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Solar Power System

Installed April 2006
Operational since June 2006

A complete system was purchased from Backwoods Solar in Sandpoint, Idaho. They provide everything: panels, batteries, charge-controller, wiring, nuts, bolts, harnesses, complete documentation and very helpful support. I installed everything myself with basic tools except for hanging the 400 lb controller on the garage wall and the final breaker box wiring which I contracted out to a local electrical engineering company.

The easiest part was mounting the panels on the south facing side of our garage roof. Backwoods provided the aluminum rails and all stainless steel bolts. Twenty Shell 165 watt 24 volt panels are wired in pairs to produce 48 volts at up to 40 amps in full sunlight. Each pair is wired into a junction box mounted in the attic with individual 9 amp breakers for each pair.

The cabeling terminates into two bus bars with separate gound lines (green wires) and positive mains (black wires) exiting below the box.

The Outback PS2 dual-inverter charge-controller unti was mounted on the garage wall above the battery bank. A 1/2 inch plywood sheet was first anchored to studs in the wall and then the PS2 mounted with a dozen lag bolts. The electrical engineers later ran conduit along the left side to channel the incoming and outgoing 120 volt Grid and mains cabling to the house's main breaker box.

Six 8-volt deep discharge Surrette lead-acid batteries were lined up along the wall below an open window for hydrogen venting. Heavy duty 00 cabeling (also supplied by Backwoods) runs to the charge-controller. As its name implies, the Outback unit both charges the batteries and converts battery power to 120 volts for home power needs.

The finished panel array on our garage in late afternoon with some tree shadows but still producing 8 amps of charging power. Currently the sytem operates in manual mode because of the complicated arrangement of having to also factor in our propane powered 12Kw Guardian AC auxilliary generator located next to the garage. It was installed the year before and was operating automatically when grid power was lost by its automatic transfer switch, a 60 amp relay that transfers 10 circuits in our main breaker box to the generator after a 20 second delay and then back again when grid power is restored.

With the solar system coming into the picture the automatic aspect of this could no longer work as you can't have more than one AC power source feeding the home's breaker box at the same time. So, at least at the present, we go out and turn the solar charging on at daybreak, then switch over to the solar inverter-battery power once the batteries are charged up full. This typically runs from 11 am to 7-9pm (depending on the season) when the batteries have discharged down to the 80-75% level. Surrette specifies limiting discharge to no more than 50%, so we could go longer if we had to.

This is our first winter using the system and we have noticed that with a lower sun angle, proping the panels up improves charging, but cloudy days have on occasion required two days to fully charge the batteries.