# testing RCD's

Discuss testing RCD's in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

#### ashdog

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Hi
With the intro of the 17th edition regs how do you carry out the testing of the RCD controlling a lighting circuit? I have seen the testing of RCD's controlling ring circuits with the use of a 'plug in' lead but not sure on how to test lighting circuit. Hope that makes sense, Thanks.

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G

#### Guest123

Hey.

You do it much the same way as you would measure Zs on a lighting circuit.

Find the furthest point on the circuit then using your three wire test lead connect line - line, neutral - neutral, and earth - earth.

Test at - half x rated current of rcd
1 x rated current of rcd
5 x rated current of rcd

This should be done at 0 and 180 degrees angle on the sine wave i.e positive and negative side of the wave to get a true reading. Your tester should have a button on it to enable you to do this.

Cheers

cheers

#### ian.settle1

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Mentor
Arms
Hey.

You do it much the same way as you would measure Zs on a lighting circuit.

Find the furthest point on the circuit then using your three wire test lead connect line - line, neutral - neutral, and earth - earth.

Test at - half x rated current of rcd
1 x rated current of rcd
5 x rated current of rcd

This should be done at 0 and 180 degrees angle on the sine wave i.e positive and negative side of the wave to get a true reading. Your tester should have a button on it to enable you to do this.

Cheers

Agreed with this but two things

1-You dont need to be at the furthest point to test the RCD.

2-If you are on your own it can be a pain as if the position you are testing at is up a ladder then you are up and down to reset the RCD whether it is a tester which does the tests automatically or a seperate meter that you need to change the settings for each test.

So if you have croc clips it might be a good idea to use them if you have a meter thatcan do the tests automatically then you only need to be by the DB to reset the RCD.

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#### [email protected]

And if it's a dual RCD Consumer unit the sockets and lighting should be split with socket circuits on each RCD. Therefore when you test the RCD you can plug in your tester to each ring, and no need to "rcd" the lighting.

Mark

G

#### Guest123

I feel it's good practice to take a reading at the end of the circuit, as its the furthest point all cableing is tested also - especially on a periodic inspection.

Also presumably as you would have opened up the last light on circuit to measure R1+R2 and Zs it just makes sense to carry out your RCD test there too.

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#### Spudnik

No need to test at end of circuit as its only the functionality of the RCD being tested.

The wiring should have been tested before the RCD test as per GN3.

G

#### Guest123

As I said in my post presumably you would already have the last light on the circuit opened up having already measured R1+R2 and Zs so it's just as easy to measure your RCD times there aswell.

M

#### [email protected]

I wouldn't say easy to test from a step ladder up and down to reset 4x times. Plug it in i say!

Mark

S

#### Spudnik

I wouldn't say easy to test from a step ladder up and down to reset 4x times. Plug it in i say!

Mark
Too right!!

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