Problems with 12 V and 110 in Same Conduit?

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Problems with 12 V and 110 in Same Conduit?

Postby GrundgeDog » Tue Feb 17, 2009 4:26 pm

I am wiring my teardrop and need to run both 12 volt and 110 from the rear of the trailer to the front. In an effort to keep the wires out of the elements, I am running the line under the tear enclosed in EMT conduit. An electronics guy here at work tells me I should not put both sets of wires in the same conduit. He says it may mess up electronics by having the wires travel together.

I realize these are two completely different types of electricity and they are completely separate circuits, but has anyone had trouble by placing the wires side by side when running lines somewhere?

There will be a CPAP in there, and eventually there may be a laptop or a radio.

Whadya think?

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Postby planovet » Tue Feb 17, 2009 4:39 pm

I've read comments here previously that recommend against putting them in the same conduit. I can't find the specific threads right now but I'm sure someone with more knowledge will speak up.
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Postby Miriam C. » Tue Feb 17, 2009 4:53 pm

:( :thumbdown: You should never run 12vdc and 120vAC together. If you have a short for any reason the you could have 120vAC flowing through the 12vDC. Bad Bad Bad! Not only are you risking a fire but electrocution.

Not only would I run them in different conduit, I would mark the conduit and put it on different sides. Electrical mistakes are rarely forgiving. :?
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Postby Mr shorty » Tue Feb 17, 2009 7:18 pm

The biggest problem I see would be after time the wires would rub through from road vibration and such... then it would most certainly be ugly.
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Postby Greg M » Tue Feb 17, 2009 7:37 pm

It's also against the electrical code. The insulation on the 12 volt wire isn't rated for the voltages that household wire can carry. If the 120 volt conductor becomes exposed it could, theoretically, arc through into the 12 volt wiring. Then bad things happen, and all the smoke comes out of your stuff.

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Postby caseydog » Tue Feb 17, 2009 7:47 pm

Miriam C. wrote::( :thumbdown: You should never run 12vdc and 120vAC together. If you have a short for any reason the you could have 120vAC flowing through the 12vDC. Bad Bad Bad! Not only are you risking a fire but electrocution.

Not only would I run them in different conduit, I would mark the conduit and put it on different sides. Electrical mistakes are rarely forgiving. :?


I have seen what happens when Low Vot DC gets crossed up with 110C-AC -- nobody got hurt, but a very expensive piece of audio equipment died -- it's last sounds were something like, "zzzzzzzap-pooof," followed by a nice puff of white smoke.

I don't even want to mix 110 and 12V in the same trailer. I'm kind of over careful with that kind of stuff.
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Postby caseydog » Tue Feb 17, 2009 7:48 pm

WOW! A triple post. Do I get a prize for that?

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Postby starleen2 » Tue Feb 17, 2009 7:49 pm

There will be some that have done it with no problems, however, that doesn't mean it's right - i prefer to keep things separate to eliminate the possibility of problems -electricity is so silent until it strikes - you wouldn't run drinking water and sewer water in the same pipe - would you? :thumbdown:
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Bad idea

Postby ssrjim » Tue Feb 17, 2009 8:04 pm

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Postby brian_bp » Tue Feb 17, 2009 8:06 pm

Greg M wrote:...Then bad things happen, and all the smoke comes out of your stuff.

... and we know that it's the smoke that makes the stuff work, so you should never let it out! :lol:

The electronics guy's reason to avoid 120V AC and low-voltage DC wiring so close together is that all the wires act like antennas, and the DC wiring can pick up a 60 Hz "hum" from the AC wiring, which can go through some equipment power supplies can cause problems. My guess is that this is probably not a big deal anymore, but I don't know about that CPAP machine.

There is also a chance for confusion if you have a colour code system for AC (normally white=neutral, black=hot, red=alternate hot), and one for DC (in trailers this is commonly white=neutral, black=+12V, but sometimes is black=neutral and red=+12V)... the wrong wires can get connected together, since we're all just human. Keeping the two systems physically separate reduces the opportunities for thos unforgiving examples of Murphy's Law to take effect.

starleen2 wrote:There will be some that have done it with no problems, however, that doesn't mean it's right - i prefer to keep things separate to eliminate the possibility of problems -electricity is so silent until it strikes - you wouldn't run drinking water and sewer water in the same pipe - would you? :thumbdown:

Well, it's not really the same pipe we're talking about here, but it's like running the drinking water and sewer water pipes side-by-side in the same trench. I agree, this seems like an invitation for unpleasantness.
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Postby bobhenry » Tue Feb 17, 2009 8:09 pm

Greg M wrote:It's also against the electrical code. The insulation on the 12 volt wire isn't rated for the voltages that household wire can carry. If the 120 volt conductor becomes exposed it could, theoretically, arc through into the 12 volt wiring. Then bad things happen, and all the smoke comes out of your stuff.

-Greg


And if you use 120 volt 2 wire extention cord for your DC It should be rated high enough to survive?

I have ran 220 440 660 explosion proof in chemical enviroments and many ran the 120 ac switching circuits in the same conduit. The continued berating of this electrical falicy is a continuing source of amusement to me. I have 120 volt ac and 12 volt dc in the same lamp ficture and they have somehow survived without cremeating me in my sleep for over 2 year. If you have fused the 12 volt dc and the 120 volt ac is protected you will probably survive the night. Let's no scare the kids with these fairytail.

I have built many dual voltage fictures and they continue to serve after 2 years of camping. Just fuse each properly and you will live to tell the tale.

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Postby bobhenry » Tue Feb 17, 2009 8:24 pm

I don't want to scare you but I just converted a Tap- A - Lite to ac - dc- and battery just imagine what will happen when the batteries contact the AC

OH MY GOD !!!


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Postby caseydog » Tue Feb 17, 2009 9:09 pm

If you cool gasoline down to where it doesn't evaporate, you can put out a match in it. Really.

I'm not going to try it, but it can be done. So, maybe we need to kill this myth about matches and gasoline.

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Postby wannabefree » Tue Feb 17, 2009 10:14 pm

Wow! I've just gotta post on this one! I swore off the electrical posts; there are so many expert opinions. But this one I can't resist.

Wires can rub together and insulation wear away whether they carry 110VAC or 12VCD. This is a good reason to run you 110V hot line in a separate conduit from the neutral. And add a third conduit for ground. Plus one for the 12Vplus and and a separate Ground. If you work it right, you can put so much conduit in this trailer you won't need walls!

OK, I apologize for being annoying. My solution was to use good stranded wire with really tough insulation. Ran it wherever I wanted, sometimes 12VDC right next to 110VAC -- and no conduit for any of it. I have fuses and breakers and I will take the chance of blowing out something when the 12V shorts to the 110V, if that ever happens. There are no doubt other solutions just as good; perhaps some better. Mine's good enough for me.
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Postby Greg M » Wed Feb 18, 2009 12:37 am

Hey, all I'm saying is that it's against the code, and why. If I did it that way in my job (alarms, home theatre, networking etc.) I'd have the electrical inspector all over me. Things are in the code for a reason. The likelihood of having a problem may be remote, but is it worth it when following the code is still pretty cheap?

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