Sunny Boy with tracker [RE-wrenches]

[Allan Sindelar, Positive Energy, Inc.]

Dear Wrenches,
Just for the fun of it, how about a grid-tie topic that's not focused on
Trace's troubles...

We're doing our first Sunny Boy installation. (We have no state incentives,
so batteryless intertie takes a certain type of committed, green pioneer.) I
have planned ten Solarex SX120s @ 24V each on a Wattsun DA model 200
tracker; a second tracker pole set for a future doubling of the array; and a
Sunny Boy 2500. I need some advice on methods that have worked and pass
code. This will be a closely watched and carefully inspected installation.

1. Original plan is to mount DC disconnect and inverter in an indoor laundry
room that is close to an AC panel, with conduit run through house framing
and underground 40' to each pole. I see that 690.14 (C) (1) wants the
disconnect to be "inside nearest the point of entrance of the system
conductors" which would be an awkward corner of the basement, while 690.14
(C) (5), newly added for 2002, wants disconnects grouped together. Any
suggestions before I ask the AHJ?

2. The tracker motor uses 24-35 (+/-) VDC to run. Wattsun offers a standard
power supply accessory that takes 230VAC to create 30VDC. Code won't allow
this to run off of the inverter 230VAC output (source and load
differentiation; no attachment point). So that means two conduits: one PV
input, one tracker motors. Also, the power supply needs its own enclosure,
and if it's grouped with other equipment, that's bigger conduit to carry 4A
@30V DC. OK, it's doable. We're looking for an easier way. We're also
looking for a simpler 120AC or 240AC-24-30V DC power supply.

3. We could mount everything on the pole, and bring in one standard AC
conduit. Wiles sez that we could use a raintight load center to serve as
both PV AC disconnect and supply to a 1P or 2P breaker to run the tracker
power supply. But that means a (big) 600V DC disconnect (Sq D HU361),
inverter, AC disconnect, and power supply enclosure all mounted on one
little 6" pole. There's gotta be a better way.

4. Wiles also suggested a Sq D QO/QOB-PLPS "24Vdc Panel-mounted Power Supply
for QO-QOB-PL Breakers" as a possible power supply for the tracker motors.
It's a 120VAC-24Vdc power supply that fits in 1 pole of a QO box. It's used
to power their Powerlink line of circuit breakers with remote switching
capability. Has anyone tried this? Will it work?

Who has done an installation like this successfully? Can you suggest some
simpler approaches? Thank you in advance.

Allan at Positive Energy

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