r1+r2

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stringy

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just been looking through my osg at the testing section.. shows a picture of checking r1+r2 of a lighting circuit at the switch.

i was told at college to do it at the pendant.....am i missing something?

cheers

 

springcrocus

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Yes, a few milliohms - the resistance of the return wire from the switch to the pendant

 

Deano

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just been looking through my osg at the testing section.. shows a picture of checking r1+r2 of a lighting circuit at the switch.i was told at college to do it at the pendant.....am i missing something?

cheers
Many moons ago - when Eddison was a lad it was acceptable to measure R1+R2 (and the Zs) at the switch. However the few milliohms that you end up not measuring can prove to be vital when taking the safety of persons and 'livestock' and property into account.Guiness DrinkGuiness DrinkGuiness Drink

R1+R2 (and Zs) should always be measured at the furthest point of the circuit. the only exclusion from this is Zs - which can be calculated instead of measured.Guiness DrinkGuiness Drink Hic

 

PAUL M

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have you ever tried measuring Zs at a ceiling rose with a 3 lead tester,its well dodgy,Guiness Drink

 

Deano

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have you ever tried measuring Zs at a ceiling rose with a 3 lead tester,its well dodgy,Guiness Drink
Do the maths then! It aint hard buy a calculator from tesco's

 
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have you ever tried measuring Zs at a ceiling rose with a 3 lead tester,its well dodgy,Guiness Drink
With a bog standard pendant & rose its not too bad...

But some of these flippin decorative & ornamental fittings!!! phtt!! X(

Have you seen any of them plug in bulb holder connector things?

you put them where the bulb goes & then just plug your L & N lead in..

just need to get a place to stick your earth probe!

I have been thinking about getting some..

but bit steep around

 

stringy

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they sound like a brilliant idear.....like you say most of these modern light fittings are designed to be tested easy thats for sure.

 

Admin1

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I remember seeing them somewhere and thought they were a bulbous idea.

 
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just been looking through my osg at the testing section.. shows a picture of checking r1+r2 of a lighting circuit at the switch.i was told at college to do it at the pendant.....am i missing something?

cheers
Spose the Two key points are

1/ you need to verify earth continuity & polarity at all accessories.

2/ you need the Zs at the furthest point..

and the furthest point for Zs will be dependant upon the method of wiring..

e.g.

'loop at light' - VS - 'loop at switch'.

If we say the wiring is looped at the light then...

The longest R1 length will be up the supply to light.. out to switch.. through switch and back to light.

Whereas the longest R2 length will be up the supply to light.. then out to the switch!

If the wiring is loop at the switch then longest runs should be at the lights.

However long 2-way switch runs could change things again!!!

Which is why Slipshods, 'test every point', answer would be the only strict ways to establish exactly where the furthest point is. :eek: :|

If it is a compete circuit you have designed and installed...

you will (or should) know where the furthest bit of the cable is...

Cuz you put it in! :^O :^O:^O

In practise I do tend to test at lights if they have a ceiling rose!

;) :x

Its a common sense & personal judgement situation...

Obviously if readings are looking dodgy you would delve in deeper. :)

 

maccarooni

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Have seen these lamp test connection units and they do look good, however i didn't see one for a low energy pendant fitting eg. lep18s, the 4 pin PL type lamp. Now that all properties must have a percentage of low energy fittings , seems the old bc lamp tester may go out of fashion .

Macca

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Have seen these lamp test connection units and they do look good, however i didn't see one for a low energy pendant fitting eg. lep18s, the 4 pin PL type lamp. Now that all properties must have a percentage of low energy fittings , seems the old bc lamp tester may go out of fashion .Macca

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Don't them 4pin types have a choke or somthing in the fitting?

so there is not a direct R1 connection?

or have I missed somthing?? ?:| :( :|

 

maccarooni

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Don't them 4pin types have a choke or somthing in the fitting?so there is not a direct R1 connection?

or have I missed somthing?? ?:| :( :|
SL you know your right...

Thats why i haven't seen them...

Macca

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R1+R2 (and Zs) should always be measured at the furthest point of the circuit. the only exclusion from this is Zs - which can be calculated instead of measured.Guiness DrinkGuiness Drink Hic
And the switch is one of the many furthest parts of a circuit, and what if more than one cable has left the breaker (that's another discussion) or the circuit has been 'spider-ed'

 

sparkyork

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is the sw/wire at the light fitting not the farthest point. if you go to a job with more than one cable at the breaker then id measure the one thats supplying your circuit and if replacing cu put it on its own breaker. (mayeb put a note on minor works?)

if its spidered then your never really gonna know about it so you just use common sense i reckon?

 
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is the sw/wire at the light fitting not the farthest point. if you go to a job with more than one cable at the breaker then id measure the one thats supplying your circuit and if replacing cu put it on its own breaker. (mayeb put a note on minor works?)if its spidered then your never really gonna know about it so you just use common sense i reckon?
How do you think you could justify issuing a MWC on a CU change?????

If you`ve tested everywhere, you`ll have found the furthest point of the cct, and therefore have the max r1r2 / Zs

KME

 

sparkyork

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i wasnt talking about a minor for a consumer change. the "put a note on minor works" is applying to the point that 2 circuits are fed from one mcb, which i would insert "a note" on a minor and on dic cert

 
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i wasnt talking about a minor for a consumer change. the "put a note on minor works" is applying to the point that 2 circuits are fed from one mcb, which i would insert "a note" on a minor and on dic cert
OK. Sorry, it didn`t read lioke that ( to me, anyway). Didn`t want anyone thinking they could do CU & issue Minor:(

As an aside, I`d insert a notation to this effect on ANY cert I filled in; be it PIR, EIC, DEIC, MWC or whatever. (sorry, did I forget the DPIR and the DMWC?)

 
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