Hello everyone,
I will admit up front that I electronics is not my forte. I am taking Sean's suggestion from a thread earlier this year and have checked out several books on basic electricity and electronics. :P Now to my question:
In another post there is a statement that stranded wire is not required but is better. I have always thought that solid wire would be better. For the same gauge wire, the wires are thinner as the resistance drops on one single wire vs. stranded wire. Granted, it is also probably stiffer, but if given the choice, I would want to opt for the less-resistant wire. Because it has less flexibility, there would also be less chance of the wire kinking up. Also, much harder to break a thicker wire than several little ones wrapped around each other. Is my thinking wrong on this? What are the rules, either written (i.e. code) or unwritten on wire selection.
Thanks for the continuing education.
Mike
Mike -
This topic has been beaten to death over and over and over again on this and the other major busnut bulletin board BNO. (www.busnut.com (http://www.busnut.com))
Use the search function on both BBS's to see what's been said before.
It's an on-going debate!
FWIW & HTH. . .
;)
Let the experts determine! biggest thing to keep in mind is anchor which ever and protect from sharp edges(rubber bushing going thru holes drilled for passage from one area to another).Movement and rubbing is the enemy with either. Bob
Oh No. Here we go again. I should not have even mentioned it. However, it probably needs to be discussed again. I don't have the time right now to search out all the other threads, but there are a ton of them.
The big controversy is the "CODE". Others will discuss that. But my understanding is that the approved code is the same NEC or NFPA code as your house (thin ice here). There is a specific NFPA code for RVs (1192?) Here is a thread on that part of the subject:
http://www.busconversions.com/bbs/index.php?topic=13369.0 (http://www.busconversions.com/bbs/index.php?topic=13369.0)
There are a few diverse thoughts on the subject. I think everyone agrees that THHN is acceptable and meets code (when installed properly). THHN comes in both solid and stranded.
As far as current carrying capability that is a matter of sizing the wire appropriately. As I understand the theory, stranded wire carries a bit more current, but not significant.
Then the issue of wire fatigue comes up. Stranded wire is probably better in that respect, but lots of RV vehicles have solid wire and have for many decades. Properly installed, fatigue should not be a problem.
Next is the issue of securing (terminating) the wire to things like outlets. The typical outlet is designed to be used with solid wire. Lots of discussion that stranded wire is more difficult to get a good connection (that lasts). I used stranded wire and then secured with crimped connectors.
Then the real discussion starts when (shudder ::)) folks start discussing marine cable. This cable is approved by the Coast Guard, but does not meet the applicable code for house or RVs. Not because it is inferior, just because the manufacturers have not spent the funds to seek approval.
OK, that all sounds like I know what I am talking about. Not the case. I have mixed my thoughts with what I recall from previous threads. I am posting it here to get the issues mentioned and then let the folks who really know clean up my mess :o.
I think Sean is pretty busy right now, but if/when he responds, take his comment as being expert.
Jim
Are you building it like a house, or like a vehicle?
Most houses use solid wire.
ALL cars use stranded wire.
Stranded wire is easier to work with in some installations, where sometimes, solid wire is easier.
For me, I'm hoping to be able to run all my wire in conduit to increase the protection from damage.
My bus has 4 skylights that will leak sooner or later, so I'm probably going to use stranded marine wire with the proper end terminals. ;D
LOL, I saw that comment, and wondered if this would come up again.
We used stranded. So far so good ;).
God bless,
John
I used marine stranded some say it is not approved but it was my bus and I used it never was a problem and millions of RV"s on the road with romex solid wiring for the ac side in no conduit doesn't mean it is right but that the way the manufactures do it
good luck
having training in both electronics and commercial electrical, I use solid ["single core"] for AC according to building electrical codes [proper terminations and strain relief] and stranded for DC [the more strands the greater the flexibility] - tinning the exposed copper ends of stranded wires will reduce connection problems from oxidation, and always better to solder connectors [preferably copper] than just crimp them - any wiring, in dedicated wireways or not, needs proper mechanical protection against penetration or abrasion - pretty much common sense
Bill
I use stranded wire for DC low voltage circuits and Romex for 120 VAC circuits. All of the termination equipment is designed for solid wire and if it's well supported there is no realistic vibration issue. Plus it meets code and insurance requirements and all of the RIVA units are made that way.
