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Topic Title: EICR and IR Testing the whole installation
Topic Summary: Help me please!
Created On: 17 April 2013 08:50 PM
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 17 April 2013 08:50 PM
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Grumpy

Posts: 407
Joined: 09 January 2009

I am obviously doing something wrong. I turn off the main switch, I disconnect the earth and main bonds, I connect a temporary link between L & N and test between the link and the circuits' cpc's. (TNCS). Everytime I get ridiculously low readings. So I end up disconnecting and testing each circuit which takes FOREVER and comes out with acceptable results. Never mind drive by PIR's my life would be immeasurably improved if you could help me crack this one.
 17 April 2013 08:55 PM
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Ampman

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Have you disconnected the neutral or took test link out ?
 17 April 2013 08:56 PM
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leckie

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What size installation?

If you have say ten circuits, the l/n to e readings are all parallel paths and will reduce the overall reading of the combined circuits to earth.
 17 April 2013 08:59 PM
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leckie

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Originally posted by: Ampman

Have you disconnected the neutral or took test link out ?


He said he disconnected the earth, I assume the earthing conductor, the main bonds and turned of the main switch
 17 April 2013 09:02 PM
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Grumpy

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Sorry Ampman I don't understand your question.
Leckie, today there were 10 circuits but the IR was in Kohms.
 17 April 2013 09:12 PM
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leckie

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What, K ohms to each circuit or overall reading?
 17 April 2013 10:02 PM
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RB1981

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Originally posted by: Grumpy

I disconnect the earth and main bonds


The means of earthing should be connected when conducting the insulation resistance test.
 17 April 2013 10:22 PM
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Grumpy

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Hi Leckie, 0.26 kOhm. Overall.
RB1981, eh?
 17 April 2013 10:39 PM
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DOUGIE1000

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Originally posted by: Grumpy

Hi Leckie, 0.26 kOhm. Overall.

RB1981, eh?


Try removing surge protector ext leads and try retesting, look behind TV's and computers normally for the surge protectors.

D

-------------------------
Dougie
Power Plus Electrical.co.uk

My mission is to live as long as possible......so far so good!
 17 April 2013 10:48 PM
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John Peckham

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Well done RB1981 someone has been reading GN3 or attending my classes and had it drummed in to them.

The installation must be connected to earth and all bonds connected otherwise it is a waste of time doing the test.

For an EICR.

1. Seek permission to isolate.
2. Isolate and lock off supply.
3. Using your Approved Voltage Tester. Prove it. Test between all poles. Re-prove tester.
4. If 3 phase board remove neutral link or disconnect neutral using insulated tools. Be careful may become live when disconnected. If you get any sparking on the neutral or detect a voltage on the end or the neutral bar with your Fluke Voltstick re-connect and abandon test.
5. Unplug any equipment or turn off anything with electronics in it etc if you can. All light switches on.
6. Disconnect any functional earths to RCBOs.
7. Place temporarily link between all live conductors.
8. Select IR tester and check condition, batteries and calibration.
9. Select GS38 leads and clips/probes. Inspect for damage.
10. Connect leads to meter and test short and open circuit for lead continuity.
11. Connect one lead to live conductors connect one lead to earth,
12. Set meter to 500V. Press test button and record result. Release test button and wait before disconnecting leads.
13. Change 2 way switching and repeat test.

Most likely there will be 0M ohms reading. Flick over instrument to continuity and highly likely there will be a dead short neutral to earth as the installation was only even 240V bang tested and this test does not reveal neutral earth faults.

Now before you do anything else for heaven sake re-connect the neutral. If you don't you will have an indoor fireworks display and a very large claim on your insurance. Then remove temporary link.

-------------------------
John Peckham

http://www.astutetechnicalservices.co.uk/
 18 April 2013 07:57 AM
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leckie

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An excellent summary of the requirements John.

Grumpy, as John says the earthing and bonding should be in place during the ir test.

If you test as John explained and you have an overall low reading you need to test individual circuits. Leave the cpc connected during this test.

When you test the individual circuits remove the neutral and isolate the line, link together, test to earth and record the result. You will probably find a very low reading to one of the circuits and can investigate further. You may find that if you then disconnect the cpc to that circuit that the low reading disappears or is not as low. If you then test between the lives and the earth bar it may be low. Hence why you need to have all earthing, bonding and cpc's connected initially as you may "miss" a fault. You could have a line or neutral conductor fault to a pipe or other earthed metalwork and have a lack of continuity to the circuit cpc which may result in the above readings, for example.

Alternatively you may find quite few circuits with lowish results. If this is the case the combined result of these values will decrease the overall insulation value. Calculate using resistors in parallel formula, 1/rt = 1/r1 + 1/r2 + 1/r3 etc.

