testing

[snowplough]

Hi Guys,

Im at college at the moment in my second year and have loads of questions to ask.

One of m questions is regarding testing of lighting circuits,

When you do a continiuity test on a lighting circuit and you put the crocodile clip on line and neutrel at the fuse board and then put your low ohm meter test leads at the furthest ceiling rose in the house to test for continuity , would this reading on the meter be your r1 and r2 reading or say if when you then tested the line and earth at a light switch for continuity and you got a higher ohm reading would this reading be the r1 and r2 reading, i think i am a little confused with continuity and where you take your r1 and r2 reading from and do you have to go in every single light switch and lamp say in a house.

Sorry if im not very clear as i am confused myself re continuit and r1 and r2 ,

Thanks for your patience

snowplough

 

[kung]

Hi Snowplough

R1 = line R2 = cpc
so link these ! go to every light point on that circuit test between cpc and switch line bulb end with switch operated and record highest reading and remember operate switch to confirm pol and two way switching will need testing both ways !
Regards
Kung.

 

[snowplough]

Many Thanks Kung,

When you say go to every light point , do you include every switch point as wel in the entire lighting circuit as well as ceiling roses ?

Many
Thanks Snowplough

 

[kung]

you are buddy ! covered by testing at switch return in rose ! if you cant get cover off rose you could test at switch if cpc there !
Regards
Kung.

 

[Graeme Harrold]

Hi Guys,

Im at college at the moment in my second year and have loads of questions to ask.

One of m questions is regarding testing of lighting circuits,

When you do a continiuity test on a lighting circuit and you put the crocodile clip on line and neutrel at the fuse board and then put your low ohm meter test leads at the furthest ceiling rose in the house to test for continuity , would this reading on the meter be your r1 and r2 reading or say if when you then tested the line and earth at a light switch for continuity and you got a higher ohm reading would this reading be the r1 and r2 reading, i think i am a little confused with continuity and where you take your r1 and r2 reading from and do you have to go in every single light switch and lamp say in a house.

Sorry if im not very clear as i am confused myself re continuit and r1 and r2 ,

Thanks for your patience

snowplough

In the learning phase try and remain consistent with your use of R1 and r1, they are two different tests..............

 

[kung]

Yep r1 & r2 are ring as is rn these are end to end tests !

 

[castlon11]

For R1 + R2 readings on lighting circuit, put link in consumer unit between live and earth (turn off mcb), find last light on circuit, continuity test between live and earth at light.

To my knowledge you do not have to do this reading at every socket and light fitting as previously stated. You roughly want to find the furthest away though. It is usually obveous where the last point is as on a lighting circuit wired in loop, there are only two cables rather than three.

Once you have this reading (e.g 0.60 ohms) you can add it to your Ze (base reading at consumer unit) (e.g 0.08 ohms) to get a calculated Zs (loop impedance) reading (0.68) ohms).

(R1+ R2) + Ze = Zs
0.60 + 0.08 = 0.68

However, if you use this method to get your Zs reading you have to state on the certificate that the Zs reading is a calculated reading, also you cannot use this calculation the other way around on a test certificate (e.g Zs - Ze = R1 + R2)

 

[slocm3105]

Testing r1+r2 on a lighting circuit as mentioned above you link out line (r1) and cpc (r2) and the consumer unit and test at the light fitting between switch line and cpc. The light switch must be in the on position. This will give you your r1+r2 reading for that circuit. However when you test for your Zs (live earth fault loop impedance test) you must test at every outlet on that circuitl.

Hope this helps

 

[SirKit Breaker]

Snowplough,

Invest in the IEE Guidance note 3 testing and inspection, it covers everything you need to know and a bit more, second best book in the van after the OSG.

Regards.................Howard

 

[kung]

For R1 + R2 readings on lighting circuit, put link in consumer unit between live and earth (turn off mcb), find last light on circuit, continuity test between live and earth at light.

To my knowledge you do not have to do this reading at every socket and light fitting as previously stated.

Dont take anything for granted and as he is a trainee id advise to do the testing the long NOT short way ! plus there are rewirables as well as mcbs out there.
Regards
Kung.

 

[snowplough]

Many thanks for all your input guys much appreciated,

I still trying to get my head round it, i think im trying to define coninuity , and r1 and r2 readings on the lighting circuit.

If you go to the furthest ceiling rose on the circuit say last one in the house upstairs then test between live and earth and get the ri and r2 reading there, then if say there is a weak earth link,or a broken earth which wouldnt show up from the ceiling rose test because the single earth wire runs down to the switch then surely the r1 and the r2 reading at that switch if it is the worse reading would be the true reading for the r1and r2 test for that entire circuit , escpecially under fault conditions when working out the Zs.

Sorry im not sure if im correct but our input might help me understand it a bit more,

Many thanks for your patience

Snowplough

 

[castlon11]

This is a valid comment and should be considered, obviously you would then have to go to every switch to carry out these tests, certainly on a full periodic or installation report, i'd say you are correct.

 

[snowplough]

I just wodered if any of guys out there could try and explain continuity testing as i am trying to get my head round it more at college but it seems to throw more questions then answers the more i think about it.

First question i have , when you do an R1 AND R2 test ,it says to go to the furthest point in the circuit , say the furthest ceiling rose in the circuit , is this because the longer the cable ,the more resitance , hence the worst reading to write down. But if this is the case what about the switch that runs from that ceiling rose , if the earth ends there in the (switch back box) is that the furthest point even though the line wire terminates in the rose , i find it confusing. In the on site guide it shows a picture of the probes being placed in the switch , not sure if it means you can do an R1 and R2 test there as thats where the earth terminates or is it always taken at the last ceiling rose regardless?.

My second question is do you have to go in and out of every switch as well to test continuity like say two way and intermidiate , because im thinking wouldnt you have to test the strappers to make sure the resistance of them is low , and where do you put you probes to do this?.

Thirdly , when you are testing for continuity using the line and earth link in the c.u even tho your testing for continuity of cpc, are you also testing for contin of line as well?

Sorry for sounding confused hope you can explain it easily

Many Thanks

Snowplough