Brian
I'm too lazy to look for it, but I have read a very well presented explanation of why soldering connections is a bad thing - the solder wicks back up the wire & makes it stiff, then it sees more flexing at the end of the solder & leads to fatigue failures. The article talked about the proper crimp will cold fuse the connector to the wire & not have that problem.
Seems there are pros & cons no matter which way you go. ???
Of all the wiring jobs I have seen, it is the installer, not the materials, that makes the difference between a good (safe) or a bad (fire hazard) install.
What ever your wire choice is, if you:
1- use the correct wire size for the circut breaker
2- use proper end connections for the wire & devices used
3- use the correct wire insulation type for the environment
4- use the correct supports
You should enjoy success.
I too read the subject line and said oh no. Might as well bring up the other dreaded topics.
LOL
John
The guys who build the wiring harnesses for high-buck race cars - the Grand-am prototypes, the Le Mans LMP cars, the Indy cars - use crimped connectors exclusively. The harnesses these days are high frequency data busses, and some low voltage stuff like lights, motors etc. Crimped gold plated connectors, no solder in sight. It's been years since I researched the physics of it, but I recall something like gas-tight joints and micro-cold-welding so that no corrosion could occur and such like. Proper strain relief is important.
regardless, if you do a good job of any technique it will probably be fine. At the end of the day, it's a bus, not a space rocket.
Brian
If I remember correctly, my MCI9 uses tin covered stranded wire in the original wiring.
I've posted this quite a few times... it tells the story clearly.
I set up my vertical mill with a chuck that goes up and down- it holds one end of a wire in the chuck and the other in a vise... then I bent various kinds of wires an equal distance and counted the times I bent them until they failed.
Enjoy again... and use STRANDED if you can. The finer the better...
Oh, and since someone brought up crimps, here's a long photoessay on my OPINION of how to do a proper crimp...
http://www.heartmagic.com/crimps.html (http://www.heartmagic.com/crimps.html)
(https://busconversionmagazine.com/forum/proxy.php?request=http%3A%2F%2Fwww.heartmagic.com%2F00WIREstory.JPG&hash=ecb42d9d0cdf261e650fdcac498c5c7bac9970cf)
Most talk about "the code" and Da book" Has anyone actually had their bus inspected? How do you get an RV electrical inspection? Nobody is going to pass or fail your job so you can do anything you want?
The one sure way to get an inspection is have an electrical fire, that injures someone or you try put in a claim for. The insurance company or plaintiffs will be happy to provide the finest inspectors in the country to give your bus a thorough inspection to make sure it was done by Da book!
JIm
Quote from: Jriddle on January 20, 2011, 12:55:39 PM
I too read the subject line and said oh no. Might as well bring up the other dreaded topics.
LOL
John
John,
Want me to ask about next? What kind of coolant, or what kind of oil to use? ;D
Just kidding...
God bless,
John
More important than what kind of wire you use is how well it is secured to prevent movement and/or vibration and how good the connections are at the terminations. If it is a wire that has to flex evert time a door is opened, it should definitely be stranded. Jack
somewhere in a bus conversion tips type site, I read that someone recommended using heavy extension cords for the coach wiring. They based this on cost, but also I'm sure because it is heavy enough for a 120 VAC load, and flexible???
Boyce
edit: I also assume he meant to cut the ends off and hardwire the ends..
Wow, not only has this thread been civil, but it has had some great responses.
Gary, I don't recall seeing your page (at least the crimping part). I recall seeing your test. The crimping part of your page has some great tips. Thanks for posting the link.
I hope most of you have an infrared temperature gun and use it on things like your tires and bearings. It ****SHOULD**** also be used on your electrical connections periodically. Any loose or bad connection will generate heat. Many years ago, I used to borrow one from work (when they were over $200!!! :o) and take it home. Our house had aluminum wiring through out (not just the main supply) and it was a terrible problem at the time. The aluminum would "flow" and the terminations would loosen up. Anyway, I would check our breaker box and outlets at least every six months. Try to check the bus connections once a year.
