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AC Wiring
The AC system wiring was pretty
straightforward, so I tackled it first. Since it involved four
inverters, I elected to use four 15-amp two-pole circuit breakers in a
sub panel to combine their outputs into a single pair of conductors that
travel via disconnects and private meter to the main utility panel. I included
the private kWh meter to monitor system performance.
The system is a 120-ft walk from the main utility panel, so there is a local disconnect next to the
sub panel. The signage, required per NEC, was designed to SDG&E specifications
and was laser-engraved at a local trophy shop.
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I used #8 THWN building wire for the individual inverter circuits,
and #4 THWN from the sub panel bus bar through the disconnects and meter
and on to the main panel. All of
these conductors are housed in schedule 40 sunlight-resistant PVC
conduit. The planks form a catwalk for inspecting and cleaning the
PV surfaces (bird problems mostly).
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Here the system ties into the utility panel. Wiring
from the disconnect to the panel is in the wall. The circuit terminates in the main panel at a two-pole
40-Amp breaker. The paint on the main panel had started peeling, so I scraped it off
before affixing the signage. I'll repaint sometime this summer
when I paint all the above-ground PVC conduit.
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DC Wiring
The DC field wiring presented a few challenges,
beginning with selection of an appropriate type of
wire. The PV panel wiring is exposed, but the conductors are
gathered into PVC conduit runs for protected delivery to the
inverters.
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I accomplished the transition
to conduit with PVC LB conduit
bodies, drilled and fitted with elastomeric squeeze bushings similar to
those included with the Kyocera panels.
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Inverters 1, 2, and 3 each serve a cluster
of five PV bays (strings) and are physically located a few feet north of
their respective
center bays. Inverter 4 serves a partial cluster of three bays with capacity for
future expansion to two more bays. DC conductors to each
inverter are housed in two 1-1/4" conduit branches. |
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Here's a helpful hint. If pulling a bundle of wires
through conduit takes more effort than you'd like, wipe each of them
lightly with Armorall as they enter the conduit. It works much
better than the "snot" they sell at the electrical supply
house.
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At last it was time to call for inspection, then sit back
to enjoy the view. |
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