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Topic Title: Earth Leakage
Topic Summary: Which cables?
Created On: 19 March 2013 05:56 PM
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 19 March 2013 05:56 PM
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bak1950

Posts: 75
Joined: 24 June 2009

When testing for earth leakage on an appliance using a leakage tester, does it matter if the jaws of the tester are over all three cables(if an earth cable is present) or should it only be around the live and neutral?
Also what is an acceptable leakage for an appliance say a vaccume cleaner?
Thanks
 19 March 2013 06:03 PM
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daveparry1

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If testing for earth leakage you only really want the clamp meter on the earth cable,

Dave.
 19 March 2013 06:06 PM
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OMS

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Clamp the live and neutral with a good high resolution clamp meter - if you get any current measured that's the leakage as live in and neutral out will cancel any other load current

Dave - measuring the earth conductor assumes the leakage current is flowing through it - it could just as easily be going down a gas pipe


Regards

OMS

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Failure is always an option
 19 March 2013 06:25 PM
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daveparry1

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Agreed OMS but as the OP is testing appliances (vacuum cleaner he said) he only needs to know if anything's going down it's earth conductor, different for an installation test of course,

Dave.
 19 March 2013 06:32 PM
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michaelbrett

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Originally posted by: bak1950


Also what is an acceptable leakage for an appliance say a vaccume cleaner?

Thanks


Take a look at CoP for In-service Inspection and Testing of Electrical Equipment 4th Edition page 96.

You should also read page 95.

Regards

Mike
 19 March 2013 06:49 PM
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OMS

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Good point Dave - probably not credible that the vacuum has another means of earthing other than the CPC -

Although I'm sure we could construct a case where a class 1 hoover was situated on an earthed steel flooring system just to be awkward - in the tradition of the forum of course -

regards

OMS

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 19 March 2013 06:59 PM
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Patnik

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Maximum for a class 1 vacuum cleaner is 0.75mA. Might be safer and easier to borrow a dedicated PAT instrument and run the appliance through it. Can a clamp type meter even measure that low? (I don't know)
 19 March 2013 07:02 PM
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OMS

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I was "playing" with one the other day that has a resolution of 0.001mA

regards

OMS

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Failure is always an option
 19 March 2013 07:11 PM
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Legh

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Originally posted by: OMS

I was "playing" with one the other day that has a resolution of 0.001mA

regards

OMS


I use a vacuum cleaner for cleaning the carpet........

Table 15.3 plus notes

legh

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 19 March 2013 07:33 PM
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mikejumper

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Originally posted by: bak1950
When testing for earth leakage on an appliance using a leakage tester, does it matter if the jaws of the tester are over all three cables(if an earth cable is present) or should it only be around the live and neutral?
Thanks


You could make yourself up a test lead by cutting off around 500mm of flex, slice open the outer sheath carefully about half way along and pull out a loop of earth conductor, then tape the sheath back up.
Put a plug on one end and a trailing socket on the other end and you have the means to test individual appliances with a suitable clamp meter.
 19 March 2013 08:17 PM
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Patnik

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Originally posted by: OMS

I was "playing" with one the other day that has a resolution of 0.001mA


That sounds useful - makes ours look like a toy at minimum 10mA.
 19 March 2013 10:46 PM
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M.Joshi

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This short video from the Learning Lounge may be of use:

http://www.youtube.com/watch?v=5hL13UjRSoY

It shows the modifed extension lead as mentioned by 'mikejumper' above.

I think someone may have posted this video link on here before?

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 20 March 2013 07:34 AM
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Patnik

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Originally posted by: M.Joshi

This short video from the Learning Lounge may be of use:



http://www.youtube.com/watch?v=5hL13UjRSoY



It shows the modifed extension lead as mentioned by 'mikejumper' above.



I think someone may have posted this video link on here before?


Oh dear! What is that guy trying to show with the class 2 equipment It doesn't have a protective earth so he tries to measure leakage via the protective earth of an extension lead it's plugged into!
 21 March 2013 06:03 PM
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Legh

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Originally posted by: Patnik

Originally posted by: M.Joshi

This short video from the Learning Lounge may be of use:

">http://www.youtube.com/watch?v...RSoY



It shows the modifed extension lead as mentioned by 'mikejumper' above.

I think someone may have posted this video link on here before?


Oh dear! What is that guy trying to show with the class 2 equipment It doesn't have a protective earth so he tries to measure leakage via the protective earth of an extension lead it's plugged into!


Lol, Why didn't he just clamp the two core cable? The difference between the phase and neutral would indicate the leakage.....would somebody then like to give an example of what type of appliance might cause this residual current?

Legh

-------------------------
Why do we need Vernier Calipers when we have container ships?

http://www.leghrichardson.co.uk

"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."
 22 March 2013 12:47 PM
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Patnik

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I'm surprised at his 2mA 'blip' in the reading for the PS3. He seems to have the PS3 still connected to the TV which is plugged in somewhere else and has it's own earth. Presuming the PS3 has the mains earth connected to the data earth then he has 2 possible earth paths, only one that he's metering, and 2 sources of leakage, the TV and the PS3.

I doubt he would get that very precise 3.09mA if he just plugged all the appliances into the lead and measured the total, I suspect less than half that.
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