Boyce, there have been "strong" discussions about extension cords. The overwhelming consensus of the folks that I consider to be "practical experts" is that they should ****NOT**** be used for 120 volt application. First, much of that type of wire is really cheap in terms of both wire and insulation. Second the application is based on "open air" use. That allows the wire to dissipate heat better. If you bury it in a wall with no exposure to the open air, it can (possibly) heat up. Not sure it would cause a problem, but why risk it. Wire designed to be enclosed is pretty darn cheap.
Folks have advocated using extension cord for low current 12V/24V wiring. Recall here that low voltage applications can have some pretty high amperage and that wire gauge sizing is quite important (i.e. you would not want to use extension cord for something like a headlight circuit.
Jim
Hobe is the guy who advocated using extension cords. As long as you use adequate guage wire for the load, which is easily found in wiring charts, there should not be any problem. Also, there is no law keeping you from using heavier gauge wire on any given circuit; 12g in place of 14g, 10g in place of 12g, etc...
I remain impressed with the electrical systems in the old GMC Buses we scrapped, it was very comparable to aviation quality. Quality end connectors with nut and bolt connections, well routed and securely attached wire clusters and conduits, and heavy gauge well insulated wiring. The old 3751's and 4104's still plying the highways are a testament to the care and quality put into those systems.
There is no reason the AC side of an RV couldnt be built as well, without it costing any more than a residential grade system. All AC outlets have screw connectors, no reason they cant be used with good end connectors on multistrand wire.
boogies "tutorial" on crimping and soldering is exactly right [and I think NASA would generally agree], it matches my experience over years in USAF aircraft electronics - any "hardening" by solder wicking back under the insulation indicates poor workmanship, and breakage at the termination indicates the same, from improper strain relief
Bill
I have to respectfully disagree with the use of extension cords for permanent installation. The real concern here is the aging of the insulation, rather than adequate wire size. If you refer to the appropriate section of NAPA 70, the National Electrical Code, you will find the details. As an experienced fire investigator, I can tell you these standards were developed over many years, as a result of the investigation of fires that resulted in the loss of property and sometimes the loss of lives. Now, I'm a laid back kind of guy, who believes that many rules can be bent, but this isn't an area to take shortcuts. The insulation on extension cords will become brittle as it ages, and fall from the conductors leaving them bare. I have personally seen the old cords, and even seen the results.
On another note, the best set of battery jumper cables I have are made up of fine stranded welding cable. When lesser jumper cables won't do the job, these cables will allow cranking like a new battery! If you look at the cheapest cables you can buy, they are made up of a few relative large copper strands. The best quality cables might be of equivalent size, but are made up of fine stranded cable. The current travels along the outer surface of the wire. The cable made of finer strands provides more surface for conducting the current.
My opinion.
Dennis
Oh yeah, one more thing while I'm on my soapbox. Throw away the RVIA book. (Do I have those initials right? Anyhow, the RV manufacturers group) That's the standard that Fleetwood and other RV builders follow in slapping together those flimsy trailers like the new Fleetwood I use to have, that could have burned to the ground on two occasions, had it not been for Lady Luck. Those are minimum standards, sometimes followed with the absolute cheapest components installed. In my qualified opinion, Romex is not designed or intended for use in RVs or boats where terminals are subjected to constant vibration, whether "sufficiently anchored" or not.
Further evidence of the need for stranded wire is found on railroad diesel locomotives. You won't find solid wire anywhere on one. It's strictly stranded conductors.
Great thread. Be safe!
Dennis
This has been some very good information... I was wondering why when I got my bus all the 110v wiring was stranded. Now I know and can sleep better at night.
Thanks to all your input
Gary
Gary, read through this thread again, and you will see that stranded wire has to be terminated properly. Open up an outlet and make sure they used crimp-on fittings. If not, I would put a load on every outlet and then take a look at the temperature in the box.
Jim
Quote from: Hi yo silver on January 21, 2011, 05:45:40 PM
I have to respectfully disagree with the use of extension cords for permanent installation. The real concern here is the aging of the insulation, rather than adequate wire size. The insulation on extension cords will become brittle as it ages, and fall from the conductors leaving them bare. I have personally seen the old cords, and even seen the results.
Dennis
I know what your saying about poor insulation that falls off the conductor, I have seen this myself. But I would argue it has nothing at all to do with extension cords, per se, as much as it has to do with general wire quality. The wire on the spools at the auto parts stores isnt always any better than the stuff inside the cheapo chinese extension cords sold at Home Depot. You need the stuff that stays flexible below zero.
