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Topic Title: Which one would you save?
Topic Summary: A sort of Desert Island tests
Created On: 30 March 2015 09:48 PM
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 30 March 2015 09:48 PM
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Zs

Posts: 3814
Joined: 20 July 2006

hello,

I have been looking at my test certificates and the outcome of my reports this evening. The ones where I know what happened after my words were submitted. In a not-very-scientific look at where I go right and where I go wrong. Just personal CPD and not earth shattering stuff, no notebook by my side.(, that's rare for me, we are usually joined at the fingertips).

I can see, from my stuff, that one particular test tells me more about a circuit or perhaps an installation than all of the others and that it is also the one most acted upon and indeed most promptly by my clients. I am pondering over whether it is my confidence on the subject of that test i.e a small degree of better being able to write about it, or real. I'll not let on for the time being because I genuinely would like to know yours.

If all of your tests except one were to be washed away by the tide, which one would you keep? Why?

Zs
 30 March 2015 09:52 PM
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geov

Posts: 387
Joined: 22 February 2004

My visual inspection (does that count as a "test"?).
 30 March 2015 10:08 PM
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IronFreely

Posts: 322
Joined: 06 November 2014

I'm with Geov... But in terms of actual testing I generally find that when it comes to fault finding that it's Insulatin resistance testing that reveals the sins.
Edit.
On EICR i'd say I generally find fault with continuity of CPC's
 31 March 2015 01:35 AM
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Legh

Posts: 4029
Joined: 17 December 2004

Lol - The invoice - the biggest test of the lot - well it is, isn't it?

Legh

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http://www.leghrichardson.co.uk

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 31 March 2015 02:11 PM
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burn

Posts: 242
Joined: 06 June 2003

When I review test results I pay most attention to earth loop impedance. If it is low enough for the CPD then the circuit should be safe. It will show poor continuity if there are loose connections etc.

Anyone else willing to stick their head above the parapet and answer the original question?

burn

(another CDP point - to address another topic)
 31 March 2015 03:51 PM
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OMS

Posts: 22359
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Originally posted by: burn

When I review test results I pay most attention to earth loop impedance. If it is low enough for the CPD then the circuit should be safe. It will show poor continuity if there are loose connections etc.

Anyone else willing to stick their head above the parapet and answer the original question?

burn

(another CDP point - to address another topic)


but what does the loop test rely on ? - ie it may be a loop, but which loop ?

And as for showing loose connections, given that it's only delivering fractions of an amp, how is that a test for "goodness" - you need to drop GB's gold spanner across L and E for that - sparks 'n all

Regards

OMS

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Let the wind blow you, across a big floor.
 31 March 2015 04:07 PM
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Legh

Posts: 4029
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Anyone else willing to stick their head above the parapet and answer the original question? [/Q

Well, if I must....lol

This is an interesting question as I believe that there is no definitive test result that confirms or denies good working order for an installation

when you think about it
A low IR doesn't mean that the insulation has failed
A high ELI result doesn't mean the circuit/s are faulty.

For EICs, you test as you go, bottom up, and make sure you don't connect up equipment that is likely to give false readings at the time of testing. This should supply you with a steady increase in acceptable circuit results

For EICRs, I think you have to look at a combination of results, top down, particularly, the methods for S/C, basic/fault protection, and overload when taken together, with a VI to make an assessment as to whether its safe.

that's my pennyworth.

Legh
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http://www.leghrichardson.co.uk

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 31 March 2015 05:53 PM
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mapj1

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If all of your tests except one were to be washed away by the tide, which one would you keep? Why?



R2 or ring round on a socket circuit CPC.

If the CPC is not continuous, other things are likely also missing.

closely followed by L_N polarity and grossly odd choices of fuse or circuit breaker rating.

Serious insulation weakness normally reveals itself anyway, sometimes spectacularly, as do high resistance conductors once the load comes on.

the lost earth has the potential to be a silent if rather tingly killer.

-------------------------
regards Mike
 31 March 2015 06:05 PM
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Zoomup

Posts: 3286
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Originally posted by: burn

When I review test results I pay most attention to earth loop impedance. If it is low enough for the CPD then the circuit should be safe. It will show poor continuity if there are loose connections etc.



Anyone else willing to stick their head above the parapet and answer the original question?



burn



(another CDP point - to address another topic)


I agree that earth fault loop impedance is a very important test. With tongue in cheek I also say that insulation resistance testing is second, but with so much R.C.D. protection these days it is often redundant unless there is a serious loss of insulation resistance due say to water ingress or rodent attack and no R.C.D. protection.

EDIT. One of my test instruments works with about a 20 Amp. test current. A nice testing current.

Bye,

Z.
 31 March 2015 06:12 PM
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Zs

Posts: 3814
Joined: 20 July 2006

Interesting,

Mine is an earth fault loop impedance test but specifically it is the two-lead Line and Earth Variety. Low or high current depending on RCBO or not. Using the real line of the circuit in question I might add.

I think it paints a thousand words.

Zs
 31 March 2015 07:10 PM
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JonSteward

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I like to see the mA loss when clamped round L & N
 31 March 2015 09:51 PM
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AJJewsbury

Posts: 15855
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If I was only allowed one test only, I'd probably go for a wander lead R1 test. While not as good as a loop test for ensuring ADS as such, it would spot a L-PE reversal (the fault that killed the plumber installing a washing machine a while back), which a 2-wire loop test wouldn't. Ensuring continuity back the the MET should provide some degree protection from shock indoors (providing I could visually check the main bonding was present) even if the external earthing arrangement was dodgy or even absent - bonding actually works better with high external impedance earths. A bit of an old school 'alternative method' approach, but the physics still works just the same.

Other (L/N) polarity issues are less of a worry, especially with modern CE style appliances. Provided the earthing to the MET is OK, the poor insulation L-PE is mitigated a bit, so I'd still rank R1 above insulation. Poor L-N insulation isn't an immediate shock hazard and it would probably be rare to start a fire without failing to a short and taking out the overcurrent device (my feeling is that fires are more usually caused by high resistance joints and/or overload).

An interesting 'thought experiment'!
- Andy.
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