SC calcs and current limiting fuses and IEEE 551

[xptpcrewx]

Item c allows for use of things that are not in the code, so they would be impossible. For instance, suppose someone came up with a practical room temperature superconductor. would not be allowed because it is not in the current NEC. So it would otherwise be impossible without some kind of special permission.

I disagree. A rule like this to allow for flexibility with innovative/progressive designs and alternatives that meet the same intent as the original rule.

 

[jim dungar]

the code specifically allows for an engineered solution for existing systems. It does not make that allowance for a new system.

Only when you are talking about 110.09, and existing overcurrent protective devices. The NEC provides no guidance for complying with 110.10 and items like relays, terminals, and busbars.

 

[xptpcrewx]

Only when you are talking about 110.09, and existing overcurrent protective devices. The NEC provides no guidance for complying with 110.10 and items like relays, terminals, and busbars.

This is a good point especially when applying unlisted equipment. Chances are those acting on behalf of the AHJ will not be qualified or trained in many aspects of design review beyond spot-checking codes, and have no way of really doing a proper evaluation where specialized skills or techniques are involved.