When Is 0.5ohms Not 0.5ohms?

[NickD]

I think it boils down to you can't predict whats going to happen in the future, you can only play with the cards dealt to you now!

Yes, but relying on a parallel path in a test where it could have been avoided strikes me as a case of pulling an extra Ace Of Spades out of your sock

Plus of course we all know people only use "competent/registered tradesmen" to do their work for them. And through their training and experience these tradesmen would clearly be appreciative of the problems they could cause .....

Oh of course, very much so. In other news, sources suggest Malaysian airliner may have changed course to avoid large flight of pigs.

 

[NickD]

Because as a "competent person" you are supposed to know this, lol, GN3 and associated literature is only to guide you as far as the regs are concerned, it not meant to teach you how to T&I, only how to comply with the requirements of BS7671.

But then why does GN3 p53 bother to tell you to disconnect means of earthing for a Ze test? If you're competent you know that anyway, equally.

 

[spark 68]

Sigh,

It gives you the minimum requirements to T&I to comply with BS7671, it gives suggested methods on what is required, it also says other methods are not precluded so long as the basic requirements are met.

The 239X courses are "bolt on" courses that supplement your underpinning knowledge.

 

[NickD]

Just because I'm a very sad man,

a) I whipped off one of the offending sockets and confirmed that it is repeatedly showing a resistance circa 0.5ohms from rear earth terminal to front earth receptacle which no amount of cleaning up the contacts has been able to remove.

b) Did a little test with an measured 18.6m length of 1.0+1.0 T&E, nominal calculated R1+R2 of 0.65ohm at ambient. R Low Ohms measures it at 0.68ohm. Then (carefully) energised it from a source with Zs 0.44ohms and got a total Zs measurement of 1.14ohms. Difference of 0.70ohms which at least gives me faith that my tester on EFLI range isn't just making up readings to suit itself. Bit pointless you may argue when the tester is in cal, but whatever.