Bus Electrical Systems - AC

[bus-bro]

The bus shell is connected to the ground wire, and grounded by the AC supply circuit. The white neutral circuit wire is not connected to the bus shell, its ground bonding is at the supply.

[Will]

Only bond the ground to neutral at the point of origin of the power. If the power comes from dockside (campground) then it is bonded there and you don't bond it. If it comes from your generator, it should be bonded inside the generator and you don't bond past the generator. It's the same thing if you add a sub panel in your house--the main panel in the house is bonded--nothing past the main panel is bonded.

I used solid wire everywhere. This is where the theory and the practice diverge. There is barely any movement in a vehicle on the wiring. Immeasurable if you have it secured every 6". You need heat to deteriorate the wire--you won't get it. It won't work loose of the connections. I got rid of a '71 Winnebago 2 or 3 years ago and everything worked great. It was solid wire.

[lornaschinske]

From a Professional Coach Converter http://users.cwnet.com/~thall/fredhobe.htm

Way to save money on wiring

I buy 100 foot extension cord when they're on sale number, 12/3 conductor wire size. I can get them for as little as $15.00 and they come in different colors. I get several different colors and use yellow for air conditioners, orange for lights, black for wall plugs (120 volt) and green for 12 volt. They are UL approved and very flexible. You need to tin the ends when you hook them up to your main and on other connections use High lugs. Use an indent squeezer to make good connections. You can buy 100 ft. cords with plugs on them cheaper than you can buy the wire by the foot. I use about 500 ft. of wire on a coach.


This shows how wires are run in the roof. Run them where they will come down the wall to the fuse panel.

We have a lot of long heavy extension cords left from our remodeling days. We saved them along with all the stranded wire we salvaged from the Eagle. guess what we will be using.

[chopperdr]

i have worked as an Commercial Electrician for a few years and in that time I wired a lot of Transformers, and due to the vibration of them, we had to use stranded wire, and the few that ive seen that were wired with BX ( Solid wire wrapped in flexible steel armor) we were back in a few months to replace the solid wire with stranded, and now i am an Aircraft Mechanic, and i see large aircraft having both 24vdc and 110vac wired into them, and the FAR's (Federal rules and regulations) strictly prohibit the use of solid wire in aircraft, (with a lot of research to back it up) due to work hardening and breakage. so in my humble opinion, the stranded is well worth the few extra pennies. and yes the travel trailer companies who build their trailers for the majority of owners that will use them 1 to 3 weeks a year, the solid works ok, and i have seen people who use them alot more than that have problems like plugs that dont work, or switches that audibly buzz for a few seconds when you turn on a light, so take my thoughts and ramblings with a grain of salt, and maby a shot of tequila, and enjoy

[lornaschinske]

Originally Posted by AlleyCat67

... would 15A be enough to run a rooftop A/C unit (would be the only thing on that circuit)?

NO

[Ryan Grimm]

Make certain that lines running AC units are sized for PEAK LOADS, in other words the surge anticipated when the compressor kicks in. Having a 15A circuit is not a good idea....a MINIMUM 20A wiring and breaker is in order.
Once upon a time, my mother decided to plug in a large and ancient AC unit with a 15A zip cord extension, I was in the basement looking for the 'real' extension cord.
Before I could get upstairs, the AC started up, and the cord MELTED, leaving molten copper embedded in the wood trim and the carpeting!
I'M NOT KIDDING. I was 14 when this happened.
Needless to say, she changed her mind about doing that again.

I sincerely hope you keep in mind that electrical loads are a potentially dangerous thing.
REMEMBER, 50% of ALL electricians in the 1920's died of electrocution. House fires were a LOT more common, and one of the scariest things I've seen were additions to post & tube wiring in old houses, with no idea of what is the hot side, what is neutral, and forget having a ground!
Electrical Code is there for good reason, based on the number of fatal and tragic fires that have occurred in the past...learn from others' mistakes, instead of making new ones identical to the old ones.

I firmly believe that using solid wire is based strictly on two criteria:
#1) EXPENSE. Solid wire is cheaper, and electrical connections/boxes/outlets are cheaper for it.
#2) Useful Life. Most RVs have very little use over a lifetime...I see MANY, MANY RVs that have less than 40K miles on them in scrapyards, and they are there due to shoddy workmanship/leaks/structural problems.

We in Skoolies have a great foundation in bus construction, and I believe I will give my best shot at surviving long-term in a vehicle set up my own way.
I have YET to see ANY vehicle that uses solid wire for it's own factory wiring; it's all stranded.
Since that has worked for about 100 years now, I'll keep on with that idea.

