Best method for floor wire pass-through?

Hey ya'll, I've scoured the forum and have seen a few different threads covering different methods for how to pass wires through the floor of the van. The main ideas are I've seen between them are:

1. Rubber wire boot (similar to https://www.amazon.com/Daystar-Univ...ywords=rubber+wire+boot&qid=1610247855&sr=8-1). This is also how the pass-through under the driver seat from Mercedes works. If you've done this, does it work well? Seems as if it would be challenging with the ribs of a sprinter floor.
2. Standard cable glands (similar to https://www.amazon.com/TUPARKA-Wate...1&keywords=cable+glands&qid=1610247972&sr=8-5). These seem good for a single wire, but not for a group of wires going across under the van.
3. Simply drill a hole & fill with polyurethane caulk. This is what I've heard most pros do. The challenge with this method is modifying or adding the wires.
4. Anything else?

In my mind the main goals of a floor wire pass through are:
1. water tight
2. removable (so you can add or remove wires)
3. simple (replaceable if damaged)

What have you guys done and what do you think is best?
 

sparkplug

Well-known member
Depends on how many wires and where they need to go I suppose.

I'm not a big fan of running wires on the underside of the vehicle unless you have to.

I've had to do it for the fuel pump on my heater and for the solenoid valve on my propane tank.

Heater cable runs through the existing rubber wire boot in the cab and the propane tank wire runs through a cable gland which I drilled into the plastic cubby under the driver's seat and up round the footwell and up the B-pillar.

I don't like cutting holes in the van body unless I have to, so routing through the plastics or through existing entry points is always preferable IMO. Easy to undo if needed later.

Battery box plastic tray would be another option potentially.

If you really need to go through the metal floor then a rubber grommet would be a good option or if you needed a bunch of cables then you can buy enclosures with multiple cable glands on them so you could cut a large hole in the floor and run pretty much as many cables as you like through them.
 

hein

Van Guru
SAE standards call for 1/2" clearance between metal and electrical conductors.

I like to make a generous hole and then line the metal edge with edge guard or thick rubber grommet. Then protect wires/cables with split loom. If there is extra space to fill then some scrap minicell or pipe insulation works well. If water proofing is needed then slather the outside with some sealant or spray with undercoating. I have no problem routing wires under the vehicle if well protected (split loom), away from heat and well supported with vinyl coated P-clamps and zip ties where appropriate. Routing along OEM wiring is a good strategy. Tying to brake lines is not so good.

Torque nuts and bolts holding lugs to proper specifications. Spray cable connections on batteries or fuse blocks with clear acrylic to reduce chance of moisture wicking into crevices.

Cover all bare positive (and exposed negative) connections with insulators. I have found that wrapping with VHB tape and then cloth electrical tape is a good method. Saturating the cloth electrical tape with CA glue will harden it into a highly durable cover.

This is one area where a bit of overkill is not a bad strategy. Think in terms of lots of miles over bumpy roads or what might happen in an accident.

All the best,
Hein
DIYvan
 
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sparkplug

Well-known member
This is one area where a bit of overkill is not a bad strategy. Think in terms of lots of miles over bumpy roads or what might happen in an accident.
Agreed on that point. This is why I personally prefer to keep external wire runs to a minimum, but split conduit, P clips and zip ties are a minimum requirement to keep it all protected.

Aside from road dirt, salt, grime, moisture, extremes of temperature your other enemies are vibration friction and chafing.

Choice of cable can also be important. Some cope better with the above listed hazards better than others. Avoid anything with rigid cores or with thin insulation like the plague. Embrace anything designed to cope with extremes of temperature and to remain flexible.

You still haven't really told us what you're trying to achieve here, so it's hard to advise further.
 
These are great suggestions, thanks guys.

I have my electrical compartment over the back passenger wheel well and need to run ~3 wires to the drivers side rear wheel well and~3 wires to behind the drivers seat.

I'll need 3 holes to pass wires through (1 in the electrical compartment, 1 in the water compartment, 1 in the bench seat). I am very much the kind of person who likes everything in the van to be removable, so these ideas are great to think about as I ponder my solution.

In my last van I ran wires above the ceiling. This time I want to try run them under the floor.
 

Aqua Puttana

Poly - Thread Finder
If future changes are anticipated a weatherproof box might be a possibility. The concept can work under the floor as well as on the roof.

