Hello Bernd,
Thank you for the links to the additional material on the IEC website. I didnt realise there was such a wealth of material in the documents from the subcommittees. Also, thank you for taking the time to write a considered reply. I understand your interpretation and the notes from the committee. Reliable earthing of the handles appears to be the simplest way to comply with the requirements of the standard. I will advise the customer appropriately. Longer term Im going to do some more reading of the outputs from TC 61, TC 66 and TC 108. Good to know about this useful resource - https://www.iec.ch/technical-committees-and-subcommittees#tclist All the best James From: Dürrer Bernd <[email protected]> Sent: Wednesday, April 12, 2023 7:48 AM To: [email protected] Subject: [PSES] AW: [PSES] Safety: 60335-1 conflicting clauses question - earthing (or not) of handles Hello James, Thank you for providing this additional information and the sketch. My conclusion that the handles are a class II construction was based on your statement in your original post that the handles are not reliably earthed. As I understand now from your additional information they are not earthed by a dedicated wiring to the protective earthing conductor, but incidentally the measured resistance complies with the requirements of IEC 60335-1, clause 27.5. Please remember that the protective earthing connection shall be reliable over the whole lifetime of the appliance. Apart from wear and grease build up that you already mentioned you should check whether the parts providing the connection comply with clauses 27.4 (corrosion) and 28 (screws and connections). With respect to the question whether the requirements of clauses 22.35 and 22.36 also apply to handles of a class I appliance that are reliably earthed (and therefore are not a class II construction), I recommend to check the decisions of TC 61 that are published at <https://www.iec.ch/dyn/www/f?p=103:227:100193794009456::::FSP_ORG_ID,FSP_LA NG_ID:1236,25> IEC - TC 61 Dashboard > Documents: Working Documents, Other Documents, Supporting Documents: I have found decisions on the interpretation of clause 22.35 in the archives TC 61 Inquiries 2011 and previous ( <https://assets.iec.ch/public/tc61/2011%20and%20previous%20Inquiries.zip?202 3041235> https://assets.iec.ch/public/tc61/2011%20and%20previous%20Inquiries.zip?2023 041235) and TC 61 Inquiries 2015 ( <https://assets.iec.ch/public/tc61/2015%20Inquiries.zip?2023041235> https://assets.iec.ch/public/tc61/2015%20Inquiries.zip?2023041235). It seems that the committees view is that these clauses are applicable to class I constructions. However, as defined in the second paragraph of clause 22.35, stationary appliances are exempt if their handles are reliably earthed. Kind regards, Bernd Von: James Pawson (U3C) < <mailto:[email protected]> [email protected]> Gesendet: Dienstag, 11. April 2023 12:22 An: <mailto:[email protected]> [email protected] Betreff: Re: [PSES] Safety: 60335-1 conflicting clauses question - earthing (or not) of handles [EXTERNAL E-MAIL] This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender. Thank you to everyone who has replied to this query so far, your thoughts were very helpful in refining my thinking. To give some further context (some of which I should have provided earlier) 1. The appliance is stationary and of class I construction 2. The handles are held continuously in normal operation 3. For a basic overview of construction please see the attached sketch (or this link <https://www.unit3compliance.co.uk/wordpress/wp-content/uploads/2023/04/iec- 60335-clause-22.35-and-22.36-context.png> if the email reflector eats the attachment) 4. Whilst the grips are foam, it is light/porous in nature (not good enough for Supplementary insulation) and it would be very easy for the user to hold the metal instead 5. We made some earth bonding resistance measurements on the equipment. The handles are not explicitly earthed (via a Protective Bonding Conductor) but the contact to the metal frame through the bearings and shafts (not shown on sketch) gives a resistance of approx. 