Wednesday, August 20, 2008

Wiring the Micro home II by Walt Barrett

The electrical system for the Micro Home will consist of the following components.
1. Solar power modules and mounting racks.
2. A solar charging regulator.
3. A battery bank of solar type deep draw batteries in a sealed and vented to the exterior storage bin. Batteries perform better at normal room temperature.
4. A 12 volt DC to 120 volt A/C inverter.
5. A 120 volt circuit breaker panel.
6. Standard house wiring consisting of electrical boxes for plug sockets, light switches and light fixtures. Number 12 and 14 wire will be used as required.
If the batteries are to be stored inside the building then the sealing and exterior venting of the battery storage box is very important because the hydrogen and other gasses emitted from the batteries during the charging process can be toxic and explosive.
During the process of pre cutting all of the framing material we ran all of the studs through a drill press and pre drilled all of the 1/2" holes for the wiring. It's a lot easier than on site drilling. Each hole is exactly 24 inches off the floor and is on center exactly. This is particularly handy when you have to snake the wire around a corner inside the walls. I have personally seen electricians "butcher " the inside corner of a wall in order to get wire around the corner. They really weaken the structure for one thing and it is also just plain sloppy work in my opinion.
Another important point is that the electrical codes should be followed implicitly at all times. You have to figure the total load on each electrical circuit and size the wire and breakers accordingly. When designing a solar power system you need to start by figuring the wattage on every electrical appliance and light. You have to then choose the proper inverter, wire and electrical supply panel and circuit breakers. The total wattage consumption and solar insolation (Watts or BTU per sq ft per hour for your climate also determines the number of storage batteries and number of solar modules and the amperage rating off the solar charging regulator.
Obviously, if you tone down the number of appliances and use low wattage lighting you can have an almost bargain basement price on the solar electric system. We are investigating all of the low wattage refrigerators. These units will determine how low we can go on the cost of the system. We have found one 5.8 cu ft unit so far that runs on one 85 watt solar module and two deep draw batteries. They also offer the unit as a freezer.
I hope to post some photos of the wiring soon. We are experiencing heavy sales of tractors and generators right now, and it is really eating into our time schedule. That's what pays the bills and finances our micro home research project. Our goal is to develop the lowest priced and most efficient micro home design.
Any questions,
We welcome your suggestions and ideas.

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