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Christopher Clay
Member - 2 posts
Good Morning,
I have recently organised for a member of my team to carry out PAT test training and he has passed this. I am now looking at options for testers and i am wondering about re-calibration certificates - is this mandatory and if so how frequent does this need doing?
Can anybody help me with the above?
Thanks
Chris
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Ian Gardner
Member - 18 posts
It's not mandatory to get your test equipment calibrated, but it makes very good sense. The calibration certificate is your evidence that the test instrument is making true readings, otherwise, if you can't trust the readings of your instrument, what's the point in using it?
Also, worst case scenario, you may need to prove in a court that the tests performed by your tester were accurate, in which case, a calibration cert is a no-brainer.
The usual practice is to send of the instrument to a calibration service annually.
Some manufacturers, such as Seaward, make calibration boxes (http://www.seaward.co.uk/products/PAT_checkbox.asp). Although not a substitute for a certified calibration, they are a good method for users to check that an instrument is still in calibration, on the job.
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David Smith
Member - 3 posts
Hi Ian. I'm new to the website, but looking throught the forum on this subject you would appear to be the Jedi of PAT testing and was wondering if you could assist?! I have recently taken on a new role at my workplace which includes, amongst many other things, the overseeing of a maintenance contract that includes PAT testing of Class 1 "static" equipment (3amp, 220 - 240v) As this is the only type we are testing it has been relatively easy getting up to speed with the various tolerences etc, but am struggling to find a table of results for the acceptable levels of earth bond measurements for the varying lenghts of supply leads. We use the Seaward PT100 which indicates a Failed reading above 0.1 ohm (which is the general guideline as set out by the IEE) but understand that there is a tolerence to be taken into consideration dependant on the lenght of supply lead. For example what would be the maximum allowance for the specified piece of equipment should the supply lead (8mm CS) measure 3m in length? Any info on this would be greatly appreciated. Thanks
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Ian Gardner
Member - 18 posts
Hi David, not sure about the Jedi thing!
There certainly is a tolerance when considering supply cords for Class I items.
The earth bond limit should be taken as (0.1 + R) ohms, where R is the resistance of the supply cord.
Some PAT instruments have built-in calculators for supply cord resistance (such as the Seaward PrimeTest 350), but failing that, your best bet would be to get hold of a copy of The IEE Code of Practice for In-service Inspection & Testing of Electrical Equipment, 3rd edition (if you are doing any PAT testing, then I'd say get it). This is pretty much the bible of PAT testing, and should have all the answers you're looking for, including a table of 'nominal resistances of appliance supply cord protective conductors (for cables to BS 6500 or BS 6360)', page 124.
For the example you give, I'm assuming you've measured the diameter of the whole cable, whereas what the table refers to is the 'conductor cross-sectional area', in square mm (8 sq mm conductor CSA would be a whopper!).
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Colin Sanders
Member - 4 posts
On the subject of PAT testing can anyone point me in the direction of some easy to follow guidance on PAT testing in what should be tested and when, how soon after purchase should new equipment be tested.
When carrying out fire risk assessments I almost always come across items that show no sign of PAT testing and comment so in the assessment, but I would like some additional infomation to help me.
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Terry Mathieson
Member - 3 posts
Hi Colin
As Ian said in his last post, The IEE Code of Practice for In-service Inspection & Testing of Electrical Equipment, 3rd edition has all the answers including a table on page 20 giving suggested test frequencies for different classes of equipment in different types of premises. As to how soon after purchase, I personally test all new equipment before it goes into service.
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David Smith
Member - 3 posts
Ian. Thanks for the info. IEE COP arrived this morning and like you say, seems to be the PAT bible!!! Further to my original query, looking at the COP I think I'm right in saying that if I had a Class 1 static item with a supply lead length of 2m, a nominal condustor of 1mm sq then the resistance can be a max 0.139 ohms? Does that sound about right? (ref Table VI on page 76)
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Ian Gardner
Member - 18 posts
Yep, that looks right to me...
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Ian Gardner
Member - 18 posts
Further to Terry's post above, the table he mentions is on page 34 of the new 3rd edition CoP.
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Phil Riley
Member - 5 posts
For anyone starting doing PAT testing who is unfamiliar with guestimating mains lead sizes it may be worth going to an electrical shop that sells flex by the metre and buying short lengths of a range of different sizes such as 0.75, 1.0, 1.5mm. These could be kept with the test equipment for comparison purposes.
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