I know you all like a challenge so here's one for you all.
We were called out last year by one of those companies who act on behalf of insurance companies.
According to the girl on the phone the reported fault was an RCD tripping. When I called the client the lady of the house said the RCD had been tripping intermittently all day.
The insurance company had already sent out one NIC (very relevant) contractor who said they had found the fault and isolated the circuit pending approval to re-wire it. However, the RCD tripped twice after the guy had left so the client called them back. They said they could not get back for a few days so we ended up getting smooth talked into taking the job.
The property was a very nice 6 bedroom house at the end of a single track private road. It had been fully re-furbished and re-wired by the previous owner 5-6 years ago.
The electrical installation was TT and the wiring was T&E. The CU was an 8 way 3 phase MG disboard linked out for single phase.
There was an AMF panel above the cut-out with a 50kVA set located behind the house. The complete installation was protected by a 100mA RCD which seemed odd given the standard of the install.
When the dis board cover was removed there was a neutral out of the bar which had been taped up. It fed the outside lights which is where the other chap said he found the fault. Before going any further our engineer had a quick flick around the board with a volt stick and discovered that the polarity was reversed feeding the DB. after some investigation it turned out there had been a fault in the AMF panel and the generator guy had removed the contactors some 6 months previous. When he put the cables into terminals to by-pass the contactors he reversed the polarity.
After re-wiring it our engineer started to do some testing. As it was an RCD fault the first test was IR. Below are the results.
Bearing in the mind the cabling was only 5-6 years old does anyone fancy going to the top of the class by guessing what had happened?
We were called out last year by one of those companies who act on behalf of insurance companies.
According to the girl on the phone the reported fault was an RCD tripping. When I called the client the lady of the house said the RCD had been tripping intermittently all day.
The insurance company had already sent out one NIC (very relevant) contractor who said they had found the fault and isolated the circuit pending approval to re-wire it. However, the RCD tripped twice after the guy had left so the client called them back. They said they could not get back for a few days so we ended up getting smooth talked into taking the job.
The property was a very nice 6 bedroom house at the end of a single track private road. It had been fully re-furbished and re-wired by the previous owner 5-6 years ago.
The electrical installation was TT and the wiring was T&E. The CU was an 8 way 3 phase MG disboard linked out for single phase.
There was an AMF panel above the cut-out with a 50kVA set located behind the house. The complete installation was protected by a 100mA RCD which seemed odd given the standard of the install.
When the dis board cover was removed there was a neutral out of the bar which had been taped up. It fed the outside lights which is where the other chap said he found the fault. Before going any further our engineer had a quick flick around the board with a volt stick and discovered that the polarity was reversed feeding the DB. after some investigation it turned out there had been a fault in the AMF panel and the generator guy had removed the contactors some 6 months previous. When he put the cables into terminals to by-pass the contactors he reversed the polarity.
After re-wiring it our engineer started to do some testing. As it was an RCD fault the first test was IR. Below are the results.
Bearing in the mind the cabling was only 5-6 years old does anyone fancy going to the top of the class by guessing what had happened?
