photos.

Thanks hope that helps please ask any more questions that you want to. I appreciate the help!


Also i redone the IR test and took the dodgy outside light down and its still tripping. The IR test again came back perfect.

 

[Lewis Curle]

Hello. Please would you tell me:

1. The make, model and power of your gaming PSU. Do you have more than one?
2. Do you plug them directly into a socket or via a surge suppression socket strip?
3. When you say nothing is on do you mean the PC, IT and gaming equipment including PSU is switched off on the equipment or at the socket?
4. Co-incident with moving the equipment to the sunhouse have you added any equipment or changed any of it?
5. Have you tried leaving the 40A mcb off for a few days to isolate power to the sunhouse and the equipment in there?
6. What white goods do you have ie washer, dryer, dishwasher and microwave? Have these changed recently?
7. Do you have an induction hob?
8. Have you had a smart meter fitted recently or at all?
9. Do your lights ever flicker? Do your neighbours ever?
10. Has any digging been done in the garden near the cable to the sunhouse?
11. Have you had any water leaks or rain water ingress to your home of sunhouse?
12. Who did the electricity supply to the sunhouse? Do you have a test certificate if it was done after the main house? How long is the cable run?
13. Would you say the problem never happened until the shift of equipment to the sunhouse?
14. Do you have an electric vehicle charger?
15. What exactly is fed by each circuit breaker - a labelled picture would be helpful.
16. Do you have air conditioning units or heat pumps?
17. Please post a picture of your supply intake and meter.

My hypothesis is you have a loose line, neutral or earth connection(s) - within or without your property - which is causing high dV/dt of the supply voltage; a or several connected loads have mains filters within them which are reacting to the high dV/dt with a high albeit brief current as their capacitors change their state of charge. I suspect the circuit for the sunhouse since it has used unusually split concentric cable which needs care terminating well. The reliable conduction of a connection or joint can vary with current density.

 

[marconi]

Thank you.

For now it would be helpful if you opened up each CU (House and sun house) and with power off carefully inspect where the lower terminals of mcbs connect to busbar to confirm they are clamping or being screwed onto busbar. Tighten up all lower mcb screws and note down any which appeared loose. Do the same for RCDs and mains switches

Check solidity and security of neutral and cpc connections by tug and wiggle check. Again note any loose ones and tighten up. While you are at it remake the neutrals for the split concentric at the house CU.

With all sunhouse IT and gaming powered up go to intake and meter board and gently wiggle - not tug - the tails and feeds. Any trips?

Is the surge socket strip a simple type with a glowing neon or is it a professional one which contains inductors, capacitors and over voltage protection Eg by Olson?

Try plugging your sunhouse IT and gaming equipment directly into mains instead of via the surge socket strip. Leave for say a few days or until another mob trip happens.

Try leaving your IT and gaming equipment unplugged from mains for a few days or until trip happens.

Try turning off main switch of sunhouse CU but house 40A mob on for a few days or until trip happens.

What is the answer to 12 please? I will not give you a hard time if it was you.

Probably enough for now.

 

[Lewis Curle]

Thank you.

For now it would be helpful if you opened up each CU (House and sun house) and with power off carefully inspect where the lower terminals of mcbs connect to busbar to confirm they are clamping or being screwed onto busbar. Tighten up all lower mcb screws and note down any which appeared loose. Do the same for RCDs and mains switches

Check solidity and security of neutral and cpc connections by tug and wiggle check. Again note any loose ones and tighten up. While you are at it remake the neutrals for the split concentric at the house CU.

With all sunhouse IT and gaming powered up go to intake and meter board and gently wiggle - not tug - the tails and feeds. Any trips?

Is the surge socket strip a simple type with a glowing neon or is it a professional one which contains inductors, capacitors and over voltage protection Eg by Olson?

Try plugging your sunhouse IT and gaming equipment directly into mains instead of via the surge socket strip. Leave for say a few days or until another mob trip happens.

Try leaving your IT and gaming equipment unplugged from mains for a few days or until trip happens.

Try turning off main switch of sunhouse CU but house 40A mob on for a few days or until trip happens.

What is the answer to 12 please? I will not give you a hard time if it was you.

Probably enough for now.

Ok mate i will do as you say at some point today and come back with results!

The surge protection strip is LOGIK which i think is just a standard one of the shelf electrical wholesalers.

I will try and see if the error occurs when nothing is plugged into the sunhouse, Can a bad PC power unit cause things like this to happen?

So the cable to the sunhouse i know little about as it was all here when we moved in. The sun house is an extension of the old garage so i imagine the its the original cable from when the whole place was built. I have considered wiring a temp 6mm SWA from my DB to the garage. To see if the duct or something is crushing the cable underground where i cant see but surely any issues would show up on the testing i have done?

