Adding a 12 volt power point

[fdwrench]

Hello,
I am working on my Outdoors TT. I would like to add a 12 volt power point. I can get 12 volts at the battery switch easy but am having a hard time finding a decent ground without making holes in the floor. There is a 120 outlet very close.
Is there any reason I could not tie into the ground at the outlet? I believe that it goes straight to the frame.
Thank you
Ed

[F1bNorm]

The previous owner of my RV added several 12v power plugs by tapping into the light housings before the switch. Both ground and hot are there because the lights are mounted on wood cabinets. He used a Molex plug which is much smaller than the standard cig lighter type.
We find it very handy for charging devices, portable fans, lights etc.

Norm

[TomG2]

budwich wrote:

TomG2 wrote:
Some of these answers remind me of the old "knob and tube" house wiring where single lines were interconnected all over the place to save a little copper wiring.

Reminds how those houses are still "in use" today.

Now you know where the original phrase, "Hot wire" came from. It's a wonder there were not more house fires as modern appliances were added to the string.

To the OP: I tied into an unused converter fuse and ground connection to run the two wires to a nearby 12 volt outlet. (#10 twisted wire and 20 amp fuse.)

[budwich]

TomG2 wrote:
Some of these answers remind me of the old "knob and tube" house wiring where single lines were interconnected all over the place to save a little copper wiring.

Reminds how those houses are still "in use" today.

[ezrydrs]

I would have thought 120VAC would use an earth ground from the shore cable. Never saw how it was wired before.

[TomG2]

Some of these answers remind me of the old "knob and tube" house wiring where single lines were interconnected all over the place to save a little copper wiring.

[budwich]

I think you need to ensure that the circuit (AC) in question is not going back to a GFI which you will be tripping if you "mix" the "groundings".

[fdwrench]

Thanks for all the replies,
What I am finding is that because the 120 volt AC common and ground are not connected in a RV the ground is connected to the chassis as is the ground for the 12 volt DC.
It should work fine. "A ground is a ground" The only problem is when I forget why I did it next week.
The reason for the power point is to get power near the bed for my cpap machine. The machine pulls 2 amps without the humidifier and 5 amps with the humidifier. I will try not to use the humidifier.

Reminds me of a story,
One of our firefighters said that she would get shocked when she got into the engine at the station. None of the other firefighters complained about it. I went to the station and got into the engine and nothing. Asked for her to come out and show me. She walks out in her stocking feet. So the diagnostician that I am I took one boot off and grabbed the handle. Yes she she was not lying. We found an open ground at the shore line connector.

Ed

[Chuck_and_Di]

A ground is a ground, however the 12 V supply typically has much higher currents so the wire size might not be appropriate. But the best reason to not do this is that it contravenes code. If there is ever a fire, even if you are sure it has nothing to do with wiring, your insurance may not cover you. For a couple bucks worth of wire and drilling 1 hole, why risk it? Also do yourself a favor and run the 12V return to either the ground window or the actual battery, not the frame or you'll be messing with it a couple times per season for as long as you own the camper.

[budwich]

?

120v shorts to the same ground whether its at the box or back at the terminal strip, if you look at the posted diagram.... a ground is a ground.

[westend]

Connecting a 12V (-) phase wire to a 120 V AC receptacle ground opens the possibility of a 120 V device shorting to ground and putting 120 V AC on the (-) phase of the 12 v circuit. That is not a good thing.

Any connection to frame or the battery negative, either directly or through the (-) phase wiring in the 12V distribution panel is what you need.

An alternative is to connect to (-) at another 12 V device but since you may be using this power port with devices that draw significant current, you would have to make sure the originally wired 12 V device has sufficient wire size for both that device and the device powered by the new power port. In most cases, that will not be true. Better to wire directly to frame or battery negative.

[TUCQUALA]

I put a 12V socket just under the edge of the kitchen counter. Tied into the LP/CO detector wiring just below near the floor. Possibly just need to pull a drawer out and find the wires going to the detector. Should be at least 16ga wire there, possibly larger.

[RoyB]

All of my 12VDC items that is controlled by the 12VDC Power Distribution Panel has two wires running to it usually from a 2-conductor marine grade cable. The Black wire is positive +12VDC and the White wire is negative -12VDC. Nothing that these DC cables control need to go to the actual trailer frame ground. Both the positive 12VDC and the negative 12VDC leads are terminated at the 12VDC Power Distribution panel where the fuses are located.

Mine looks like this


This is another pictorial on using my ON-BOARD Power Distribution Panel for wiring




When I am working with the batteries and battery switches etc then I do run some frame ground DC wiring, This is usually under the trailer or outside on the tongue area or maybe on the basement wall next to the front of the trailer.

My on-board Converter/charger and power distribution panel do have a frame ground cable installed. If I have an optional INVERTER installed inside the trailer than I will run a frame ground cable to it as well.

The point I am bringing here is all of the inside DC appliances and the lights etc all have a 2-conductor cable feeding them that is carrying both + and - 12VDC wires.

Just the high current paths around the battery banks may use the frame ground as an conductor...

This is the way my OFF-ROAD POPUP camper is wired at any rate...

Roy Ken

[CavemanCharlie]

donn0128 wrote:
You cannot mix voltages. Do not do it!!!!!!
Your far better off drilling holes to run dedicated 12VDC.
Remember, you need to complete the 12VDV circuit to have it work.

X2 !!!!

[budwich]

Interesting, I haven't closely at the AC versus DC wiring on trailers... but I am not sure why a ground isn't a ground for either systems. I think you just have to make sure that the ground is indeed a ground and NOT the neutral.