Electric wiring in floor - Bad idea?

I am running most of my electrical wiring through the walls and ceiling however there's a few places where it would be easier to run through the floor. For example, connecting my battery which is front of the rear right wheel-well to the heater which is under the passenger seat. I would have to go up and around the sliding door, or I can just go under the floor. What do you think about running electric in the floor? My gut tells me it's a little risky due to spills, but in reality there's 2 layers of insulation on the wires. Any thoughts are helpful!

IMO there's no problem with this, and I have some wiring run this way too. Just make sure it's free of excessive bends, isolated from abrasion, not subject to foot traffic, and worry not. As long as you're not running bare copper then you have nothing to worry about from spills. If you were running bare copper you'd have bigger problems on your hands anyway, such as what the hell are you doing....

You could also run it under the black plastic cover on the sliding door step. There is a channel on the inboard side of the cover big enough to fit 2'0 cable, I ran my cables from my Sterling B'B charger located under the passenger seat to my house battery bank behind the rear passenger wheel. The cover is held down with 5 or 6 machine screws hidden under round plastic covers. Pop the covers up and unscrew the screws, good practice for when your sliding door fails!

Suggest routing under the vehicle in split loom. Grommets where wires exit and enter.

All the best,
Hein
DIYvan

hein said:

Suggest routing under the vehicle in split loom. Grommets where wires exit and enter.

All the best,
Hein
DIYvan

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I'm seconding this for low voltage wiring. Everything I have added is under the van in split loom. I have used grommets but also used the plastic liquid tight strain reliefs / cable glands. All wiring is stranded.

For high voltage AC wiring, everything I have added is stranded and in some kind of conduit, sometimes flexible metal conduit. I already had original wiring I didn't install rub against the chassis and short out. Inverter charger saved me from electrocution or a fire. So, I'm kind of paranoid about that.

Regards,

Mark

Even full immersion in water is not a problem for proper spec wiring, I use UL rated fully tinned fine-stranded boat cable wherever exposure to the elements is possible (actually throughout, easier to keep just a half dozen spools on hand.)

Wherever you "bury" wiring, do not have any terminations or connections like splices in there, only where they're easy to access.

Abrasion / hot spots / vibration / strains to be avoided as much as possible.

Draw and keep updated an annotated and complete map of the electrickery work FFR.

Running cable/wire under the flooring isn't completely unsafe. Particularly with the 12 volt system.

Properly fused/sized/insulated wire is protected against catastrophic failure from shorts and overload. As with any installation make certain all is protected from abrasion. There is danger of someone running a screw into the floor and damaging the conductors, but that can be said of wiring in the walls or top area. I would not hide any splices or connections under the floor. That is true for any connections. It is never a good idea to bury splices and connections because they have a greater chance of failure vs straight through conductors.

If it is convenient for your installation it can be a good option.

vic

Added:
Composing while John61ct posted. What he said too.

I have three SO cords in the floor. One part of the floor sandwich is a layer of 1" polyiso so I just cut narrow slots in the polyiso for the cords. One 14/3 for the 120 volt AC outlets on passenger side, one 12/2 for the 12 volt DC power between the two Blue Sea fuse blocks and one 14/3 for the electric 750 watt air heater. No connections in the floor. Used two fuse blocks to limit wiring in the floor. 12 position on the driver side and a 6 position on the passenger side. All the 12 volt DC wiring on passenger side powered from the 6 position.

I agree with all others, and I too ran wiring like Island Jim from my passenger cabinet at rear of slider to front passenger seat base via the slider door step trim. I created my own step trim with a channel for wiring within it, including 2/0 and some smaller DC circuits. I also ran AC and DC wires and hot and cold water lines all together (I know, seems scary but no terminations or splices until routed up into cabinets on each end) in the recessed floor channel from driver's side to passenger side at rear of slider. Within that I have several DC circuits, including some #2 wires from main electrical panel to DC sub panels and also from AC main to AC sub panel. This recessed channel works great for a number of these wires and hose without having to run them under the van and over the exhaust pipe, plus keeps the water lines in the insulated interior. My subfloor goes right over these at the same surface level and I don't have any screws going thru the floor, so no concerns there. In floor works great for electrical power transfer from front to back and side to side. Here's some photos of this section.

kcshoots said:

I agree with all others, and I too ran wiring like Island Jim from my passenger cabinet at rear of slider to front passenger seat base via the slider door step trim. I created my own step trim with a channel for wiring within it, including 2/0 and some smaller DC circuits. I also ran AC and DC wires and hot and cold water lines all together (I know, seems scary but no terminations or splices until routed up into cabinets on each end) in the recessed floor channel from driver's side to passenger side at rear of slider. Within that I have several DC circuits, including some #2 wires from main electrical panel to DC sub panels and also from AC main to AC sub panel. This recessed channel works great for a number of these wires and hose without having to run them under the van and over the exhaust pipe, plus keeps the water lines in the insulated interior. My subfloor goes right over these at the same surface level and I don't have any screws going thru the floor, so no concerns there. In floor works great for electrical power transfer from front to back and side to side. Here's some photos of this section.

