12 volt dc queston

[Bob Gil]

I know it has been hashed and rehashed that you should not use extension cord for wiring the AC power in a bus.

But my question can they be used for the 12 DC side of it?  I have several 12-3 and 10-3 100 footers  that are not good for cords any more but would work well for this if it is acceptable.   It would help tell the difference from the ac and dc sides.

Did you use the same type switches as you did for the ac side?  Or did you use some kind of auto or truck type switches?

I don't have any dc power grid at this time any suggestions? 

What did you use for a fuse panel? 

I guess I could see if there is a RV scraper around here and see if I can adapt any thing from there. 

What ever I do it is going to be a chore the person that built this thing did some crazy things, glued the headliner over the power wires and the cabinets have bottoms in them under the drawers where you can't pull them out and work with the stuff that runs under them.  Seams like ever thing has a false bottom to keep you from getting to the back side and under it.

He did a nice job but well over done.  I guess it goes back to each person build to what they are planing on doing with the bus.

Bob

[Len Silva]

I would not use extension cords, not because of any code issues but because some of them tend to deteriorate over a few years.

Switches are rated for AC or DC or both.  DC rated switches are much more rugged that AC, operate faster and have a greater air gap when opened because of the tendency of DC current to arc more than AC.  Typically a dual rated switch might be 10 AMPS AC and maybe 3 AMPS DC.

Use automotive type wire and switches,  search the online surplus places for deals.

[Blacksheep]

Bob on a couple items I used wire that was for underground outdoor lighting like patio lights and such and to me its just like extension cord! I have had no problem!
As for my 12v switches, I used a breaker panel from a boat! Neat and easy!
Ace

[DrivingMissLazy]

I would not use extension cords, not because of any code issues but because some of them tend to deteriorate over a few years.

Switches are rated for AC or DC or both.  DC rated switches are much more rugged that AC, operate faster and have a greater air gap when opened because of the tendency of DC current to arc more than AC.  Typically a dual rated switch might be 10 AMPS AC and maybe 3 AMPS DC.

Use automotive type wire and switches,  search the online surplus places for deals.

My opinion, for what its worth, is that extension cords do not deteriorate over time if they are not out in the elements. The advantage of them is that they are double insulated. The outer insulation covering and then the insulation on the individual conductors.

Richard

[JackConrad]

Bob,
   You said the extension cords were no longer usabale as extension cords, Why?  That may have a bearing on whether they would be OK for DC use.  As far as switches, best to use DC rated switches within the ratings of the switch.  That said, I have used some standard "house type" 120 volt/3 way 20 amp switches.  These switches control a total of 6 amps.  This is much less than their rated 20 amps and are still working fine after 8 years. I would not use 120 volt switches at close to their rated capacity.
   A good source for 12 volt fuse holders, circuit breakers, switches, wire, etc. is WayTek Wire  www.waytekwire.com  I purchased circuit breakers in different amp ratings and ganged them using "buss bar" connector strips.  The breakers are available in automatic or manual reset.  Jack

[Bob Gil]

Bob,
   You said the extension cords were no longer usabale as extension cords, Why?  That may have a bearing on whether they would be OK for DC use. 

Two of the were cut while triming the hedges with an electric trimer and one has a bear spot where it was pulled across a sharp metal edge.

Other have the same kind of problem in them at one place or another.

[DrivingMissLazy]

FWIW, I believe Fred Hobe uses extension cords for all his electrical wiring and he has been doing that for many many years. I feel certain that he would have quit that practice if he ever had any problems with it.

Richard

[PP]

Correct me if I'm wrong, but I think I just read something on Fred's site the other day about buying good extension cords when they're on sale to use for wiring in your bus to save a few bucks, Will

[Bob Gil]

Who is this Fred Hobe that you-all speak of?

Bob

[Brassman]

Extension cords as hard wired are non code. Check the RV wiring code.

You can do what you want (as in non code--but you assume total liability.)

[Nick Badame Refrig/ACC]

Who is this Fred Hobe that you-all speak of?

Bob

Hi Bob,

Fred is a long time member here and own's North Florida bus conversions.
http://users.cwnet.com/~thall/fredhobe.htm

Good Luck
Nick-

[JohnEd]

Len,

Thirty years in electronics and AC wiring and I had not a clue that a DC switch had a faster throw time than a comparable rated AC switch.  Now that you mention it, AC does break the arc at the next voltage null and that never occured to me. 

