information is for those who are already skilled at house wiring and need to
have a list of changes to consider in an independent power home. This page
does not teach house wiring skills. If you need a professional
electrician, in some
states we can recommend licensed electricians familiar with solar installation. Please
go to our Solar Helpers Page.
Otherwise print out the advice below and give it to any licensed electrician who
is wiring your home.
Independent powered homes use standard 120 volt AC wiring just like any city home. But
with independent power, you will need a few extra wires. Some will bring solar, wind, or
hydro generated power from outside to the battery area. Extra equipment in the house, like
a battery meter and generator start/stop switch will need wiring. And to save power, you
will have more than the usual number of wall switches to control many local task
lights. Extra wall switches also control AC outlets so any appliances that steal your
power even when they are turned off can be cut off dead by the switch. Perhaps you will
need a few low voltage outlets for some energy saving DC appliances like phone message machine,
fans, special refrigerator, or pump.
While planning your unique home, don't forget outlets outside. Summer is when solar
electric homes have lots of extra free power, so you may want an electric lawn mower and
weed eater or fountain pump. You might want light and power in a shed or detached garage, for power tools,
or an emergency battery charger to start the car. Special 12 volt DC motion sensor lights
at each entrance, the woodshed, or the outhouse will light up for you even if the inverter
(your AC power source) is in idle mode. Even an outhouse should have its chandelier! Plan
ahead and wire for all these needs while you build.
CHECKLIST FOR HOUSE WIRING
- AC BREAKER BOX:
The inverter in your power system produces 120 volt AC. Normally no 240 volt
AC will be used in the house, only 120 volt AC. So you just feed the same
120 volt hot wire to both legs of the AC breaker box. Since most inverters
are limited to 20 to 60 amps maximum output, you donít need a 200 amp main
breaker. Eliminate the expensive main breakers by "back feeding"
the entire box through two of the load breakers, one for each
"leg" of the breaker box. This passes electrical code.
GENERATOR AC WIRING: Power from the generator should go into the
power equipment room on a separate wire, (never fed back through the same
wire that carries inverter power out to the generator location). Mark this
wire generator direct. This will supply power directly from the
generator to the AC IN terminals of standby inverter, and to any special
generator direct outlets you might want to add in the power room for other
battery chargers. Standby option feature on most inverters
(or a separate transfer relay catalog #O-TS30 if the inverter lacks this
feature) will automatically switch generator power through to house circuits
when the generator runs. When the generator is shut down, household circuits
automatically switch back to inverter power. Never connect the generator
output directly to the house circuit breaker box if inverter power is
You may also want to run a generator direct wire
to its own outlet in the garage, or shop. Here you plug in battery chargers which should run only
from generator power, as well as a welder, air compressor, or other items the inverter is
not large enough to run. Also run a generator direct line for any 220
volt power you might use directly from the generator, like a very deep well
pump. No need for separate generator and inverter wiring elsewhere in your
home, because generator power automatically comes through all the regular
wiring when the generator runs.
LIGHTING IS MORE EFFECTIVE WITH LESS POWER if you have lots of local
area "task" lights. Use 15 watt fluorescent lights under cabinets to
be close to the kitchen
counter and in workshops. Put each wall or ceiling light on it's own wall switch so you
can select lighting precisely where it is needed. More, smaller lights use less power with
more lighting options than a large central light.
- Timer light switches are great for lights often turned on and then forgotten, as in
children's rooms, closets, stair wells, and particularly outdoor lights. The tap of a
button or a wind up timer starts the light and sets the time anywhere from a few seconds
to an hour, then the light goes out. The timers help keep the peace if lights are often
forgotten and carelessly left burning.
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SPECIAL PURPOSE 12 or 24 VOLT DC CIRCUITS
Plan a few DC circuits in
the house for items that have great energy saving advantage using DC power direct from
your battery. One DC circuit to each room is usually enough for "low power,
long hour" applications: recharging flashlights and cordless tools, doorbell,
intercom, phone answer machine, cordless phone, 2 way radio, desk calculator, or portable
stereo. Some energy saving refrigerators, especially small ones, are DC powered, also
water pumps, and ceiling fans may also need a DC circuit. DC hot water circulating pumps
are used for floor heat systems, water-bed heating, or compost toilet heating. You may
want DC circuits to front door or outdoor motion sensing lights so they can operate
whether the AC power inverter is active or not.
DC OUTLETS are not standardized. Beware the old RV cigarette lighter
plug. They are poor quality, illegal in houses, and will burn. For quality and durable 12
or 24 volt outlets, just use standard 240 volt 20 amp AC outlets. These usually pass code
inspection used as DC outlets if there are no actual 240 volt outlets in the same house.
They fit the same outlet boxes and same cover plates as regular 120 volt AC outlets, and
just as easily attach to wire with a screwdriver. These are listed in our catalog as
#O-DC OUTLET and #O-DC
To figure the correct wire size to use for 12 and 24 volt DC circuits, use the wire
size chart printed with the solar module wiring in our catalog. Generally, use 12 gauge
wire up to 35 feet or 10 gauge for runs up to 50 or 60 feet. (Stranded wire and
solid wire of the same gauge carry the same ampere rating).
OTHER WIRES TO ADD
- TELEPHONE WIRES should be kept far from your AC power wires. Inverters
that are not True SineWave can cause a buzz in the background on your phone if
the wires are run beside each other for any length. Use shielded and twisted pair
telephone wire with the shield connected to ground to minimize this common noise problem.
- SOLAR MODULE WIRES You will need appropriately sized
COPPER wires to
bring power from solar modules to the battery / utility area. Our
mount and wiring catalog page has charts showing the wire gauge to use
for various distances for 12, 24, or 48 volt battery.
- POWER MONITOR WIRING You may want a battery monitor meter
somewhere in the home other than the battery room. While wiring the house, install some
4 or 6
conductor twisted pair intercom or phone type wire for the remote meters like
- START AND STOP CONTROL FOR GENERATOR will be needed in the house
if you get a remote control generator. 4 conductor wire
12 gauge does it.
- AND ALL OTHER usual extras are more difficult to add after the house is
built than when the walls are still open: TV antenna cables, extra telephone wires and
outlets, speaker wires for stereo, doorbell and intercom or other special wiring.
SOME APPLIANCES STEAL POWER -- EVEN WHEN TURNED OFF
PHANTOM LOADS : Some appliances need to be disconnected from power
completely just like pulling the plug, when not in use. Remote control TV, VCR, stereo,
and microwave oven, office equipment (computers, fax, etc.) and garage door
openers may use a little power 24
hours a day even when switched off! These are called "phantom loads", and taken
together, will keep an inverter turned on and waste a large part of your power, if not
- The cure is to have many of your AC outlets controlled by a wall switch to shut off
power completely. This is preferable to pulling the plug every time. In existing houses,
just use the outlet strips, (an extension cord with an outlet strip and built in switch)
to easily disconnect power robbing items. One strip can switch your whole stereo/TV
assortment, or all your computer items together.
To learn the rest of the story that the above was selected from, read the BACKWOODS
SOLAR ELECTRIC SYSTEMS solar electric catalog/guidebook, and the other
books listed in the catalog.
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