How to run wires in a bus (order of operation)?

[Brewerbob]

I scrolled thru the first 5 pages of posts but couldn't find anything that fits. I've just about finished the roof raise and I'm ready for the next stage. Only I don't know what the next stage should be:



1) Foam insulation
2) Wiring
3) Plumbing for sinks, shower
4) Plumbing for radiant heat
5) Solar


Should I spray foam the walls and then run electrical? Run the electrical and encase it in the foam? I'm figuring water should probably do the same as electrical. Both encased or neither encased.


If I leave the wiring until after foaming, run conduit in the ceiling? Run all the wiring at the same height thru-out the bus (to prevent putting nails/screws thru it once wall coverings are up), say 2 feet off the floor instead of the ceiling? Run conduit and encase that, fishing wires thru it later? What size conduit?

What did you do on your build, why, and did it work? Would you do it the same way again?

[Sleddgracer]

Originally Posted by Brewerbob

I scrolled thru the first 5 pages of posts but couldn't find anything that fits. I've just about finished the roof raise and I'm ready for the next stage. Only I don't know what the next stage should be:



1) Foam insulation
2) Wiring
3) Plumbing for sinks, shower
4) Plumbing for radiant heat
5) Solar


Should I spray foam the walls and then run electrical? Run the electrical and encase it in the foam? I'm figuring water should probably do the same as electrical. Both encased or neither encased.


If I leave the wiring until after foaming, run conduit in the ceiling? Run all the wiring at the same height thru-out the bus (to prevent putting nails/screws thru it once wall coverings are up), say 2 feet off the floor instead of the ceiling? Run conduit and encase that, fishing wires thru it later? What size conduit?

What did you do on your build, why, and did it work? Would you do it the same way again?

- in a house under construction, it would be #1, wiring and rough plumbing #2 insulation, #3, paneling, ceilings cupboards etc, #4 flooring, #5 fixtures

[Brewerbob]

Originally Posted by Sleddgracer

- in a house under construction, it would be #1, wiring and rough plumbing #2 insulation, #3, paneling, ceilings cupboards etc, #4 flooring, #5 fixtures

Totally agree but buses are a different beast. Tho if I were to build a house it would probably be different since I don't build 50 of them at a time. Drawings, measured, repeated, ....

[Danjo]

I would t run anything in spray foam. If you need to get to it later it’s going to be a mess. For electrical it wouldn’t be to code.

The only thing I’d do prior to foam is install conduit or build some other kind of raceways.

Radiant heat in spray foam. Dunno.

[Brewerbob]

Originally Posted by Danjo

I would t run anything in spray foam. If you need to get to it later it’s going to be a mess.

True but wires don't go bad. You might need to move them which would be just as much of a pain. Or you could do something stupid like drill thru them.

For electrical it wouldn’t be to code.

I dunno about that. Houses get spray foamed all the time.

The only thing I’d do prior to foam is install conduit or build some other kind of raceways.

Maybe a raceway would be better. A conduit that will hold 6 romex wires would be fair size even at 14 gauge and 2 conductor. I bought 12 gauge 3 conductor.

Radiant heat in spray foam. Dunno.

I think I'm going to do 1 inch spray on the floor and then get 2" or maybe 2 1/2" rigid. Then I can router the radiant into the rigid and everything will be nice, flat, and even. And cheaper for the overall thickness.

[Danjo]

Originally Posted by Brewerbob

True but wires don't go bad. You might need to move them which would be just as much of a pain. Or you could do something stupid like drill thru them.



I dunno about that. Houses get spray foamed all the time.


Maybe a raceway would be better. A conduit that will hold 6 romex wires would be fair size even at 14 gauge and 2 conductor. I bought 12 gauge 3 conductor.

I think I'm going to do 1 inch spray on the floor and then get 2" or maybe 2 1/2" rigid. Then I can router the radiant into the rigid and everything will be nice, flat, and even. And cheaper for the overall thickness.

