Hello Charlie. Thank you for your reply. The harnesses are in the fire enclosure which also contains PS3 circuits but are located well away, both electrically and physically from the PS3 & PS2 circuits.
My query is really with the 6.4.6 clause below: Within the fire enclosure, combustible materials that are not part of a PS2 or PS3 circuit shall comply with the flammability test of Clause S.1 or be made of V-2 class material, VTM-2 class material or HF-2 class foamed material. These requirements do not apply to: - parts with a size of less than 1 750 mm3; - supplies, consumable materials, media and recording materials; - parts that are required to have particular properties in order to perform intended functions, such as synthetic rubber rollers and ink tubes; - gears, cams, belts, bearings and other parts that would contribute negligible fuel to a fire, including, labels, mounting feet, key caps, knobs and the like; - tubing for air or fluid systems, containers for powders or liquids and foamed plastic parts, provided that they are of HB75 class material if the thinnest significant thickness of the material is < 3 mm, or HB40 class material if the thinnest significant thickness of the material is ≥ 3 mm, or HBF class foamed material. It seems to imply that any component in a fire enclosure notwithstanding the exceptions listed and a mass of >4g must have a V-2 flammability rating regardless of the distance from a PIS. Kind regards; Ian McBurney Lead Compliance Engineer Allen & Heath Ltd. Kernick Industrial estate, Penryn, Cornwall. TR10 9LU. UK. Tel: 01326 372070 Email: [email protected] From: Charlie Blackham <[email protected]> Sent: 04 February 2020 19:43 To: McBurney, Ian <[email protected]>; [email protected] Subject: RE: 62368-1 fire enclosure Ian Are these harnesses and connectors: 1. within the part of the enclosure that needs to be a Fire Enclosure due to presence of PS3 circuits, 2. or are they in other parts of the enclosure that doesn't need to be a Fire Enclosure, as all circuits are PS1, but it just happens that the enclosure material is the same? If (a), then there are restrictions on them as explained in PD IEC/TR 62368-2:2015 6.4.6 Control of fire spread in a PS3 circuit Source: IEC 60950-1 Rationale: There are two basic requirements to control the spread of fire from PS3 circuits: a) use of materials within the fire enclosure that limit fire spread. This includes the same requirements as for components in PS2 circuits and includes a requirement from IEC 60950-1 to address all combustible materials that are found within the fire enclosure; b) use fire-containing enclosures - Product enclosures will have a design capable of preventing the spread of fire from PS3 circuits. The criteria for fire enclosures is based on the available power. Rationale: PS3 sourced circuits may contain a significant amount of energy. During single fault conditions, the available power may overwhelm the safeguard of material control of fuels adjacent to the fault or any consequential ignition source making a fire enclosure necessary as part of the supplementary safeguard. A fire enclosure and the material controls constitute the necessary supplementary safeguard required for a PS3 circuit. If (b), then my understanding is that that part of the enclosure is not acting as a "fire enclosure", so the rules don't apply to those harnesses providing they are suitably separated from the volume requiring a Fire Encloure Regards Charlie Charlie Blackham Sulis Consultants Ltd Tel: +44 (0)7946 624317 Web: https://sulisconsultants.com/<https://url6.mailanyone.net/v1/?m=1iz460-0009Fp-3p&i=57e1b682&c=1xfADfbhq9d84XtqhQH22JROmXtBsIUUw7x-eFnI7v8_5VltshTe6xCSt1mFlVK1ugmj6YafHjU5vdouZ6S_4OgLE_O1J0Vaocy_vwD4hP0VELnBQYVQzGgcIZvAlQaYRM7XmvV0Kw62pwuf-t3ULVbhRFQL9sQQgmEqBHAAJ3mh0njX653lRRO7ALmPCMLVdzIz_TJLbDZB_MgimsvaSImNgR1m1qXrmTraY9hYtKw> Registered in England and Wales, number 05466247 From: McBurney, Ian <[email protected]<mailto:[email protected]>> Sent: 04 February 2020 13:55 To: [email protected]<mailto:[email protected]> Subject: [PSES] 62368-1 fire enclosure Dear colleagues. I have a question regarding the flammability rating of components located within a fire enclosure. We have been told by a safety approval engineer that under clause 6.4.6 of 62368-1:2014 that all combustible material within a fire enclosure and not part of a PS2 or PS3 circuit must have be V-2 or better flammability rating. For example, internal harnesses & connectors which carry low level signals between PCBs and do not carry supply voltages must have a rating of V-2 or better. Does this mean that any component within a fire enclosure regardless of location must have a minimum flammability rating of V-2 or pass the convoluted Annex S.1 test? Many thanks in advance; Ian McBurney Lead Compliance Engineer Allen & Heath Ltd. Kernick Industrial estate, Penryn, Cornwall. TR10 9LU. UK. Tel: 01326 372070 Email: [email protected]<mailto:[email protected]> Allen & Heath Ltd is a registered business in England and Wales, Company number: 4163451. 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