A long while ago I deduced that a camp trailer had LARGE caps in the wiring system due to the behavior of a VOM on the circuit.  They were there as I predicted and the size of those 24 oz. beer cans and there were six of them wired in parallel.  Arc suppression is the only thing I could come up with.  What do you think?

Thanks,

John

[DrivingMissLazy]

Len,

Thirty years in electronics and AC wiring and I had not a clue that a DC switch had a faster throw time than a comparable rated AC switch.  Now that you mention it, AC does break the arc at the next voltage null and that never occured to me. 

A long while ago I deduced that a camp trailer had LARGE caps in the wiring system due to the behavior of a VOM on the circuit.  They were there as I predicted and the size of those 24 oz. beer cans and there were six of them wired in parallel.  Arc suppression is the only thing I could come up with.  What do you think?

Thanks,

John

I also spent many many years in servicing and building electrical equipment for the regular electrical market place (computer power systems) and for the marine market place (1950-2001). All to UL and/or the applicable marine code requirements (there are several depending on the equipment, the application etc.) 

None of the DC equipment require special DC switches for DC voltage that is under 50 volts dc. Therefore I always used standard AC rated items for anything under 50 vdc.

I also did a lot of work with both 300 vdc and 600 vdc. I can assure that at that level you do not want to use devices that are not rated for that voltage. Please do not ask me how I know. LOL

For the 600 volt equipment it took 50 12 volt batteries in series and we typically would have three or four strings in parallel. With up to 400 batteries in one system you really do not want to ever make an error.

Richard 

[Len Silva]

I stand corrected.  From the Carling Switch website:

Q:    What DC current and voltage will an AC rated switch handle?
A:    The DC current “rule of thumb” holds that the highest amperage rating on the switch should perform satisfactorily up to 30 volts DC. For example, if you have an F Series toggle switch which is rated at 10A 250VAC, 15A 125-250VAC, the DC rating is 15A up to 30VDC.

My background is in telephony which operates at 48 volts DC and switch ratings were critical.  Apparently not so at 12-24 volts.

Len

[JohnEd]

Len and Richard,

Thank you both.  I sure learned somthing and it looks like you did also.  Great place, this.

John

[Bob Gil]

Thanks to all I have got lots of info from this discussion.

Extension cords as hard wired are non code. Check the RV wiring code.

You can do what you want (as in non code--but you assume total liability.)

Where would I find this RV wiring Code that you speak of?

I have not heard of a code for 12 v DC and am unaware if there is one.  That again is the basic reason for this posted question.

Bob Gil

[DrivingMissLazy]

Len, I suspect that the DC telephone voltage was a nominal 48 volts as I recall from many years ago. If in fact that is correct, then the float voltage would be in the 52+ voltage range and all UL requirements would apply.

High voltage DC breakers are very special with a special arc chute and long throws to extinguish the arc. These items are also extremely expensive.

I did develop a procedure for breaking this high DC voltage by using a three pole AC contactor and connecting  all three poles in series so that there were three actual sets of contacts breaking the voltage. I really do not recall if that met UL requirements or not. It did work great and I could interrupt several hundred amps of 600 vdc this way.

Richard

[JackConrad]

Thanks to all I have got lots of info from this discussion.
Where would I find this RV wiring Code that you speak of?
Bob Gil

Bob,
    When referring to extension cord not meeting code, I believe they are referring to code for AC (120/240) wiring. This would be the RV section of the NEC (National Electric Code). There are also several other AC electric codes including a USCG and a couple yacht codes that do not pertain to us.  I am not familiar with any 12 volt code, although it would be very prudent to make sure any load does not exceed the rating of the wire used (amps+ length of wire).  Jack

[Kristinsgrandpa]

For the record, the NEC in article 551, which covers RV's and RV parks, says this about low voltage systems.

 "For information on low voltage systems, refer to NFPA  1192-2002 Standard on Recreational Vehicles and ANSI/RVIA 12V-2002, Standard for low voltage systems in Conversions and Recreational Vehicles"

The NEC no longer covers low voltage systems.
 I haven't seen the new publication yet because my souce (freebies) for new NEC hand books doesn't get the low voltage publication. 

Ed

[DrivingMissLazy]

For the record, the NEC in article 551, which covers RV's and RV parks, says this about low voltage systems.

 "For information on low voltage systems, refer to NFPA  1192-2002 Standard on Recreational Vehicles and ANSI/RVIA 12V-2002, Standard for low voltage systems in Conversions and Recreational Vehicles"

The NEC no longer covers low voltage systems.
 I haven't seen the new publication yet because my souce (freebies) for new NEC hand books doesn't get the low voltage publication. 

