Electric keeps tripping - possibly found source

victor2

silvercar said:

victor2 said:

silvercar said:

victor2 said:

Do you have a smart electric meter? If so, does the IHD show high usage at any point? Or you could install the Bright app on a smartphone and see your usage history in 30 minute intervals and look for any unusual spikes. Of course, if it is a sudden spike, these won't catch it before it trips.

I have a smart meter. But it is all sudden spikes.

Can you relate those sudden spikes to anything? Such as the fridge cutting in or the central heating pump running? It sounds like you're looking for something that you don't run on demand, but is controlled by a thermostat or other switch.

Nothing. First time it happened, there was nothing switched on.

It’s just flipped again, with nothing at all on!

Could be faulty wiring or socket then, which needs an electrician. Hope your insurance comes up good.

Edit:
Do you have a long extension lead you could run from the sockets on the other circuit that isn't tripping, to power your fridge while you get it sorted? If you do, just make sure it's fully unwound to reduce the possibility of it overheating 

victor2

Before anyone points out the dangers of running an appliance on an extension lead, I should add not to leave it unattended or on overnight. If the fridge has been running all day, it should be OK left off overnight. And check the extension for getting too warm.

Section62

GDB2222 said:

The MCB is rated at 20 amps. Do you know why it is not 32 amps, which is usual for a ring main?

With nearly everything switched off (and **unplugged**, I hope!, so as to be quite sure), it’s unlikely to simply be overloaded. So, you either have a faulty appliance or faulty wiring. If you unplug everything and it still trips, it’s the wiring and you need an electrician. 

Furthermore, something that trips the mcb can get seriously overheated and cause a fire, so don’t delay. 

This^.

The MCB which has tripped (position 8) is also labeled "Ring Circuit First Floor" - which suggests the fault could be somewhere other than just the lounge/ground floor. The labelling should never be relied on, but in this case I'd have more doubts about it than normal.

The MCB's in positions 8,9 and 10 (unidentified) are all 20A, which implies the installer considered it necessary to downrate the circuits - we had a case on the forum a while back where a council contractor did just that because they believed the cables were run under loft insulation. Another possibility is radial wiring perhaps.

While the electrician is there I'd also ask them to investigate why positions 1 to 4 have 10A MCB's, in particular the circuits identified as lighting.  It would be more common for lighting circuits to be protected at 6A. This, in combination with the use of 20A MCB's on circuits you'd anticipate are rings, suggests an installer has done something rather unusual.

silvercar

victor2 said:

silvercar said:

victor2 said:

silvercar said:

victor2 said:

Do you have a smart electric meter? If so, does the IHD show high usage at any point? Or you could install the Bright app on a smartphone and see your usage history in 30 minute intervals and look for any unusual spikes. Of course, if it is a sudden spike, these won't catch it before it trips.

I have a smart meter. But it is all sudden spikes.

Can you relate those sudden spikes to anything? Such as the fridge cutting in or the central heating pump running? It sounds like you're looking for something that you don't run on demand, but is controlled by a thermostat or other switch.

Nothing. First time it happened, there was nothing switched on.

It’s just flipped again, with nothing at all on!

Could be faulty wiring or socket then, which needs an electrician. Hope your insurance comes up good.

Edit:
Do you have a long extension lead you could run from the sockets on the other circuit that isn't tripping, to power your fridge while you get it sorted? If you do, just make sure it's fully unwound to reduce the possibility of it overheating 

Brilliant idea. Thank you!

Electrician booked for sometime today. Just hope that the problem shows itself when they appear. 

silvercar

Section62 said:

GDB2222 said:

The MCB is rated at 20 amps. Do you know why it is not 32 amps, which is usual for a ring main?

With nearly everything switched off (and **unplugged**, I hope!, so as to be quite sure), it’s unlikely to simply be overloaded. So, you either have a faulty appliance or faulty wiring. If you unplug everything and it still trips, it’s the wiring and you need an electrician. 