Wiring has ampacity ratings based on certain conditions. Fiberglass house insulation isn’t as tight as closed cell spray foam. I think that encasing wiring in spray foam changes ampacity values because it’s not going to be able to dissipate heat well.

If I were to install conduit I wouldn’t run romex in it. It’s bulky. According to NEC, chapter 9, table 1, a conduit or raceway can be filled to 53% using romex in which the sheathed multi conductor cable is treated as one conductor for the purpose of making that calculation. It’s also hard to pull through conduit. It’s also only technically allowed to be used with romex to provide physical protection. In the context of a bus I’d say that’s applicable because physical protection for romex run through “air” as in between “studs” is considered an 1 1/2” of space from the surface of the stud.

I think metallic or non-metallic conduit is is the way to go. You can fit a lot more conductors if using THHN or THWN. For instance in 3/4” EMT you can run 16 12 gauge conductors.

[Brewerbob]

Originally Posted by Danjo

Wiring has ampacity ratings based on certain conditions. Fiberglass house insulation isn’t as tight as closed cell spray foam. I think that encasing wiring in spray foam changes ampacity values because it’s not going to be able to dissipate heat well.

I dunno if I buy that with a 15-20 amp 110v circuit. I doubt you're anywhere near capacity.

If I were to install conduit I wouldn’t run romex in it. It’s bulky. According to NEC, chapter 9, table 1, a conduit or raceway can be filled to 53% using romex in which the sheathed multi conductor cable is treated as one conductor for the purpose of making that calculation. It’s also hard to pull through conduit. It’s also only technically allowed to be used with romex to provide physical protection. In the context of a bus I’d say that’s applicable because physical protection for romex run through “air” as in between “studs” is considered an 1 1/2” of space from the surface of the stud.

Thx for looking it up but I bet NEC doesn't have a chapter for buses.

I think metallic or non-metallic conduit is is the way to go. You can fit a lot more conductors if using THHN or THWN. For instance in 3/4” EMT you can run 16 12 gauge conductors.

I don't know what THHN or THWN is but I'll google it.

[PNW_Steve]

Danji said it well.

I would add:

Non metalic is handy as you can bend it to conform to irregular routes using a heat gun to soften it a bit. If you are anything like me.... Practice with some scrap first....

[PNW_Steve]

Originally Posted by Brewerbob

Thx for looking it up but I bet NEC doesn't have a chapter for buses.

If the bus is hauling school kids then you are correct.

Once you start adding the fitments that make it an RV it is a different story. NEC does have sections that apply to RV's.

[Brewerbob]

Originally Posted by PNW_Steve

Danji said it well.

I would add:

Non metalic is handy as you can bend it to conform to irregular routes using a heat gun to soften it a bit. If you are anything like me.... Practice with some scrap first....

What's the worst that can happen?

Originally Posted by PNW_Steve

If the bus is hauling school kids then you are correct.

Once you start adding the fitments that make it an RV it is a different story. NEC does have sections that apply to RV's.

Under NEC or does it become something else? Aircraft isn't NEC but is damn sure regulated. Figured RVs and auto in general would be under something else.


ISO900 isn't good enough for the automotive industry. That's QS9000. And that's not good enough for telecommunications. That's TL14000. And none of it is good enough for space. That's AS9000. At least MIL-STDs are finally dying off. Bunch of out of work, over-paid QA pukes. I hate them all.


P.S. I work in QA and I assure no one hates them more than me.

[Danjo]

Originally Posted by Brewerbob

What's the worst that can happen?

Under NEC or does it become something else? Aircraft isn't NEC but is damn sure regulated. Figured RVs and auto in general would be under something else.


ISO900 isn't good enough for the automotive industry. That's QS9000. And that's not good enough for telecommunications. That's TL14000. And none of it is good enough for space. That's AS9000. At least MIL-STDs are finally dying off. Bunch of out of work, over-paid QA pukes. I hate them all.