Jim, thanks I'll look in the outlets tomorrow and make sure all is OK.
Gary
just my 2 cents. but hear in costa rica and i think all of centro america .
solid wire is not sold and cant be used all wire is stranded
most of europe also uses stranded wire also.the wire i used in my bus in from italy
a fine stranded 12 gauage rated for 120 v / 240 v. i used conectors on ends where neaded. john
I am not going to take sides on this one because there is what I wish I had, and what I have. I'm not about to rewire my bus so I am using what the PO put in back in '79. Stranded for DC, Romex for AC. Thirty two years later and I haven't had an issue yet. I will post asap as soon as my bus burns to the ground, if I live to see it. :'( I don't have a lot of flexing in my bus, so I am fairly confident that the wiring will be fine for a long, long time. This is not a black and white, right or wrong thing for me. I look at wiring choices as Good, Better, Best. Good will work and is what I have, better is wonderful if you can, but there are many examples of Good doing just fine, and that doesn't necessarily make it bad, just not the best. Don't loose any sleep over this one guys.
I appreciate all the input. I didn't realize when I started this thread that it was a hot button for many folks. I appreciate that the discussion has been cordial and polite.
One thing that seems to be a common in many answers is that we need to be careful of the quality of the wire. So the next question is how can you tell what is good quality wire and insulation? Before I started this thread, I most assuredly would have opted for solid wire, but now I think I would go with stranded. But if I walk into one of the big box stores and start looking at spools of wire, how can you tell whether it is quality or not? No sense opting for the "better" type of wire only to be foiled because the insulation peels off in a couple of years. That is clearly not "better".
Any clues on this? Do you look for a certain kind of manufacturing stamp, or do you ask the salesman what they use for coating?
Thanks. So far I am now slightly less clueless than before.
Mike
The latest code I am aware of is to use thwn in an approved enclosure (conduit etc). That will come in stranded or solid and the insulation "should not" deteriorate.
HTH
Melbo
Quote from: Melbo on January 23, 2011, 03:38:29 PM
The latest code I am aware of is to use thwn in an approved enclosure (conduit etc). That will come in stranded or solid and the insulation "should not" deteriorate.
HTH
Melbo
Did you mean thhn instead of thwn? I just never heard of thwn myself. If you meant thhn then that is a stranded wire.
I was wrong on the thhn.. it also comes in solid
THWN is for outside use and inside use --- I didn't look up what is necessary in an RV just normal code --- THWN is available like THHN in stranded or solid --- Last time I needed some they had it at Lowe's or an electric supply house.
HTH
Melbo
From Wikipedia :
THWN stands for "Thermoplastic High Water-resistant Nylon-coated
THHN stands for "Thermoplastic High Heat-resistant Nylon-coated
For more information, see also http://www.usawire-cable.com/pdfs/THHN_THWN.pdf (http://www.usawire-cable.com/pdfs/THHN_THWN.pdf)
Both are gas & oil resistant. I don't believe NM romex is. Then again, If I've got oil & gas inside my coach, I probably have bigger problems than what wire I used . . . . ::)
In My conversion I will be using all Stranded. I am used to the Aviation industry and NO aircraft ever uses a solid conductor in any application. I believe it is a vibration thing. All large wiring is not only crimped but soldered after for better connection.
Yup, here we go again.... lol
This is taken from our tech archives section under Green Book.
This is why you should NOT use extention cord wire for your bus wiring...
http://www.magnet.fsu.edu/usershub/safety/documents/extensioncord.pdf (http://www.magnet.fsu.edu/usershub/safety/documents/extensioncord.pdf)
Disallowed Uses Of Extension Cords
The following uses of extension cords are not permitted at the NHMFL:
• Extension cords may not be used in place of permanent facility wiring. Cords shall not be attached to building surfaces or structural members. They shall not be permanently concealed in walls, ceilings, or under floors - including raised computer floors.
• Do not run cords through moisture, tied to over-head pipes, across traveled roads, under carpets, or across areas of high foot traffic.
• Extension cords may not be run through doors, ceilings, windows, holes in walls, or through hinged door openings in enclosures. This is to prevent "pinch" damage to the cord. If it is absolutely necessary to run an extension cord through a doorway or open window for short-term use, the cord must be protected from damage should the door or window slam shut; it must be removed immediately when no longer in use; and must not be a trip hazard.