40mR @ 25A even under motion of all joints. We have not accounted for any wear, grease build up, etc) My views: a. I agree with the below discussions - it feels like the standard could benefit from a wording change for clause 22.35 and 22.36 with each clause starting For class II constructions, [ ] b. The construction of the appliance, and lengths of wiring involved, means that if the Basic insulation fails (see 60335-1 Class I definition below) then there is a very low likelihood of the handles becoming live. The wires will only contact the earthed frame instead. At the moment, I dont agree that the handles would form a class II construction as protection is still provided by Basic + Earthing (but Im willing to be persuaded by a convincing argument) 3.3.9 class I appliance (basic plus earthing) in such a way that conductive accessible parts cannot become live in the event of a failure of the basic insulation c. The low resistance of the incidental bearing connection is further mitigation against having to explicitly earth the handles d. If live wiring or basic insulated wiring is routed anywhere near the handles on different versions of the appliance then they will need an explicit earth connection e. Im sure the standards committee had a specific case in mind when they wrote these clauses, I just wish there was an explainer document like EN 62368-2! Again, with thanks. All the best James James Pawson Managing Director & EMC Problem Solver Office hours: My mornings are reserved for full attention on consultancy, testing, and troubleshooting activities for our customers projects. I am otherwise contactable between 1300h to 1730h from Monday to Friday. For inquiries, bookings, and testing updates please send us an email on <mailto:[email protected]> [email protected] or call 01274 911747. Our lead times for testing and consultancy are typically 4-5 weeks. Unit 3 Compliance Ltd EMC : Environmental & Vibration : Electrical Safety : CE & UKCA : Consultancy <http://www.unit3compliance.co.uk/> www.unit3compliance.co.uk | <mailto:[email protected]> [email protected] +44(0)1274 911747 | +44(0)7811 139957 2 Wellington Business Park, New Lane, Bradford, BD4 8AL Registered in England and Wales # 10574298 From: Dürrer Bernd < <mailto:[email protected]> [email protected]> Sent: Thursday, April 6, 2023 12:19 PM To: <mailto:[email protected]> [email protected] Subject: [PSES] WG: AW: [PSES] AW: [PSES] Safety: 60335-1 conflicting clauses question - earthing (or not) of handles Hi James, Please find below some additional thoughts on the subject that have accidentally been discussed off-list. Kind regards, Bernd Von: Dürrer Bernd Gesendet: Donnerstag, 6. April 2023 11:36 An: John Woodgate < <mailto:[email protected]> [email protected]> Betreff: AW: AW: [PSES] AW: [PSES] Safety: 60335-1 conflicting clauses question - earthing (or not) of handles Agreed. The standard would be clearer if clauses 22.35 and 22.36 would start with For class II constructions, [ ]. However, I am neither a member of the national nor international committee for IEC 60335-1. Kind regards, Bernd Von: John Woodgate < <mailto:[email protected]> [email protected]> Gesendet: Donnerstag, 6. April 2023 11:14 An: Dürrer Bernd < <mailto:[email protected]> [email protected]> Betreff: Re: AW: [PSES] AW: [PSES] Safety: 60335-1 conflicting clauses question - earthing (or not) of handles [EXTERNAL E-MAIL] This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender. Noted, but the standard doesn't explicitly address that situation, which is surely very rare, and I understand that the handles could be reliably earthed. I still recommend the simple solution of covering them with reinforced insulation, but the standard needs to be clarified. ============================================================================ ========== Best wishes John Woodgate OOO-Own Opinions Only <http://www.woodjohn.uk/> www.woodjohn.uk Rayleigh, Essex UK I hear, and I forget. I see, and I remember. I do, and I understand. Xunzi (340 - 245 BC) On 2023-04-06 10:00, Dürrer Bernd wrote: As I understand from James explanations, the metal handles of the appliance in question are not reliably earthed. As such, these parts of the appliance do not comply with the requirements for a class I appliance (IEC 60335-1, 3.3.9) that all conductive accessible parts shall be connected to the protective earthing conductor in the fixed wiring of the installation. Therefore, these handles shall be assessed as class II construction (IEC 60335-1, 3.3.11 and 5.14) for which the requirements of clauses 22.35 and 22.36 are applicable. Kind regards, Bernd Von: John Woodgate <mailto:[email protected]> <[email protected]> Gesendet: Donnerstag, 6. April 2023 10:46 An: Dürrer Bernd <mailto:[email protected]> <[email protected]> Betreff: Re: [PSES] AW: [PSES] Safety: 60335-1 conflicting clauses question - earthing (or not) of handles [EXTERNAL E-MAIL] This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender. It still doesn't make sense to require double or reinforced insulation for a Class I product. Doing so, causes the safety of Class 1 construction to be questioned. ============================================================================ ========== Best wishes John Woodgate OOO-Own Opinions Only <http://www.woodjohn.uk/> www.woodjohn.uk Rayleigh, Essex UK I hear, and I forget. I see, and I remember. I do, and I understand. Xunzi (340 - 245 BC) On 2023-04-06 