Happy on One Kilowatt
(Page 3 of 4)
June/July 2000
By Bill Isely
While awaiting delivery of the inverter that would convert our batteries' DC to 120V of AC, we turned to the problem of how to tie the hydropower to our house. We were able to fit a transfer switch box containing eight circuits in the wall adjacent to our existing circuit breaker box. The seven circuits we wanted to have energized, regardless of power source (grid or hydro), were moved into the transfer switch box. The water heater was then connected to the eighth circuit, though this meant modifying it to run on 120V rather than 240V. We replaced the existing water heater elements with lower wattage elements, so that the unit would draw no more than 550 watts. Even so, we can still run one warm washer load and enjoy two leisurely hot showers each day.
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For convenience, we ran a special wire between the house and battery bank that allows us to remotely monitor the battery voltage. We've also got an AC meter that we can clamp onto the 120V hot wire where it enters the transfer switch box, to monitor the current being drawn.
Once the inverter arrived, we went about installing all of the control elements in a corner of our nearby greenhouse, along with the batteries. Because we wanted to be able to start motors and operate shop equipment, we needed at least a 2.5 kW inverter with good surge capacity. Cost being an important consideration, we bought an inexpensive modified sine-wave device.
Lessons Learned
Not long after going on the hydro system, we realized we'd made some crucial mistakes that would need addressing.
Belatedly, we discovered that batteries will off-gas hydrogen and that a simple cover and vent will not necessarily prevent nearby electrical equipment from sparking an explosion. We needed to move the batteries.
Second, we found that the modified sinewave inverter produced a power noticeably inferior to the pure sine-wave power we'd gotten used to from the grid. Many of the florescent lights we'd installed to reduce our power load would not start. The computer started crashing a lot and a VCR motor burned out in a way the repairman couldn't explain.
Worse still, a portable gauss meter revealed a very high level of electromagnetic field (EMF) radiation in the greenhouse where we'd installed the control equipment - most of it coining from the inverter. The level was high enough to make the greenhouse uninhabitable while the inverter was operating.
We returned the modified sine-wave inverter to the dealer and replaced it with a pure sine-wave device, which was twice as expensive but well worth the cost. It's now impossible to tell if we're operating on the grid or hydro without checking meters.
Even before the new inverter had arrived, we built a new shed for all of the control equipment, with a separate compartment for the batteries and water heating elements. We located the building in brush away from all normal foot traffic, to safeguard against the effects of any remaining EMF pollution. (Though the new sine-wave inverter runs clean, the battery regulator and battery cables emit a small amount of EMF radiation.)