[ol trunt]

Just for fun and from the never say never file--- While repairing a late model Ford Focus that had sustained flood damage I discovered that the standard stranded copper automotive wire had been substituted with solid aluminum "wire" in the area adjacent to the rear wheel wells. I suppose that the manufacturer managed to cut a bit of weight that way. I have no idea what the normal life expectancy is for this "stuff" but I will continue to use stranded copper wire--mostly because I am an old stick in the mud and I've yet to see a case made for solid Al. wire.

[roadfamily6now]

We need some help.
We have a 1991 Thomas School bus, diesel.
It ran when we bought it and drove it the 50 miles to our house. We have ran it several times in the past 3 months while parked in our driveway during our conversion.
My husband desperately needs a wiring diagram as he has somehow inadvertently done something to the wiring and now the bus will not start.
We are attempting to wire up a 12volt water pump to the existing electrical system.
Any help would be greatly appreciated.

Thanks


The RoadFamily
www.theroadfamily.com

[Ryan Grimm]

Remember, any appliance or accessory you add needs it's own fuse and shutoff switch.
I have seen many RVs with an additional shutoff switch in the bedroom, for the pump...the pumps sometimes ''start up" in the middle of the night if pressure in the water line drops....annoying at best.
This adds complexity to the wiring, not to mention voltage drops to the pump due to length of added wire for this feature.

I hope the debate of stranded-vs-solid wire continues. I still believe best practice is to use stranded for long-term safety and viability.

Let the thread know if any of you experience any problems or solutions of problems.

Thanks!

[chev49]

first of all the road fam needs to have separate house batteries for the water pump, etc and not run them off the coach batteries if ya want the thing always to start.
if the bus won't start and you have done something to the wiring, go back and hook up what you did. school busses like my thomas wont start if they have the door system wiring disconnected, and the buzzer will always sound if parts of it is disconnected improperly. so hook the wires up as they were originally. other people on here have had the same problem.

about aluminum wiring.. i have found several newer cars that have aluminum wiring in various places..so that i suppose is the future for automotive wiring... i am sure its a bit cheaper when bought in huge rolls...

i always use stranded wire for rv's except when using the 110v solid rv wire that is out there...

[thommassey]

During a year long project I was on, it had in the specs #10 and smaller to be solid. I asked this engineer why and his reasoning was that it is a long standing engineering practice due to human error at the terminations. Some of the strands on the solid wire can break or fray out at the termination if the installer is not careful reducing the ampacity of the conductor. He also said when following conduit fill maximums and 360 degree maximum bends that the #10 solid is not any more difficult to pull.
Well, this guy has obviously never pulled any wire in his life! #10 Solid is a bear to pull. I don't buy the termination excuse either. How many problems can be traced to a stranded termination where a couple of strands were inadvertently cut? I bet zero.

Some pros of stranded:

Stranded has more surface area. The electricity moves on surface area.

Stranded is less likely to break from a small nick.

Stranded is less likely to suffer from metal fatigue if exercised.

Stranded pulls easier.

====
Some cons of stranded:

Stranded costs more for the client.

Stranded can be harder to terminate on screws.

Stranded cannot be backstabbed (wait, that's a good thing!).

Stranded has a larger diameter.

Stranded fills up the wire nuts faster.

Stranded is hard to self-fish. You can't unlock your car door with stranded.

Stranded must be run off spools (well usually anyway). Otherwise you end with a hairball.

IMHO...

[Ryan Grimm]

1) You CAN terminate stranded without problems...I solder the ends, making that part (essentially) solid, OR I use properly-sized electrical crimp connectors and the RIGHT tools.

2) I NEVER use the push-in (or back-stabbed) connections on outlets, switches, etc. Those need a SPECIFIC SOLID wire size, and no one ever uses the right sizes anyway. When I connect at a screw terminal, I either solder the end, or crimp on (using the RIGHT tool) a ring connector. If I use a ring connector, I ensure it is an insulated one, or use a bit of shrink tubing to ensure no extra metal is exposed for possible shorts.

3) When I tighten down the screws on connectors, I make sure they are TIGHT. Too often have I found connections that were loose or partly disconnected due to a lack of energy on the part of the previous installer.

4) I ALWAYS use the BLACK/WHITE/GREEN color coding on 120VAC wiring. This prevents miss-connected wires, possible electrocution from backfeeding a fixture or switch, etc.
This **** is serious, folks.

NOTE: if you pull NM or UF wire though your job, any time it goes through a length of conduit the outer insulation must be taken off....just the insulated wires are permitted in the conduit, at least here in Massachusetts. Wire gets warm in use, and double-insulated wire INSIDE a conduit has no place for the heat to leach off.

