earth loop ez

[markymark2406]

When i do a earth loop test what is it im actully doing?

 

[Spark123]

You are measuring the phase and earth conductors impedance of the final circuit, any distribution circuits and the external DNOs cable (including the impedance of the supply transormer.)

 

[kai]

The key concept of the earth loop test, is to make sure that the circuit EFLI reading falls below the BS7671 values required, for the given circuit type, to enable the fuse or MCB to operate in the allowed time, in the event of an earth fault developing.

 

[GaryMo]

The key concept of the earth loop test, is to make sure that the circuit EFLI reading falls below the BS7671 values required, for the given circuit type, to enable the fuse or MCB to operate in the allowed time, in the event of an earth fault developing.

It's also specific to the protective device in use as well as the type of circuit though if it's a BS60898 then the figure covers both 5s and 0.4s disconnection times.

 

[ColJack]

When i do a earth loop test what is it im actully doing?

something you shouldn't be, since asking that question in the first place negates the possibility that you..

a) know what you are doing
b) are qualified to be doing it
c) have the slightest idea whether the results you are getting are satifactory

and since the other repliants missed it in the title...

it's Ze, not ez..

which is the earth loop impedance external to the supply at the point of test. ( ie the incomming mains in a standard domestic set up, or the sub main cable at a secondary or tertiary distribution board )

 

[holmslaw]

..

 

[securespark]

None of what you suggest is implied in the OP's comment....

 

[GaryMo]

Agreed, it's very easy to get all high and mighty behind a keyboard without all the facts at hand.

It may well have been a theoretical question, nothing more, nothing less.

 

[Taylortwocities]

Lay off a bit, he's asked for advice, not a lecture. Blimey.

 

[securespark]

All he asked for was the theory behind what happens when you push the button on an EFLI test. No big deal....

 

[davelx]

All he asked for was the theory behind what happens when you push the button on an EFLI test. No big deal....

Any no-one's actually answered yet...

Ignoring reactive components for simplicity:

1) You measure the voltage between Live and Earth
2) You apply a known resistance between live and earth causing a current to flow
3) You measure the voltage across the resistor, which will be slightly lower that that measured in (1)
4) You use Ohm law to work out the additional resistance contributed by the loop from the source and back, ie the loop resistance.

(if you include reactive components - which requires measuring the phase shift between voltage and current - you then get loop impedance).