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Author Topic: Romex  (Read 3873 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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« 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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« 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
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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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« 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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« Reply #11 on: February 03, 2010, 06:05:21 PM »

what is thhn ?
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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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« 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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« Reply #15 on: February 03, 2010, 09:27:59 PM »

My conversion was done in 1979 and PO did it with "Romex" (NM for the 120v stuff, stranded for 12v). Thirty-one years later and it still looks good. The only thing I don't like is that it is hard to snake around in the tight RV spaces.
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« Reply #16 on: February 04, 2010, 09:23:37 AM »

FWIW, I wired a service pole for power down at my bus gravel pad, and had used Romex to the outlets. Inspector turned it down at first because of the paper in the Romex. Romex no longer passes electrical code in North Carolina. I removed the paper and called him back, passed. I guess the paper is now considered a fire hazard.

My bus is wired with Romex for the high voltage stuff.
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« Reply #17 on: February 04, 2010, 10:26:29 AM »

The NEC is the basis for most state and local authorities but they may make the rules more strict if they wish.  Now, as for prohibiting type NM where it is otherwise accepted by the NEC seems a bit of overkill to me.

If you left the paper on the ground wire in the box or panel, that is generally not done.  I can't imagine why the inspector would not have allowed you to correct that on the spot, couldn't have taken more that a minute.  Do they charge more for a return trip?  That might explain it.
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« Reply #18 on: February 04, 2010, 11:32:40 AM »

I have only been involved in the bus conversion for about the past 12 years (very few years compaired to some of the fellas).

This sold vs. stranded wire issue was being "discussed" when I came aboard.  Don't know if it will EVER really be "settled".

We all have our freedom of choice to do it "our way", which of course is a good thing !!

Chris
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« Reply #19 on: February 04, 2010, 11:44:45 AM »

We all have our freedom of choice to do it "our way", which of course is a good thing !!

Chris

And your point is?

God bless,

John
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« Reply #20 on: February 04, 2010, 02:31:34 PM »

Sean,
        I'm sure this subject has been serviced before but why not talk about it again. What is the do's & don'ts to using extension cord wires for your 120 AC like your lighting & plug outlet circuits? It is stranded. It is incased. It is rated for certain amperages based on the quality of cord you buy. They surely are made to take a bit of abuse. Sometimes you can catch them on a real good sale. Admittedly I haven't compared price per foot but anyway what ya think? Roll Eyes
     
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« Reply #21 on: February 04, 2010, 02:59:43 PM »

... I'm sure this subject has been serviced before but why not talk about it again. What is the do's & don'ts to using extension cord wires for your 120 AC like your lighting & plug outlet circuits?     


Extremely dangerous, and also illegal.  I discussed this in more depth here:
http://www.busconversions.com/bbs/index.php?topic=8102.msg80357#msg80357

I also wrote this, on "another board":

When you ask "why" extension cords are not to be used, I assume you are asking why the code (and the cord's manufacturer) prohibits this.

The simple answer is that extension cords are made for temporary use, not covered by or enclosed in any other material. Consequently, the cords are designed so that any heating of the conductors is transmitted through the insulating materials into free air, where the heat is dissipated.

By installing an extension cord within a wall, or even covering it with, say, a rug, you have changed the conditions away from those for which the cord was designed and rated. This can result in insulation melting, conductors shorting, paper fillers (yes, paper is found in some cords) to smolder or catch fire, and insulating materials to out-gas toxins.

I will also point out that once you cut the ends off an extension cord, it is no longer an extension cord. Now it's just cord, and it's allowable uses are determined by the type and rating of the cord itself. Many heavy-duty or "contractor grade" extension cords are made from type SJ cord, which is known as "junior hard service" cord. You are certainly free to use this anywhere type SJ is permitted.

Fixed wiring inside of walls, floors, and the like, even when enclosed in rated conduit, is not a permitted use of SJ cable. In fact, there are a limited number of types of cables and assemblies allowed for this use, such as types NM, AC, and MC cable, as well as a variety of thermoplastic wire enclosed in various conduits.