DO NOT over- or under-strip the insulation off wire ends when making connections.
OVERSTRIPPING, taking off too much, leaves a dangerous amount of bare wire to short out...I found one barn I was rewiring had between 2 and 5 INCHES of bare wire ends in the electrical boxes...a fire just WAITING to happen.
Joe Homeowner should REALLY learn what's the rules. If an insurance adjuster finds that the homeowner had wired something, and it was not to code, AND that wiring had caused the fire, you are S.O.L., and they will NOT pay off the fire insurance.
UNDERSTRIPPING causes inadequate connections, and if the insulation gets caught instead of the wire, the connection will not be made, it can cause an arcing condition, dangerous, could cause a fire.

Make sure you use good, clean, properly sized connections.
Do NOT try to stuff too much wire in a connection or electrical box.
DO NOT try to 'stretch' a wire because you didn't have enough to make the connection.
DO NOT leave covers off switches, outlets or electrical boxes, this leaves their contents vulnerable to tampering, etc.
LEARN the correct way to use wire nuts, how many wires you can connect with them, and what sizes.

[Ryan Grimm]

Oh, and ALUMINUM wiring:
you MUST use only fixtures, connectors etc. that are RATED for Aluminum. You must (to my best knowledge) use a proprietary paste on the connections to prevent oxidation of connections, arcing and fires.
You MAY NOT directly connect copper to aluminum...you must use the correctly rated connectors.

There is a LOT of info lacking on aluminum wiring, so unless you really know what the hell you are doing, don't use it.

[thommassey]

Originally Posted by Ryan Grimm

1) You CAN terminate stranded without problems...I solder the ends, making that part (essentially) solid, OR I use properly-sized electrical crimp connectors and the RIGHT tools.

2) I NEVER use the push-in (or back-stabbed) connections on outlets, switches, etc. Those need a SPECIFIC SOLID wire size, and no one ever uses the right sizes anyway. When I connect at a screw terminal, I either solder the end, or crimp on (using the RIGHT tool) a ring connector. If I use a ring connector, I ensure it is an insulated one, or use a bit of shrink tubing to ensure no extra metal is exposed for possible shorts.

3) When I tighten down the screws on connectors, I make sure they are TIGHT. Too often have I found connections that were loose or partly disconnected due to a lack of energy on the part of the previous installer.

4) I ALWAYS use the BLACK/WHITE/GREEN color coding on 120VAC wiring. This prevents miss-connected wires, possible electrocution from backfeeding a fixture or switch, etc.
This **** is serious, folks.

NOTE: if you pull NM or UF wire though your job, any time it goes through a length of conduit the outer insulation must be taken off....just the insulated wires are permitted in the conduit, at least here in Massachusetts. Wire gets warm in use, and double-insulated wire INSIDE a conduit has no place for the heat to leach off.

DO NOT over- or under-strip the insulation off wire ends when making connections.
OVERSTRIPPING, taking off too much, leaves a dangerous amount of bare wire to short out...I found one barn I was rewiring had between 2 and 5 INCHES of bare wire ends in the electrical boxes...a fire just WAITING to happen.
Joe Homeowner should REALLY learn what's the rules. If an insurance adjuster finds that the homeowner had wired something, and it was not to code, AND that wiring had caused the fire, you are S.O.L., and they will NOT pay off the fire insurance.
UNDERSTRIPPING causes inadequate connections, and if the insulation gets caught instead of the wire, the connection will not be made, it can cause an arcing condition, dangerous, could cause a fire.

Make sure you use good, clean, properly sized connections.
Do NOT try to stuff too much wire in a connection or electrical box.
DO NOT try to 'stretch' a wire because you didn't have enough to make the connection.
DO NOT leave covers off switches, outlets or electrical boxes, this leaves their contents vulnerable to tampering, etc.
LEARN the correct way to use wire nuts, how many wires you can connect with them, and what sizes.

More good info!

[bus-bro]

Most of the 120 volt ac stuff is designed for solid wire, or coarse stranded wire (9 to 12 strands). If you use fine stranded wire you might experience some hot connections, with the potential for a fire.

Not going rehash the extension cord issue (not approved for fixed wiring.), but I do believe that fine stranded wire should work under the screw terminals on the receptacles (plug-ins).

You do not want to tin the wire (solder it), and then clamp it under a screw terminal. In use, the electrical current will heat the wire and connection, and the solder softens. This allows the wire to deform, and it is no longer making a good connection, which means more heat, worse connection, more heat, then a failed connection or fire. That's old school electronics 101.