Ed

I hope someone has a copy of the NFPA and ANSI/RVIA documents. I think that I have in the past reviewed every publication, including all the marine pubs up to and including LLoyds, and I never found anything discussing low voltage systems. That is not to say that it doesn't exist but if it does I would really like to see it.

Richard

[luvrbus]

If you ever been to a factory where S&S are built I don't believe they have any type codes for 12v and 110v would be questionable.I know the higher end Rv use a aircraft type wiring system all in one harness and I am not crazy about that you burn one wire the whole harness has to be replaced been there, done that                          have a great labor day guys

[Brassman]

When I stated that extension cords as being non-code, that was in reference to the cords listed use as a portable cord (not hard wired). How this relates to 12V service I don't know. The applicable code is ANSI/RVIA 12V Low Voltage System Standard. I don't have this Code, so I was coming from the NEC.

[JeffsMagicBus]

  Hello!
 I could never understand why Fred or anybody would use extension cords of any age to wire anything, ac or dc, in a motor coach! It might be good enough for a schoolie that's used for camping on weekends but I wouldn't do it on any vehicle period. I have an idea! Try going to Home Depot or Lowe's and buying some Romex. You know, wire that is made for the exact purpose. But it's expensive Blah, Blah, Blah...
 Hey people, there's a right way to do something and a wrong way and it takes just as long to do it right as it does to do it wrong. As far as being double insulated big deal! That just means that there's two layers of insulation that will deteriorate due to the heat in the ceiling area instead of a single layer. I had to look twice when I first saw Fred's site as I couldn't believe what I was seeing. I was taught that if a person uses a tool in a manner other than it was intended that's a good way to have an accident. An extension cord is not suitable and should not be used in ANY manner other than it was intended which was to temporarily supply power in an area where none is available. I don't care if Fred does it, or anybody else, it's wrong. Kind of reminds me of the saying our parents used to say when we told them "everybody else is doing it" which they replied: "Would You Jump In A Lake If Everybody Else Did It?" Of course I said it depends on the water depth, temperature, time of year, etc. but you know what I mean.
 What this boils down to is this... Is your coach, family's life, or somebody else's worth doing that just to save a few dollars? I mean Romex is maybe $30.00-$50.00 a box! Big deal!
 I'm sure the multimillion dollar Prevosts have seven miles of extension cords in there...
 Years ago I was working on an old mobile home and had to take some paneling down in the kitchen and to my dismay I found that some moron had wired one of the plugs with zip cord from a lamp! NICE...
 I didn't intend to hurt anybody's feelings but I'm entitled to my opinion especially when I'm right.
 But I'm just a crazy bus guy who glued 8,400 pieces of wood to his ceiling 14 pieces at a time...
                                  Take Care,
                                                   Jeff

http://cid-c6ec323e6ef26dd8.spaces.live.com/default.aspx

[Blacksheep]

Jeff not to dispute your theory but romex is definitely not the right wire to use. I personally would use ext cord if nothing else was availlable over romex.
By the way, I used stranded wire everywhere in the conversion except for a single cord for my water pump which is 12v.
Ace

[JohnEd]

Jeff,

C'mon now. You are among friends and fellow converters here.  Absolutely no need to "sugar coat" every little thing.

I agree with you that using extension cord in not worth the savings.  It amazes me that extension cord is so much cheaper than solid conductor house wire.  I have thrown away a lot of extension cords because the insulation was cracking and I have never seen a modern house wire deteriorate in the same manner...if at all.

I think the original suggestion to use extension cord in the bus was to have spare cables that were color coded to use for 12V apps for meter lines and the such.  That might be OK as i will be dead and gone by the time that meter fails to operate 15 or 20 years down the road.  Another nice aspect is that you can pull new cables through the chase by simply splicing the cables together and "pulling". Whatever you use will work that way.

Extension cords to carry 115 Vac in the walls of a coach?  Really a BOZO idea....in my book.

John

[JohnEd]

And please note that stranded wire is NOT approved for use in RV's according to CODE.   WHUP!   Take that White Man.

And I use stranded for everything myself.   Screw the code on this one.  

John the "mild".

[JackConrad]

And please note that stranded wire is NOT approved for use in RV's according to CODE.  
John the "mild".

John,
   Isn't THHN stranded wire approved for 120 volt if it is in conduit?  I certainly hope so, cause that is what we used for all our 120 volt wiring. Jack

[JohnEd]

Jack,

OOOPS!  In conduit you say?  OOOPS!  Forgot that.  HEH.HEH.HEH.