Post #105 here.


vic
 

Shawn182

Active member
Doing it over again knowing what I know now I would hands down install a boot similar to what is under the driver's seat. Supper efficient and now matter how much you plan there is always going to be something else that you need to run down there at some point!
 

marklg

Well-known member
For multiple wires that are not huge, I've used waterproof connectors like these:


For large wires, I've used cable glands, one per large wire. I might add some Dicor or Sikaflex around them just for additional protection.

Regards,

Mark
 

Airtime

Well-known member
What about these cable boots from TH Marine? They seem similar to the large one under the driver seat. I like the idea of being able to fit multiple cables/hoses in a bundle, and being able to add in the future without new drilling. And if you're going to drill multiple small holes then why not one 2" or 3" hole that can handle hot/cold water plus numerous electrical cables?

My thought is to put a 2" or 3" hole in the flat area in front of the wheel well on both passenger and driver side, and pass all cross-vehicle lines through those two holes with cable boots. Staying out of the BEG no-drill zone.
Cable boot.JPG
 
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Airtime

Well-known member
@gltrimble I just now noticed the two holes that say "water", looks like they go into the large frame channel at the body seam if I am not mistaken. Scanned your build thread but didn't find mention of this. Did you run water lines through that frame member?

Also, at first I thought this was a BEG no-drill area but on closer inspection (the BEG only shows an illustration of the 144) they specifically reference the longitudinal frame members and the area around the spring attachments... but not the frame member at the body seam so looks like it's OK. Knowing your attention to detail I'm sure you were all over that.

A48B2D7E-80FF-4D42-BE6F-601804EDCA59.jpeg
 

Graphite Dave

Dave Orton
Consider running the wiring inside in an insulated floor. I have a plywood floor with a 1 1/2" 80/20 floor frame bolted to the plywood with cabinets bolted to the floor frame. The space between the extrusions is filled with a layer of 1" Polyiso, a layer of 1/16" shower fiberglass and a top layer of 3/8" gym mat. (both the Polyiso and gym mat were slightly oversize).

Floor | Orton Travel Transit (ortontransit.info)

Have three SOOW cords that cross the van in the floor insulation. Just cut a slot in the Polyiso for the cords. 12/2 for DC, 14/3 for AC air heater and 14/3 for 120 v AC outlets. Have a 12 position fuse block on the driver side and a 6 position fuse block on the passenger side. Installing the 6 position fuse block on the passenger side limited the DC to one cable in the floor.
 

Airtime

Well-known member
Consider running the wiring inside in an insulated floor.
That's a good thought and i would do it if I had a thicker floor. But being tall, I sacrificed thick insulation in favor of headroom. I have to go through the floor at least for my water lines so may as well pass electrical over too.
 

gltrimble

2017 170 4x4
@gltrimble I just now noticed the two holes that say "water", looks like they go into the large frame channel at the body seam if I am not mistaken. Scanned your build thread but didn't find mention of this. Did you run water lines through that frame member?

Also, at first I thought this was a BEG no-drill area but on closer inspection (the BEG only shows an illustration of the 144) they specifically reference the longitudinal frame members and the area around the spring attachments... but not the frame member at the body seam so looks like it's OK. Knowing your attention to detail I'm sure you were all over that.

View attachment 170915
You are correct. The only new holes for the water line are just in the thin sheet metal floor. There is a large factory hole in the bottom of the frame member thru which I passed the PEX. The PEX joints are all accessible. You can make up the lower PEX elbow joint prior to sliding the PEX upward to make things easier. I found one picture of the PEX before I installed the heat tracing and insulation. The PEX to the water heater and tee connection is already insulated and wrapped with heat tracing in this picture. You can see the remainder of the heat tracing wire and plug coiled up and zip tied in the bottom of the picture.

3FF36CB9-BD26-479A-AE37-8375EED096FF.jpeg
 

Airtime

Well-known member
Here's another option. I'm sure I've seen mention of this but never had realized how easy it would be. I think this is what I will do. I can pass everything I need from one side to the other with no holes in the van floor at all. Just holes in the bottom of the wall cavities, and then going through existing 3" holes under the van.

