Measured Loop impedance

[EddieB]

On another issue how do test the loop impedance at a fixed appliance or a light, to fulfill the measured loop impedance column requirement on the schedule of tests. will the calc R1 + R2 suffice?

 

[Tiger]

take down the ceiling rose and test. with the rcd's now you will need a no trip tester

 

[DanBrown]

It doesn't require just the R1 and R2 reading it requires the full ''earth loop path'' Ie Zs?? ((R1 + R2) + Ze)

 

[Guest123]

On another issue how do test the loop impedance at a fixed appliance or a light, to fulfill the measured loop impedance column requirement on the schedule of tests. will the calc R1 + R2 suffice?

Hey.

First of all the calc for Zs (earth fault loop impedance) is Zs = Ze + (R1+R2). R1+R2 is a measurement on its own - line and earth resistance of a circuit.

To measure Zs on a lighting circuit find the end of the circuit, could be in a switch or a light fitting open up switch/remove light fitting and carry out the test.

I'm a bit confused with the fixed appliance bit, as you only need to test the circuit supplying the appliance so test at socket or iosolator for the appliance.

Hope this helps.

 

[Les Macaulay]

Measure Ze at the supply terminals and add R1+R2, the result is inserted into the Zs column. There is no doubt that a live Zs reading at the switch or light is best but we are allowed this method - see Guidance Note 3.

 

[kingeri]

Measure Ze at the supply terminals and add R1+R2, the result is inserted into the Zs column. There is no doubt that a live Zs reading at the switch or light is best but we are allowed this method - see Guidance Note 3.

They probably figured it out in the four years since this question was asked.......

 

[Geoffsd]

They probably figured it out in the four years since this question was asked.......

Ooooh. I wouldn't bet on it.

 

[GLENNSPARK]

take down the ceiling rose and test. with the rcd's now you will need a no trip tester

oh do you?
i think not...
2 ways to do this with a high current loop tester:

1)calculate the Zs from the Ze+r1 r2

2)wire out the RCD...

i use both methods to get a Zs as neither of my MFTs do a low current loop....