Furthermore, something that trips the mcb can get seriously overheated and cause a fire, so don’t delay. 

This^.

The MCB which has tripped (position 8) is also labeled "Ring Circuit First Floor" - which suggests the fault could be somewhere other than just the lounge/ground floor. The labelling should never be relied on, but in this case I'd have more doubts about it than normal.

The MCB's in positions 8,9 and 10 (unidentified) are all 20A, which implies the installer considered it necessary to downrate the circuits - we had a case on the forum a while back where a council contractor did just that because they believed the cables were run under loft insulation. Another possibility is radial wiring perhaps.

While the electrician is there I'd also ask them to investigate why positions 1 to 4 have 10A MCB's, in particular the circuits identified as lighting.  It would be more common for lighting circuits to be protected at 6A. This, in combination with the use of 20A MCB's on circuits you'd anticipate are rings, suggests an installer has done something rather unusual.

Can’t comment on the installation, other than it dates back to around 2007.

The labels are accurate, in that as things have become identifiable over the years I’ve labelled them up. So the dodgy one we thought was originally downstairs main section of the house, then I realised it also served some of the plug points upstairs so I added a second label. 

FaceHead

silvercar said:

The labels are accurate, in that as things have become identifiable over the years I’ve labelled them up. 

So are you sure it's actually a ring? Could it be a radial, which would be in keeping with the 20A rating?

But clearly the real issue isn't that it's an overloaded 20A circuit, but that it appears to draw 20A+ when nothing is turned on. This indicates either there is a live-neutral fault somewhere (i.e. a lose wire into the back of a socket) or a faulty MCB.

The solution is trial and error. I expect the electrician will replace the MCB and see if that fixes it.

If that doesn't solve it, the next step will be to open every socket and check all connections are made correctly. If that doesn't work, then it's dismantling the circuit again using a multimeter to check the right resistance in each length of wire (to look for e.g. somewhere where a wire has been half-drilled through, partly cutting the cable and creating an intermittent live-neutral fault. 

silvercar

Could well be a radial, at worst (or is it best?) a radial off a ring.

hopefully the fact it still flips when there is nothing plugged in will help the electrician. My worry is that it will work fine when he appears and he won’t be able to diagnose.

victor2

silvercar said:

Could well be a radial, at worst (or is it best?) a radial off a ring.

hopefully the fact it still flips when there is nothing plugged in will help the electrician. My worry is that it will work fine when he appears and he won’t be able to diagnose.

That's usually the way! But if he's agreeable to a cup of tea and biscuits - and the insurers are paying him by the hour, maybe he'll invest some time into tracking it down. He'll hopefully have the know-how and equipment to test the circuits. It'll probably be quite a serious fault if it's enough to trip the breaker, even a 20A one.

I'm sure you'll let us know the outcome. Can't wait.

TadleyBaggie

I had an MCB start intermittently tripping, Kitchen ring. Often in the middle of the night, so thought it was the fridge freezer, but replaced it and it still happened. Over a period of several months it got more and more regular until one day it was a solid fault.

I have an electrical background so investigated it myself. By breaking the ring halfway round and then disconnecting the ring wires at the consumer board I was able to determine which half was fault (dead short live to earth). Then worked around the sockets in turn disconnecting to see which wire still had the short. Eventually isolated the fault to between the socket behind the dishwasher and the socket at the other end of the work surface. Nothing but buried cable in between! Turns out when the cable was installed it had a twist in it and eventually the insulation wore down and caused the live and earth to come into contact.

silvercar

Small update. Guy came, but he is only the “make safe” team so just looked and booked it in for for “test and trace” to come tomorrow.

as it happens, from 4pm it’s been behaving albeit with only a few items plugged back in. His throw away comment was that electric car chargers can sometimes cause other circuit breakers to flip, so even though the charger has its own flippy switch, it could cause the others to go.