12 Volt Outlet Wire Question

[S. Heisley]

I have an outlet that has a travel path slightly exceeding the length limits for using #12 AWG wire, making it on the “iffyâ€

[Ageless]

The question I have is what do you plan to run from that plug? 10 guage is normally used for high amp requirements and most 12V plug in units don't draw that much.

[eamarquardt]

The question I have is what do you plan to run from that plug? 10 guage is normally used for high amp requirements and most 12V plug in units don't draw that much.

Yup, I have the same question. I think, in general, a lot of the wiring installed in teardrops is oversized for the actual requirements. Granted there are some subtle differences between 12 volt circuits and 120 volt circuits but 12 gauge is used to carry 20 amps in houses (120 volt) for lot longer distances than in any teardrop.

A sketch or list of what you plan to run off the circuit you're working on would be helpful. A good rule of thumb is that the wiring should be pretty close to the same size for it's entire run. You can get away with a short run of smaller gauge wire so using a larger wire for the long run and a short "jumper" is appropriate at times but connecting a ten gauge to an eighteen gauge seems to go beyond this approach.

Note: The problem with all "rules of thumb" is that there are 4 other fingers! There are always exceptions to a "rule of thumb".

You are right to be concerned about overheating a wire and causing a fire but all circuits should have circuit breakers or fuses installed close to the battery. You might, carefully, deliberately short circuit anything you install to verify that the fuse will blow or circuit breaker will trip before any damage is done to the wire (with the attendant danger of a fire). If you test before you "button" everything up, you'll be able to correct it easily. Also, knowing that your fuse or circuit breaker will positively protect your wiring and safety should allow you to put your concerns aside.

Hope this helps.

Cheers,

Gus

[S. Heisley]

It's the distance that was the problem. Although I don't plan to run anything that requires many Amps, nobody really knows what will be developed for 12 Volt plug-ins in the future.

I'm using the table/guide found on page 92 of Managing 12 Volts by Harold Barre to help me with wire sizes. Because of the way I have my trailer wired, that particular circuit run equates to about a 20 foot distance and the outlet is rated for 10 amps, which equates to #10 AWG. To rewire for a shorter route would be tedious and not very neat. I could just change the fuse to a smaller size to protect the wiring just in case; but, what if later on I forget and change it to something bigger or someone else does. I feel safer using the #10. ...Better overkill than dead.

[bobhenry]

You now have a nice heavy duty ground. What is feeding the hot side still 12 gage wire ? A DC electrical circuit is kinda like a chain it also will break at it's weeakest link. That is why fuses are much smaller than the wire. That little fuse heats up after arriving at the rated overage and self destructs to save the wireing. Put your fuse in line on the hot ( positive ) side and rest easy.

[S. Heisley]

But, since that little piece of #18 wire flew off to 'never-never land', possibly to disappear forever, my question still remains: Am I okay by simply hooking the #10 or #12 negative wire directly to the paddle of the 12Volt outlet?

....and if the answer is 'yes', why do the manufacturers bother to give us that little bit of specially-fitted wire?

[Miriam C.]

My opinion only and I know I might get jumped for it but you don't need your wire capacity to exceed your receptacle capacity. At least not in a small camper. I switched my 18avg for some 12 and it was fine. Probably didn't need better than a 14avg.

And without seeing the thing I would say yes. As long as you are wiring to and from the same place. Neg to Neg and Pos to Pos.

[S. Heisley]

Thanks to all of you for your kindness in replying. I'll see if I can get a pic of what I'm talking about.

[S. Heisley]

I went out to the garage and took pictures. This first one came out fuzzy but you can still see. This is the one that the question is about:



This next pic is of one that is using the extra little neg. wire piece sent by the manufacturer:



PS. Don’t be alarmed at the colored elect. tape…it is only being used to identify the line that the unit is on. Every line is color-matched with electrical tape, for easy identification. (Yes, I've been accused of being 'anal retentive' at times. )

[danlott]

I think the wiring is fine in the first picture. As a matter of fact I would rewire the socket in the second picture to match the wiring in the first picture. There is no need for the smaller wire. I would assume that you have fuse protection at the other end of the wire. You should not be able to draw more amps than the fuse will allow.

Dan

[S. Heisley]

Thanks, Dan. I agree that it is neater without the little factory wire. I just don't understand why the factory does that if it isn't necessary. If I can find their phone number, I might call them and ask. (...Don't know why I didn't think to do that before.)

[Miriam C.]

Thanks, Dan. I agree that it is neater without the little factory wire. I just don't understand why the factory does that if it isn't necessary. If I can find their phone number, I might call them and ask. (...Don't know why I didn't think to do that before.)

You can go to the store and buy some paddles that fit the post and wire direct with your wire. That will make fixes and stuff easier. The factory includes the extra wire to make buying a paddle unnecessary.....

[S. Heisley]

MiriamC wrote:

The factory includes the extra wire to make buying a paddle unnecessary.....

That's a possibility but most companies, nowadays, don't do anymore than they have to, profit margins to consider and all.

I'm going to go out on a limb and propose a theory that I think might be the answer:

Electrons move through the wire at a varying speed, depending on the wire size. The smaller the wire, the more they are held back, causing increased resistance, or Ohms. The backlog/resistance caused by the small factory-supplied wire may be put there to help increase the ability of the outlet. Without it, the electrons can move more freely and faster through the circuit, with less resistance. Not having that little wire there may cause the outlet to work less efficiently and deplete more power from the battery, quicker.

Now, I've got to start calling around to see if I'm right; because, if I am, I'm going to need to either get down on my hands and knees and find that little wire or I'll need to make a small replacement for it!

[Ageless]

Not quite. Your assumptions would apply to water running thru a hose (being 'pushed' by pressure. With electricity, you might have available 'pressure' of 100 amp/hours, but if the appliance only requires 4 amps; then that is what it will 'pull'

Which is why I asked what you were going to power. If your appliance is only going to 'pull' 4 amps; smaller wire will work. You will only run into resistance "IF" you try pulling 10 amps thru that little wire. Resistance is 'heat' which is why all curcuits must be fused. Since you have the larger wire already; ditch the small wire. BTW, unless you solder each connection; there is resistance at each crimp fitting or when wires are just twisted together.

[S. Heisley]

Thanks, Ageless. That being the case, I should be just fine.

However, while you were posting an answer, I was posting a question to the manufacturer, referring them to this thread. It will be interesting to see what their answer is, if they respond.