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I am concerned about unprotected Romex passing by the metal bar that I see in the picture.

Here is what can happen. It took 10 years to rub through and short hot to ground.




Regards,

Mark

marklg said:

I am concerned about unprotected Romex passing by the metal bar that I see in the picture.

Click to expand...

I think that "metal bar" is merely a bubble level laid on top to show us that the wires are definitely under the sub-floor's surface.

--dick

marklg said:

I am concerned about unprotected Romex passing by the metal bar that I see in the picture.

Here is what can happen. It took 10 years to rub through and short hot to ground.


Regards,

Mark

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Your picture is an example of what appears to be building wire and why solid conductor building wire in a vehicle/RV conversion needs to be installed with attention to detail as to routing and chafe protection. To save cost it is used in many recreational vehicles and trailers by manufacturers. *Most* of the time those units have a specific wiring method. That doesn't change the fact that stranded wire is a better choice.
Added:
A second look. Probably the abraded/smoked wire in the picture could be orange extension cord with fused conductors appearing to be solid. Typical orange extension cords have a light duty outer jacket. (Even lighter duty than SJO rated cord.)

The wire in the other pictures you reference appears to be marine grade wire. That wire has multi-strand tinned conductors and a bit tougher outer jacket vs building wire aka Romex [or orange extension cord wire]. The marine grade wire is much more forgiving as to turns and abrasion.

The above said, I would add some chafe guard (simple plastic sheet) to any metal edges as you point out. (Except the edge in question is a level as Autostaretx reminded us.)

vic

Added:
Oops. Dick is right.

autostaretx said:

I think that "metal bar" is merely a bubble level laid on top to show us that the wires are definitely under the sub-floor's surface.

--dick

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SO cords have a thick rubber covering and are stranded wires.

Graphite Dave said:

SO cords have a thick rubber covering and are stranded wires.

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SO, SOO, SOOW cord is rated 600 volt. It is heavy duty. SJO is rated 300 volts.

vic

The Class B and C RV manufacturers do this all the time. In the front of the cab you should already have a rubber grommet from hell under driver seat. Just route away from mechanical and heat sources, use protective split wire loom tubing, and have fun with zip ties. When in doubt, follow where Mercedes or RV Manufacturer has already routed wires.

Best,
-Mark

marklg said:

I am concerned about unprotected Romex passing by the metal bar that I see in the picture.

Here is what can happen. It took 10 years to rub through and short hot to ground.

View attachment 110727


Regards,

Mark

Click to expand...

To clarify in the photo, that is a level that I placed to show the level between the two sides of the trough and the floor insulation. I placed it there before I insalled the remainder of the flooring over the wiring and tubing to ensure that the subfloor would be evenly supported across this wire pathway and that none of the wires or tubing would be proud and those compressed. Additional floor padding and then the subfloor go on over that, before the finished floor.

autostaretx said:

I think that "metal bar" is merely a bubble level laid on top to show us that the wires are definitely under the sub-floor's surface.

--dick

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That is correct, the metal bar is just a bubble level placed to show the level between the front and rear section of that recess. Additional floor padding and subfloor and finished flooring were installed over the marine grade sheathed stranded wires (bubble level removed of course). No metal is touching the wire casings except those laying flat against the factory floor pan, which is smooth and continuous along the length of this recess.

Despite the fact that you don't intend to run a screw into the floor, i'd still be highly motivated to paint a red stripe along the "trough's" pathway, with "wireway -- do not drill" stencilled along its length.
Perhaps even underneath the floor (i.e. from the ground looking up) as well.

--dick

autostaretx said:

Despite the fact that you don't intend to run a screw into the floor, i'd still be highly motivated to paint a red stripe along the "trough's" pathway, with "wireway -- do not drill" stencilled along its length.
Perhaps even underneath the floor (i.e. from the ground looking up) as well.

--dick

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With my floor construction a removable 3/8" thick rubber gym pad sits on top of the slot in the 1" polyiso. Gym pad can be lifted up to expose the wiring and slot.