Again thanks for taking the time i will get back to you later today

 

[marconi]

High performance high power Pc and gaming power supplies do not last forever. They contain capacitors which are worked hard and run hot which reduces their life. One might expect 20000 hours life from the PSU but considerably less if the PSu is left on all the time. One sign of failing capacitors is mcb tripping. How old are your power supplies and do you leave them powered up all the time? Mcbs often trip faster than fuses rupture.
This is why some time with your equipment unplugged would be helpful.

what is the ambient temperature like in your sunhouse? Does it get quite warm at times or has it in the past ie over say 18-21C? Are the fans working and any filters clear of dust And unobstructed? Check there is good air flow around PSus and that one does not suck in the hot air from the other.

Last, these sort of power supplies have high inrush current when turned on. The value depends on where in the mains cycle they are energised and the state and polarity of charge on the capacitor. If there was a loose connection then it could be inrush current is tripping the mcb.

 

[Bob Geldoff1234]

It might be worth ruling out faulty breakers.The 40amp one could be very sensitive and the others that trip randomly could be going the same way.Maybe worth swapping out the 40amp breaker for a new one to see if that cures it?

 

[Lewis Curle]

It might be worth ruling out faulty breakers.The 40amp one could be very sensitive and the others that trip randomly could be going the same way.Maybe worth swapping out the 40amp breaker for a new one to see if that cures it?

I’ve already swapped it out mate! But thanks for the advice

 

[marconi]

Corsair CX750M (2021) Power Supply Review - https://www.tomshardware.com/reviews/corsair-cx750m-2021-power-supply-review/2

The inrush current from cold start at 230V ac for a single Corsair cx750M bronze according to tomsharware is circa 90A. It could be higher if the capacitors are charged such that their voltage adds to the mains.

 

[Lewis Curle]

Corsair CX750M (2021) Power Supply Review - https://www.tomshardware.com/reviews/corsair-cx750m-2021-power-supply-review/2

The inrush current from cold start at 230V ac for a single Corsair cx750M bronze according to tomsharware is circa 90A. It could be higher if the capacitors are charged such that their voltage adds to the mains.

Ok mate thanks for looking into this! I am going to test the theory of the my pc set up now being plugged in for a couple days to see if it trips. It will give it chance to discharge fully as well.

I have fully reconnected the two DBS involved to make sure it alls all tight and it tripped shortly after redoing it.

So another thing checked of the list! I will keep you informed if my discoveries

 

[Lewis Curle]

Corsair CX750M (2021) Power Supply Review - https://www.tomshardware.com/reviews/corsair-cx750m-2021-power-supply-review/2

The inrush current from cold start at 230V ac for a single Corsair cx750M bronze according to tomsharware is circa 90A. It could be higher if the capacitors are charged such that their voltage adds to the mains.

So I’ve done some testing over the past couple of days.

I totally unplugged my pc set up for two days, in that time the garage MCB has not tripped once. I spent a night in there with some mates and we had the space heater, all the lights and had things like phones charging and the MCB stayed on with no issues.

I’ve been back in tonight to try and game, I got home around 6pm. Turned my pc on and had it play a YouTube video whilst I ate and put my kid to bed. It was on for around two hours but I wasn’t at the pc, I went in to game just before 8 and within 5 minutes of me playing not even a strenuous game the breaker tripped.

So my question is now, does a pc pull more power when playing games? I assume it does when playing a graphics intensive game. So what I am now doing is having my pc plugged in alone with no monitors, just on standby to see if the MCB will trip. If this is the case I’m going to maybe move my pc back into the house for a few days to see if it trips anything.

My worry is that I move it back into my house and it just works with no issues because I don’t know where to go if that’s the case. I would rather it was the PCs power unit just so i can change it and be done with all of this

I hope all of that made sense and would appreciate any more advice you may have sir.
Thanks, Lewis

 

[marconi]

Thank you for the update. I will have a think and let you know tomorrow. Just speaking generally, as computers work harder at number crunching their power consumption will increase. This is of course what is happening in video games especially those with high fidelity graphics and game physics ie dealing with motion, collisions, interactions with objects and background and not forgetting the player(s) input.

How many Corsair power units where powered up and supplying when you tried a game this evening?

And to be clear which mcb tripped?

