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Please forgive me if this question has been asked before.

I am designing a heating device that will be sold to industrial consumers. In our past designs we have had multiple versions of the same product (one for 120 VAC (L, N, G) and another for 240 VAC (L1, L2, G)). I would like to simplify the design of this new product so that it can accept both voltages.

The voltage is not the issue. The AC-DC converters I am using will accept either, and the heaters that ultimately will be connected will be selected appropriately. The problem is that the outputs that provide 120 VAC or 240 VAC for the heaters must be fused. I would like to simply put a fuse on each leg of each output, but that means that when the device is powered from 120 VAC there will be a fuse on the neutral output leg.

I understand that the concern with a fuse in N is that it might open while the hot fuse remains closed and therefore the circuit downstream would appear "dead" when it is actually "live". I believe that this concern isn't applicable in the case of the device in question. There is a minuscule chance of user contact with any of the downstream circuit whether "live" or "dead".

Is there any other reason why fusing neutral in this case is not advised?

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    \$\begingroup\$ Which country do you intend to sell in? Can you install a two pole breaker instead? \$\endgroup\$
    – winny
    Commented Jan 17, 2019 at 16:21
  • \$\begingroup\$ It will be sold in the US. A two pole breaker is an option, but is probably too expensive for our taste. \$\endgroup\$
    – cholz
    Commented Jan 17, 2019 at 16:51

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Some countries make hardwired installations with fused neutral non-compliant.

Select the fuse for the neutral conductor to be one size larger than the phase conductor fuse. This prefers the polarized line pin to become fused but still protects reversed plug faults.

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  • \$\begingroup\$ I believe my country forbids fused neutrals. Is providing the suggestion "Select the fuse for the neutral conductor to be one size larger than the phase conductor fuse" as a general solution really a good idea? Perhaps it should be qualified with "where allowed", or include a citation indicating that is is allowed at a specific geographic location. \$\endgroup\$
    – Chris Knudsen
    Commented Jan 17, 2019 at 16:46
  • \$\begingroup\$ To me, if it is hardwired properly with neutral fused, the risk is null and the safety standard errs on the side of faulty installer. \$\endgroup\$
    – D.A.S.
    Commented Jan 17, 2019 at 16:51

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