Brian
Cant respond w.r.t. you para 1 question, but w.r.t. para 2: - IEC/EN 60799:1998 Electrical accessories Cord sets and interconnection cord sets (1998 edition is still valid AFAIK) is a good guide to cordset ratings, and Table 1 allows ratings under 1 sq mm (generally 0.75 sq mm) for cordsets rated up to 10A provided the length does not exceed 2m, and 1 sq mm for cordsets rated at 16A (but 1.5 sq mm for cordsets longer than 2m). (must admit that I thought for a long time that 16A-rated cordsets needed to be 1.5 sq mm regardless of length, but found out in a rather embarrassing way that they do not!) Regards John Allen W.London, UK From: Kunde, Brian [mailto:brian_ku...@lecotc.com] Sent: 06 May 2015 17:09 To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Wire Questions Didnt I hear there was some kind of agreement where UL/CSA approved power cordage was allowed to be used in Europe as long as the conductor size met requirements? If so, what is the official document which describes this agreement? Doesnt Europe have a minimum conductor size for detachable power cords of 1mm²? I believe the IEC 60320 allows conductor size of 0.75mm² if the overall cord length is less than 2 meter (or at least is was years ago). 18AWG conductors on UL/CSA power cords for North America does not meet the 1mm² requirement so that is why we try to use 16AWG or 14AWG cord sets even if they cannot be used outside of North America. In the real world, it is common for the plug to be cut off the power cord and replaced with something local. In those cases, we want to be sure the cordage is large enough to meet any local electrical codes. The Other Brian From: John Allen [mailto:john_e_al...@blueyonder.co.uk] Sent: Tuesday, May 05, 2015 2:09 PM To: Kunde, Brian Cc: EMC-PSTC@LISTSERV.IEEE.ORG Subject: RE: [PSES] Wire Questions Brian Grounding Conductor size An interesting question with respect to internal grounding conductors, and one which made me refer to a very old copy of CSA Technical Note TN-017 Bonding and Grounding of Electrical Equipment (Protective Grounding), dated January 13, 1993, which I have dont know if there is a newer version, but I suspect there is (if so, does anyone have a copy of this or of whatever has replaced it?) so the following comments may well be out-of-date! TN-017 refers to CSA C22.0.4, which I dont think I have, as the basic requirements for grounding of equipment, so obviously not sure what that currently states. However: Page 2 of TN-017, under Grounded (Class I) Equipment states that IEC standards require the ground path impedance to be less than or equal to 0.1 ohm. Although it is a satisfactory criteria for evaluating a path to ground where overcurrent protection is rated or set at 15A and 20A, this approach fails to provide proper protection when overcurrent devices are rated or set at 30A or higher Page 6, Under National Electric Code (NEC) states: Article 250 of NEC defines grounding and bonding requirements for installations of electrical equipment in the United States. Articles250-60, 250-95 and 250-155 also define min size of ground conductor required. Also see Articles 250-42, 250-45, 250-59, 250-113 and 250-114. NEC requires the following in particular. (a) Ground conductor must not be smaller than specified in Table 250-95 with the exceptions that the ground conductor: i. Must not be smaller than 18A AWG copper and not smaller than circuit conductors. ii. Need not be larger than the AC circuit conductors. This means that the min cord size permitted is No 18 AWG, and min size of ground conductor shall be No 18 AWG. (b) Ground conductor may be without insulation but if insulation is provided, it shall be coloured green or green with one or more yellow stripes. (c) All non-current carrying metal parts of fixed, portable and mobile equipment shall be grounded. Grounding conductors not part of cable assembly must not be smaller that No 6 AWG. NB: w.r.t. (c) above, there are exceptions elsewhere for double-insulated (etc.) equipment! Cant find any definitive statement in TN-017 as to the required internal grounding conductor sizes, but, from the above, it seems to me that the issue you mention relates to a combination of the following: - The IEC continuity test at 25A is only adequate at supply currents which would be protected by a 15A/20A external breaker, which is probably why 61010-1 states different see below; - the potential AWG size of the external supply cord and that the grounding conductor needs to be > the size of the current-carrying conductors; - the current rating of the protection in the installation and if the latter is >15A/20A, then the internal conductor would have to be larger than 18AWG. Since you were using a 16AWG power cord in some cases, then that would mean the internal conductors would need to be >16AWG, but if you were sometimes using 14AWG cords which you comment implies - then you would need 14AWG internal grounding conductors. OTOH, some more modern standards like 61010-1 Ed 3 state: 6.5.2.4 Impedance of PROTECTIVE BONDING of plug-connected equipment ..Conformity is checked by applying a test current for 1 min and then calculating impedance. The test current is the greater of a) 25 A a.c. r.m.s.at RATED MAINS frequency or d.c., b) a current equal to twice the RATED current of the equipment. If the equipment contains overcurrent protection devices for all poles of the MAINS supply, and if the wiring on the supply side of the overcurrent protection devices cannot become connected to ACCESSIBLE conductive parts in the case of a single fault, the test current need not be more than twice the RATED current of the internal overcurrent protection devices So, if you had had suitable internal all-pole protection in the equipment, then something smaller than 14AWG might be acceptable to such standards. OTOH, anybody, please feel free to correct or update any of my comments above as you are probably in a much better position in the US/Canada to know the reality of the current (sic!) situation! Power Cord Sets As for European use of US cordsets, very few suppliers can supply actual cords with both US/CSA and third-party EU certifications due to the differences in the relevant UL/CSA and the IEC/EN standards I think I only ever found one that had a limited range available (and, even then, it might only have been for extension cord sets or Jumper Cord Sets not main supply cords), but cannot now be sure which one that was. However, unless the equipment was being submitted to a European test house for certification (or to some other company to incorporate in their own equipment), then its probably doubtful if the use of US/CSA-certified mains supply cords would be picked up by most of the end-user community. As long as the plug was the correct one, and the conductor insulation colours were also correct if an unterminated power cord was supplied, for those countries then most of those people would probably not look much further! Not to say that this is right/ legal, but taking a pragmatic view of the actual situation in most countries. J Therefore, in the circumstances, it may well be better (as you appear to do) to leave the supply of appropriate power cords to the European installers! John Allen W.London, UK From: Kunde, Brian [mailto:brian_ku...@lecotc.com] Sent: 05 May 2015 16:37 To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Wire Questions Rick, Are you talking strictly about power cordage or internal hookup wire? We had a CSA inspector reject one of our products because the internal PE Conductor (hookup wire) was a smaller gauge (18awg) than what was on the power cord (16awg). He said in Canada, the PE Conductor inside our product had to be the same gauge or larger than the PE conductor in the power cord regardless of the protection device or the current rating of the wire. In our case, we were using a 16 awg detachable power cord with an IEC 60320 connector. Inside our instrument, from the IEC connector to our chassis ground we used an 18 awg green/yellow hookup wire which can handle way more fault current than the 16 awg power cord. So as a general rule, we always use 14 awg hookup wire on IEC connectors just to be on the safe size; As such power cords can come in 18, 16, and 14 awg sizes. Our power cords for North America always have UL and CSA, but no CE or harmonized (at least it is not required to have this). When products are shipped to Europe I understood that UL/CSA cordage was acceptable (you still have to change the plug) as long as the conductor size met the requirements. That is why we dont use 18 awg power cords anymore. I really dont know the details because this is handled by our installers during the customer installation. Hope this was helpful. The Other Brian From: Rick Busche [mailto:rick.bus...@qnergy.com] Sent: Tuesday, May 05, 2015 10:08 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: [PSES] Wire Questions We manufacture a product that is intended for both the US and Canadian markets in addition to the European community. Our wiring is currently UL/CSA and harmonized. Looking at the various wire vendors there are UL/CSA & CE certifications and certifications that are UL/CSA, CE and Harmonized. Is it acceptable to have wiring with just UL/CSA and CE? Also, I remember years ago a document or standard that stated that a grounding wire could be smaller than the load wires. The argument was that it doesnt have to support the load but just fault the input current. Does this sound familiar to anyone? Thanks Rick - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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