# 12 volt wiring how to



## SurvivalNut

I am building a blacksmith shop out back. It will be grid wired, but I also want it to be wired for 12 volts. 

I see al the RV type outlets and stuff, but what do you real off grid pros use for 12/110v or 12v only wiring systems?


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## hardrock

SurvivalNut said:


> I am building a blacksmith shop out back. It will be grid wired, but I also want it to be wired for 12 volts.
> 
> I see al the RV type outlets and stuff, but what do you real off grid pros use for 12/110v or 12v only wiring systems?


SurvivalNut, OHM's law rules. I'm not a 12v man, but have about 20 years as an industrial maintance electrician.
To get the same power from 12 volts, for example a 100 watt light, as from 120 volts, Power(wattage) = amps x volts.

So amps from 120 volts through a 100 watt bulb = about 0.833 amps.
With a 12 volt source,to get the same amout of power for the equivilent amount of light will require 8.3amps.

Wire size to needed do the same job would be 10 times larger.

Don't know if you will use the 120 volt source to power the 12 volt system or not but you would need a power supply large enough to handle the 12 volt load you plan to install to use with a 120 volts power supply.

Really need to know what you plan to power the 12 volts with.

Or,

You can power the 12 volt system (if you use batterys) with wind, water or solar panels or charge them with a small generator and a battery charger.

My plan is to use a small 2000 watt honda generator for emergency use.(15 hrs at 1/4 load with 1.1 gallons of fuel.


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## tommu56

by code you and use any plug that wont mate with any thing you have in the place now as long as you stay in the current rating.

That said I use 50 amp Anderson connectors I have them on my travel trailer and on my truck too to hook up chargers and jumpers for extended camping with out power.










Connector, Wire/Cable - Battery and Cable Connectors - Wire Connectors - Electrical : Grainger Industrial Supply

to


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## The_Blob

hardrock said:


> SurvivalNut, OHM's law rules. I'm not a 12v man, but have about 20 years as an industrial maintance electrician.
> To get the same power from 12 volts, for example a 100 watt light, as from 120 volts, Power(wattage) = amps x volts.
> 
> So amps from 120 volts through a 100 watt bulb = about 0.833 amps.
> With a 12 volt source,to get the same amout of power for the equivilent amount of light will require 8.3amps.
> 
> Wire size to needed do the same job would be 10 times larger.


American Wire Gauge table and AWG Electrical Current Load Limits with skin depth frequencies has a few good calculators on it

AC circuits, alternating current electricity can answer some questions

In general, Ohm's law cannot be applied to alternating-current circuits since it does not consider the reactance which is always present in such circuits. However, by a modification of Ohm's law which does take into consideration the effect of reactance we obtain a general law which is applicable to ac circuits. Because the impedance, Z, represents the combined opposition of all the reactances and resistances, this general law for ac is: *I=E/Z*
This general modification applies to alternating current flowing in any circuit, and any one of the values may be found from the equation if the others are known.

in real world applications (USA) ohm's law applied to AC circuits uses sin45 (0.7071 or 1/2 of voltage leading current theta which is 90) for calculations with _non purely resistive_ circuits... like motors.

Ohm's Law works just fine with purely resistive circuits P=I*E
P=watts
I=amps
E=volts

IMHO always use the next larger size wire than what's recommended, it's better to have it & not need it than to need it & not have it


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## SurvivalNut

Sorry, I was not clear in my original question.

My blacksmith shop is old school hand operated-coal forge, post drills, knee drills, crank or foot operated grinders, soldering irons, all 1930's and older.

I have been collecting old shop tools for years.

I do have some old restored mini hit and miss washing machine motors that I will hook up to grinders and saws for larger jobs.

The 12v system is to come off my battery bank charged by the sun and a small wind turbine. The 12v will stay 12v, not invert to 110. I will use the 12v for lighting, charging cordless power tools, radio, CB and HAM.

I believe in bigger wire is better, but the outlets I see available for 12v use are the RV type.

*Are there any better 12v outlets available?*

I don't need an inverter in the mix and it is just one more item to go bad, so I am looking at not using one.


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## Tirediron

If lighting is the main concern LED will give the most bang for your battery
As far as recepticles go all that I had seen is the Flat 2 wire connectors and lighter plugs , there is also a small 2 prong plug that is on some gens for battery charging (12v) that would be decent but I have no idea where to get them,


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## nj_m715

Any outlet that can handle the amps will work for you, especially if you're not getting an inspection. I have standard 110v outlet in my camper that is wired for 12v. The PO put it in there. He had an old tv that he plugged into it. I would have used a cigarette lighter, since most of my 12v items already have it. 

I gutted a dead battery pack for my cordless tools and wired in a standard plug. I put alligator clips on a damaged cord. Now I can run my tools from a car if needed. I just have to make sure none of my knothead buddies plug the cord into a wall outlet. It was cheap, used junk parts I already had and it works, so I'm happy with it.


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## Tirediron

If you decide to use normal household type recepticles for your 12V , you could use the ground terminal for ground and the Ground potential for 12V+ and either cut the "hot" prong off or just not hook it to any thing, If I were to do this I would cut the "hot prong off and fill the corisponding receptical hole with epoxy . Cheap and fairly fool proof


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## The_Blob

Tirediron said:


> If you decide to use normal household type recepticles for your 12V , you could use the ground terminal for ground and the Ground potential for 12V+ and either cut the "hot" prong off or just not hook it to any thing, If I were to do this I would cut the "hot prong off and fill the corisponding receptical hole with epoxy . Cheap and fairly fool proof


you know, I never thought of that, but that is an *excellent* suggestion, even though YOU may know what your system is, OTHERS may not & that could cause damage unless not prevented... THANX :congrat:


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## sailaway

get a copy of, Living on 12v with Ample Power.


