I thought short courses were fine. Just done a week on site. Now i think they're not fit for purpose.

[brianmoooore]

I there is more to testing than pressing a button on an MFT and expecting to see the right numbers, with inspecting it is simple

Anyone else feel, like I do, that MFTs have become so computerised and automated, that the operator has become disconnected from what the actual test is, and how it is done?

 

[Gurnatronics]

@Lister1987 I'm not really disagreeing, a couple of comments:

Even on an EICR doing IR tests as late as possible with everything back together is good practise, so if I've put an accessory screw through a conductor at a light switch or socket or caught something in a metal trunking cover it's picked up by the test. It's very embarrassing if a stupid mistake while carrying out T&I actually makes something worse!

Tracking down faults requires skills and thinking processes that are simply not taught as far as I can tell..
A real life EICR example from this year....IR testing an older CU with an RCD main switch.
Circuit 1, L+N bar to cpc bar is 80 Mohm (pass)
Circuit 2, L+N bar to cpc bar is 40 Mohms (pass)
Circuits 3-7, L+N bar to cpc bar is 0 Mohms.
Circuit 1 again, L+N bar to cpc bar is now 0 ohms.
Circuit 2 again, L+N bar to cpc bar is now 0 ohms.
Does anything you learn at college help you know what to do next? At this point no circuit can be turned on without tripping the RCD, and the tenant is getting cold. I'm sure a lot of the members on here would know exactly what to do next but would an average newly-qualified person who has just passed 2391-52?

Agreed.

Out of curiosty what was the issue in the end? My gut reaction is faulty coil in the RCD?

 

[timhoward]

Out of curiosty what was the issue in the end? My gut reaction is faulty coil in the RCD?

Circuit 3 identified as the problem by removing all Neutrals and testing each circuit L+N to Earth on it's own.
Circuit 3 fed sub main to shed and utility room sockets. Splitting circuit traced the problem (to my surprise) to utility room.
Unplugging appliances one and a time revealed a faulty freezer gave up the ghost and was creating a dead short N to E.

 

[Gurnatronics]

Circuit 3 identified as the problem by removing all Neutrals and testing each circuit L+N to Earth on it's own.
Circuit 3 fed sub main to shed and utility room sockets. Splitting circuit traced the problem (to my surprise) to utility room.
Unplugging appliances one and a time revealed a faulty freezer gave up the ghost and was creating a dead short N to E.

We’re any of the MCBs tripping? I don’t get how circuit 1 and 2 passed and 3 + failed and then 1 and 2 then failed once IR tested again. Unless it wasn’t a true copper to copper N-E short and instead the insulation was breaking down and inducing voltage to E whilst testing?

Curious as to how those circuits were originally clear of fault

 

[timhoward]

Before I started everything was apparently ok, nothing tripping, whether MCB's or the single main switch RCD.
When I IR tested circuit 3 at 500v it seems that I changed a dying appliance to a dead appliance (low resistance test afterwards showed < 1 ohm) so the freezer was a dead short between N and E as long as it was plugged in. As it was a single RCD board all the N's are joined, so when testing any circuit L+N to earth the same result (0) would then come back. Hence 1 and 2 passed until the freezer kicked the bucket, then after the freezer snuffed it the whole N bar to CPC bar had a dead short.

 

[Gurnatronics]

Yeah that was my line of thoughts as well thanks so much for clarifying all these extra bits of knowledge and experiences sure help! Double pole RCBOs would certainly help narrow down global faults like that eh?

Did you buy her a new fridge after killing it off haha

 

[timhoward]

Did you buy her a new fridge after killing it off haha

No, but I did spend 40 minutes on the phone to the insurance scam she pays into on her behalf, and drive her frozen food to a friends house for her. (She was over 80)