Bus Electrical Systems - AC

[Ryan Grimm]

Found this in another section of Skoolie.net:
viewtopic.php?f=8&t=13540

[D&ACaple]

ok, so im not an electrical genius.... I know not to touch the wrong wire, water is not your friend, and never urinate on a pig fence.... well got a bit more than that, my issue right now is I have a service panel. 70amp homelite panel, with a double 15 amp breaker, and a 20 amp breaker... wiring the breakers and the power legs are ready, but what im havin troubles grasping is what wires from my 50 amp cord gets hooked up to in the power box, red green black and white... I can do an outlet but this one I don't want to chance, any help would be great

[Redbear]

If the cord is molded to the plug, and has the standard color code:

Black - Hot leg #1 to one side of the main disconnect double breaker
Red - Hot leg #2 to the other side of the main disconnect double breaker
Green - Safety ground - this goes to a buss bar grounded to the panel box frame
White - Neutral - should go to a second buss bar completely insulated from the panel, ground, and the bus chassis

If someone wired the plug onto the cord with screws, you had better have it checked to be sure they used the right colors on the right pins.

At your option the panel and safety ground can also be bonded to the bus chassis, or isolated with the AC devices on non-conductive mounts.

If the panel was not previously a "sub-feed," there may be only one buss bar. The first panel off of an electric meter connects the neutrals and safety grounds together, but sub-feed panels must keep them separate. You may have to purchase an isolated buss to install in the panel. Or, if there are only a couple of circuits, you could join all the white wires together with wire nuts, and put the safety grounds into the buss bar.

If you tie the neutral and ground together anywhere in the bus wiring, it will trip any Ground Fault Circuit Interrupters "upstream" of the outlet you plug into.

You get 240 volts from the black to the red. Double breakers (two slots wide with joined handles, not two handles in one slot) will connect across the two sides to provide the 240 volts to a device requiring it.

You get 120 volts from the black to the white, and also from the red to the white. If you have heavy loads, such as two 120-volt air conditioners or heaters, it is good practice to split them half on the black/white pair and half on the red/white pair to balance the load.

When wiring 120-volt branch circuits, the white goes to white, the green or bare goes to green, and the black goes to a breaker mounted on either the black wire side or the red wire side of the panel.

(Edit: Panel board branch circuits are generally split in rows black/red/black/red from top to bottom, not in columns, e.g. left side black, right side red. Although the bars that feed them are in columns, the tabs that the breakers connect to alternate sides.)

If you are actually describing a 120-volt panel with a main that is not a double breaker, and there is only one power bar going down the panel to feed the branch breakers, then cap off the red wire with a secure wire nut, and use the black, green, and white for your 120 volts as described above. Do not let the second hot wire contact anything.

[PDBreske]

Redbear’s explanation is solid. I had the same issue when I was wiring my breaker box, but I don’t have any 240V requirements, ever. I disconnected the red wire at the shore power connection on the side of the bus, then bridged the two sides of the breaker box to feed both buses with the single black wire (120VAC). The red wire is still inside the conduit from the shore power to the box, but I doubt I’ll ever want or need to use it.

When connected to shore power, the blade of the power cord that connects to the red wire will go unused and the black wire will carry all the electrical supply on its own. I won’t ever have more than about 2000W of equipment running at the same time (in fact, I don’t think I’ll have that much if I run everything at once).

[bansil]

Only issue is when dealing with 50 amp 120V power(like campgrounds have etc) you can then bring in two separate 120V lines Red and Black and use theoretically up to 100 amps of 120v power

When I wired mine I divided loads up: one heater/AC plug on red (front of bus) and one heater/ac plug on the black (back of bus

The rest of the loads I just divided up between the red and black side

This lets me use 2 heaters and ac's etc on 50 amp power, (as well as say blender/microwave oven and rotisserie at same time...and when we are hosting parties we can use a ton of power) when I plug into 30/20 or even 15 amp power all my receptacle's are hot...I just have to remember to "count amps and usage"

At house I am plugged into a 15 amp circuit, which is plenty for 1 ac, chop saw a few lights and fridge

At camp grounds the 120 V lines are actually out of phase 180 degrees (this helps stabilize campground and such from having too much on one leg)

So while I do not have 240V in my bus (since they are not both connected to anything) I still have 2 hots coming in and could for some reason actually put in 240 for say a 12 person hot tube and sauna room

[shutterbug3]

Quick question for the electrical gurues: I am working on installing a fusable disconnect into a conversion and I have used 10/3 for running between a 6 circuit panel; I only have 8 total outlets, 1 will be powered full time for a fridge/freezor and another will be a laptop charger/cell phone charger outlet(from an inverter) on the road and the others will only be used once plugged in on shore power. With only 4 of the 8 outlets running more than 50% of the time even when on shore power, do I need 50 amps and is 10/3 gauge OK(is only running approx. 2 ft. between panel and disconnect) or will 30A be sufficient. A small pottery wheel, a task light and maybe a small electric fan being my other loads once plugged in. I know 10/3 is only rated at 30 A, so will I be in danger of using 10/3 or do I need to upgrade.