P.S. I work in QA and I assure no one hates them more than me.

Sounds like you know what you’re doing. Why did you even ask?

[PNW_Steve]

Originally Posted by Brewerbob

What's the worst that can happen?

Under NEC or does it become something else? Aircraft isn't NEC but is damn sure regulated. Figured RVs and auto in general would be under something else.


ISO900 isn't good enough for the automotive industry. That's QS9000. And that's not good enough for telecommunications. That's TL14000. And none of it is good enough for space. That's AS9000. At least MIL-STDs are finally dying off. Bunch of out of work, over-paid QA pukes. I hate them all.


P.S. I work in QA and I assure no one hates them more than me.

NEC does have sections that apply to RV's.

As far as I have found, so far, NEC does not speak to airplanes, motor scooters or submarines. I'll keep my eyes open though.

[Brewerbob]

Originally Posted by Danjo

Sounds like you know what you’re doing. Why did you even ask?

Take it easy.

I'm not terribly worried about passing or not passing code. I'm wondering more what people have done to either hide their wiring or how they've left it accessible without being an eyesore.

In normal stick build, they go drilling holes in the 2x4s for horizontal runs when they have to. I don't really want to do that as my 2x4s are only 1x2s and made of steel. If you bury them behind whatever your final wall covering is, how do you go around the hat channels?

Looks like OEM was a piece of sheet metal that was bumped out about an inch or inch and a half below the ceiling curve and above the windows. It's been so long ago that I had to go back thru my pictures. All of that sheet metal is long gone.

Make a cable run up top at the ceiling or the base of the wall? Probably a good idea to do both; water down below and electric up high.

[family wagon]

Originally Posted by Brewerbob

In normal stick build, they go drilling holes in the 2x4s for horizontal runs when they have to. I don't really want to do that as my 2x4s are only 1x2s and made of steel. If you bury them behind whatever your final wall covering is, how do you go around the hat channels?

[snip]

Make a cable run up top at the ceiling or the base of the wall? Probably a good idea to do both; water down below and electric up high.

I figure that because a) the lip on the chair rail sticks out a bit and b) I want insulation to be thicker than 1.5 inches anyway, I'm going to use spray foam to the depth of the hat channels or maybe 1/4" more, and then fit board foam over that to bring the wall surface up beyond the projection of the chair rail lip. The board is a little more economically friendly as you know.. but I may end up deciding the savings isn't that great and use spray foam exclusively..



I'll cut channels in the foam to allow a couple pieces of EMT to run the length of the bus on the left side, probably 1" and probably near the ceiling, with 4-square junction boxes at each end and 2-3 places along the way. Haven't quite worked out how to drop down the wall where necessary - maybe wires will just exit at the j-box and fit into a vertical groove in the foam without any conduit.



One of these front-to-back runs will carry chassis circuits - tail lights and whatnot - while the other will carry 120v circuits. Non-chassis low voltage circuits will probably be pulled in with the chassis stuff.


I'll also embed some kind of tubing that runs across the ceiling and down the right side wall to support the few circuits that need to be dropped over on that side. Probably use something like PEX or thin-wall HDPE of some kind for these pieces.

[mrpincher]

I didn't have a firm plan at the outset of the electrical run. So I took marking pens and drew the wiring run, fixture placement, etc. onto the foam surface. Once I got something I liked I cut wire and hot glued it temporarily to the hard spray foam. Trimmed the wire for final length, spliced it all in one big wad and shoved it behind a door. Kidding on the last part.

It wasn't very efficient because I had no clue what to do first. Just had to dive in somewhere.

Mike

[HazMatt]

Always ascertain depth to bottom, first.
Else may leave a knot...

[mrpincher]

Preferably a knot vs. a noose.

[HazMatt]

Good call.
One one may recover from...
The other'll just leave ya hanging.

