2395 Last Night ?

[mcguiness79]

Did any one else sit the 2395 last night ?
If so how did you find it ?
I did and found it an absolute night mare.
If you are looking at sitting it any time soon I would spend a good amount of time on the Inspection part of GN3 if last night is anything to go by.
An example of a questions that I struggled with.....

Q.What two conditions would allow for an RCD to be omitted from socket outlet in residential property?
Obviously I went for Specific piece of equipment i.e. Freezer. but what would be the other as I can't imagine it would be under use by skilled person.


Q.Name two hazards that existing while doing continuity of main bonding conductors.
Again I went for risk of shock but struggled for another answer.

Any how if you are sitting it soon good luck

 

[malcolmsanford]

Well for me would be either sockets exceeding 20amp or reduced low voltage systems.

The second one for me would be strange, is that question word for word or from memory?

 

[telectrix]

Well for me would be either sockets exceeding 20amp or reduced low voltage systems.

The second one for me would be strange, is that question word for word or from memory?

trip hazard over wander lead???

bonding dissed during test???

 

[malcolmsanford]

Yes quite right Tel ....................was not switched onto the HSE but more going down parallel paths etc etc but that would be one yes

 

[Sparky Ninja]

Seems easy enough to me.

The first question you mention is from BS 7671 anyway

Can you remember any more?

 

[gesl]

I sat the 2395 last night as well, equally found it a nightmare. I did about 9 old 2391 papers as revison exercise and the same questions come up over and again. learn them and learn the books and you should be sorted I thought! there must of been 3 or 4 questions i'd not come across before most knew some sort of answer, then there was one about test 2 (live test) for finding TT earth rod resistance in a TT system protected by an RCD. I've never seen this before took an educated guess which I now know is totally wrong and thats probably cost me 15 marks and £80 for a resit. Hope others got on better.....

 

[Engineer54]

I sat the 2395 last night as well, equally found it a nightmare. I did about 9 old 2391 papers as revison exercise and the same questions come up over and again. learn them and learn the books and you should be sorted I thought! there must of been 3 or 4 questions i'd not come across before most knew some sort of answer, then there was one about test 2 (live test) for finding TT earth rod resistance in a TT system protected by an RCD. I've never seen this before took an educated guess which I now know is totally wrong and thats probably cost me 15 marks and £80 for a resit. Hope others got on better.....

Come on, ...what was your educated guess?? And Who gave you the correct answer??

 

[Sparky Ninja]

there was one about test 2 (live test) for finding TT earth rod resistance in a TT system protected by an RCD. I've never seen this before took an educated guess which I now know is totally wrong and thats probably cost me 15 marks and £80 for a resit. Hope others got on better.....

Was it asking what the two methods of measuring the electrode resistance was?
One being with an earth electrode tester, the other being the earth loop impedance test. The EFLI method can only be used on a TT system with an RCD?

 

[malcolmsanford]

Was it asking what the two methods of measuring the electrode resistance was?
One being with an earth electrode tester, the other being the earth loop impedance test. The EFLI method can only be used on a TT system with an RCD?

As the criteria not changed for that in the new amendment mate and regulation 612.8.1 note

Where a measurement of Ra is not practicable the measured value of external earth loop impedance may be used

I know 999/1000 there will be an RCD on the installation but the reg amendment means it's no longer a requirement for gaining the value

 

[Sparky Ninja]

Where a measurement of Ra is not practicable the measured value of external earth loop impedance may be used

I believe it also says it must be on an RCD and form part of a TT system or something. I'll put my nose in the book on this tonight.

 

[malcolmsanford]

I've just dug the book out myself mate lol and interestingly ( or not I just think I'm sad) reg 612.7 reads

Where the earthing system incorporates an earth electrode as part of the installation, the earth electrode resistance to earth shall be measured

That is exactly the same reg in the BRB, but that same note in reg 612.8.1 is added to this reg, and no mention of RCDs only for verification of characteristics and effectiveness, which is also mentioned for TN systems

Widdler what does the new GN 3 say I don't have that with me out here, it's at home waiting for me

 

[Engineer54]

Would you in fact, be able to measure the loop impedance of the rod going through an RCD?? If using this method to ascertain the Ra of a rod, i'd be testing from the incoming supply on the DP isolator of the CU... I'd be wanting minimal contact resistances in the measuring circuit...lol!!

 

[spark 68]

Hi E54,

When testing TT system Ze (Ra) I don't test through the RCD, as Widdler pointed out the reg said you could use the EFLI method where the installation was protected by an RCD, not that you tested through the RCD.

I took this to mean you could not use the EFLI method for generator rods and the like.

 

[spark 68]

@ Malcom,

The new GN3 gives three methods now, 1) the usual earth rod tester with spikes, 2) the newer 'stakeless' rod testers, and 3) the EFLI method.
The last method does not now give any reference to RCD's whatsoever.

 

[Engineer54]

Hi E54,

When testing TT system Ze (Ra) I don't test through the RCD, as Widdler pointed out the reg said you could use the EFLI method where the installation was protected by an RCD, not that you tested through the RCD.

I took this to mean you could not use the EFLI method for generator rods and the like.

Ah ... i obviously misunderstood then...lol!!

Well, seeing as most electricians in the UK won't have an earth electrode tester, what other method is open to you?? Using a EFLI is fine to a point, it won't however, indicate when you have overlapping areas of influence between multiple rods for arguments sake. But it should give you a fairly accurate Ra value of the rod under test....

 

[Engineer54]

@ Malcom,

The new GN3 gives three methods now, 1) the usual earth rod tester with spikes, 2) the newer 'stakeless' rod testers, and 3) the EFLI method.
The last method does not now give any reference to RCD's whatsoever.

I wouldn't use these for single point testing, but are fine where multiple rods are involved....

 

[gesl]

So glad you boys are having to look the TT question up. I totally blanked on it. Not having any idea you could do an efli test instead of thee usual dead test. I put test the rcd ifvit trips in time it proves your earthing but includes parallel paths, thought it was wrong, but better owt than nowt.!

 

[spark 68]

So, with reference to the new GN3 and the removal of the RCD requirement, and the regs Malcom referred to, does this mean that we can now test all Earth rods by the EFLI method ?

 

[Engineer54]

So, with reference to the new GN3 and the removal of the RCD requirement, and the regs Malcom referred to, does this mean that we can now test all Earth rods by the EFLI method ?

To be absolutely honest, i was under the impression that's exactly what the vast majority of self employed electricians use, to measure earth rod resistances. As i say, what other method is there, if you don't own/possess a dedicated earth electrode tester?? lol!!

 

[spark 68]

So glad you boys are having to look the TT question up. I totally blanked on it. Not having any idea you could do an efli test instead of thee usual dead test. I put test the rcd ifvit trips in time it proves your earthing but includes parallel paths, thought it was wrong, but better owt than nowt.!

Hi gesl,

You used to be able to use the EFLI method (as Widdler pointed out) where the install had RCD protection, which in practice meant almost all domestic and smaller commercial sites (except when Ra was at TN levels) where high EFLI meant this was the only practical way of achieving disconnection times.
You just did a normal Ze test with your MFT, and this gave you your Ra value, as E54 said, not many electricians these days have the earth rod testing kit except on the larger sites, and possibly those working for the utility companies and other specialist contractors.

It appears that the new GN3 has removed the RCD requirement, however I would imagine that the rod testing kit is still a requirement for the more specialised sites.