[bus-bro]

10 gauge wire can only handle 30 amps. In rv's, a 30 amp circuit is 120, a 50 amp would be 240. 6 gauge wire for all 3 conductors on the 50 amp service.

[nat_ster]

Originally Posted by shutterbug3

Quick question for the electrical gurues: I am working on installing a fusable disconnect into a conversion and I have used 10/3 for running between a 6 circuit panel; I only have 8 total outlets, 1 will be powered full time for a fridge/freezor and another will be a laptop charger/cell phone charger outlet(from an inverter) on the road and the others will only be used once plugged in on shore power. With only 4 of the 8 outlets running more than 50% of the time even when on shore power, do I need 50 amps and is 10/3 gauge OK(is only running approx. 2 ft. between panel and disconnect) or will 30A be sufficient. A small pottery wheel, a task light and maybe a small electric fan being my other loads once plugged in. I know 10/3 is only rated at 30 A, so will I be in danger of using 10/3 or do I need to upgrade.

You want the common sense answer, or what is written in the code book?

Nat

[shutterbug3]

I won't be pulling any 240 circuits from the panel, only 120; the owners are planning on running the only 240 circuits from the shore power pedestal

[claydbal]

tell me what is wrong with this idea. i plan on totoally isolating my 120v ac from the rest of the body/chassis. a simple plug to the power pole or generator leading through the breaker box and on to dedicated wall plugs. no chassis gound, no body ground. if no wire can touch the metal, and can only be plugged into either the power pole or the generator, then how will this not work? how will it not be safe?

i plan an entirely seperate system for 12v dc through inverter for solar power and another system for 12v dc only for lights/fans/other.

pick it apart and chastise me!

[jazty]

Originally Posted by claydbal

tell me what is wrong with this idea. i plan on totoally isolating my 120v ac from the rest of the body/chassis. a simple plug to the power pole or generator leading through the breaker box and on to dedicated wall plugs. no chassis gound, no body ground.

It will work fine, until something goes wrong From what I understand, if you have a fully isolated system and a frayed hot wire from an extension cord touches the bus skin, you'll end up with a hot skin condition that won't be tripped by a GFCI or breaker... until something or someone makes the connection from the bus skin to a plugged in appliance (which would likely have an internal connection to ground) or to the physical ground.

For any sort of permanent solution you really have to do it the right way.. this stuff is a BIG deal. People matter. Let's keep them safe

Originally Posted by claydbal

if no wire can touch the metal, and can only be plugged into either the power pole or the generator, then how will this not work? how will it not be safe?

That's a mighty big "if". A shaking, rattling bus; sharp metal; fatiguing wires; user error; etc.. all sorts of things can happen down the road. Just like a big appliance (which the bus essentially is), the ground must be connected to the chassis. Let's think of the bus as a very large washing machine:

One of the problems with appliances and equipment which have a "floating metal case" is that a shock hazard exists if the case comes into contact with the hot wire. This so called "fault condition" may happen in many ways with some of the more common causes being a "pinched" line cord, failure of installation systems, or movement of components due to shock or vibration which will cause the "hot wire" terminal to touch the case. Naturally, if for any reason the case does become "live," then a person touching it may be shocked if he is grounded. If this "hot chassis" is connected to another chassis or instrument by a typical shielded cord, then that chassis or instrument will become hot also. The entire purpose of the present three wire system is to provide a separate ground path which will effectively eliminate any possibility of shock.

quote from http://peavey.com/support/technotes/...hockhazard.cfm

[Scooternj]

Originally Posted by claydbal

tell me what is wrong with this idea. i plan on totoally isolating my 120v ac from the rest of the body/chassis. a simple plug to the power pole or generator leading through the breaker box and on to dedicated wall plugs. no chassis gound, no body ground. if no wire can touch the metal, and can only be plugged into either the power pole or the generator, then how will this not work? how will it not be safe?

i plan an entirely seperate system for 12v dc through inverter for solar power and another system for 12v dc only for lights/fans/other.

pick it apart and chastise me!

