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EddieB

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Arms
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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?
 
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T

Tiger

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

DanBrown

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

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.
 
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

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Arms
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.......
 

GLENNSPARK

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Arms
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....
 

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