Head Scratching time lighting fault

[Superspark23]

Been doing an eicr today, went to do an R1+R2 on a lighting circuit and got no reading between earth and live but neutral to earth was 1.36 ohms. Straight away thought reversed polarity, but the luminair was working correctly before we arrived, so i put the power back on and checked the voltage at the fitting neutral to earth 0v live to earth 234 live to neutral 235v. everything there seemed to be right zs was 1.48ohms and ze was 0.11ohms. So everything added up how you would expect.

checked the r1 and r2 again encase i was doing something stupid same again 1.36ohms went back to the 1st light on the circuit as i had that down anyway and got an r1 and r2 (live to earth ) at .18 then at roughly the mid point the reading again was how you'd expect it to be 0.58 to live an earth.

any ideas? old building 30 years + old

 

[yellowvanman]

You did have the light switch on for the R1 + R2 test?

You do know theres a case for not doing a R1 + R2 test on an EICR. If you look at the example in the OSG they have just put a tick in the R1 + R2 box, implying its OK because the Zs test was OK.

 

[ringer]

When verifying voltage at the light fitting, how did you connect your test leads? Did you put them directly on to L, N, E terminals at the rose/connector or did you use a plug-in connector for your L and N leads? If the latter, it is very easy to get polarity of test leads reversed.

 

[Superspark23]

i tested with my voltage indicators, and the fact the light fitting works normally suggest the correct polarity is there when live, 3 of us where there on site and couldn't work out what was going on. To be fair the place is a mess and needs ripping out and starting from scratch, but i'm interested in knowing whats going on here.

 

[ringer]

What type of light fitting was it? Most types of light fittings will work 'normally' with reversed polarity.

 

[Superspark23]

its a really old really old 5ft fluorescent luminaire. But i think thats irreverent. Its hard to explain ill draw a picture as that may be easier to understand

 

[telectrix]

could it be possible that you got the no reading L-E with the switch off, and the N-E reading you got was a parallel path?

 

[ackbarthestar]

If you removed the live and cpc on the first run, you may have pulled the wrong cpc from the earthing terminal bar, but since you did it the second time and got an acceptable reading then all is now well?

The easiest way of achieving an R1+R2 result is to leave the cpc in the earthing terminal bar and connect the live to that bar

 

[Guitarist]

Think you mean "irrelevant" mate. "irreverent" means you don't revere it in any way :wacko:

 

[telectrix]

picky?? well, you are a guitarist

 

[D80]

could it be possible that you got the no reading L-E with the switch off, and the N-E reading you got was a parallel path?

This I'd think, TN-C-S system.

 

[Superspark23]

I switched the switch in all possible positions its a 2 way switch and still got no reading its really baffled us to what going on, other parts of the building has had many faults with shared neutrals, this board is the 1st time its been tested since 1983. And very little maintenance has been done in that time. all the neutrals go to the switches, but on one of the switches it has 2 different ciruits in in ones on red phase and the others on yellow it has 3 neutrals in it, but were' 99% certain we know what they're for and are nothing to with the circuit with this issue.

 

[Guitarist]

A classical guitarist mate, so "finger-picky" really :tongue3:

Also an HNC qualified electrical engineer with over 20 years experience, not that that has anything to do with the English language...

 

[alarm man]

Also an HNC qualified electrical engineer with over 20 years experience, not that that has anything to do with the English language...

Electrical Trainee say that every day here mate..:bucktooth:

 

[Superspark23]

it is a tncs system i allways test when i can taking the neutral off the the board and the live and if its possible to identify the earth i will take that off but in this board i left all the earths as they were