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Hi. I have a question about earth leakage meter usage/selection.

I see that people say one should test the live wires not the earth for reasons you guys probably understand. However earth leakage meters with large Jaws to loop around both tails are much more expensive.

Can I use a combination of insulation resistance testing and earth leakage testing on the earth to achieve the functionally equivalent result? I'm also assuming I'd have to test the fixed wiring and pat test the device.

I only started thinking about this but it seems reasonable so far apart from...

What if the device I'm pat testing has internal switching and the earth leakage only occurs intermittently?

Also any tips on what I should purchase are welcome.

Thanks
 
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It’s ok to clamp on the Earth conductor,check the leakage.
Also practical to measure on large installation,then using ohms law,to give an insulation resistance measurement on the whole installation
 
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Not all the leakage that leads to rcd tripping will necessarily be flowing on the earth. It could be travelling through the ground for this reason leakage should be measured by the difference between current on live conductors.

However one could first check insulation resistance of fixed wiring and appliances then check earth conductor current. This would only work if we could check insulation resistance of appliances something I don't see as actually possible because of internal switches.
 
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Deleted member 105166

If you clamp line & neutral together, then clamp earth separately, you will often get different values. Always clamp L&N together, as this will give you the value the RCD is using (assuming both RCD and clamp meter are accurate)
 

PEG

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If you clamp line & neutral together, then clamp earth separately, you will often get different values. Always clamp L&N together, as this will give you the value the RCD is using (assuming both RCD and clamp meter are accurate)
Yes,and it is worth mentioning that the characteristics of the supply,will affect how and where,you are testing.
 
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Thanks guys.

I guess I'll be investing in megger dcm300e then. I'm really surprised that there's so many smaller versions on the market when really you need the larger Jaws to get the job done.

Peg- what characteristics are you referring to exactly? Is this something to do with earthing arrangements and number of conductors? I've thought about that. Anything missing?
 
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  • #8
Good call. They are much cheaper than the dcm300e on isswww.co.uk too. Bit odd that.

Thanks for the help
 
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