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## Walker

*Another 12-volt plug/outlet option*

One option that has worked well for us and for all of the other homes I've wired this way goes as follows:

Wire all the outlets with standard boxes and 20-amp, 110-volt receptacles.

Wire the neutral screw to your 12-volt positive wire, preferably using a soldered-on terminal end.

Wire the ground screw to your negative wire, again using a soldered terminal end.

Use 3-prong plugs for your 12-volt stuff, again wiring the neutral pin to positive and the ground to negative.

This set-up works well in homes that use both an inverter for 110-volt and other stuff that's 12-volt. If you mistakenly plug a 12-volt appliance into a 110-volt outlet the appliance doesn't "see" the 110-volt "hot" tab since your cord isn't wired to it (nothing happens). If you mistakenly plug a 110-volt appliance into a 12-volt outlet the appliance doesn't "see" 110 volts since there is nothing wired to that screw (again, nothing happens).

I wired a neighbor's house with both 110-volt AC (inverter) and 12-volt DC outlets right next to each other. When workmen came to plug in a drill or saw sometimes their tools didn't work. She just had to tell them to try the neighboring outlet and all was well.


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## bunkerbob

Walker said:


> One option that has worked well for us and for all of the other homes I've wired this way goes as follows:
> 
> Wire all the outlets with standard boxes and 20-amp, 110-volt receptacles.
> 
> Wire the neutral screw to your 12-volt positive wire, preferably using a soldered-on terminal end.
> 
> Wire the ground screw to your negative wire, again using a soldered terminal end.
> 
> Use 3-prong plugs for your 12-volt stuff, again wiring the neutral pin to positive and the ground to negative.
> 
> This set-up works well in homes that use both an inverter for 110-volt and other stuff that's 12-volt. If you mistakenly plug a 12-volt appliance into a 110-volt outlet the appliance doesn't "see" the 110-volt "hot" tab since your cord isn't wired to it (nothing happens). If you mistakenly plug a 110-volt appliance into a 12-volt outlet the appliance doesn't "see" 110 volts since there is nothing wired to that screw (again, nothing happens).
> 
> I wired a neighbor's house with both 110-volt AC (inverter) and 12-volt DC outlets right next to each other. When workmen came to plug in a drill or saw sometimes their tools didn't work. She just had to tell them to try the neighboring outlet and all was well.


 You are inviting multiple disasters with what you are doing. First of all using standard outlets and wiring for 12vdc, current wise you are limiting your voltage at the outlets, current drop will be tremendous with that size wiring. 
Secondly you are setting yourself up for a very bad lawsuit wiring your neighbors house that way. Doing it for yourself is one thing, doing for others is asking for trouble.
By the way I also live off the grid with battery back-up, 30-T105 and 10 AGM battery bank, have so for over 6 years and about 4 years grid-tied in previous home. I have wired my house when it was built for 12vdc but did not use standard outlets.


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## Walker

Sorry you feel that way about it Bunkerbob but this option has been working very well in the 12-volt homes in my neighborhood for over 20 years. Before that people were blowing up lights and TVs.

I never mentioned wire sizes in my post so to assume that I'm "limiting my voltage at the outlets" and causing "tremendous voltage drop" is pretty reactive. Obviously with a 20-amp outlet you're limited to around 250 watts at 12 volts. Above that point maybe you should consider some other sort of connection. The folks around here are plugging in small 12-volt loads, not 1-horse motors. Both wire runs and outlets have to be sized by length and load.

In terms of law vs. what works well I'll always side with what works. The NEC rules are good at preventing fires so I stick to standard ampacity tables for all the wire runs, but I draw the line at unnecessary expense and excessively rigid standards that only function to make everything look the same.

And I work with my neighbors, not for them, so they are aware of how and why something is wired a certain way and what the limitations are. Some have used different colored faceplates for AC and DC, or even labeled the covers, but it's really unnecessary, except if they want a reminder of what's what.

In other words, relax


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## bunkerbob

Walker said:


> Sorry you feel that way about it Bunkerbob but this option has been working very well in the 12-volt homes in my neighborhood for over 20 years. Before that people were blowing up lights and TVs.
> 
> I never mentioned wire sizes in my post so to assume that I'm "limiting my voltage at the outlets" and causing "tremendous voltage drop" is pretty reactive. Obviously with a 20-amp outlet you're limited to around 250 watts at 12 volts. Above that point maybe you should consider some other sort of connection. The folks around here are plugging in small 12-volt loads, not 1-horse motors. Both wire runs and outlets have to be sized by length and load.
> 
> In terms of law vs. what works well I'll always side with what works. The NEC rules are good at preventing fires so I stick to standard ampacity tables for all the wire runs, but I draw the line at unnecessary expense and excessively rigid standards that only function to make everything look the same.
> 
> And I work with my neighbors, not for them, so they are aware of how and why something is wired a certain way and what the limitations are. Some have used different colored faceplates for AC and DC, or even labeled the covers, but it's really unnecessary, except if they want a reminder of what's what.
> 
> In other words, relax


Sorry, relaxing is like throwing caution into the wind.
And I hope these circuits are fuse protected as well.
Neighbors are friends until they have had a catastrophe such as a fire from your work and recommendations, just be cautious.


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