Please tell me the type of the 40A MCB which supplies the sunhouse and also the rating and type of the mcb for the ring in sunhouse. Eg 40A type B and 32A type B? It may be the waveform of the current drawn by the corsairs power supplies has a form which has a high crest factor which means it has a high peak current compared to the average current. If this is the case The MCBs responds to waveform as if this was a short circuit And trips. But this is my thinking at the moment So no changes yet please.

how long is the cable run from house db to sunhouse db? What mm2 is the cable? Volt drop with increasing current may be a factor. The Corsair has an input voltage range something like 100 to 230V without the need to change any settings. What happens is that at lower voltages the current increases as required to deliver the same power output.

ps: crest factor is peak current/rms current

 

[James]

Can you post a picture of the 40A breaker that is tripping?

 

[nicebutdim]

Can you post a picture of the 40A breaker that is tripping?

Been thinking, perhaps, along similar lines, but scrolled up and see the OP posted images in #6. It is indeed a 40A MCB.

 

[Lewis Curle]

Thank you for the update. I will have a think and let you know tomorrow. Just speaking generally, as computers work harder at number crunching their power consumption will increase. This is of course what is happening in video games especially those with high fidelity graphics and game physics ie dealing with motion, collisions, interactions with objects and background and not forgetting the player(s) input.

How many Corsair power units where powered up and supplying when you tried a game this evening?

And to be clear which mcb tripped?

Please tell me the type of the 40A MCB which supplies the sunhouse and also the rating and type of the mcb for the ring in sunhouse. Eg 40A type B and 32A type B? It may be the waveform of the current drawn by the corsairs power supplies has a form which has a high crest factor which means it has a high peak current compared to the average current. If this is the case The MCBs responds to waveform as if this was a short circuit And trips. But this is my thinking at the moment So no changes yet please.

how long is the cable run from house db to sunhouse db? What mm2 is the cable? Volt drop with increasing current may be a factor. The Corsair has an input voltage range something like 100 to 230V without the need to change any settings. What happens is that at lower voltages the current increases as required to deliver the same power output.

ps: crest factor is peak current/rms current

The MCB in the home DB feeding the garage is a 40A type B that is using a 6mm core live and a bunch of little neutrals. Inside the sun house itself it’s on a 16A MCB currently. The original circuit in the sun house was just a 16A radial, but I changed it to a ring and made the MCB a 32A for a while but I have since changed it back to the 16A(all type Bs)

I made the change because I wanted to be able to have more on the circuit, without it being an issue. I have changed it back to a 16A MCB but I’ve left it as a ring instead of the radial. It’s been about three weeks since I made the move Into the sun house and it worked for about two weeks and now this issue has been going on for a week.

I’m confident the cabling is all good in the sun house and the cable going to the sun house has tested out good as well. I put it out of my mind that my PC set up could be the issue since it’s worked perfectly when it was in my house on the upstairs ring main.

I’m having my brother round on Thursday and he is bringing his pc. He’s going to plug his pc into my setup and see if we have the same issue. If we don’t then it just be my pc.

Thanks all for your replies! I really do appreciate you taking the time to help me out.

 

[marconi]

Do you have a fridge in the sun house?

 

[Lewis Curle]

Do you have a fridge in the sun house?

I do but it and the freezer is not plugged in, hasn’t been for a while!

 

[marconi]

How many Corsair power units where powered up and supplying when you tried a game yesterday evening?

Do you have LED lighting in the sunhouse? If you do how many lamps? Are they normally on when you are gaming?

LED lamps have a high crest factor waveform too.

I will await your post after Thursday's trial.

 

[marconi]

If you look at ‘Test results - Final thoughts’ you can see a table showing some test data for your Corsair PSu for different game loads and see how power consumption increases with game computing load.

Corsair CX750M 750W 80 PLUS Bronze Power Supply Review - https://www.tweaktown.com/reviews/7125/corsair-cx750m-750w-80-plus-bronze-power-supply-review/index.html

 

[Lewis Curle]

If you look at ‘Test results - Final thoughts’ you can see a table showing some test data for your Corsair PSu for different game loads and see how power consumption increases with game computing load.

Corsair CX750M 750W 80 PLUS Bronze Power Supply Review - https://www.tweaktown.com/reviews/7125/corsair-cx750m-750w-80-plus-bronze-power-supply-review/index.html

So I did some digging into what my pc can use in terms of power.

Over the last 6 months I’ve changed the graphics card to a 3070ti. Added a 2 TB SDD and changed the water cooling system to a fan (the water cooling killed my old graphics card from leaking, was a nightmare so I got rid).

After doing the power calculations it recommended I should have a 700W power supply and that’s without taking into account all my USBs plugged in for mouse and keyboard etc.