09:40, Dürrer Bernd wrote: Hi James, actually, these two clauses address two different, but related risks: Clause 22.35 addresses the risk that the handle itself may become live. In any case, a conductive surface (like the handle) has to be separated from live parts by basic insulation. Due to the higher risk that handles are actually touched in the event of failure of basic insulation, the standard requires additional precautions. Either the handles itself shall be covered by insulating material (i.e. supplementary insulation) or they shall be separated by supplementary insulation from their fixing. In both cases, the handle will be protected by double insulation from live parts. Clause 22.36 addresses the risk that other parts than the handle in the vicinity of the handle may become live. Again, there is a higher risk for the user in the event of failure of basic insulation that these surfaces may be actually touched, so also for these neighbouring conductive surfaces either double or reinforced insulation is required. Kind regards, Bernd Von: James Pawson (U3C) <mailto:[email protected]> <[email protected]> Gesendet: Mittwoch, 5. April 2023 12:23 An: <mailto:[email protected]> [email protected] Betreff: [PSES] Safety: 60335-1 conflicting clauses question - earthing (or not) of handles [EXTERNAL E-MAIL] This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender. Hello experts, In running through some safety checks on a customers product Ive come across what appears to be a conflict between two clauses. This resulted in some head scratching! Im sure it is my misunderstanding or misreading, but I could do with some pointers in how to unpick this. Context 1. Standard is IEC EN 60335-1:2012 (+amendments) 2. Context is an exercise machine (the appliance) 3. Supply is AC mains Class I 4. Appliance has metal handles that are held during normal use. These are connected through bearings to the metal frame but are not reliably earthed (no explicit wired connection) Earthing of metal parts is acceptable 22.35 For constructions other than those of class III, handles, levers and knobs that are held or actuated in normal use shall not become live in the event of a failure of basic insulation. If these handles, levers and knobs are of metal and if their shafts or fixings are likely to become live in the event of a failure of basic insulation, they shall be adequately covered by insulating material or their accessible parts shall be separated from their shafts or fixings by supplementary insulation. For stationary appliances and cordless appliances, this requirement does not apply to handles, levers and knobs, other than those of electrical components, provided that they are reliably connected to an earthing terminal or earthing contact or separated from live parts by earthed metal. 1. Class I appliance, with metal handles held during use so this requirement is applicable 2. Handles are not reliably earthed so we are advising manufacturer to make an explicit bond to PE 3. With Basic insulation and Earthing we have our two safeguards between live and user = reduced risk of shock 4. No complaints with this clause Earthing of metal parts is not accpetable Then the next clause seems to contradict this: 22.36 For appliances other than those of class III, handles which are continuously held in the hand in normal use shall be constructed so that when gripped in normal use, the operator's hand is not likely to touch metal parts unless they are separated from live parts by double insulation or reinforced insulation 1. This clause appears to not allow for earthing of the metal handles 2. Instead, only rouble or reinforced insulation are acceptable 3. Thoughts / speculation: 1. Would this clause make more sense if it read For appliances other than those of class I ? i.e. unearthed 2. Talks about appliances (whole product) rather than constructions (parts of appliance) Conclusion Im happy that the approach of reliably earthing the metal handles will reduce the electric shock risk in the context of the equipment, this approach being consistent with other safety standards I know like 62368-1 and 61010-1. I just cant rationalise this with clause 22.36. As I say, Im sure Ive misread or misunderstood something so any help would be greatly appreciated. Otherwise, if anyone has a link to an explanatory document or contact for someone who could help at standards or committee level again that would help. All the best James James Pawson Managing Director & EMC Problem Solver Office hours: My mornings are reserved for full attention on consultancy, testing, and troubleshooting activities for our customers projects. I am otherwise contactable between 1300h to 1730h from Monday to Friday. 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