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Author Topic: Romex  (Read 3974 times)
Lin
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« on: February 03, 2010, 11:20:47 AM »

I plan to run future use wires from the front to back of the bus by threading them through the old condenser piping.  I was going to buy some stranded wire, but have a lot of #12 romex.  My thought now is that, since the wire will be in enclosed pipe, this should be okay.  What say you?
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« Reply #1 on: February 03, 2010, 11:52:30 AM »

Enclosed wires are good, in fact, you could strip the outer cover and just use the actual wires (black and white and red?) running inside the pipe. That would give you room for a few more wires. Once they are pulled in, it may be difficult to add more, so pull a few extra, if you can, for later.
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« Reply #2 on: February 03, 2010, 12:31:30 PM »

We don't use solid Romex for one simple reason. From what I have heard, the solid Romex isn't good in a moving application, because it can get brittle and break. Who knows if it would happen in the life of our buses? But, we didn't risk it. We used stranded, because the stranded tends to be just fine, over the years (from what I understand).

Not to mention, the creeping death Wink.

God bless,

John
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Lin
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« Reply #3 on: February 03, 2010, 12:57:11 PM »

I just wanted to clarify one thing.  The wiring would probably end up being used for 24 and 12 volt.  Does that make a difference?
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« Reply #4 on: February 03, 2010, 01:16:41 PM »

I was just about to ask what the application was, and I personally wouldn't use Romex for low voltage applications like that.  I'd pull through some stranded wire, a selection from 10 ga to 16 ga.  In fact, I'm going to do the same thing in the spring.  Now, what I don't know is the best type of wire to use.  That stranded marine wire looks good for that, but I don't know all the facts about wire rating in conduit, which is what this amounts to.

Brian
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« Reply #5 on: February 03, 2010, 01:35:13 PM »

Stranded marine wire is a very expensive way to go. A 500 foot roll cost almost 900 at a marine supply. I got it for 150 due to store closing.I did read on a previous post that marine wire was not acceptable by code,but am not sure why. I am still using it in my coach. It is tinned and will resist corrosion in the worst conditions.

mike
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belfert
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« Reply #6 on: February 03, 2010, 01:56:29 PM »

Stranded marine wire is a very expensive way to go. A 500 foot roll cost almost 900 at a marine supply. I got it for 150 due to store closing.I did read on a previous post that marine wire was not acceptable by code,but am not sure why. I am still using it in my coach. It is tinned and will resist corrosion in the worst conditions.

Nothing says you can't use marine wire for low voltage usage.  If not properly supported the fine strands can potentially break off.  The problem with marine wire for regular 120/240 volt AC is it has not been tested to the proper standards to meet code for RV use.

$900 for 500 feet is probably a ripoff unless it is a very large gauge.
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Sean
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« Reply #7 on: February 03, 2010, 02:14:21 PM »

I just wanted to clarify one thing.  The wiring would probably end up being used for 24 and 12 volt.  Does that make a difference?


Lin, I would advise against using type NM cable (Romex is actually a brand name, for type NM made by Rome Cable) in a low voltage application.  The principle reason is that it can too easily be confused with high voltage runs; you would not want the possibility of accidentally connecting the two systems, or of someone cutting into a high voltage cable thinking it was low voltage.

Beyond that, most low voltage applications in a conversion will require crimp terminals or compression connections -- few things will have the proper screw posts for #12 solid wire.

I agree with Brian; get a couple spools of stranded wire for this purpose.  I also recommend the DIN color convention of using Brown for ground wires, other colors for hots, and avoid black if at all possible.

We don't use solid Romex for one simple reason. From what I have heard, the solid Romex isn't good in a moving application, because it can get brittle and break.


I hear this all the time.  Yet in nearly two decades of working on RVs, I have never, ever seen it happen.  Moreover, I have challenged this board (and the other one) to show me even one single case of properly installed and supported solid wire in a conversion suffering a stress failure.  (Note that properly installed implies that solid wire can not be used for certain applications; for example, the connection from the generator to the coach junction must be stranded.)

