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EiCR sampling size

Former Community Member over 5 years ago

Hi all I'm just trying to get my head round this, I hold a copy of guidance note 3 already.

Let's say we have a domestic CU with 8 circuits and we inspect/test only 4 of these does this equate to a sample size of 50% and if we ended up testing all 8 would this equate to a 100% sample.

The bit that's bothering me is sampling to me means that we look at the wiring accessories/connected equipment for safe continued use including signs of over heating, arcing, smell, touch, suitability for location etc in addition to the physical tests deemed necessary with your test meter.

So even if we tested all 8 circuits and carried out a 25% sample size this would equate to 2 circuits being sampled ,is this correct?

Regards

Ts

0 AJJewsbury over 5 years ago

So even if we tested all 8 circuits and carried out a 25% sample size this would equate to 2 circuits being sampled ,is this correct?

That sounds to me like a 100% sample for testing, but a 25% sample for inspection.

- Andy.
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0 John Peckham over 5 years ago

Just try this test first. You carry out a portable appliance test on 50% of items in a building, what do you conclude about the other 50%?

Have a look at my standard specification described on the thread below. That clarifies the difference between inspecting and testing and sampling.
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0 Former Community Member over 5 years ago

AJJewsbury:

So even if we tested all 8 circuits and carried out a 25% sample size this would equate to 2 circuits being sampled ,is this correct?

That sounds to me like a 100% sample for testing, but a 25% sample for inspection.

- Andy.

Thank you Andy, put like that it makes total sense, it was the wording within guidance note 3 that was causing the concern. I would be happier if a few people could concur though, but it does stand to reason when put like how Andy described it ?
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0 Chris Pearson over 5 years ago

Beware of taking a sample of samples!

If a circuit has one appliance (e.g. a cooker) it cannot be sampled.

Ideally, from a scientific point of view, a sample should be random, but I don't suppose that anybody does that.

You cannot sample something like a whole-board IR test.
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0 Former Community Member over 5 years ago

If a circuit has one appliance (e.g. a cooker) it cannot be sampled.

Good point Chris.

Regards

Ts
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0 whjohnson over 5 years ago

Have things changed? All circuits have to be tested, not just a percentage of ways in a board - surely?

MY 2391 back in 2003 said that you should start with 10% of points on each circuit, so 1 light fitting if there are 10 on circuit 1.

2 x socket outlets out of 20 on circuit 2 and so on.

Then increase sample size incrementally if defects found. If defects continue to be found then 100% I&T all pts on circuit.
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0 Former Community Member over 5 years ago

whjohnson:

Have things changed? All circuits have to be tested, not just a percentage of ways in a board - surely?

MY 2391 back in 2003 said that you should start with 10% of points on each circuit, so 1 light fitting if there are 10 on circuit 1.

2 x socket outlets out of 20 on circuit 2 and so on.

Then increase sample size incrementally if defects found. If defects continue to be found then 100% I&T all pts on circuit.

My understanding is that you agree with the client the scope of testing & inspection and depending upon your findings wether that scope should be increased.

For example if an installation is well documented, maintained and has past EICR certs available for inspection then depending upon the previous reports I may suggest we o my test 25-50% depending upon the size of the installation. However if no documentation is available then I may suggest a 100% test with a 25% inspection to start with.

Regards

Ts
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EiCR sampling size

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