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Industrial machinery functional safety wiring - minimum size?

Industrial machinery functional safety wiring - minimum size?

Industrial machinery functional safety wiring - minimum size?

(OP)
Hi All,

I am reviewing functional safety requirements according to US and international standards. One question I have not been able to answer is whether there is a minimum allowed wire gauge for both single conductor and multiconductor cable scenarios. I vaguely recall being told years ago that discrete wires should be minimum 18 AWG, but I can't trace this back to ISO 13849, NFPA 79, or UL 508 & 508a. I have not checked ANSI B.11 as we do not have a copy.

Is anyone aware of any such requirement? Is there another place I should look?

Thanks!

RE: Industrial machinery functional safety wiring - minimum size?

I'm not aware of anything in the standards, but the various component manufacturers may specify wire sizes for use with their components, in which case, that's what has to be done. For but one example, https://www.farnell.com/datasheets/1712548.pdf (see second-last page under "Precautions" - that's the extent that they discuss it). 0.75 mm2 is 18 AWG.

Ethernet cables use conductors quite a bit smaller than 18 AWG.

RE: Industrial machinery functional safety wiring - minimum size?

(OP)
Thanks for the reply Brian. Regarding your comment on ethernet cable, part of my recollection was that multiconductor cables have a different requirement than individual conductors.

I also found in NFPA 79, section 12.6.3: "Conductors shall not be smaller than 18 AWG for control circuits within control enclosures or operator stations." This may be what I was thinking of.

RE: Industrial machinery functional safety wiring - minimum size?

AS/NZS 4024.1204, that is based on ISO 13849, Cl 12.2 states in summary, minimum AWG 18.

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