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.

 

[brman]

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!!

I was going to say the same thing but didn't dare :lol:

On my 2395 I am sure i was taught that the EFLI was only valid if a RCD was present as accurancy was not so important in that situation but it does appear from the regs that this bit has been dropped now. To be fair the updated GN3 wasn't available when I did mine!

To the guys that found the 2395 harder than expected, don't panic! I felt the same after mine - from revising 2391 I thought I would be ok but found a number of questions I didn't get the point of until discussing them with colleagues afterwards. But I passed

 

[spark 68]

I was going to say the same thing but didn't dare :lol:

On my 2395 I am sure i was taught that the EFLI was only valid if a RCD was present as accurancy was not so important in that situation but it does appear from the regs that this bit has been dropped now. To be fair the updated GN3 wasn't available when I did mine!

You put it clearer than I did lol, that is partly what I was trying to say in the previous post.

E54,
I have never (up to now) needed to test the earth mats/multiple rods on the larger industrial or commercial sites since being self employed (and doubt that I will), but if I did I would have probably either bought or hired the rod testing kit, and I suppose it would depend on the specs/standards of the job whether this is still a requirement or not.

 

[Engineer54]

I was going to say the same thing but didn't dare :lol:

On my 2395 I am sure i was taught that the EFLI was only valid if a RCD was present as accurancy was not so important in that situation but it does appear from the regs that this bit has been dropped now. To be fair the updated GN3 wasn't available when I did mine!

To the guys that found the 2395 harder than expected, don't panic! I felt the same after mine - from revising 2391 I thought I would be ok but found a number of questions I didn't get the point of until discussing them with colleagues afterwards. But I passed

Using an EFLI test to acquire the Ra value of a rod, is a reasonably accurate method of testing!!

Virtually ALL TT systems in the UK would require RCD protection, with such a high max requirements, let alone the lack of stability that's given to TT systems these days...

 

[mcguiness79]

The only other one that I can think of at the moment was

Q.Under what conditions may you exclude the testing of continuity of ring final circuits.

Again in the cold light of day I have since found an answer of sorts in GN3 but as gesl says the 2391 past papers we were practicing on lead me to concentrate on certain questions that kept coming up such as earth fault paths, resistors in parrell etc and it caught me completely off guard.

 

[ackbarthestar]

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.

Read more: http://www.electriciansforums.net/i...ns/59460-2395-last-night-2.html#ixzz1z27zEfK5
​

From what I can see there has never been a requirement to include a RCD in testing the Ze(Ra) of a TT installation

Earth electrode, clamp measurements and ELI testing are all still valid and do not require a RCD to be present. In fact RCDs are one hell of a hindrance and IMO you would test up stream or with the earthing conductor disconnected.

RCDs make allowances for a Ze (Ra) coupled with R1+R2 of the largest circuit when the required Zs for disconnection time is non compliant with table 41.1.

Having said that both Ia and IAN are valid (411.5.2)

 

[spark 68]

From what I can see there has never been a requirement to include a RCD in testing the Ze(Ra) of a TT installation

Earth electrode, clamp measurements and ELI testing are all still valid and do not require a RCD to be present. In fact RCDs are one hell of a hindrance and IMO you would test up stream or with the earthing conductor disconnected.

Hi Ackbar,

That is basically what I said in some previous posts in this thread:

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.​

​

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.​

​

As Widdler pointed out, the 17th Ed pre Amd 1 and the previous GN3 does mention having an RCD present to be able to use the EFLI method.

The new GN3 has removed the references to RCD's altogether.

Cheers, S68

 

[ackbarthestar]

Hi Ackbar,

That is basically what I said in some previous posts in this thread:

As Widdler pointed out, the 17th Ed pre Amd 1 and the previous GN3 does mention having an RCD present to be able to use the EFLI method.

The new GN3 has removed the references to RCD's altogether.

Cheers, S68

I think it refers to Zs testing not earth electrode testing.

Since RCDs are mentioned in both GN3 17th ed (page 51) and 17th ed amd 1 ( page 53) when referring to Zs testing.

Moreoever, RCDs are mentioned when electrodes testing 17th ed (page 47) and amd 1 (page 51). But GN3 17th ed amd 1 removes the ambiguity that earth electrode testing should be tested through a RCD, which is a bit of a facility when you consider the rubbish being pumped along the supply cables and your tester is set to something in the order of mA......

 

[spark 68]

Hi Ackbar,

The previous GN3 (P47) says:

Earth Electrode for RCD's

If the electrode is being used in conjunction with a residual current device the following method of test may be applied as an alternative to the earth electrode resistance test described above (refers to spike type testers), in these circumstances, where the electrical resistances to earth are relatively high and precision is not required, an EFLI tester may be used.

