Please help me decipher the National Electric Code for RVs

[belfert]

Ok, so a friend brought over a copy of the 2008 NEC.  He even flagged the page where the RV section starts.

I'm still confused about materials to be used in an RV.  The Materials and Equipment page says "Electrical materials, devices, appliances, fittings, and other equipment installed in, intended for use in, or attached to to the recreational vehicles shall be listed."

Huh?  How is one supposed to know if a particular item is listed for use in an RV?  Does one have to check the UL listing for every possible item they want to put in an RV?

[Len Silva]

There is nothing different used in RV wiring that in regular home or commercial wiring.  Article 551, the section on RV's deals mostly with the differences or special conditions found in RV's.  There is very little difference from normal house wiring.

It does address situations like the location and length of the power supply cable, generator compartments, isolated neutral and proper labels.

You cannot just isolate that section of the code without being familiar with all other sections.  T

The part you may be most interested in is 551-47 Wiring methods which talks about the types of wiring systems that are acceptable.  Metal conduit, non-metallic conduit, Type MC cable, type MI, Type AC and type NM are all acceptable.

I am working from a 1990 code book so there may be changes that Sean will point out.

Len

[gumpy]

Brian,

Can you scan the RV section of the NEC and send it to me?  I've never actually seen it. Might be interesting reading.

craig

[belfert]

Sorry Craig, no scanner.  I could probably get ahold of the book again if you want to look at it.  I don't know that I will make next weekend.  I might still be working on the bus next weekend at the rate things are going.

[Gary '79 5C]

Gumpy,

I will try to remember for Monday, I just received the latest NEC code book, working on getting current with ArcFlash requirements.

I will look for the RV section.

Remind me.

Gary

[gumpy]

Gumpy,

I will try to remember for Monday, I just received the latest NEC code book, working on getting current with ArcFlash requirements.

I will look for the RV section.

Remind me.

Gary

Thanks Gary.

[belfert]

There is nothing different used in RV wiring that in regular home or commercial wiring.  Article 551, the section on RV's deals mostly with the differences or special conditions found in RV's.  There is very little difference from normal house wiring.

You're right, there isn't much difference from home wiring, but I wouldn't use solid wire in an RV.  I'm trying to determine why boat cable is not allowed.  The only thing I can see would be the issue of being listed for use in an RV.  Everything I have read indicates solid or stranded wire is allowed.

The part you may be most interested in is 551-47 Wiring methods which talks about the types of wiring systems that are acceptable.  Metal conduit, non-metallic conduit, Type MC cable, type MI, Type AC and type NM are all acceptable.

Section 551-47 has been changed to refer to about a dozen other sections for types of wiring systems allowed.  Basically, just about anything that can be used in a house is okay in an RV.  It says any of the wiring systems may used as specified unless an exception is listed in section 551.

[Sean]

I have the 2008 code in electronic format.

The reason "boat cable" is not allowed is because it is not one of the wiring methods listed that is allowed.  Those methods are very clearly spelled out in the code.  FWIW, it's not allowed in a house or a business, either.

Again, for it to be allowable under the code, it would have to be listed and marked as one of the allowable types, such as Type NM.  If you have boat cable that is so marked, it would be fine to use.  It's not the fact that it's "boat cable" that makes it disallowed -- it's the fact that it is not NM (or any other allowable type).

The reason why boat cable is not so marked is because the manufacturers of such cable have chosen not to mark it that way.  Having the cable tested to standards, even if you are certain it will pass, costs real money; money they will never recover from you and me.

Note that part of the testing for such cables, and included in the listing requirements, is a section wherein the connection to devices is specified and tested.  Boat cable would fail mechanical connection testing without first using crimp connectors (which are mandatory, BTW, on boats), and so if any cable manufacturer wanted to have their boat cable listed, it would have to be stipulated which mechanical connections were allowed in order to make a compliant installation.

-Sean
http://OurOdyssey.BlogSpot.com

[belfert]

To be clear, I am not disputing that boat cable is not allowed.  I am just trying to understand why not.  It appears why not is it is not labeled as NM cable.  I looked at some of my boat cable and it is indeed labled as boat cable with no NM marking.

I assumed any wire labeled as THHN will work in a conduit, correct?

Sean, what type of wire is used in your bus?

[Sean]

I assumed any wire labeled as THHN will work in a conduit, correct?

Yes.

Sean, what type of wire is used in your bus?

Most of my circuits are run with Type AC (armored cable).  This is similar to NM in that it is a complete assembly with hot, neutral, and ground, but instead of a thermoplastic sheath it is enclosed in flexible metal jacket.  I prefer this to NM, when possible, because it provides more protection for the conductors.  Note that this is mostly solid conductor; when properly installed and secured, I see no problem using solid conductors in a coach.

My larger circuits, such as from the shore inlet to the ATS, generator to ATS, ATS to inverter, and inverter to main panels, are all THHN in liquidtight flexible conduit.

Some of the specialized stuff I built, such as some of the ATS wiring and the HVAC controls, are inside enclosures and done with AWM.

-Sean
http://OurOdyssey.BlogSpot.com

[Hartley]

I saw an early travel trailer once that had a fire. Found out that the Manufacturer
had wired it with aluminum wire so save weight and money.

Some old mobile homes were also wired with aluminum 14 gaugeor 12 gauge romex.

I use stranded automotive wire for low voltage stuff and 12-2 NM and 10-2 NM for most everything and have had no issues with mechanical failures.

The armorflex works too if you have the tools and patience but doesn't like being kinked and where I have used it I usually left a blood trail a blind CSI could follow.

THHN works if you do it right in conduit or flexible conduit. Just have to watch that you limit any movement of the wire where you attach or splice it. There are so few strands that they can work harden and break if vibrated too much.

Thanks for Watching...

Dave...