Friday, April 29, 2016

Solar Power: Part 4-Transfer switches

A transfer switch is optional but a big convenience. The transfer switch automatically switches between the inverter and shore power. Shore power is any outside source of electric such as the tradional electrical grid (extension cord) or a generator.

Living off-grid, we get most of our energy from the sun but sometimes, we do not get sufficient energy from the solar panels to completely charge our batteries (such as during long winter snow storms). I use my generator as a backup to charge my batteries. Or we may want to use more current that our inverter will permit (such as a big tablesaw). On these occasions, I also use the generator.

The transfer switch has three wires. You may need to provide your own wiring for some transfer switches but the same wires will connect to your sources. One wire will plug directly into the outlet of the inverter. The other two wires connect to AC input (shore power or generator) and AC output (house electrical panel). The transfer switch automatically switches the energy to the inverter. Normally, my inverter converts my 12V battery to 120V AC power. When I use shore power, the transfer disconnects the inverter and automatically connects the shore power to provide energy to my home. There is a very short time lag for the switch over so it is best to turn off any computer and such unless they operate on an internal battery or APS battery backup.

A transfer switch is not mandatory, it is possible to do this task manually with either an electrical switch or series of electrical plugs. However, I like the lazy approach, just power up the genny and poof, I have power. My primary use of my genny is to charge my batteries or work on construction projects that require my air compressor or other tools.

Transfer switches are rated for a maximum amperage. My needs are minimal so I have the Xantrex 15A unit but most will want a 30 amp unit or even a 60 amp unit. Transfer switches are available at electrical supply stores and amazon. I have linked the Xantrex and Go Power transfer switches at the bottom. The Xantrex is limited to 15 amps and the Go Power to 30 amp.

In part 5 I will cover connecting to shore power including generators. Thanks for being a part of this on going discussion.

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