• Do not use extension cords that are frayed, cut, or damaged such that inner conductors show, or that have outer sheaths which have pulled loose from their molded plugs exposing the inner conductors. In particular, do not use a cord that has a bare conductor exposed.
• Detachable multi-tap adapters may not be used on extension cords nor on receptacles.
• Cords may not be repaired with electrical tape, nor may tape be used for other purposes on a cord. It may conceal damage.
Cord overload and overheating:
In addition to the total electrical load, the conditions of use affect extension cord safety. Rated capacity for an extension cord assumes it will be used in an open-air and straight configuration.
As electric current passes through a wire, electrical resistance causes some voltage drop and heating of the wire. Coiling or winding excess cord length can concentrate this heat and overheat the cord. Similarly, covering a cord with a rug or rag can trap heat and overheat the cord. This trapped heat can damage the cord and lead to a fire. Tying a knot in a cord can have a similar outcome.
I've been away for a few days and missed all the fun. A couple of comments;
THHN, THWN and hundreds of others are insulation types and have nothing to do with cable types. They are only of concern if you are wiring in conduit. What we are interested in is the CABLE TYPE. Type NM (Romex) or type MC (Metal Clad, similar to BX) are what we commonly use.
Fred Hobe is a very talented bus builder and I have long admired his workmanship and common sense approach. However, I very strongly disagree with his use of extension cords for wiring. If I ever bought one of his conversions, I would have to rewire it before I could sleep in it.
Dennis,
There is no RVIA book, it is the NFPA 1192, Standard On Recreational Vehicles, published by the same people who publish the National Electric Code. It has nothing to do with the manufacturers and does not cover AC wiring. It does cover low voltage wiring (stranded), plumbing, propane, ventilation, etc., and would be a very valuable and inexpensive ($40.00) addition to any bus converters library.
Whether to use stranded or solid wire for your AC wiring depends on whether you have separate waste tanks or a single tank :)
Technically speaking, is an "extension cord" still an extension cord if you cut the ends off and permanently wire it and fasten it in place? I suspect that it is not. At that point it becomes "wire" of a particular type and with whatever approvals it carries. I bet the rules related to extension cords don't cover the use of "extension cord wire".
Brian
Quote from: bevans6 on January 25, 2011, 06:16:42 AM
Technically speaking, is an "extension cord" still an extension cord if you cut the ends off and permanently wire it and fasten it in place? I suspect that it is not. At that point it becomes "wire" of a particular type and with whatever approvals it carries. I bet the rules related to extension cords don't cover the use of "extension cord wire".
Brian
It has nothing to do with whether or not it is called an extension cord or "cord set" in NEC speak, it is the cable type which is not permitted. Extension cords are typically type SJ and it's many variations, (SJE, SJO, SJEO etc.
Article 400-8 is what prohibits their use.
It's not really a subject for debate. It's use is against the NEC. Whether or not you choose to follow that code is your business. You will not go to jail.
that's interesting. I knew the use of the cable type wasn't allowed, I just didn't know if there were separate rules for extension cords. I guess you can get or make extension cords of different kinds of cable other than the typical. I make extension cords of different types of cable sometimes, for example for the 30 amp cable to a generator. Regardless of the cable type, I don't think you can run them through doors permanently, or all the other restrictions. Those are use restrictions, not just cable type restrictions.
Brian
To this uneducated person if I saw a extension cord used as wiring I would think it was a cheap move and not trust the rest of the conversion Quality. Being proper for a particular use in the mind of a uneducated potential buyer;might question the rest of the systems. After finding a brown 2 wire cord in present project(a pro converted coach) I replaced all of those areas and Questioned the rest of the conversion. The use or non use is perceived application decision. I use stranded run in conduit. Price difference is very minor between the two. Bob
When I got my bus home, the ac wiring was extension cords and power bars... everywhere! Step one, complete rewire...
Brian
You guys need to spend a few hours at a converter for the buses they make a wiring harness on a long board for that floor plan tie strap it together and go throw the harness in put a few tie downs and off to races, same with the ac side except they install it on the opposite side and sometimes they don't even do that
good luck