Rich, I have only one question concering the deterioration, initally tested at higher cuurent for ground bond, then over months?(time)..a lower current would be used.. is there a chart for what current might be used? based on: age humidity of installation current running thru it continously. I'd like to get a feel of whats acceptable when you go to do the test much later after the initial installation thank you, Richard,
From: richhug...@aol.com [mailto:richhug...@aol.com] Sent: Thursday, May 22, 2003 8:15 PM To: ri...@sdd.hp.com; gr...@test4safety.com Cc: bar...@melbpc.org.au; emc-p...@majordomo.ieee.org Subject: re: Safety testing after equipment repair Rich, Gregg, Gregg, your memory is slipping - clearly you have been away from the UK for too long, or you're enjoying the American wine too much! The referenced document is "The Electricity at Work Regulations 1989" and they were implemented as a Statutory Instrument under the "Health and Safety at Work etc. Act 1973". The former piece of UK legislation has kept many a UK electrician in gainful employment over the years. It is also why, if you come to the UK, you often see paper labels saying 'tested for safety' or the like on mains powered products. Within the UK trade association for IT Equipment (EEA it was at the time) we developed a set of Guidelines to enable customers to both meet the requirements of the Electricity at Work Regulations and not damage equipment too much. We did not recommend repeated dielectric withstand testing because this could lead to premature damage to insulation, as has been pointed out already. For earth bond test we suggested that only a low current would normally be required because the equipment would have been type tested at a higher current anyway and the intention of these Regulations is to show up deterioration of products in the workplace caused by normal wear and tear. We did recommend that insulation resistance tests be conducted: we also recognised that the insulation resistance test would produce values far higher than those previously contained within IEC 380 (2 Mohms for Basic and 5 Mohms for Reinforced if memory serves) and so we recommended that successive readings be recorded so that any downward 'jumps' in resistance could be investigated further. Of course, if you try and compare readings >from a cold, dry, winter day to a hot and humid summer day then that is going to give variability, as will different test equipment and a whole range of other variables. Still, it beats degrading the equipment's insulation. Since then EA became FEI who are now called 'Intellect'. Space for comments here... The EEA worked with the IEE and I believe that the IEE Guidelines are still available, for a fee. See http://www.iee.org/Publish/ Within the EEA we did not see much point in measuring leakage current (now called protective conductor current in IEC 60990) since the major component of such current for IT equipment will be due to RFI capacitors. Of course, if you can find some inexpensive test equipment that is able to provide an accurate measurement of the dc component then that's another matter... Of course, if you really wanted to be fancy then you could conduct a partial discharge test. However, most repair shops are not likely to have such kit sitting around. Regards, Richard Hughes Safety Answers Ltd From: ri...@sdd.hp.com [mailto:ri...@sdd.hp.com] Sent: Thursday, May 22, 2003 7:07 PM To: gr...@test4safety.com Cc: bar...@melbpc.org.au; emc-p...@majordomo.ieee.org Subject: Re: Safety testing after equipment repair Hi Gregg and Barry: > Australia has an actual standard which lists the tests and procedures for > the regular testing of equipment in use, and equipment that has been > So has the UK. it was called (something like) The Electricity at Work > Act generally a good thing put a dangerously and poorly implemented > concept that allowed untrained unprofessionals to destroy a huge amount of > IT equipment and charge the customer for it. > As a result we had several thousand monitors damaged by 25 Amps being passed > between the RGB Coax- grounds and PEG Another anecdote (read "horror story") from the UK requirement for periodic safety testing... We had the unfortunate experience of the same UK requirement for periodic testing of Class III equipment for 25 amps from accessible conductive parts. This test destroyed a run on the circuit board, which was a failure of the 25-amp test, which resulted in destruction of the unit! The customer demanded replacement of the units because they failed the test! He did not realize that the test itself was causing the failure, nor that the test was causing destroying the unit. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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