Mains (120v) Off the Grid
When not connected to “the grid”, 120v AC loads require an “inverter” to convert DC voltage (usually in the form of 12v deep-cycle batteries) to 120v AC. For example, if you wanted to power your home 120v Television in your RV, Skoolie, or from your solar array at home, you wold need an inverter to supply 120v to the TV from your DC batteries.
An important consideration about using an inverter is the amp draw on the battery bank. Typically if an appliance needs 1 Amp AC, the inverter will draw 10 Amps DC.
If an appliance draws 1 Amp AC, it will draw 10 Amps DC. If you have a 100 Amp Hour battery bank, you could safely run the appliance for 5 hours. Assuming there is no other load on the battery bank. You can run it safely for 5 hours, not 10 hours, because we don’t really want to drain our batteries past 50%. This is not true for all battery types as some can be drained much lower; however, it is never a bad idea to have extra, just in case.
- If you had a Solar setup putting more than 10 Amps into the battery bank, you could run the appliance as long as you could keep the solar panels facing the sun.
Our plan is to take solar energy stored in the battery bank, and using an inverter, supply 120v electricity to a fuse panel, supplying 120v electrical outlets throughout the bus. It is important to oversize your inverter needs; since our goal is to be as sustainable as possible we want to ensure we’ll be prepared for whatever we may need or want.
Wiring – “Romex”
- The solid green wire (or green with a yellow stripe or stripes, or bare copper wire), green screws, and round hole in power outlets is the safety ground and connects the housing of all equipment to ground at the electrical service entrance point completely independently of any other wiring.
- The water lines, natural gas lines, metallic air conditioning lines, air conditioning ducts, etc. is also supposed to be connected to the safety ground.
- The “zero volts” or the return wire is white. The whitewire, the silver screws, the wide slot on power outlets and the threaded sleeve of the light bulb sockets are all the neutral connection.
- This is insulated from ground everywhere EXCEPT at the service entrance where it is ALSO tied to the ground buss
- The black wire, brass/gold screws, the narrow slot on 2-prong or 3-prong power outlets, and the center button / center contact of the light bulb sockets are always the hot wire
- Any color except green (green-yellow) or white / grey is a HOT wire….ALL OTHER COLORS ARE HOT. It may save your life or that of a family member, friend or co-worker.
Wire Gauge by Distance
120v 15amp 30amp 50amp
25ft #14 Gauge #10 Gauge #8 Gauge
50ft #12 Gauge #8 Gauge #6 Gauge
Your typical outlet may look like this.
It will have 5 screws: 2 gold, 2 silver, and 1 green. The ground wire connects to the green screw. The white wire connects to the silver screws. And the black wire connects to the gold screws.
The switch should ALWAYS be in the hot lead, so that when it is off the fixture or outlet is electrically DEAD…
*In case you are curious, the international standard green-yellow marking of the ground conductors was introduced to reduce the risk of confusion by colorblind installers. Between 7% and 10% of men cannot clearly distinguish between red and green, which is a particular concern in older schemes were red marks a live conductor and green marks safety ground. If you are purchasing wire for a new wiring project, and you have a choice between green / yellow and solid green, please pick the green / yellow.