[bapos]

I am going to be putting the ac wiring phase in the bus here soon so I was kind of brushing up on reading here and thought I would add these notes. I have never claimed to be the sharpest tool in the shed but far from the dulest either. I am a College graduate with a degree in Radio TV and film (my concentration was in tv engineering btw) I am also former Interior communications electrican from the US Navy (we are considered bastard electricians cause we work on electrical and communication sytems) and I am currently going through HVAC school and just revisited basic and advanced electricty.... so not saying I know it all cause that would be foolish to do but Ive wired a few things in my 43 years.

People who work with electricty know this but those who dont please make note of this.... a electrical safet device (AKA a fuse or circuit breaker) is there to PROTECT THE WIRE NOT THE DEVICE ITS HOOKED UP TO. When you pass too much current to a load it heats up the wire... melts insulation... and STARTS fires, in worse case senerios. So choosing the right type of inuslation is a key factor. If you base it on price i think your being foolish. Do the right thing and take your time. Your life (and others) may depend on it.

There is some REALLY good information being passed on here. Yes some of it is advanced so dont scratch your head and just accept it. If it doesnt make sense find out why. There are lots of supply houses that can help you. They want to help you cause yes they may sell you something but none of those people want to see things done half assed or poorly. And not everyones build is going to be the same so PLEASE keep that in mind.

Again this is a very good info area. Please keep the good info coming.

Bapos

[family wagon]

Thanks to Les for the notes about neutral-ground bonding. It should've been obvious to me that the bond needs to be switchable: bond in the RV when using locally-generated power (genny or inverter) and UN-bonded in the RV when using shore power. Really it's no different from the bonding rules in fixed buildings -- the RV is kind of an odd-ball case because of its ability to sometimes operate like a building sub-panel and other times operate like a main panel. I guess I just hadn't sat and thought it through well enough yet!

Regarding some of the other tips here: I respectfully submit "don't!"

Soldering: yeah, it's handy how it makes the wire firm and easy to tighten a screw onto. But as already mentioned by another, WHEN the connection gets hot (not "if") the solder will melt, the connection gets loose, heats further (if it doesn't just completely separate), and next thing you know you've got a fire. Connections should be crimped, and with a good crimper. IMHO the crimpers with the oval-shaped die don't make a good crimp; the type with a finger/spike in the jaw do much better (and the tool doesn't cost much more either). Note though that type is for uninsulated crimps; if I can't find uninsulated terminals then I pull the red/yellow/blue insulation band off, make my crimp, then cover with heat shrink tube if it's in a place where insulation is appropriate.

It's UL-listed, so it's good to use for anything! Not true. UL listing is typically surprisingly limited in scope and applies only for very specific use conditions. Don't assume that your use of a device is safe simply because the thing has a UL sticker on it.

Extension cords as fixed wiring: Saves money up front, yes, but not a good idea. The thread has already speculated why many RV manufacturers use solid wire (it's cheaper). The manufacturers are aware as much as we are that extension cords are even cheaper than non-metallic (NM or "Romex") cable. Why don't they use it? It's the wrong wire for the job. The insulation is thin, easily torn, and easily melted for one thing. I trust that there's good reason why the US National Electric Code, written in part by the National Fire Protection Association, specifically disallows these cords for permanent installations or for use, even temporary, in concealed locations. I doubt it involves being paid off by Southwire (makers of Romex brand cable).

If I may, here's a little personal story. When I was a kid, maybe 6-8 years old, I slept on the top bunk and wanted a night light up there. I went rummaging in the garage and came up with a j-box, receptacle, wall plate, replacement male cord end, and... a length of 24-gauge phone wire. I'd seen my dad wire stuff lots of times and knew I needed to connect the silver screw on the outlet to the silver screw on the cord end and the brass to the brass. I probably connected the grounds even though my night light didn't have a ground pin. Got the assembly finished, installed it on my bed, and plugged in my little neon-bulb night light. And you know what? It worked fine. Those neon bulbs draw a tiny amount of current so the 24-gauge wire was well within its ampacity limit. The voltage was maybe reasonable too: phone wire regularly sees 90+ volts when ringing. But did that make it appropriate or acceptable for the job? NOOOO! Admittedly, this is an extreme example of using the wrong kind of cable. But the point is the same: "price is right" and "gauge is heavy enough for the intended load" and "it's labeled for more volts than my circuit" do not make a cable appropriate for the use. As proved by my experience, even "I tried it and nothing bad happened.. yet.." doesn't prove that the setup is actually safe.