You can read that entire thread here:
http://www.busnut.com/bbs/messages/11/29229.html

I also discussed pontificated on the topic here:
http://www.busnut.com/bbs/messages/11/28863.html

-Sean
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« Reply #22 on: February 04, 2010, 04:06:08 PM »

The problem is that we who are uneducated in this science, tend to look at a wire and see wire.  We generally think we're pretty good because we know the differences in wire gauge.  Hence, since 12 extension cord looks and smells like other 12 gauge wire, we find it hard to accept that it is not equal.  Although I still have doubts, I feel most comfortable listening to someone who knows a lot more about this stuff than I.

My original question was not meant to start the same questions and debates we have seen before, but just to see if it mattered about using my old Romex stock for low voltage.  It seems that there is nothing inherently dangerous about that other than creating confusion about which runs are high and which are low voltage.  That seems significant enough for me.  That, and the realization that the Romex is really a 2+1 set up rather than 3 usable wires.  This increases the sloppiness of concept that much more.  Since it is low voltage, I would not feel bad about using extension cord.  Correct me if wrong, but there is no danger there, and since I will not use extension cord for 120 volts, there is little chance of confusion.  However, the only reason to use extension cord inside the condenser piping would be that it is cheap.  I have just spoken to a local electrical supply shop.  They sell stranded 12 gauge wire in assorted colors for 18cents/foot, so there is no real financial incentive to using extension cord for even low voltage.  I would however, consider using it in a less protected, dedicated run.
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« Reply #23 on: February 04, 2010, 04:36:28 PM »

Thanks Sean,
                  I'm not far from the elctrical part of my conversion so this has been very helpful. Looking forward to doing things right.
John
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John Mellis
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« Reply #24 on: February 04, 2010, 06:31:44 PM »

...  Since it is low voltage, I would not feel bad about using extension cord.  Correct me if wrong, but there is no danger there, and since I will not use extension cord for 120 volts, there is little chance of confusion.  ...


"Automotive" circuits of less than 30 volts are not covered by the NEC, and therefore the code has nothing to say about what wire can or can not be used.  There are other standards, including those published by the SAE, for specific circuits dedicated to vehicle operation, and I can not speak authoritatively on those since I do not have a copy. 

RV house circuits under 30 volts generally are covered by ANSI/RVIA 12V, “Low Voltage Systems in Conversion and Recreational Vehicles.”  I confess I do not have a copy of this standard and so I can not speak to whether type SJ cable (what most contractor-style cords are made from) in an appropriate gauge is or is not permitted for these circuits.  ANSI/RVIA 12V is incorporated by reference into NFPA 1192 and is therefore mandatory code in any state that has adopted 1192.  To the best of my knowledge, most wire and cable types found in the NEC are allowed, and that would include SJ.

Not that it's relevant here, but there are, in fact, low-voltage systems that are covered by the NEC and must use appropriately rated cables.  These include communications systems (covered in Chapter Cool, as well as fire alarms, emergency systems, and other signaling applications (covered in Chapter 7).  I suppose one could make the case that if you were to install a telephone system in your bus, it would need to use the proper cable.

-Sean
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« Reply #25 on: February 04, 2010, 08:35:31 PM »

Doesn't the amp load heat the conductor - NOT the voltage?

So,
Amp load determines wire size.
Voltage & environment determine the insulation.

When insulation fails, a short circut is more likely.
All the more reason to use wire with the appropriate insulation. Things don't usually go well when the insulation fails.
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« Reply #26 on: February 05, 2010, 02:26:42 AM »

Kyle it's more correctly the resistance that provides the "heat" - SJ cord (or equivalents) should NEVER be used in any "enclosed" environment - NO IFS ANDS OR BUTS - PERIOD! END OF STATEMENT!

Specifically loads such as coffee pots and electric heaters among others will push SJ, et.al to or above their design limits, and encasing them in any way would eliminate their ability to dissipate the heat generated by such a resistant load - Not any radical science here - Simple "magic" for all the disbelievers - here's the rules for the rest of you (no NEC for the code naysayers)

http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_id=9882&p_table=STANDARDS
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