IR testing...again!

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avinalarf

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Can someone explain to me why it's ok to keep appliances connected when performing an IR test between earth and joined neutral and line conductors?

 

Admin1

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I don't. I unplug them when I do a R1&R2 (cont) at each S/O.

 
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Can someone explain to me why it's ok to keep appliances connected when performing an IR test between earth and joined neutral and line conductors?
An IR test puts 500v DC down the pair of wires you are testing..

(table 61, Pg 158, 612.3.2)

Some electronic devices can be zapped and sent to lectwick heaven by this test voltage.

The power to the appliance is normally connected to "Live" and "Neutral"...

so if "Live" & "Neutral" are joined together there can be NO potential difference between the two supply wires into your applaince...

Therefore it cannot be Zapped!

This method obviously only verifies the live & neutral with respect to earth..

it is preferable to fully isolate & disconnect all Appliances to do full tests.

L-N

L-E

N-E.

In some situations (e.g. on a PIR) it may not be practicable to access and isolate everything...

e.g. something plugged into a socket mounted on the wall...

with a very heavy sideboard / wall unit / full of delicate china plates etc..

On an unknown installation it can be beneficial to do a test at 250v first to verify if anything is still connected...

(250v won't zap anything bad! as the accessories are designed to work at 230v ) ;)

On a rewire... there is NO valid reason why you cannot fully test all combinations properly L-E, L-N, N-E all @ 500v:)

 

avinalarf

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An IR test puts 500v DC down the pair of wires you are testing..(table 61, Pg 158, 612.3.2)

Some electronic devices can be zapped and sent to lectwick heaven by this test voltage.

The power to the appliance is normally connected to "Live" and "Neutral"...

so if "Live" & "Neutral" are joined together there can be NO potential difference between the two supply wires into your applaince...

Therefore it cannot be Zapped!
Ok, understand that bit!

This method obviously only verifies the live & neutral with respect to earth..In some situations (e.g. on a PIR) it may not be practicable to access and isolate everything...
Ok, so if you've got something on the circuit which can not be disconnected (eg your PIR), do you still bother to disconnect everything else?

On an unknown installation it can be beneficial to do a test at 250v first to verify if anything is still connected...(250v won't zap anything bad! as the accessories are designed to work at 230v ) ;)
Great tip. Applaud Smiley

 

steptoe

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Ok, so if you've got something on the circuit which can not be disconnected (eg your PIR), do you still bother to disconnect everything else?

why cant you just disconnect that part of the circuit?

if you do go down the route of disconnecting or not and testing only across L&N to E you MUST put this on your limitations with the reasons why.

(LIMITATIONS=outside light not tested due to...)

IMHO this is usually only valid for commercial/industrial situations where you may have something like 50 or so high level florries, or some such like.

I dont see why it would be needed muh in standard domestic, (exceptions being as has been said totally inaccessible socket behind china cabinet/built in furniture).

 

stringy

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An IR test puts 500v DC down the pair of wires you are testing..(table 61, Pg 158, 612.3.2)

Some electronic devices can be zapped and sent to lectwick heaven by this test voltage.

The power to the appliance is normally connected to "Live" and "Neutral"...

so if "Live" & "Neutral" are joined together there can be NO potential difference between the two supply wires into your applaince...

Therefore it cannot be Zapped!

This method obviously only verifies the live & neutral with respect to earth..

it is preferable to fully isolate & disconnect all Appliances to do full tests.

L-N

L-E

N-E.

In some situations (e.g. on a PIR) it may not be practicable to access and isolate everything...

e.g. something plugged into a socket mounted on the wall...

with a very heavy sideboard / wall unit / full of delicate china plates etc..

On an unknown installation it can be beneficial to do a test at 250v first to verify if anything is still connected...

(250v won't zap anything bad! as the accessories are designed to work at 230v ) ;)

On a rewire... there is NO valid reason why you cannot fully test all combinations properly L-E, L-N, N-E all @ 500v:)
excellent post :p

 

avinalarf

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why cant you just disconnect that part of the circuit?
I was referring more to if only one circuit was being tested, not the whole installation, but I definitely see your point.

if you do go down the route of disconnecting or not and testing only across L&N to E you MUST put this on your limitations with the reasons why.(LIMITATIONS=outside light not tested due to...)

IMHO this is usually only valid for commercial/industrial situations where you may have something like 50 or so high level florries, or some such like.

I dont see why it would be needed muh in standard domestic, (exceptions being as has been said totally inaccessible socket behind china cabinet/built in furniture).
Am I right to assume you don't get a true IR result then? Does it get to a point where you would HAVE to make sure everything on the circuit being tested was disconnected and do L-N, L-E and N-E?

 

steptoe

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obviously on a L&N to E scenario you are not testing the integrity of the insulation between L & N .

remember on lights you need to test twice(if 2 way switch fitted, 3 tests for intermediate)

on doing standard domestic PIR I can barely remember the last time I had to do a combined L&N test.

always wise(as has been said) to test at 250v first. :)

 

seajayess

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You must remember that you can only do the L/N joined, to CPC insulation test when filling out periodic reports, as you can put limitation in the results page, this is not possible if doing a installation certificate as all insulation tests must be completed CJS

 

dave2

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Page 83 OSG says it is permissible to do test with live conductors joined and earth.

dave

 
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