S-250, S-788, and larger tactical shelters are not only chassis ground, but Earth-grounded, as is the generator they're hooked up to. The grounds are to protect your equipment *and* you. Even if you'e the victim of a lightning strike, the grounds to chassis will keep you, your guests, and your equipment safe, to say nothing about a loose/worn wire on bare metal. The last S-250 shelter I worked with, as a Guardsman, had a radio system called an AN/GRC-206 in the back. The power cable was grounded to the radio chassis (it ran off 24 VDC), and grounded to the shelter itself. The shelter had a chassis ground lug and strap running from the shelter itself to the frame, which was mechanically bonded to the vehicle chassis, and chassis ground. The power distribution panel that the generator hooked up to had yet *another* ground lug for earthing. All this was done because the shelter is, essentially, a giant metal box, and if there was an electrical arc somewhere, the guy in the shelter was safe from shock until power could be decoupled.

[claydbal]

thanks guys. im thinking of wood fllor, wood paneled walls and running all wires through plastic conduit to wall or cabinet mounted plug ins. i definately dont want anyone shocked, and do want to be safe, so that being said, is anything wrong with my plan? im thinking about the old houses i grew up in. they were all wood and the only way to get a shock was to actually touch the wire itself.

thanks for all input as i am obviously ignorant to ac power. i do have a very good grasp on dc.

[jazty]

Originally Posted by claydbal

is anything wrong with my plan?

Yes. You aren't planning on grounding the bus. Really can't say much more about it.

[jazty]

Originally Posted by claydbal

they were all wood and the only way to get a shock was to actually touch the wire itself.

A log cabin is very different from a steel bus.

[The Painted Lady]

I am beginning the a/c wiring stage of my first skoolie conversion and I am looking to install 50 amp 120/240-volt service. I would like some suggestions on what brand/type to buy and where to buy.

[missingTexas]

What determines which outlets are 15amp versus 20 amp?

Some of my appliances (Fridge, AC units) say they should be wired with 18 gauge. I just figured I would run everything 18gauge but there are so many options.. red black twisted, red black separate wires, just black, just red .. omg my head is spinning

I was thinking I would do all of my outlets in the special CFCI plug just to be safe, but all of this talk of 15 versus 20 amp has me a tad confused.

[jazty]

Originally Posted by missingTexas

What determines which outlets are 15amp versus 20 amp?

Some of my appliances (Fridge, AC units) say they should be wired with 18 gauge. I just figured I would run everything 18gauge but there are so many options.. red black twisted, red black separate wires, just black, just red .. omg my head is spinning

I was thinking I would do all of my outlets in the special CFCI plug just to be safe, but all of this talk of 15 versus 20 amp has me a tad confused.

Well, for starters you should be looking to run 12ga wire for 20amp receptacles and 14ga wire for 15amp receptacles. You'll also want to use properly colour coded wire: green for ground; white for neutral; black for hot. Using any other colours will just confuse things. I'd seriously recommend getting a homeowners guide to electrical wiring from the library. You'll learn a lot.

[headinthetrees]

Originally Posted by bansil

So while I do not have 240V in my bus (since they are not both connected to anything) I still have 2 hots coming in and could for some reason actually put in 240 for say a 12 person hot tube and sauna room

Is it sick that just yesterday I was considering the logistics of a steam room in a shuttle bus? Spray on bedliner and well caulked FRP walls and ceiling - check, drainhole - check, rocket mass heater with water heater coil - check, pressure relief valve wired to a bike cable you can reach from across the room - check, suspension for the fat girl party that inevitably insues - back to the drawing board.

Seriously tho, good info on this thread. If anyone needs help or advice with anything A/C, feel free to pm me. I've worked as a resi and commercial electrician for many years now. D/C and coach wiring is not my specialty by any means and I still have some things to learn about solar, but I can try to point you in the right direction there.

And of course I'll have to chime in on the solid vs stranded debate... Stranded is absolutely a better choice if you're trying to make a quality product to last, especially in harsh environments. It just takes more time to work with and romex is stupidly fast and simple. But again stickframe houses don't rattle down the street. I wouldn't bother going so far to solder everything, but it never hurts if you're a perfectionist. I would make sure to properly crimp ring or spade terminal connectors to any stranded wire and use distribution blocks instead of wire nuts wherever possible especially for large groups of wires. I'm also a huge fan of conduit wherever possible. You don't have to worry about future issues because you can always pull new wire. You can pull exactly the amount of wires you need no more no less. Of course conduit might be pretty challenging to get to some places, so you have to make concessions. Avoid aluminum at all costs, there's a reason it was outlawed to be used in mobile homes. It gets brittle much faster than copper and cracks, creating gaps which arc inside your walls.

Biggest thing is don't guess if you don't know. It matters and you might not get a second chance. Please dont hesitate to pm me if you need advice. I'd rather see it get done the right way than hear any horror stories.

Also, I'm always down to barter for work in northern california and surrounding. Especially if you have cool stuff for my future skoolie. =)

[claydbal]

thanks for the offer to help, HITT. i will be taking you up on that! but a quicky that i think lots of folks have asked and are confused about. what is a floating ground?