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I am currently getting some custom cables made and having a serious communication issue with several cable manufacturers. I want several low voltage (5V DC) insulated conductors in a jacket that can protect from 600V external contact. And, I want the cable to be UL marked for flammability and voltage compliance.

If I am understanding my communications correctly, the different manufacturers have all indicated that the insulation for the individual wires must also resist 600V on their own for UL marking which makes the cable diameter very large. To me this does not make sense. I have been going through UL documents to try to see where this might be stated. Looking at AWM (appliance wiring) standards, I see detail about the jacket, but not about the individual conductors as in UL 20201 and UL 2057 for example. Given that AWM wires can contain twisted pair (assuming for communications), I would like to understand what I might be missing that would require cable internal wires to have such thick insulation.

I have looked at the "UL Marking and Application Guide Wire and Cable" in their tables and virtually every cable option requires UL marking with the UL symbol and voltage.

Is this possibly a case of the manufacturers trying to comply to a different standard than would apply? Is this a case of my application not being covered directly in the standards? Other options?

Any explanations and possible directions would be appreciated.

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  • \$\begingroup\$ The standards are really there to protect external things from contact with the voltage in your cables. Which means it makes perfect sense to have the same insulation between the individual wires as you'd never have them within a few volts of each other but all at around 600V. \$\endgroup\$ – Finbarr Jun 5 '20 at 6:53
  • \$\begingroup\$ Running communications cable in a high voltage environment is a simple example where the voltages on the individual conductors would be much less than those of the external environment. Are you making your observation based on experience with standards? \$\endgroup\$ – Jason K. Jun 5 '20 at 14:56
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Maybe the problem here is that the UL voltage of 600V printed on the jacket of a cable does always mean that the inside individual wires are capable to have 600V difference in voltage to each other. It automatically means an insulation withstanding at least 600V to the outside of the jacket. Those who demand the value of 600V printed on the jacket should reconsider their request. The insulation voltage of a (signal) cable's multiple inside low voltage wires to the cable's outside is only mentioned in the cable's specification, but never printed on the jacket, since it would be misleading.

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  • \$\begingroup\$ It might be that the individual wires must be insulated to 600V, but I am looking for some expertise in that matter. The simple case of running twisted pair communications cables in a high voltage environment would suggest that there are situations where it would make sense to to have a rated cable to ensure safety so that communication lines did not experience that high voltage. \$\endgroup\$ – Jason K. Jun 5 '20 at 15:02

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