I threw away my 2003 copy of the code a year ago.  Not that I ever read it since highschool.  I read a post long ago that said that that spendy "marine grade" stranded was not legal as it wasn't code, but the THHN solid was legal.  I have since read a lot of posts that said the solid was legal and that it was used in "all" S&S.  Now, how could you know that "all" used it, just to be picky?

I would use the stranded on anything that vibrated or moved and I wouldn't suggest any do otherwise.  Code or no code.  I have had a brain fart experience with this however.  I have heard so many people say that Marine stuff wasn't legal and solid was that i assembled the info as "stranded" is not legal and that is a very strange thing. 

I wonder how many more of these are spinning around inside me?  Thanks for not starting your post off with "Hey, Stupid".  That would have better than silence, however.  A lot better.

Thanks,

John

[DrivingMissLazy]

Years ago, most marine cable was not UL listed because none of the marine standards did not require anything be UL listed. UL was for the commercial market place, not the marine market place. Building any product to UL standards is a costly and time consuming process.

More recently I have noted that many marine cables are also UL listed so I feel certain that you can now buy marine rated cable that is also UL listed.

I suspect that many of you would be surprised that the marine standards are generally much easier to meet than UL. When I started manufacturing marine products I just continued using our UL procedures and met all of the marine standards without any problem.

Richard

[PP]

OOOPS!  In conduit you say?  OOOPS!  Forgot that.  HEH.HEH.HEH.

I threw away my 2003 copy of the code a year ago.  Not that I ever read it since highschool. 

I'm trying to do the math here to see just how old you are. I would have guessed much more than the numbers suggest  You threw away a 2003 version and hadn't read it since highschool......

[Lin]

Personally, although definitely not an expert, I am comfortable with using romex if it is secured well, especially near connections.

[JohnEd]

P squared,

You are a hard guy to please.  Have to be special clear hear now.  Graduated HS in 60 and had a background in industrial tricity.  Had copies of the code off and on through the years.  The last copy I had was dated 2003 but I never used it really except to research a grounding bar requirement.

Spent 8 years as a RADAR maint work center soopervisor NCOIC.  Rewired a lot of the Site AC for conveince outlets mostly.  Used the code for wire and conduit info.  Working for the fed I used to check up on my contractors and I used the code to verify their work from a safty standpoint and found more than a few mistakes that could have hurt somebody.  Since 90 i have done little in the field but I picked up a copy of the code in 2003 when I rewired a rifle range out-building/shop.  Threw that away recently.  OK?   Scheesh!

Almost forgot:  Installed a heat pump this past spring but I had all the requirements laid out by our friendly city inspector.

Your detective work is finished here....66 in Aug and getting dumber as time goes on.

John

[HighTechRedneck]

OOOPS!  In conduit you say?  OOOPS!  Forgot that.  HEH.HEH.HEH.

I threw away my 2003 copy of the code a year ago.  Not that I ever read it since highschool. 

I'm trying to do the math here to see just how old you are. I would have guessed much more than the numbers suggest  You threw away a 2003 version and hadn't read it since highschool......

Hmmm, held back a few times?  

Of course, I'm just kidding John.

[JohnEd]

High Tec,

Uh!  I knew you were kidd'n.  I'm sure....I think

Yeah!  As a matter of fact I was held back in the fourth grade.  After my repeat year that witch suggested that I had made no progress and should be relieved of all further obligations to attend public schools due to retardation.  The Super of schools and the School Board had me evaluated by the U of Pittsburgh over the following summer.  I won't tell you their findings as it would seem a brag on my part but I will tell you what action was taken.  That "teacher" was retired impromptu and didn't teach the following year and the principle of that school, the teacher's sister, was allowed to stay an additional year and then sacked.  Yeah, I failed the fourth grade.  You betch'em I did.  The teacher failed teaching and full time employment.  I don't mind telling that story and I am not embarrassed by it in the least, Red.

Have fun,

John

[PP]

Thanks for clearing that up John And thank you all the more for sharing your knowledge and experience with all of us kids, Will

[JohnEd]

Will,

I had a friend that had a daughter that was being set apart in school on the teachers say so.  The kid was crushed and her Dad was really concerned and was crying on my shoulder...as a friend should.  I told him my tale of historical woe and ....I'm sure you know how that worked out for my friend.  I repaet my sad story at every opportunity for just that reason.  And i assure you I greatly value the experience of others and treasure the opinions of experts.

If I ever repay even 1 percent of what i have gotten out of this board I will be amazed and grateful.

I Gnu youn's guys was josh'n me a little.

John