Help checking lighting circuit

[IQ Electrical]

iQ electrical i understand were your coming from there are easy methods im just talking about a particular job we were doing on raft lighting in a office area that was the method we used the conuctors were the same cross sectional area ie 1.5mm so if the r2 was 1 ohm r1 would be 0.50 ohms so we then calulated the zs on are engineers instructions long winded i know but there you go

I think I'm losing the will to live, if the conductors were the same csa, why would you have different values?

You should ask your 'engineer' to show you where this procedure is documented in Guidance Note 3.

I'm not 'having a go' at you but it's important to show the correct procedures on the forum as many use these threads for answers and as study aids for 2391-10 etc.

 

[nickblake]

Get you self a light mate kit like howard has said dont half save time and stress so easy and the megga set come with a sexy crock clip lead set , Paul thats one hell of a complex way of testing and as Iq has said correct procedures should be followed ,

i belive you cant get the fitting off the ceiling , gently run a knife round the paint , or gently tap the fitting then it may well come away with out damage ,

 

[andekoch]

Seem to remember reading somewhere (in a guidance note) that if the light fitting/ cable is not easily accessible you can check r1 + r2 at the switch and note it on the cert.

 

[malcolmsanford]

I know i'm getting old, and my lass tells me that as I get older I'm getting worse, but you read on here guys wanting to do the 2391-10 and worry about this and worry about that, the scenario is stressful and what RCD protection for what purpose and this thread is well confusing. I thought we were talknig about a lighting circuit, but it seems there must be a ring final circuit also involved as we are doing r1 + r2, and I ignored the rn.

It is and always has been, and I think always will be Zs = Ze + (R1 + R2), never as it be Zs = Ze + (r1 + r2). It may be a poiint of just being a crotchity old git, but C&G love marking you down on this and the eternal ring main, which is a ring final circuit.

If we get use to using the correct terminology on here, it will help all those doing the 2391-10 and also help to answer questions.

Rant over

 

[rmc86uk]

For lighting circuits Zs like above can always be calculated Ze + R1 + R2. If you do an actual Zs test on a lighting circuit its value is usually the same or there abouts results as your calculation. It takes a couple of minutes to get your calculator out and go through all the Zs on the test sheet providing you have the Ze and R1 + R2 readings. Always do a Zs test on sockets though and not a calculation as this is the most dangerous part of a circuit as it enables the consumer to plug an appliance in with their hand.

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