Vertical Cable Supports 300.19

[Carultch]

I'm looking at 300.19, and I want to ask about practical experience with this rule.

I have a situation with a vertical run that is about half of what the table prescribes for where a support is required. We're talking 50 ft, when the table prescribes 100 ft. Is this a situation where best industry practices are to build above and beyond the NEC? Or would that be ignorant overkill?

Given no supports, this would mean that the tension to restrain the weight is supported at the terminations. For less vertical distance than what 300.19 provides, is this tension usually within reasonable limits?

 

[kwired]

If your 50 foot vertical rise of say a 500kcmil is to be supported somehow by equipment with terminals only designed to accommodate say 2 AWG conductors (don't ask how or why, just trying to introduce an extreme situation) - you might want to consider additional support, otherwise equipment with terminals that accept 500kcmil likely have reasonable physical ability to handle the weight. Also remember the bottom end can be supporting some of the weight.

 

[Carultch]

If your 50 foot vertical rise of say a 500kcmil is to be supported somehow by equipment with terminals only designed to accommodate say 2 AWG conductors (don't ask how or why, just trying to introduce an extreme situation) - you might want to consider additional support, otherwise equipment with terminals that accept 500kcmil likely have reasonable physical ability to handle the weight. Also remember the bottom end can be supporting some of the weight.

I know exactly why and how that might be the case. One example is if you have to step down to a smaller conductor, and install a small whip of it with an in-line splice reducer, in order to adapt to your equipment terminals. Or if you have to use a pin terminal for the exact same application. A situation I've been in, requiring parallel 500kcmils on a 400A MCP panelboard that only had capabilities of up to 250 kcmil when in parallel, although that example had a horizontal run so this wasn't an issue.

Thank you for the advice, and it makes perfect sense. My understanding is that if the equipment comes with factory terminals capable of long run wire size in question, it should be able to withstand the tension of its weight on any vertical rise less than the height that the NEC table prescribes.

 

[kwired]

I know exactly why and how that might be the case. One example is if you have to step down to a smaller conductor, and install a small whip of it with an in-line splice reducer, in order to adapt to your equipment terminals. Or if you have to use a pin terminal for the exact same application. A situation I've been in, requiring parallel 500kcmils on a 400A MCP panelboard that only had capabilities of up to 250 kcmil when in parallel, although that example had a horizontal run so this wasn't an issue.

Thank you for the advice, and it makes perfect sense. My understanding is that if the equipment comes with factory terminals capable of long run wire size in question, it should be able to withstand the tension of its weight on a vertical rise less than the NEC table prescribes.

That example is sort of what I was thinking but is still a little extreme to see the need to reduce 500kcmil to fit a 2 AWG lug when the length of run is only 50 feet which is why I requested to not ask why/how.