Saw a novel slant on the theory of a PME system today. Class 1 light fitting on a non-cpc lighting circuit with the fitting earth lead connected to the neutral terminal of the supply.
RF Lighting said:I seem to remember hearing somewhere that TN-C was often used on lighting circuits in mines.
Adam_151 said:I thought it was IT that was common in mines?
it certainly doesn't sound any worse than using copper or aluminium concentric with a live down the middle and CNE arround the outside which is what the recs do.Adam_151 said:I'm told by a rather old lecturer that TNC systems were used on some department store buildings in the 1960's using single core MI, I guess the reduced voltage drop in the CNE sheath due to its much larger CSA, combined with the un-likelyness of it being broken made it somewhat acceptable.
quite a sensible setup actually, lets you mix 120V single phase, 240V single phase and 240V three phase loads on the same supply system. Main downside is you cant balance it properly unless your total 240V load is more than double your total 120V load.*At least domestically where they have one 220v phase centre grounded, but they also have more interesting arrangements such as three of them in delta, and leaving the ground on the centre of the first one, resulting in two conductors 110v above ground, and the third 208v above ground!
plugwash said:how often do you sparkies work on circuits that are only single pole isolated, my guess is quite often. Do you feel at risk while doing so? have you ever had a shock while doing so? do you trust the neutral to be safe to touch?
hmm? i thought it was usually live from downstairs and neutral from upstairsRF Lighting said:I have been got by neutral feedback, hence the habit. It was the good old live from upstairs lights neutral from downstairs lights scenario.
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