[Brewerbob]

Originally Posted by family wagon

I figure that because a) the lip on the chair rail sticks out a bit and b) I want insulation to be thicker than 1.5 inches anyway, I'm going to use spray foam to the depth of the hat channels or maybe 1/4" more, and then fit board foam over that to bring the wall surface up beyond the projection of the chair rail lip. The board is a little more economically friendly as you know.. but I may end up deciding the savings isn't that great and use spray foam exclusively..

Your dimensions are either 1) wrong or 2) a fair amount different than mine. My hat channels (ribs) are 2" by themselves. I measured the lip of the chair rail. I don't remember the number but I want to say it is 3/4". Might be 7/8" or even an inch but it was no less than 3/4". That's a 2 3/4" wall thickness.

I do like this approach of using both. I'm certainly no expert but from the numbers I saw, the rigid foam board has almost the same R value per inch as the spray does. I wouldn't use spray at all except for the sealing aspect. Spray an inch or inch and a 1/4 and use 2" rigid? That'll get a 1/4" to 1/2" past the rail. Use a dado blade and cut a notch for the rail. That should keep the thermal bridging people happy.

I'll cut channels in the foam to allow a couple pieces of EMT to run the length of the bus on the left side, probably 1" and probably near the ceiling, with 4-square junction boxes at each end and 2-3 places along the way. Haven't quite worked out how to drop down the wall where necessary - maybe wires will just exit at the j-box and fit into a vertical groove in the foam without any conduit.

As long as you stay away from the ribs, that would probably be ok. I'm just worried about an errant screw while putting up cabinets or something.

One of these front-to-back runs will carry chassis circuits - tail lights and whatnot - while the other will carry 120v circuits. Non-chassis low voltage circuits will probably be pulled in with the chassis stuff.

I've been wondering about the 120 circuits too. EVERYTHING in a stick house is 120 but how many do you need on a bus?

Fridge
AC
Outlets

Maybe stove and water heater (pilot lights)

I want to use diesel for a stove. Haven't looked so far as to see what they use for a pilot light. Would be really nice to use diesel heat for radiant as well. Anywho, that's a grand total of four circuits above. Solar to controller is a different ball of wax but will only need to run vertically.

I'll also embed some kind of tubing that runs across the ceiling and down the right side wall to support the few circuits that need to be dropped over on that side. Probably use something like PEX or thin-wall HDPE of some kind for these pieces.

What circuits are those and why are they different than the other side?

Oh speaking of the same, I want the 50 amp service and water on both sides of the bus just "because". I won't be forced to back in, carry a 50' cord, etc. I like options.

Originally Posted by mrpincher

I didn't have a firm plan at the outset of the electrical run. So I took marking pens and drew the wiring run, fixture placement, etc. onto the foam surface. Once I got something I liked I cut wire and hot glued it temporarily to the hard spray foam. Trimmed the wire for final length, spliced it all in one big wad and shoved it behind a door. Kidding on the last part.

It wasn't very efficient because I had no clue what to do first. Just had to dive in somewhere.

Mike

Fixture = electrical boxes?



That's another thing about stick build. All of those are installed then sprayed. Deciding where to out outlets should be fairly easy. Every rib, both sides!! I hate looking for outlets. I won't put quite that many in but every other rib most likely. Kitchen ones will need to be higher is all.


Spray foam, rigid, or both?

[mrpincher]

Fixtures = the small toilet fan, the big roof fan, 14 LED lights, switches. All the wire for this is sandwiched between the wood ceiling and the foam insulation. BTW - I have been able to feed a wire snake back up to a couple of the LED lights. It turns out the LED lights I bought cannot be wired in series. Should read the directions first.


I ran the wire for most of the wall outlets and big appliance receptacles under the floor in plastic conduit. I recessed the conduit in channels cut into the 2" pink foam insulation.


I still had to drill down through the bus floor to run a wire between the generator plug and the (soon to purchase) transfer switch.



I'm like you...I hate to hunt for a place to plug in my stuff.



Mike