690.16 fuse disconnecting at combiner

[SolarAlternativesDesign]

2014 NEC 690.16(A) requires disconnecting means to disconnect a fuse from all sources of supply if the fuse is energized from both directions and that such a fuse in a source circuit be capable of being disconnected independently of fuses in other PV source circuits. Is it OK to put the disconnect at the downstream side of the combiner as in this drawing, even though a fuse would be energized at its downstream side by the other two source circuits? (I may not have drawn this correctly for the Midnite MNPVHV Disco. I think it might disconnect all the fuses from each other instead of just disconnecting the combiner output from the downstream PV output circuit. But in principle, the drawing looks like the case where a disconnect disconnects the downstream PV output circuit from the combiner output.)


In a system with only 1 combiner, is it OK to put the disconnect between the fuses and the strings as in this drawing, even though the fuses would all have to be disconnected together - not independently? This is a less expensive disconnect and it would isolate each fuse from the outputs of the other two fuses.

 

[jaggedben]

In your first diagram I think that if you have finger safe fuse holders then it's already compliant. If you don't have finger safe fuse holders then you could add connectors (e.g. MC4) in each conductor right outside the combiner in order to be compliant. There is no requirement for all the disconnecting means to be load break.

I see what your saying about the 'independently' requirement regarding your second diagram. That requirement is really nonsensical since (unless you have finger safe fuse holders) you have to disconnect all combined source circuits to denergize a fuse. Fwiw, that language is gone in 2017 and your diagram would be compliant under that code.

 

[jaggedben]

Also, in your second diagram you're showing the part number for a 4-pole disconnect when your diagram shows you needing a 6-pole. And three 2-pole discos from that company are cheaper than one 6-pole. So that's how you'd get 'independently' and not cost yourself money.