Routing 12Ga. Romex and drip line for Roof AC

[summerj]

On my 1966 Overlander the Previous owner installed an old dometic roof top ac unit toward the forward half of the trailer (about even with the door) I know that these trailers came pre wired in the rear section however I have this existing opening to work with. Previous owner screwed some flex conduit to the ceiling. to wire the old unit.(looks like crap) and then ran electrical PVC under the belly pan to rear of trailer. I would like to try and use an electricians snake to pull some wire and drip line hose between the outer aluminum and ceiling once I remove the old AC unit. any suggestions? What would be the best route to take? I am not sure how the old AC unit drained since it does not work? I don't want water rolling off the roof so I need to pull a 1/2 hose and 12 Ga 3-wire romex

[AirsDream]

Can't help you with the routing, but note that Romex is not a good idea in an RV ... the vibration will sooner or later cause the solid copper wire to fail. Best to use stranded wire, and best bet is marine grade ... it's designed to take the vibrations that a boat (or in this case an RV) will encounter. Good luck ... I expect that in Fla., A/C is highly desirable!

[Melody Ranch]

12 2 Romex will work fine. Make a short run to the front cap where there are no stringers in your way. You will have to drill and use a firewall type grommet at the one forward overhead stringer. Then down by the window try to fish it along the frame to the floor area where you can route the wire to a circuit breaker and power supply. The drain line can be fished thru the roof directly to the side (street side, 'cause you don't want a puddle where your outside living area and entrance are.) I find it easiest to cut a small flap in the wall inside the cabinet and bring the tube bcd inside and route it in the cabinets to the floor and thru to the exterior. I use 1/2 in ID reinforced tubing....the type that does not kink.

[lewster]

Romex may work fine........BUT FOR HOW LONG??????????

I have a list longer than my arm of circuits that failed in motor homes and travel trailers where the solid copper Romex split due to work hardening from road vibrations. Great for a house.......but your house doesn't bounce along down the road......

The best ones are where the copper split but still made partial contact....every so often for an intermittent problem. Great fun to track down!!!! If you are willing to expend the effort to re-do the poor existing wiring DO IT RIGHT!!

Best to use: 12/3 stranded marine cable. You will NEVER have a problem with it and you 'll never find Romex on a boat!

[Chuck]

Interesting...but the original wiring in my trailer is all romex. what of that?

I would think you'd have a hard time "fishing" much of anything. There are lots of cross-pieces and frame members behind those walls; not much of a straight shot for anything.

[crabbey1]

Lewster, do you have a source for the Marine Grade cable? Is it easy to come by?

[lewster]

Look here: Marine Cable | Marine Wire | Waytek, Inc

[SuperTrouper]

Originally Posted by crabbey1

Lewster, do you have a source for the Marine Grade cable? Is it easy to come by?

Looks like there's several West Marine Stores near you. They carry Marine 12/3.

http://www.westmarine.com/webapp/wcs...&storeId=11151

[crabbey1]

Thanks guys! I thought it would be more expensive. I paid more per foot for the plastic trim J Track than I am going to pay for this. LOL.

[crabbey1]

Do you guys use this Marine Cable for both AC and DC systems? Or just for the AC and use regular 12 gauge stranded wire for the DC?

[lewster]

Originally Posted by crabbey1

Do you guys use this Marine Cable for both AC and DC systems? Or just for the AC and use regular 12 gauge stranded wire for the DC?

I use 2 types of wire: marine cable for AC and most DC work and Class K welding cable for batteries, inverters and solar. Keeps it simple when it's the best!

[crabbey1]

lewster - Do you have some kind of labeling system for all the wires to keep it all in order since it won't be color coded? Specifically the DC side...

[lewster]

Originally Posted by crabbey1

lewster - Do you have some kind of labeling system for all the wires to keep it all in order since it won't be color coded? Specifically the DC side...

When I do more than a couple of wire runs, I usually write on the white outer sheath of the cable (nice feature of marine cable) the circuit description or other identifying information with indelible marker. I also use a Dymo label maker for the electrical trade to further detail the wires.

After making the final connections at the device or circuit breaker/fuse box, I always make sure that the information is still on the wire and is visible somewhere on the sheath or directly on the wire. This is invaluable if you have to trouble shoot a problem or are going to modify the system.

[crabbey1]

That is what I am worried about. Troubleshooting later on down the line... Once I button up these walls, they aren't coming off again.

[lewster]

Originally Posted by crabbey1

That is what I am worried about. Troubleshooting later on down the line... Once I button up these walls, they aren't coming off again.

All AC wire runs are by nature 'home runs' that start at the device and terminate at the circuit breaker box. If any splicing is to be done, it must be in an accessible, approved junction box.

On the DC side, I always run both positive and ground back to the source, be it the fuse panel or a bus bar. This has 2 benefits: You have a single, uninterrupted wire run from source to device for BOTH wires and you are not dependent on frame grounds as a return path for the DC current. Since many DC electrical problems are traced to bad grounds, this method eliminates many of those problems too.

A little more work and a little more wire, but you'll be happy with the results!

[crabbey1]

So you have every outlet run separately? Every light fixture? Etc.? How do you handle that at the fuse box? How do you tie in multiple outlets to the same fuse or breaker?

Thanks!

[lewster]

Originally Posted by crabbey1

So you have every outlet run separately? Every light fixture? Etc.? How do you handle that at the fuse box? How do you tie in multiple outlets to the same fuse or breaker?

Thanks!

You can run wiring in series or parallel; like all lights on one side of the trailer on one run. You just have to make all of your connections accessible, either in separate junction boxes or at the individual devices.

For example, a 12/3 wire comes from your breaker box and it is to run 20 amps worth of wall outlets. wire goes to outlet #1, then splices at #1 to run to #2, then splices at #2 and runs to #3. All splicing is accessible if you remove the wall outlet. This is a series connection

Others might run a separate wire from each outlet into a junction box located in a cabinet or otherwise out of site, but still accessible. All wires from the outlets are then connected to the feed wire from your breaker box. this is a parallel connection.

I like to use screw-type bus bars for all DC main feeder connections. You can wire as above for DC also.

[crabbey1]

OK I got it now. The current wiring of the AC outlets are run in series. I like that setup. Thanks for the clear explanation.

[Melody Ranch]

An RVIA tech is the best source of info. I just use article 551 of the code and RV electrical component company info. And, my 62 year old Airstreams safe and operational electrical systems using Romex for the AC systems. Nowhere does it say to use Marine 12 gauge....it does say, however, to use 12 gage ROMEX....in both sources. http://www.parallaxpower.com/Dist_Pa...%20rev%20A.pdf
I do like the idea of stranded 12v and 110 v wire.

[lewster]

It's your trailer.......use what you like! It certainly isn't 'my way or the highway!'

I merely suggest what I use in my daily professional routine. My clients demand and expect excellence from my installations and I exceed 'code' on a regular basis. Why???? Because I don't want to be called back for a problem that could have/should have been avoided with a little insight, planning and a few more $$$. The other area is professional liability.

Individual's preferences and usage often vary.........so be it..........as long as it's not MY NAME signed at the bottom of the work order

PS: A quick look at the specifications of Parallax products should tell one a great deal about their commitment to quality...........