Zs test on light circuit

[swes]

Hi can someone please explain how to Zs test a light circuit.
do you have to do it at the light fittings only and what is the procedure of the switches on the fittings and the c/unit many thanks to all ,

I have a megger 1502 with three lead output

 

[STI]

Hi its a live test. So if you feel capable of doing a live test.

I dont know the 1502 so does it have different settings for a circuit with or without an RCD. You will need to set it appropriately.

I was taught you do the test at the furthest fitting on the circuit, connecting in the case of lights to the Switch live, neutral and earth. I usually only have the circuit i am testing live the rest of the circuits switched off at the board

 

[swes]

ok and yes i am capable of doin live test ,im in early stages of training.

is it right to have the light switches in the open position .....what about two oo three way????

 

[JohnnyG]

The light switch has to be closed (lamp on) else they'll be no continuity of the switched line at the fitting, as long as the light is 'on' it doesn't matter how any 2 way switches are set.

 

[flameport]

Hi can someone please explain how to Zs test a light circuit.

The information given by STI is correct.

However live tests on light fittings are not necessary and should be avoided.

Live testing while standing on a ladder with 3 test prods in your 2 hands is just asking for things to go wrong.

 

[Spark123]

You can always do an R1+R2 test and add it to Ze (or Zdb)

 

[securespark]

Live testing while standing on a ladder with 3 test prods in your 2 hands is just asking for things to go wrong.

Which is why we use the Kewtek lampholder adaptors, then you just have a croc clip (or a probe) for the earth.

 

[dingbat]

There is only one reason you want to know the Zs for any circuit and that is to be sure your overcurrent devices will operate.

Given the huge measurement variability between different loop testers, it is not only safer, it is desirable to calculate rather than to directly measure Zs. In any case, as the measured value will always be less then calculated in a real installation, you have a built-in bias on the side of safety.

You said:

"ok and yes i am capable of doin live test ,im in early stages of training. "

If this is the case then your training is out of date. It has been some years since the direct live testing of any circuits other than those of socket outlets has been taught.

(For the experienced tester, with a full knowledge of the risks, live testing may be a more practicable option for reporting on existing installations, but a risk-based approach should be adopted.)