As Dougie said, surge protectors on leads or equipment can also cause low readings and require isolation. If you carry out an ir test at 230v the readings on surge protected leads, etc often disappear. The Code of Practice for testing of electrical equipment accepts the testing of surge suppression leads to be carried out at 230v for this very reason. So if you carry out an additional test, after the 500v test, at 230v and the fault disappears this may indicate that surge suppression equipment is still connected somewhere. So then you need to find it, isolate it and retest at 500v.
 18 April 2013 08:44 AM
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Jaymack

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Originally posted by: John Peckham
11. Connect one lead to live conductors connect one lead to earth,

Your students, require to be instructed on the proper sequence of applying probes/clips!

Regards
 18 April 2013 09:38 AM
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AJJewsbury

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The means of earthing should be connected when conducting the insulation resistance test.

Agreed. It was a not very well publicised change when the 17th came in (reg 612.3.1) - the words "connected to the earthing arrangement" were inserted.
- Andy.
 18 April 2013 09:56 AM
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Grumpy

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Thank you John and Leckie for your comprehensive replies. The property is unoccupied so no surge protection etc. Shall go back there this afternoon and finish test. Groan!
 18 April 2013 11:49 AM
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acsinuk

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Once you have got the insulation resistance figures above 2megs [ by removing surge suppression or capacitors from fluorescent fittings] and have proved that the loop resistance to far end of the wiring is low enough to allow a fault current to trip the mcb or blow the fuse with a 2.5 times safety factor; will the installation then comply with the low voltage directive or just guidance note 3 ??
Will you need to add some extra words to cover unseen possible defects! What notes should you add to protect yourself against insurance claims?
CliveS
 18 April 2013 11:59 AM
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AJJewsbury

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with a 2.5 times safety factor

Where do you get 2.5 from?

will the installation then comply with the low voltage directive or just guidance note 3 ??

Of itself, neither - there's an awful lot more to an I&T then just insulation and Zs tests...

- Andy.
 18 April 2013 01:56 PM
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Jaymack

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Originally posted by: acsinuk
Once you have got the insulation resistance figures above 2megs [by removing .................... capacitors from fluorescent fittings]

If relevant, what's the quickest way in doing this?

Regards
 18 April 2013 03:04 PM
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ebee

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Originally posted by: AJJewsbury

The means of earthing should be connected when conducting the insulation resistance test.


Agreed. It was a not very well publicised change when the 17th came in (reg 612.3.1) - the words "connected to the earthing arrangement" were inserted.

- Andy.


I`ve always felt it should be anyway even before it was stipulated

-------------------------
Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 18 April 2013 08:21 PM
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hertzal123

Posts: 296
Joined: 26 August 2007

Originally posted by: John Peckham

Well done RB1981 someone has been reading GN3 or attending my classes and had it drummed in to them.



The installation must be connected to earth and all bonds connected otherwise it is a waste of time doing the test.



For an EICR.



1. Seek permission to isolate.

2. Isolate and lock off supply.

3. Using your Approved Voltage Tester. Prove it. Test between all poles. Re-prove tester.

4. If 3 phase board remove neutral link or disconnect neutral using insulated tools. Be careful may become live when disconnected. If you get any sparking on the neutral or detect a voltage on the end or the neutral bar with your Fluke Voltstick re-connect and abandon test.

5. Unplug any equipment or turn off anything with electronics in it etc if you can. All light switches on.

6. Disconnect any functional earths to RCBOs.

7. Place temporarily link between all live conductors.

8. Select IR tester and check condition, batteries and calibration.

9. Select GS38 leads and clips/probes. Inspect for damage.

10. Connect leads to meter and test short and open circuit for lead continuity.

11. Connect one lead to live conductors connect one lead to earth,

12. Set meter to 500V. Press test button and record result. Release test button and wait before disconnecting leads.

13. Change 2 way switching and repeat test.



Most likely there will be 0M ohms reading. Flick over instrument to continuity and highly likely there will be a dead short neutral to earth as the installation was only even 240V bang tested and this test does not reveal neutral earth faults.



Now before you do anything else for heaven sake re-connect the neutral. If you don't you will have an indoor fireworks display and a very large claim on your insurance. Then remove temporary link.


John,
Are you saying that rcbo,s will not be damaged by 500v insulation tests
with only the functional earth disconnected?Also,I thought it was recommended to test at 250v first in case electronic devices were still in circuit.
Regards,hz
 18 April 2013 09:38 PM
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lyledunn

Posts: 607
Joined: 13 August 2003

IR testing is probably best avoided in periodics.

-------------------------
Regards,

Lyle Dunn
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