2394 IR question had Tuesday

[DaveS]

Evening chaps

Had my 2394 exam this Tuesday think all went pretty well but had one question worth quite few points not sure of.
How to IR test whole installation from tails before connection to supply. Spoke to few guys and few different answers were given. I basically Answered main switch and all breakers on disconnect any loads and remove any sensitive equipment. Communicate dangers to client Erect barriers and warning signs and then join N and L of tails then test between these and steel armoured? I've re read GN3 since and it looks like I may of Answered better by testing N and L separately and then these to earth separately with a earth connection made to suppliers means of earthing from steel armour of tails. Have i made a glaring error? Or am I likely to pick up some marks do you think atleast? Had few people say that should of been tested separately and no earthing would be required which surprised me and that even with joining N and L should still of made connection to earth. My understanding is that when you join L to N that your not supplying an actual voltage because you have now not got a return path (2 poles)

 

[Leesparkykent]

Evening chaps

Had my 2394 exam this Tuesday think all went pretty well but had one question worth quite few points not sure of.
How to IR test whole installation from tails before connection to supply. Spoke to few guys and few different answers were given. I basically Answered main switch and all breakers on disconnect any loads and remove any sensitive equipment. Communicate dangers to client Erect barriers and warning signs and then join N and L of tails then test between these and steel armoured? I've re read GN3 since and it looks like I may of Answered better by testing N and L separately and then these to earth separately with a earth connection made to suppliers means of earthing from steel armour of tails. Have i made a glaring error? Or am I likely to pick up some marks do you think atleast? Had few people say that should of been tested separately and no earthing would be required which surprised me and that even with joining N and L should still of made connection to earth. My understanding is that when you join L to N that your not supplying an actual voltage because you have now not got a return path (2 poles)

Where does the swa come in to the answer as the question you have written says tails?

 

[DaveS]

Oh ****. That's the answer I was dreading Lee. Not much experience of dealing with supply side of things always general install on larger jobs. Isn't the tails an armoured that comes from CU board to Meter?

 

[DaveS]

Earthing link is made before this isn't it xxxx

 

[Leesparkykent]

Oh ****. That's the answer I was dreading Lee. Not much experience of dealing with supply side of things always general install on larger jobs. Isn't the tails an armoured that comes from CU board to Meter?

Meter tails are like this

 

[DaveS]

So supply armoured to Cut out. If TNCS Pen conductor linked at cut out. Then armoured again to Meter??? Then tails above away from meter to CU?

 

[DaveS]

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[Leesparkykent]

The question says before connected to supply. So the tails will be connected to the main switch of the consumer unit but not yet terminated in to the meter.

 

[DaveS]

Xxxx xxxx xxxx looks like resit : ( cheers Lee anyway mate. Get there in the end. Hopefully picked up enough on rest never no. Servere lack of domestic experience

 

[DaveS]

The question says before connected to supply. So the tails will be connected to the main switch of the consumer unit but not yet terminated in to the meter.

In regards to rest then Lee would I of just tested L to N L to E N to E and made a earth connection from earth tail to means of earthing?

 

[Leesparkykent]

Did it say what the final circuits connected to the board were?

 

[DaveS]

Not that I can remember it may well of though

 

[Leesparkykent]

In regards to rest then Lee would I of just tested L to N L to E N to E and made a earth connection from earth tail to means of earthing?

Was the main earthing conductor installed?

 

[Leesparkykent]

Not that I can remember it may well of though

This chief examiners report of a previous exam mentions a similar question page 4.

http://cdn.cityandguilds.com/Produc...-302_Chief_Examiners_Report_December_2013.pdf

 

[DaveS]

This chief examiners report of a previous exam mentions a similar question page 4.

http://cdn.cityandguilds.com/Produc...-302_Chief_Examiners_Report_December_2013.pdf

I think this is pretty much it Lee. I can't remember it saying main earthing conductor was present though. If this was the case would test be carried out at MET?

 

[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