I also had my brother round last night and he used his pc in my setup and it worked for 3 hours no issues playing intensive games. So straight away I bought myself a new 1000W CPU so it had the power for sure and to make sure it wasn’t my 750W PSU causing the issue. I was pretty confident that changing the PSU would fix my issue. It’s arriving tommorow so I’m going to try it but my confidence was knocked when I got home today and the 40A MCB was off. All of my screens and cables were plugged in at the wall but none of it was turned on and my PC is currently in bits in the table so that definitely wasn’t plugged in.

I’m just a bit confused now as it always seems like my pc was causing the issue but now I’m not convinced. My partner has had a busy day in the house using a lot of the white goods units(washing machine, dryer and dishwasher), kettle and what not.

But I can’t see how if any of that was causing an issue. That the 40A MCB for the garage would be the only circuit to trip when there was literally no load going down the cable.

As I say I’m going to change my PSU anyway to make sure but I’m doubtful that’s the issue now. I’ll let you know how it goes. Thanks for reading!

 

[marconi]

Ta. Will have a ponder. I have been thinking about sending you a simple circuit to detect a L-N arc ie a brief short circuit. I will say more tomorrow. I suspect the cable between the house db and the sunhouse db has an L-N defect.

I need to have a rummage in my den for some components tomorrow.

 

[Lewis Curle]

Ta. Will have a ponder. I have been thinking about sending you a simple circuit to detect a L-N arc ie a brief short circuit. I will say more tomorrow. I suspect the cable between the house db and the sunhouse db has an L-N defect.

I need to have a rummage in my den for some components tomorrow.

Alright mate take your time, appreciate it though. I might run a temp cable from the house to the garage to see what that will do.

 

[marconi]

If you have the time and inclination would you disconnect the sunhouse cable completely at both ends and then separate the blue neutrals at both ends.

Then would you do some pair-wise insulation resistance checks of the blue neutral conductors using as as a guide what I have shown in the attachment. The 6mm2 scc has 7 blue neutrals wrapped around it.

I am just wondering whether the cable is damaged and if this damage includes individual neutral cores coming into contact. If this unintended contact is present then maybe whatever has caused it has also damaged the insulation of the central brown conductor at the same place.

 

[UNG]

overloading is a common reason .

I doubt you have read all of the posts in this thread with a comment like that

 

[marconi]

Another simple test after the one I mentioned before this post is we could disconnect and isolate all the neutral conductors at both ends and then energise the SCC with only its line and cpc connected at both ends and wait to see if the sunhouse mcb trips. The sunhouse db mains switch is off for this test. It would have to be left this way for a few days to see if we have removed the N path and thereby stopped the fault current operating the sunhouse mcb. Swap the sunhouse 40A mcb for a 3A B preferably or 6A B maximum for this test as we want a sensitive response.

After a few days reconnect Ns at both ends and still leave sunhouse mains switch off. Keep the 3 or 6 A mcb in place and leave for a few more days to see what happens.

A feature of this cable fault - (arcing between L-N?) - is there may indeed be current flowing between L-N intermittently and regularly but a 40A mcb requires a sizeable current to trip it so most of the time the fault is tolerated. The 3 or 6 A mcbs should respond quicker.

 

[Lewis Curle]

Another simple test after the one I mentioned before this post is we could disconnect and isolate all the neutral conductors at both ends and then energise the SCC with only its line and cpc connected at both ends and wait to see if the sunhouse mcb trips. The sunhouse db mains switch is off for this test. It would have to be left this way for a few days to see if we have removed the N path and thereby stopped the fault current operating the sunhouse mcb. Swap the sunhouse 40A mcb for a 3A B preferably or 6A B maximum for this test as we want a sensitive response.

After a few days reconnect Ns at both ends and still leave sunhouse mains switch off. Keep the 3 or 6 A mcb in place and leave for a few more days to see what happens.

A feature of this cable fault - (arcing between L-N?) - is there may indeed be current flowing between L-N intermittently and regularly but a 40A mcb requires a sizeable current to trip it so most of the time the fault is tolerated. The 3 or 6 A mcbs should respond quicker.

Hello mate I will do the neutral resistance test tonight that you described in the other post! I will also look into getting some smaller MCBs to try what you have mentioned in this one.

I’m burnt out with trying to fix it but I will come back with my findings over the next couple of days!

Thanks again for taking the time to try and help

 

[Lewis Curle]

Another simple test after the one I mentioned before this post is we could disconnect and isolate all the neutral conductors at both ends and then energise the SCC with only its line and cpc connected at both ends and wait to see if the sunhouse mcb trips. The sunhouse db mains switch is off for this test. It would have to be left this way for a few days to see if we have removed the N path and thereby stopped the fault current operating the sunhouse mcb. Swap the sunhouse 40A mcb for a 3A B preferably or 6A B maximum for this test as we want a sensitive response.

