[RE-wrenches] Inverter Placement

[Jason Szumlanski]

Are they maybe talking about 690.31 that states that circuits over 30V in
readily accessible locations need to be guarded? I can't tell if the
conductors from the modules to the inverter are in a raceway from your
picture. If so, the guarding requirements they are referring to may be
110.27(A)(4)(b).

However, I think 110.27(B) would be more important in a carport situation,
in which case your suggestion to place inverters as high as practical seems
like the prudent option. On the other hand, the Guarding of Live Parts
section is for the protection of persons specifically. Common sense would
dictate that you want inverters out of the reach of typical vehicles that
would use the parking facility or have them adequately protected. I see the
desire to get them up as high as possible.

Ultimately, if they are going to be placed up high and require portable
ladders or lifts for service, what's the difference between 8 feet and 16
feet? It's not much harder to install or service at the higher height.

On the flip side, cost be damned, I won't specify anything but
microinverters or MLPE that isolates module DC output on a carport due to
an uncontrolled smoldering fire I was called to help with. The DC combiners
were not readily accessible, and even with the fire department's ladder set
up for me to help to shut them down, it doesn't stop the DC current from
flowing as wires melt together. There are just too many ways DC conductor
strings can be damaged in a carport situation. At a minimum, I think there
should be a readily accessible DC disconnecting means for each string to
compartmentalize shorted conductors to the extent possible, and the
quantity of DC conductors bundled together should be minimized. That's just
my design theory. I realize that cost is important and DC systems are safe
in theory... but why take the risk? I have no problem convincing consumers
to spend the extra $ on micros once I tell my story. Plus, the cost
difference is much less when warranty is considered. Anyway, another debate
for another day. I don't mean to get too far off-topic. My point is that
height is not necessarily safer in this case. A readily accessible means of
DC disconnect might be a good idea.

Jason Szumlanski


On Tue, Nov 24, 2020 at 2:48 PM petertor at pobox.com <
peter.parrish at calsolareng.com> wrote:

> I am providing consulting services to a school district in Southern
> California, and I came up with an issue regarding the placement of
> inverters.
>
> These are PV arrays are "solar carports" and the inverters (usually 60
> kW-class) are mounted on columns. The advice I have given the School
> District is to stipulate in the contract with the EPC company that these
> inverters should be "placed as high as practical" on the columns. Their
> counter-offer was to cite a section of the NEC 2017 that places a minimum
> height above grade (parking lot asphalt).
>
> But they have failed to do so, as of this morning.
>
> I remember that the NEC code distinguished between secure locations (e.g.
> switch gear in a closet under lock and key) and locations accessible to the
> general public.
>
>
>
> My case would be the latter. The above photo shows placement lower than
> "practical" IMHO.
>
> Any help with a citation in the 12017 NEC Handbook would be appreciated.
>
> - Peter
>
> Peter T. Parrish, Ph.D.
> President, California Solar Engineering
> 1107 Fair Oaks Blvd Ste. 351
> South Pasadena, CA 91030
> (323) 839-6108
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