Got called out to a friends house last Tuesday around lunch time.
The circuit breaker for the sockets had tripped and would not reset. 30A plug in MCB in an old wylex CU.
I got there and tried to reset the circuit breaker. It went with a real pop. A quick IR test of the circuit showed it was a dead short L>E.
I spent a couple of hours breaking the circuit down and found where the fault was.
Here's the odd bit.
Fault was in an attic conversion. Wiring up there is about 4 years old. There is a spur somewhere from the RFC, presumably via an inaccessible junction box. This enters the attic straight into an RCD FCU, then supplies the lights and sockets from here.
The FCU had not tripped, and the 13A was still intact.
I disconnected the faulty part of the attic radial, and IR showed about 40MΩ. I was happy enough with this. Powered back up no problems. Assuming the FCU hadn't tripped as it was faulty, did an RCD test, and it tripped out perfectly. About 40ms and 19ms.
Fast forward to friday night. Got a call at about 8pm, and got there for about 10. Circuit had tripped and wouldn't reset again. It was another L>E dead short. Went straight to the attic and and another part of the radial had gone down. Disconnected this too, and IR showed 40MΩ again.
Powered up and left.
Got a call 30 mins later to say the FCU was growling and then set on fire
Found this:
God knows whats been going on. I think I could be there a while sorting everything out
The circuit breaker for the sockets had tripped and would not reset. 30A plug in MCB in an old wylex CU.
I got there and tried to reset the circuit breaker. It went with a real pop. A quick IR test of the circuit showed it was a dead short L>E.
I spent a couple of hours breaking the circuit down and found where the fault was.
Here's the odd bit.
Fault was in an attic conversion. Wiring up there is about 4 years old. There is a spur somewhere from the RFC, presumably via an inaccessible junction box. This enters the attic straight into an RCD FCU, then supplies the lights and sockets from here.
The FCU had not tripped, and the 13A was still intact.
I disconnected the faulty part of the attic radial, and IR showed about 40MΩ. I was happy enough with this. Powered back up no problems. Assuming the FCU hadn't tripped as it was faulty, did an RCD test, and it tripped out perfectly. About 40ms and 19ms.
Fast forward to friday night. Got a call at about 8pm, and got there for about 10. Circuit had tripped and wouldn't reset again. It was another L>E dead short. Went straight to the attic and and another part of the radial had gone down. Disconnected this too, and IR showed 40MΩ again.
Powered up and left.
Got a call 30 mins later to say the FCU was growling and then set on fire
Found this:
God knows whats been going on. I think I could be there a while sorting everything out