Waterproof wiring: tongue box to trailer

[lfhoward]

Hi everyone,

I recently picked up an aluminum tongue box to hold my three 12 volt deep cycle batteries.


The next job is figuring out how to wire these batteries to the trailer in a waterproof fashion. The fuse box and 1000 watt inverter live inside the trailer, so I need some heavy gauge wire to span the gap between the battery box and the inverter.


I've been looking at flexible conduit like this, with waterproof glands on each end.

Or

With


The waterproof fittings will work nicely on the tongue box, which is thin enough metal to drill and have the fittings mount on. The trouble would be how to make a waterproof seal & pass-through on the trailer side of things. My walls are 1-1/4 inch thick (1/4 ply sandwich with 3/4 inch foam insulation in between). The fittings above would certainly not screw into wood. They seem to be designed for an electrical box, but I don't want an electrical box hanging off the front of my trailer.

So here's where you give me some ideas! Is there a better way to connect the wiring between the tongue box and trailer? If I'm on the right track looking at this kind of conduit, how would you have it connect through the trailer wall?

Thanks for your help!
Lauren

[KCStudly]

Here's how I did mine thru the bottom of my front locker bump out: http://tnttt.com/viewtopic.php?p=1081874#p1081874 .

I would prefer to see you do this in a solid wood block, as I don't think the caulk sealant will live going thru a foam sandwich. The CPVC union half was bedded in caulk and press fit into the 1x (3/4 thk) board. You could cut a hole thru your inside panel, and glue in a block (1x with a 1/4 shim sandwiched, or 5/4 stock) with a routed counter bore (or chiseled) to set the correct final thickness needed to suit the press fit.

[GuitarPhotog]

Common practice is to put a junction box on each end of that flexible conduit, using fittings such as you show.

Then you can use a polyurethane caulk, such as TremPro to seal the place where the conduit penetrates to tongue box and the cabin wall.

<Chas>

[lfhoward]

That's an elegant solution, KC. I may have to cut out a section of interior plywood I already installed to be able to put in a 3/4 inch thick board to support the PVC union half (bulkhead fitting), or else I could drill through one of my existing 2.5 inch wide x 0.75 inch thick beams that's already in the wall.

Chas, I can see how a junction box would be helpful on the interior of the camper, to help the wires make a 90 degree turn to the utility closet on the port side where the electronics reside. Thanks for the idea.

[Socal Tom]

Personally, I would consider putting the inverter in the box with the batteries. Its a lot cheaper to pull the 120V wires to the TD, than to pull some heavy guage DC wires.
Tom

[lfhoward]

Personally, I would consider putting the inverter in the box with the batteries. Its a lot cheaper to pull the 120V wires to the TD, than to pull some heavy guage DC wires.
Tom

The inverter's manual says not to install in the same compartment as batteries, as electrical sparking from the unit can ignite H & O2 gasses that may come from the batteries. Big boom. I hear what you're saying, though. Routing chunky 1 AWG cables back to the camper will be more of a pain than some 14/2 AC wire and some smaller gauge DC wires for the lights and fans.

[les45]

I used clear silicon based plastic tubing to run my DC wiring from the battery box on the tongue to the cabin wall. Drill the holes small enough that the tubing fits tightly and effectively seals itself. You can add some silicon around the hole if you want but I had no leakage without it. In the pic below, one tube holds two #8 primary wires from the battery and the other holds the four smaller wires for the trailer running lights.

[bobhenry]

If they enter and exit from underneath they are shielded by the box and the trailer floor. My theory is it's difficult to get water to run up hill .