By contrast, I've had no fewer than three stranded wires in my coach fail in less than five years, because the contractor soldered in places where they shouldn't have.

All that said, my own preference is for stranded as well, as I find it easier to install.  For low voltage, pretty much anything can be used, with "automotive primary wire" and "bell wire" being two common types.  For high voltage, THHN is an approved type that is inexpensive and available at most home stores.

Enclosed wires are good, in fact, you could strip the outer cover and just use the actual wires (black and white and red?) running inside the pipe. ...


I don't have a problem with this for low voltage, but you are not permitted to strip the individual wires out of NM cable and use them separately for high voltage unless the wires themselves are individually marked for that purpose.

Stranded marine wire is a very expensive way to go. A 500 foot roll cost almost 900 at a marine supply.


Marine wire is expensive just because it is marine wire, in the same way that, for example, RV faucets are more expensive than household faucets of similar design, just because they are for the RV market.  It's a result of supply and demand, as well as manufacturing quantities, more than a consequence of it being fundamentally "better" or utilizing more expensive materials.  In part, you are paying for the listing.  Since it is not required, I would not personally choose to pay the premium for the marine listing.

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... not acceptable by code,but am not sure why. I am still using it in my coach. It is tinned and will resist corrosion in the worst conditions.


To clarify, you no doubt heard this in regard to high voltage systems.  For low voltage, almost anything is acceptable.

Even for high voltage, it is not the case that marine wire is not acceptable by code.  What is the case is that the code says wire used in a coach must be listed to one of several standards that are permitted for that use.

Marine cable certainly can be listed to those standards.  However, listing costs money, and AFAIK, no manufacturer of cable for the marine market has chosen to submit their product to listing agencies for the land-based market.  There's no point, since almost no one will pay the marine premium for wire when it is not required.

FWIW, this discussion has come up here many times in the past; just do a search on "boat cable".  It is a very contentious subject, so much so that I wrote an article on it for the magazine several years ago.

-Sean
http://OurOdyssey.BlogSpot.com
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Lin
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« Reply #8 on: February 03, 2010, 03:06:08 PM »

Thanks for the input.  The possibility of creating confusion between high and low voltage wiring is something to seriously consider.
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« Reply #9 on: February 03, 2010, 05:18:33 PM »

Thanks Sean,
    I  do believe cost is a major reason marine wire is not used.  That being said,one of the reasons I do like it though ,is that it is extremely flexible and much easier to work with.
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belfert
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« Reply #10 on: February 03, 2010, 05:52:47 PM »

I  do believe cost is a major reason marine wire is not used.  That being said,one of the reasons I do like it though ,is that it is extremely flexible and much easier to work with.

RV manufacturers certainly won't use it due to cost as code allows it for cheaper options.  Right now, they can't use marine wire because it doesn't meet code, but a wire manufacturer would probably get marine wire properly UL listed if they thought there was a large enough market.

I choose to use marine wire for the 120 volt wiring in my conversion even with the higher cost, but I am now going to be pulling it all out and starting over with THHN at some point.  I mistakenly thought since marine wire is UL listed that it would be fine.  The problem is that it is not UL listed in the right category for RV use.
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Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
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« Reply #11 on: February 03, 2010, 06:05:21 PM »

what is thhn ?
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James77MCI8
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« Reply #12 on: February 03, 2010, 06:23:34 PM »

Thermoplastic High Heat-resistant Nylon-coated suitable for dry and damp locations and up to 600 volts
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« Reply #13 on: February 03, 2010, 06:30:23 PM »

In the USA, THHN is sold on spools or by the foot in just about every hardware store and home improvement center.

It is a single conductor wire available in solid or stranded, but stranded should be used in an RV.  It must be placed in a conduit when used for 120 and 240 volt AC wiring.  A standard 120 volt circuit will use three seperate strands of THHN wire.  One ground, one hot, and one neutral.  Blue plastic conduit (ENT) can be used and it is pretty inexpensive.
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Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
James77MCI8
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« Reply #14 on: February 03, 2010, 06:38:58 PM »

500 ft rolls of 12 guage is about 47.00 per roll at Consolidated Electrical Distrubutors
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