[Ryan Grimm]

When I was 14 my mother decided to plug in the ancient and massive window AC unit in our house. She could not find the dedicated cord, so she decided to use a zip-cord type (two conductor) extension cord. She plugged it in, turned it on...AND MELTED THE CORD! Molten copper droplets all over the carpet!

WHY she did this I have no idea, as I had told her I was going downstairs to get the right cord.
She got yelled at by dad when he got home....that scorched carpet stayed there for 8 more years as a reminder to her!

[lornaschinske]

I've posted this whole post before but looks like it needs to be posted again. Do your own research. We are following the advice of a professional coach converter with over 25 years experience who has converted many high end highway coaches and no electrical problems. We are following how he wired his own coach. Many sticks-&-staples RVs have made it many years on the road using solid romex. Our 1976 Class C did and still is. Only thing we did was to separate the circuit loads. To be completely honest, I believe your expertise in making a good connection is more important than the type of wire used. This is a grey area where the "facts" are ambiguous. But hey, some of you put death-trap-accident-just-waiting-to-happen RV refrigerators in your conversions. I think the ones that do that are off their nuts, ditto the woodstoves. BUT IT'S YOUR CONVERSION! I figure that you will do the research needed to make your own decisions. Just like we have done the research needed to make our own decisions. I do have the electrical code book in storage. It had been read many times. One thing that you do need to understand, mobile electrical systems are not wired up exactly like a house. Even experienced electricans get confused about the grounding.

From NFPA 1192 Standard on Recreational Vehicles (what the RV manufacturers supposedly follow to get the all hallowed RVIA emblem you find on sticks-n-staples RVs).


IMPORTANT NOTICE ABOUT THIS DOCUMENT

The RVIA and the NFPA codes, standards, recommended practices, and guides, of which the document contained herein is one, are developed through a consensus standards development process approved by the American National Standards Institute. This process brings together volunteers representing varied viewpoints and interests to achieve concensus on fire and other safety issues. While the RVIA and the NFPA administer the process and establish rules to promote fairness in the development of consensus, they do not independently test, evaluate, or verify the accuracy of any information or the soundness of any judgments contained in their codes and standards.

The RVIA and the NFPA disclaim liability for any personal injury, property or other damages of any nature whatsoever, whether special, indirect, consequential or compensatory, directly or indirectly resulting from the publication, use of, or reliance on this document. The RVIA and the NFPA also make no guaranty or warranty as to the accuracy or completeness of any information published herein.

In issuing and making this document available, the RVIA and the NFPA are not undertaking to render professional or other services for or on behalf of any person or entity. Nor are the RVIA and the NFPA undertaking to perform any duty owed by any person or entity to someone else. Anyone using this document should rely on his or her own judgement or, as appropriate, seek the advice of a competent professional in determining the exercise of reasonable care in any given circumstances.

The RVIA and the NFPA have no power, nor do they undertake, to police or enforce compliance with the contents of this document. Nor do the RVIA and the NFPA list, certify, test or inspect products, designs, or installations for compliance with this document. Any certification or other statement of compliance with the requirements of this document shall not be attributable to the RVIA and the NFPA and is solely the responsibility of the certifier or maker of the statement.


RVIA - Recreation Vehicle Industry Association

NFPA - National Fire Protection Association

Now I'm not the smartest person out there and I am not proficent in "legalese" but the disclaimer in the front cover of the NFPA 1192 (formerly ANSI 119.2/NFPA1192) seems to suggest that the manufacturers of RVs make the guideline on how to build an RV, then they do not enforce the guidelines. but that's okay, there's no penalty for not following the guidelines nor do they stand behind the correctness and safety of their own guidelines. That's how it appears to me. But what do I know. Buy a copy for yourself. It's an..... interesting.... read. I bought a copy to use as a guideline when we were going to convert an Eagle 05 highway coach into an RV. I wanted it to be "right". After getting the book and reading it twice, I was uncomfortable with what I had read. Thinking I must not have understood what I read, I had my husband read it. David is very familar with all phases of house construction including wiring and plumbing. David & I decided the "standards" were wrong in several instances. We believed we would be putting our lives at risk if we followed the standards. The electrical section was shaky at best. Parts of the plumbing section was either poorly written or just plain wrong. It's hard to believe the whole book was poorly written when you read the disclaimer in the front of the book. I am left with the strong feeling that the book plainly advocates bad electrical and plumbing standards. The LP section, such as it applies to our own use, seems to be adequate. This is based on other sources I researched. It appears the LP section seems to follow marine standards for LP fairly consistently.

[bapos]

Not that it is 100% fool proof but if those who have converted and ran electrical can post up some pics of how they brought in and wired up their system? I think there is a lot of good information on here.