2394 IR question had Tuesday

[Richard Burns]

You do not need the main earthing conductor for an IR test.
It is a dead test of the existing circuits.
All breakers and main switch on, test from Line tail to earth bar, neutral tail to earth bar, line tail to neutral tail.
Record results

If equipment is installed then it is permissible to join the tails together and test to the earth bar.

 

[Jay Sparks]

Just to play devils advocate, isn't the 2394 "initial verification"? If so, there should be nothing connected as it is a brand new install. And I was always told that you should only connect the L & N for the IR test when doing an EICR? Obviously with the new technologies and accessories coming out nowadays, a lot of the accessories might well have some electronics built in to them, so this test will be time saving.

Cheers

Jay

 

[telectrix]

with all breakers and main switch on, no loads connected,you would test L-N tails, L-E, N-E, with the E being the MET.

 

[Jay Sparks]

with all breakers and main switch on, no loads connected,you would test L-N tails, L-E, N-E, with the E being the MET.

Exactly! If this was a 2395 questions then it would be acceptable to connect the L & N together and test to earth. When I did the 2391, you had to read the questions carefully because you needed to know what type of install it was (New or Existing) you were testing because the answer would be different.

But of course if you fit a new CU/DB, technically it is a new install but a lot of loads will be connected to the existing circuits. So for time saving and if i couldn't disconnect everything, I would connect the L & N together for the IR test.

Cheers

Jay

 

[DaveS]

You do not need the main earthing conductor for an IR test.
It is a dead test of the existing circuits.
All breakers and main switch on, test from Line tail to earth bar, neutral tail to earth bar, line tail to neutral tail.
Record results

If equipment is installed then it is permissible to join the tails together and test to the earth bar.

Cheers Richard. Just to clarify then if MET is outside CU and no link earth connection is present between these do I add this myself to required size and then test MET so if a fault is present it will then flow to Earth

 

[Leesparkykent]

You have to carefully read the question as it might say something along the lines of the consumer unit feeds x amount of lighting circuits. So In your answer you would have to include the operation of 2-way switches if any whilst carrying out the IR tests.

 

[Richard Burns]

Cheers Richard. Just to clarify then if MET is outside CU and no link earth connection is present between these do I add this myself to required size and then test MET so if a fault is present it will then flow to Earth

If you were doing an IR test of the entire installation then you could test either at the MET or at the earth bar in the first distribution board.
It is likely that there would be limited chance for there to be a insulation resistance fault that would give rise to danger in the conductor from the MET to the earth bar as this is usually a separately run cable for simple installations on which you could reliably test IR.
As part of the initial verification you would be testing the continuity of that conductor anyway even if it was only via a Zs test on a circuit.
But for completeness one should test at the MET.

If you were doing your own install then you would be expected to provide the earthing cable from MET to CU.
The DNO would only provide a "means of earthing" (assuming it is not to be TT).

 

[DaveS]

Thanks again Richard and Lee and rest of guys. Clears things up, obviously still have alot to learn and get experience of unfortunately. Can I just clarify aswell about my understanding of voltage supplied to system when joining L and N and testing these to Earth are you or are you not putting 500 v through the install. My understanding upto now has been that by joining these you have removed the return path( pole) if this is so how does voltage flow and test system other than if there if there is a live conductor to earth fault......I'll get there in the end!

 

[Richard Burns]

Try this explanation and see if it helps clarify things.

 

[DaveS]

Try this explanation and see if it helps clarify things.
View attachment 29870

Sorry for late reply been away weekend. Thanks Richard post just what I was looking for.