MC Cable Direct Burial

[user789]

I am working on a solar system that will have 6 DC home run circuits (combiner boxes to inverter station) and the plan is to have one trench for all circuits using 3-conductor MC cable rated for direct burial. Are there recommendations for maintained spacing between the circuits and what type of supports, if any, should be used? For PVC, we would typically use plastic spacers. The NEC specifies support every 6ft for MC cable however I'm not clear on whether this applies to direct burial.

Also, is there a maximum depth for direct burial MC cable? Currently, we have two rows (spanning 3 cables each) with the depth of the second row being 38" (from finished grade to the top of the cable).

NEC Figure 310.60(C)(3) specifies 24in spacing between cables and a maximum depth of 36" to the top of the cables but this specifically relates to tables with ampacity correction factors for systems 2000V or higher.

 

[Krusscher]

AFAIK there is only a minimum cover required in table 300.5. 310.60 is referring to medium voltage which I assume you are not dealing with so there should be no maximum depth or spacing to concern yourself with. Shouldn't need to worry about supporting either in a direct burial situation as long as your trench is relatively level. I would try to make sure they don't over lap each other in the trench and not have any large rocks or debris in the trench when back filling.

Would it make more sense to connect all circuits in j-box and run a large pvc with just 3 conductors instead? I know little of PV systems so this might not be practical but i was thinking something like this
AFAIK there is only a minimum cover required in table 300.5. 310.60 is referring to medium voltage which I assume you are not dealing with so there should be no maximum depth or spacing to concern yourself with. Shouldn't need to worry about supporting either in a direct burial situation as long as your trench is relatively level. I would try to make sure they don't over lap each other in the trench and not have any large rocks or debris in the trench when back filling.

Would it make more sense to connect all circuits in j-box and run a large pvc with just 3 conductors instead? I know little of PV systems so this might not be practical or cheaper but i was thinking something like this

https://www.pinterest.com/pin/621144973600875299/