After a few days reconnect Ns at both ends and still leave sunhouse mains switch off. Keep the 3 or 6 A mcb in place and leave for a few more days to see what happens.

A feature of this cable fault - (arcing between L-N?) - is there may indeed be current flowing between L-N intermittently and regularly but a 40A mcb requires a sizeable current to trip it so most of the time the fault is tolerated. The 3 or 6 A mcbs should respond quicker.

Hello sir, sorry for disappearing for a week I needed the break from trying to solve it. I have been back at it over the past few days and this is what I’ve discovered.

So I changed my PSU in the pc for a 1000w one, I did that because when my brother came round with his pc it worked with no issues for about 2 and a half hours. After the change in my pc it lasted about half an hour before it tripped (again the 40A MCB in the house).

So I sourced some 4mm tri rated SWA and ran it temporarily from my house to the garage DB to see if the cable was causing the issue. I was on my pc for about an hour just watching videos, then I jumped onto total war Warhammer 3 with my brother and before we even got into the game the trip occurred.

So basically the cable can’t be the issue anymore. Which is good and bad because it would have a nightmare to change anyway but now I’m stuck again. The issue definitely happens more when I am gaming at my pc. But the trip has happened when my pc wasn’t even plugged in. So I’m finding it hard to believe that my pc is causing the issue when it happens without it being involved. It just seems that when I’m gaming and using more power in the sun house it trips a lot more.

So from the top I have now changed
1. The house DBs MCB
2. The cable running from the house to the garage
3. My PSU
4. The MCB in the garage DB

5. I have checked the wiring twice in the sun house and I can find no issues when doing IR test and continuity from end to ends. The sockets have all had the connection made off again to check for loose connections.
6. I have tightened up all the Connections inside each DB and again can find no issues.

What I am now considering doing now is changing the garage DB for a brand new one to rule out the main switch in there being the issue. Then if that doesn’t work I’m honestly considering just rewiring the whole of the sun house just to say it’s been done properly. To be honest whoever done it hasn’t done a great job with cable routes and it looks very rushed (when you look at it all above in the rafters).

I am also considering whether the RCD on the house DB can cause any wierd issues like this.

I just can’t get my head around why the 40A MCB is tripping and not the 16A.

Again thanks for taking the time to read and I would be very grateful for any more of your time.

Cheers, Lewis

 

[Lewis Curle]

Hello sir, sorry for disappearing for a week I needed the break from trying to solve it. I have been back at it over the past few days and this is what I’ve discovered.

So I changed my PSU in the pc for a 1000w one, I did that because when my brother came round with his pc it worked with no issues for about 2 and a half hours. After the change in my pc it lasted about half an hour before it tripped (again the 40A MCB in the house).

So I sourced some 4mm tri rated SWA and ran it temporarily from my house to the garage DB to see if the cable was causing the issue. I was on my pc for about an hour just watching videos, then I jumped onto total war Warhammer 3 with my brother and before we even got into the game the trip occurred.

So basically the cable can’t be the issue anymore. Which is good and bad because it would have a nightmare to change anyway but now I’m stuck again. The issue definitely happens more when I am gaming at my pc. But the trip has happened when my pc wasn’t even plugged in. So I’m finding it hard to believe that my pc is causing the issue when it happens without it being involved. It just seems that when I’m gaming and using more power in the sun house it trips a lot more.

So from the top I have now changed
1. The house DBs MCB
2. The cable running from the house to the garage
3. My PSU
4. The MCB in the garage DB

5. I have checked the wiring twice in the sun house and I can find no issues when doing IR test and continuity from end to ends. The sockets have all had the connection made off again to check for loose connections.
6. I have tightened up all the Connections inside each DB and again can find no issues.

What I am now considering doing now is changing the garage DB for a brand new one to rule out the main switch in there being the issue. Then if that doesn’t work I’m honestly considering just rewiring the whole of the sun house just to say it’s been done properly. To be honest whoever done it hasn’t done a great job with cable routes and it looks very rushed (when you look at it all above in the rafters).

I am also considering whether the RCD on the house DB can cause any wierd issues like this.

I just can’t get my head around why the 40A MCB is tripping and not the 16A.

Again thanks for taking the time to read and I would be very grateful for any more of your time.

Cheers, Lewis

Also I gamed with no issues for about 3 hours when my partner was out of the house and nothing inside was being used. But after about 10 minutes of her getting home and turning stuff on in the house. It tripped and continued to do so two more times until I stopped turning it back on.

I’m very confident she isn’t turning it off just to make that clear!