The new GN3 (p50) has removed the references to RCD's altogether

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.​

​

​

This now appears to allow the use of EFLI testers whether an RCD is present or not.

In neither case does it mention testing through the RCD, which is what I said previously ie. you would test the rod as you would normally do a Ze test, and not through the RCD.

 

[ackbarthestar]

This now appears to allow the use of EFLI testers whether an RCD is present or not.

Read more: http://www.electriciansforums.net/i...ns/59460-2395-last-night-3.html#ixzz1z2WE8Cwl
​

GN3 16th ed, 17th ed and 17th ed amd 1 recognize EFLI as one method of testing the earth electrode.

When GN3 was first introduced Circa 1992 RCDs were just finding prominence. So the standard methods of testing were propriety earth electrode testing, EFLI testing and Clamp testing.
There is nothing new here...

 

[spark 68]

GN3 16th ed, 17th ed and 17th ed amd 1 recognize EFLI as one method of testing the earth electrode.

There is nothing new here...

I have the OSG 16th ed and the two 17th ed GN3 (I cannot find my 16th Ed GN3)

The 16th ed test (in the OSG) and the 17th Ed:2008 (GN3) both say you may use the EFLI method if the rod is used in conjunction with an RCD


The 17th ed amd 1 GN3, has now removed this RCD requirement. This is what is new :cheesy:

 

[ackbarthestar]

I have the OSG 16th ed and the two 17th ed GN3 (I cannot find my 16th Ed GN3)

The 16th ed test (in the OSG) and the 17th Ed:2008 (GN3) both say you may use the EFLI method if the rod is used in conjunction with an RCD


The 17th ed amd 1 GN3, has now removed this RCD requirement. This is what is new :cheesy:

Ah, now I see where you're coming from.

I can see why they changed it. Testing through a RCD will always give spurious results. Maybe this test was invented so that the novice always had the protection of the RCD if testing live, but then decided that anybody testing live should know what they're doing.

There is nothing new here, as I said before. Testing across a RCD is more likely to give overestimated results rather than referring to 411.5.2 and .3

 

[spark 68]

No, No, Ackbar it has never suggested that you test through the RCD, you would Isolate the supply and test as you would have normally tested for Ze, disconnecting the earthing conductor and testing directly on that.

What it was saying previously was, that so long as the installation was using an RCD that you could use the EFLI method, but now it just says using the EFLI method may give less accurate results.

I think it was as brman said here:

On my 2395 I am sure i was taught that the EFLI was only valid if a RCD was present as accurancy was not so important in that situation but it does appear from the regs that this bit has been dropped now. To be fair the updated GN3 wasn't available when I did mine!​

Anyway it seems as if the new GN3 has relaxed the regs a bit, and what I was asking was " can we use the EFLI method for generator rods and the like ?" , as previously we couldn't according to the regs, maybe some did anyway and that was why the regs have been relaxed, who knows ?

 

[ackbarthestar]

I've always read this test as:
1/ Where there is a supply connected then you have a choice of electrode testing using the spike method or EFLI test or Clamp test
2/ Where there is no supply then apply the proprietary earth electrode test.

I think we are speaking the same language

 

[spark 68]

I've always read this test as:
1/ Where there is a supply connected then you have a choice of electrode testing using the spike method or EFLI if to be used in conjunction with an RCD (now relaxed, Amd1) test, or Clamp test
2/ Where there is no supply then apply the proprietary earth electrode test Good point.

I think we are speaking the same language

Yes we are saying broadly the same things, I have added the bits in red.

The part with no supply obviously makes sense, how else could you test it ? lol

I wonder now about how to test the generator rods using the EFLI method, if it is at all possible ?, maybe if there is a supply on site it would, but would the results be accurate enough ?

It is good to talk about these things, I must thank Malcom too, for drawing my attention to the updated regs, as if he had not pointed them out I would not have noticed the subtle changes here.

 

[ackbarthestar]

I wonder now about how to test the generator rods using the EFLI method, if it is at all possible ?, maybe if there is a supply on site it would, but would the results be accurate enough ?

Read more: http://www.electriciansforums.net/i...ns/59460-2395-last-night-4.html#ixzz1z4l0bDfA
​

I agree, some good points made.
How i see it, Using class I equipment, or more appropriately where an earth return path is required for fault currents, you are likely to need 2 electrodes, one at the source and one at the point of utilization.

An established TT installation has an electrode already So by using a separate source, such as a generator with a change over switch, will utilize this electrode. I think the problem comes when the generator has built in RCD protection in the loop.

To get a realistic result then I think you will need to use a proprietary electrode tester.