Discuss Should I earth bond test Class I appliances? in the UK Electrical Forum area at ElectriciansForums.net

HandsOffEngineer

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Hello,

I am a Trainee here on the Forum. I am seeking some further advice/input on a specific technical matter of importance to me.

Briefly, I have completed C&G level 1 in electrical installation (distinction) and I am currently on the level 2 course, and things are going well on that score.

However, I am having problems securing unpaid work experience or employment, so I have decided to start my own business making handcrafted luminaires that I will sell to the public. Initially these will be mostly of a steel industrial aesthetic design. I understand the business/legal side of this quite well and don't need advice on that. I also know how to make the lamps and how they function electrically. That's not a problem.

But I decided that I would also need to test the lamps before sale. This is chiefly out of a genuine concern for safety but also partly for marketing reasons. I know it's not mandatory, but I still think it's a good idea. To this end, I enrolled on the C&G 2377-22 course (in-service inspection & testing - i.e. "PAT testing"), and I've now completed this.

I did score 94% in the online theory assessment and I sailed through the practical - I mention this to show you that I am serious - however I am NOT yet qualified or competent. I realise that I still have further reading/experience and training to undertake before I actually attempt to undertake any in-service inspection/testing, whether professionally as an appliance inspector or as part of making luminaires for others.

One question I still have is about the high current earth bond test and its possible relevancy to my lamps. Obviously these will be constructed as Class I appliances. I asked my tutor and he advised that I should not run that test on my lamps. He told me that, for the purposes of testing earth, I should just stick to the low current continuity test, which I must admit makes sense. (Obviously I would complete the other Class I machine tests as well, per the Code of Practice).

After considering his advice and doing some further research/reading of my own, I have come to the view that he is correct. My understanding is that I should limit my testing of protective earthing on steel lamps I make to an ‘IT-safe’ low current soft test at up to 200mA.

The reasons are:

(i). the low current test is adequate for steel lamps (and also most common types of equipment and appliances – ordinary cookers, washing machines, toasters, computers, and so on - in the event I also decide to go into PAT testing professionally);

(ii). it minimises the possibility of damage as a result of testing; and,

(iii). it is also the case that an earth bond test can be unsafe in the context of routine testing as the higher current can mask earth resistance faults which would be more easily picked up on by a low current test.

Obviously, if - in my reasonable judgement - I believe that a particular equipment/appliance will require earth bond testing, or (when testing appliances made by somebody else) such a test is recommended by the manufacturer, that would be a different matter.

Is my thinking here along the right lines? If there are flaws in my reasoning, I'd appreciate some constructive input. Obviously I appreciate this is all on me at the end of the day, just looking for pointers.

If you decide to respond, please understand that I am not holding myself out as a qualified electrician or pretending that I know what I am talking about. I am still a trainee/novice in these matters and would value some advice/guidance - if only just out of an abundance of caution. I have too much respect for my customers and the dangers of electricity to take risks.

Without wishing any disrespect to the PAT testing sub-forum, I felt this is something that should be posted to the main/general forum for consideration by electricians. However, if the moderators believe this should be re-directed to the sub-forum, that's fine.
 
(i). the low current test is adequate for steel lamps (and also most common types of equipment and appliances – ordinary cookers, washing machines, toasters, computers, and so on - in the event I also decide to go into PAT testing professionally);

(ii). it minimises the possibility of damage as a result of testing; and,

(iii). it is also the case that an earth bond test can be unsafe in the context of routine testing as the higher current can mask earth resistance faults which would be more easily picked up on by a low current test.

This sounds a bit backwards to me.
I would have thought a high current test is always preferable as it will find more poor connections than a low current test.

Low current tests will pass a poor connection whereas a high current test will melt it or otherwise highlight it. The high current test far better simulates what will happen in reality of a fault develops.
A low current test can pass an inadequate connection which in reality will melt under fault conditions before the fuse operates thus leaving the case of an appliance live and ready to kill a person.

Also there is more to testing an appliance for sale than just carrying out a PAT test, you need to satisfy the requirements of CE marking.
 
This sounds a bit backwards to me.
I would have thought a high current test is always preferable as it will find more poor connections than a low current test.

Low current tests will pass a poor connection whereas a high current test will melt it or otherwise highlight it. The high current test far better simulates what will happen in reality of a fault develops.
A low current test can pass an inadequate connection which in reality will melt under fault conditions before the fuse operates thus leaving the case of an appliance live and ready to kill a person.

Thanks - let me give this some more thought.

Also there is more to testing an appliance for sale than just carrying out a PAT test, you need to satisfy the requirements of CE marking.

Just to be clear - I am already au fait with all the legal/compliance/business side of things. That, in and of itself, is not the issue for me.
 
Also there is more to testing an appliance for sale than just carrying out a PAT test, you need to satisfy the requirements of CE marking.

That's easy, £4.20 for 100,, Proper job.
 
Hi,
Go and find the required BS or EN standard and design to it. For comparison BS EN60950 (computers and domestic electronics) requires something like a 25A 60 second test on the earth bond for type testing.
 
As above, I can't see why anyone would recommended doing the low current 'IT' earth bond test for a metal lamp.

And yes, obviously the CE compliance is vital.
 
Practical memories!
Historic notes of rivet/panel location that gives best reading -Spings to mind.
( To my mind, dealing with failures -low current test -to show high current test is even worth re-trying !)
(Current advice based on a lazy skim of OP- apologies )
 
I am aware that the BS product standard (which is the underlying recommended benchmark for CE compliance) requires 10A in most cases, but it's not mandatory. I was looking for electrical judgement on the issue, because I'm not going to be running a mass production line. I will be making these lamps myself and in small volumes initially.

However, weighing this up, it does look like I am going to need to purchase a mains-powered tester. What I will do is take a closer look at the BS standard and possibly obtain a copy via Athens or a library and read it through word-for-word.

Thanks for all the advice. It's good to bounce things off people who are more experienced.
 
Hi - this one has the option of low or high current tests :) .
 
Hi - this one has the option of low or high current tests :) .

Thanks. Here again this is where my electrical naivety shows. I note that the above model will only run the high current test at 20A. I believe the relevant BS standard says a minimum of 10A but the product approval organisations actually recommend 25A.

I would prefer to have the option of 10A because these are handcrafted lamps that I make (and therefore closely-inspect anyway). This is not a mass production venture.

My concern is that I could damage my lamps and maybe inadvertently cause a safety issue if I am testing at 20A to 25A. Or am I worrying for nothing? I do have a tendency to over-think things.
 
My concern is that I could damage my lamps and maybe inadvertently cause a safety issue if I am testing at 20A to 25A. Or am I worrying for nothing? I do have a tendency to over-think things.

If that test current damages your lamps then what will an actual fault do to them?
Part of the reason a high current test is recommended is to, as far as possible, ensure that the appliance doesn't become dangerous when a real fault occurs.
 
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