Afternoon
W.r.t. Doug’s comments, & FWIW, here are a few of my experiences & suggestions: 1. Many years ago I had a customer complain that a model of monitor that HP supplied to the UK exceeded the 0.75mA limit. After a lot of investigation (including building a small measuring set with switchable IEC and other bypass networks) and discussion, I concluded that the monitor was OK but the customer must have been using a measuring set with no IEC HF “body simulation” network – and that resulted in his measurements being higher than the IEC limit and that’s why he had complained. I explained that out to him and no more complaints were then heard! Nevertheless, do be aware of that “problem” because I later found that many of the cheap combined “hipot/ leakage/touch current” test-sets on the market ( at least in the UK/Europe) still don’t (or at least didn’t a very few years ago) include an IEC-type network to filter out the HF currents – therefore they are VERY prone to giving very high & fluctuating readings that can provoke customers to complain, as per my experience above!!! (I had to use several of those on occasions and simply had to ignore the touch/leakage current readings because I knew why it was happing!) 2. As has been said here, racked systems pose specific issues because of the multiple leakage paths which the assembler can only partially control in many cases due to the difficulties in removing filters on individual units, and, even then, how does one ensure that subsequent field-placement units are similarly modded before installation? (generally you can’t, unless you create specific part numbers for the modded units and accompanied by very specific replacement instructions!) 3. Isolation transformers for fully loaded racks will be both heavy and expensive – if you can even find space for them? Not really realistic in most environments, except possibly medical, unless there is an overriding reason to limit possible leakage currents into other associated equipment? 4. Personally, with IT & Industrial electronics systems, I found it easier, quicker and cheaper to take advantage of the relaxed 5mA leakage limit afforded by specifying that an additional heavy duty grounding cable be installed from the rack to the building distribution system – it’s relatively easy to require in the installation instructions and then relatively easy to actually install in most well-controlled & managed industrial (and even office)-type buildings. That gets you out of the problem of having to minutely control the overall rack configuration - in my experience both suppliers and end-users are prone to changing rack assemblies for something “better” or “new” without telling the engineering compliance guys. That extra cable should give a reasonable “safety margin” for someone to add (unbeknown to you!) additional units to the rack to “upgrade” / “enhance” its facilities. OTOH, just make sure you stick a (preferably several!) large “High Leakage” /”Touch current” label on the rack near the power inlet (and possibly on the control /connector panels) to alert users to the situation, and explain the requirements in the installation & operation instructions. 5. As has been noted, the possible effects on GFCI’s/RCDs etc., will vary somewhat unpredictably around the World according to the distribution systems and the actual GFC/RCDs in use. Therefore there may well be no “fits all solution” and one might have to negotiate with individual local inspectors (etc) on what will be acceptable (&/or even actually test those on sale locally to try to identify ones less sensitive to nuisance tripping??) FWIW, in one “extreme” case I had to resort to a separate RCD to cover a particularly leaky rack subsystem which couldn’t be otherwise “fixed” as it had to have multiple “military-grade mains filters” with very low frequency bandpass characteristics, and thus high value X/Y capacitors and leakage! My “3 pennyworth ” / “5 cents” contributions, and anyone is welcome to take issue – but please do consider possible “real life” situations before you fire the big guns! John E Allen W. London, UK From: Douglas E Powell <doug...@gmail.com> Sent: 24 August 2022 23:22 To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] High Touch Current and GFCIs Brian, Depending on the class of that circuit breaker, the answer is probably yes. See this article <https://code-authorities.ul.com/about/blog/understanding-ground-fault-and-leakage-current-protection/#:~:text=It%20states%20that%20a%20Class,Ground%2D%20Fault%20Circuit%2DInterrupters.> Sometimes when dealing with high leakage current the relevant safety standard allows you to go to a much higher level if you provide secondary chassis grounding (earthing) and a warning label. Of course, this all depends on how the product is configured. Check for this provision in the safety standard you are using. This may be a case where your rack system has multiple devices, each with their own EMI line filter. And the "Y" caps in all the line filters add up to a larger contribution of leakage current. One option might be to remove the individual filters (if possible) and provide a single low-leakage EMI filter on the rack power inlet. Alternatively you could entertain the idea often used on equipment that requires very low leakage current in the 50 uA range. That is, an approved isolation transformer built into the rack power distribution. -Doug Douglas E Powell Laporte, Colorado USA <https://www.linkedin.com/in/coloradocomplianceguy/> LinkedIn (UTC -06:00) Mountain Time (US-MDT) On Wed, Aug 24, 2022 at 2:27 PM Brian Kunde <bkundew...@gmail.com <mailto:bkundew...@gmail.com> > wrote: If I have a rake of electrical equipment with a single power cord and a combined touch current exceeding 6mA, and I plug the rake into a circuit with a GFCI, will it trip? Thanks. The Other Brian - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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To post a message to the list, send your e-mail to <emc-p...@ieee.org <mailto:emc-p...@ieee.org> > All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) <http://www.ieee-pses.org/list.html> List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Mike Cantwell <mcantw...@ieee.org <mailto:mcantw...@ieee.org> > For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org <mailto:j.bac...@ieee.org> > David Heald <dhe...@gmail.com <mailto:dhe...@gmail.com> > _____ To unsubscribe from the EMC-PSTC list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC <https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1> &A=1 - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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