Under the van on the outer walls, just forward of the mid-body seam, are these 3" diameter plugs:
IMG_2004.jpg

Removing the plug and looking up at the underside of the floor, you can see a sheet metal piece:
IMG_2008.jpg

That piece is the lower side of the sheetmetal at the base of the wall cavities. Here's the same spot looking down from above, inside the van wall cavity. You can see it is over 2.5" wide, plenty wide for all kinds of holes for cables, water lines, etc. (with grommets added of course).
IMG_2003.jpg

And then the 3" cable boot I mentioned above fits nicely on this hole:
IMG_2010.jpg
 

Airtime

Well-known member
Here's another option. I'm sure I've seen mention of this but never had realized how easy it would be. I think this is what I will do. I can pass everything I need from one side to the other with no holes in the van floor at all. Just holes in the bottom of the wall cavities, and then going through existing 3" holes under the van.

Under the van on the outer walls, just forward of the mid-body seam, are these 3" diameter plugs:
View attachment 171254

Removing the plug and looking up at the underside of the floor, you can see a sheet metal piece:
View attachment 171252

That piece is the lower side of the sheetmetal at the base of the wall cavities. Here's the same spot looking down from above, inside the van wall cavity. You can see it is over 2.5" wide, plenty wide for all kinds of holes for cables, water lines, etc. (with grommets added of course).
View attachment 171255

And then the 3" cable boot I mentioned above fits nicely on this hole:
View attachment 171253
I did use this method and it worked out pretty well. Here's the semi-finished result, not yet fully secured. Covered in my detail and pics in this post in my build thread. Shorter summary:
- the method coming down through walls and through this existing 3" opening on both sides worked great.
- the conduit I used is a bit sticky so I recommend pulling your wire first and then installing conduit+wire
- use grommets in the lower wall penetration, and don't pull conduit too fast or you'll pull them out
- there is a sharp sheet metal edge up inside the wall, install edge guard before you start pulling conduit and pipt
IMG_2125.jpg
 

jmole

Active member
Great approach, thanks for sharing. Do you have multiple cables in those conduits? You mentioned they were a bit "sticky"; do you worry about needing to run additional cables in the future?
 

Airtime

Well-known member
Great approach, thanks for sharing. Do you have multiple cables in those conduits? You mentioned they were a bit "sticky"; do you worry about needing to run additional cables in the future?
Thanks! Just one 12/3 cable per conduit. I thought of using larger conduit with multiple cables but then you lose the bending flexibility of the 1/2" conduit, also would need larger holes in the bottom of the wall cavity. As I learned afterward, the stickiness could have been addressed with cable pulling lubricant. Not carried at my local Home Depot but I assume available at an electrical supply shop.

I don't foresee needing to run any more large cables or plumbing across the van. All large gauge DC and both AC and DC panels are all on the driver side along with the battery bank and inverter. Any smaller gauge wire for branch circuits I'll run in walls and ceiling. Here's a couple more pics showing the transition to interior wiring.

Holes in bottom of wall cavity with grommets installed (tight working area but got it done...)
IMG_2115.JPG

I terminated the conduit using the liquid tight junction box connections. Really I just used them as a simple way to secure the conduit and prevent it from pulling back down through the holes. I had thought about running the conduit through the walls as well, but really with the sheathed Ancor marine cable I'm using, plus edge guard, clamping etc. it would just be overkill. Under the van I was concerned about brush scraping the AC wires so I wanted the conduit. Inside, it's just too bulky and more difficult to route.

Here's a pic of the semi-finished product. My shower stall is going in front of the wheel well, battery box on top of the wheel well. Where the cables come out of that square factory opening will be inside a narrow tall pantry cabinet in front of the shower, and panels will be on the front wall of that, behind the bench seat.
IMG_2281.jpg
 

Sumteacher

New member
I did use this method and it worked out pretty well. Here's the semi-finished result, not yet fully secured. Covered in my detail and pics in this post in my build thread. Shorter summary:
- the method coming down through walls and through this existing 3" opening on both sides worked great.
- the conduit I used is a bit sticky so I recommend pulling your wire first and then installing conduit+wire
- use grommets in the lower wall penetration, and don't pull conduit too fast or you'll pull them out
- there is a sharp sheet metal edge up inside the wall, install edge guard before you start pulling conduit and pipt
View attachment 174299
I can’t tell you how thrilled I was to find this. I searched and searched for a way to get to the rear ground without drilling through the floor. Awesome. Thanks for sharing!
 

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