Confused about type of 120V wiring to use...

[cheetah1]

I could use some advice regarding wiring. Background - we have a 1968 30' Sovereign (rear bath - twin bed) and the wiring overall is in great working order! I replaced and moved the original breaker box with a modern breaker box which then gave me a couple of more breakers (vs the original four) to use.

I opted to run an additional 120v 12-2 copper line down the curbside length of the trailer culminating by the front entrance door which gives me an outlet next to the kitchen stove that I can use for a microwave (on its own breaker). I am also going to run a second 12-2 copper line on its own 20 amp breaker around the rear bath wall and down the street side wall to give me another 20 amp outlet culminating right outside the fridge wing wall on that side of the trailer. Don't know what I'm going to use it for yet - but - I am taking the opportunity to run it before I put that rear bath back together.

My confusion is coming from reading some of these forums that say that normal household 12-2 NM copper wire with ground wire is fine to use - and others say to ONLY use #12 stranded THHN copper building wire. My Question is that since I am running only these two additional lines down either side of the trailer - do I need to use THHN stranded wire or can I use regular household 12-2 NM wire?

Any input would be greatly appreciated! Thanks in advance!

[BIGED52]

cheetah1, The problem is that standard house wire is made of a more rigid copper and that can cause it to break under the conditions that your trailer would be exposed to. The road bumps and trailer flexing does create undo stress on solid copper wiring. That is why all trailer manufacturers use stranded copper in their coaches and the same applies to motor homes. The bigger problem in the older (60's) trailers is back then Airstream used aluminum wiring that has had a history of breaking and shorting out in the walls. Fires have also been found to occur due to aluminum wire overheating. Most owners have upgraded to stranded copper during the re-wire process because of these issues. Hope this helps, Ed

[Trailbob]

You might consider 12/3 marine stranded wire. That will give you a wire for hot, neutral and ground. I've found the best selection on e-bay, but if you have a West Marine, or similar, near you they should have it. Here's one source:

http://www.ebay.com/itm/12-3-AWG-Gau...nMyfpnI1DMafxw

[David F]

My opinion is that solid wiring (Romex) is fine. If supported properly, the movement the wire will experience is negligible and thus not likely to break from fatigue. It is not like the trailer is going down the road vibrating every day. Also, solid copper wire is less susceptible to corrosion due to the high humidity swings RV's usually experience.

If the aluminum wiring in my '67 has held up fine all this time, I think you will be fine with solid 12 ga. copper wire (which is more common for 120v circuits). Not to mention the extra protection Romex offers (i.e. outer insulation). Excessive heat generated from aluminum wiring is due to poor connections...which is usually caused by corrosion at the connection. Dielectric grease on the wire before the connection is made up will help keep the corrosion down. Check/clean connections each year.

[waninae39]

The only issue with solid wire is that It can fatigue over time in an environment that is very bumpy and/or vibrates . That is why multi-strand wire is used in those conditions. Removing the Aluminum wire is likely the best move. It does oxidize faster and that causes the resistance to built up at joints and connections. The higher resistance creates heat which leads to fire

[Greg1410]

I re did all my wiring. The solid wire in the trailer lasted 40+ years just fine. But I still replaced with 12/3 marine wire. Was a bit more expensive, but gives me some peace of mind. One bonus of working with the marine wire, since it is stranded, is it is very flexible and so much easier to work with. I think that is worth the extra cost in itself!
Greg

[Wabbiteer]

When solid conductor(s) sway like a tree branch in the wind then you have major risks! Long unsupported wire runs trampolining up and down from even people moving around in the trailer would be very bad, the pivoting would focus at a hinge point and fatigue the wire.

This is where the pink fiberglass insulation did some double duty on Vintage Airstreams: However assembly line electrical crews left the romex wiring it got frozen in place when the shell cavity got stuffed with fiberglass... all of the romex was in good shape on my 27' '73 too.

Keeping the sheathed wire immobile along its entire run and anchoring it within four inches of every termination point would be a very good start to using solid conductor. Also - use a purpose-built insulation stripper tool, if you nick the conductor cut it off and try again, that is real bad mojo if the structure is to be occupied especially with sleeping people.

Marine stranded is 'limp' so that it lays down in wiring troughs and is nearly effortless to loom together in tight spaces and resists 'swaying' when being slapped around by constant chop/waves/wake on board a boat, and it resists water intrusion much better...

Everything I've said aside, I went with 250' spools of Marine stranded 10 & 12awg for my Promaster conversion van with the remainder to be used on my '73 project trailer... Visualizing 75 miles of washboard road outbound and back somewhere like Fairbanks Alaska kinda made the purchase easier.

https://www.waytekwire.com/products/...f-Conductors=3 <-- this might be a good case of do as he does not as he says, 14awg solid $62+tax at home depot, stranded marine $107+shipping at waytek...

[prairieschooner]

Stranded better than solid conductor. But let's throw a wrench into the discussion! Double Pole Main Circuit Protection with Polarity Indication and Ground Fault Circuit Interrupter. scroll down to get an idea;
http://www.airforums.com/forums/f106...-122678-7.html

You will be camping so be safe.

[mbenedict]

I'll add another vote for Ancor marine, tinned, 3-wire stranded cable - West Marine. More corrosion resistant than automotive.
Much easier to work with, in the quantities you are looking at, a small extra price for the quality.

[USAtraveler]

EITHER solid or stranded work fine. In fact, 14-2 would have worked. With either, use grommets where wire passes thru frame members to prevent chafing. Incidental contact with aluminum skin is no big deal unless wire is so loose it constantly rubs up and down A LOT. In such cases stranded is no better than solid (and may be worse since it is more flexible). Fasten the wire down well where you can. If rub contact looks like it may be an issue, enclose the wire at those points with some split seam plastic insulation. You'll be fine.

[Jacob D]

Originally Posted by David F

My opinion is that solid wiring (Romex) is fine. If supported properly, the movement the wire will experience is negligible and thus not likely to break from fatigue. It is not like the trailer is going down the road vibrating every day. Also, solid copper wire is less susceptible to corrosion due to the high humidity swings RV's usually experience.

If the aluminum wiring in my '67 has held up fine all this time, I think you will be fine with solid 12 ga. copper wire (which is more common for 120v circuits). Not to mention the extra protection Romex offers (i.e. outer insulation). Excessive heat generated from aluminum wiring is due to poor connections...which is usually caused by corrosion at the connection. Dielectric grease on the wire before the connection is made up will help keep the corrosion down. Check/clean connections each year.

My '67 is almost completely original and has the aluminum wire which has never given any trouble. It also has the original Dometic reefer which had an old fashioned brown 2 prong bakelite plug and was plugged in behind the oven where I coiuldn't see it. About 3 years ago the wires shorted inside the bakelite plug and popped the breaker. I had always thought the reefer was hard wired but I found out different when I traced the wire using a mirror. After removing the oven I put in a 3 prong receptacle and new plug and all was well. I appreciate the above comments because I am reminded I forgot to use dieletric grease so my next move is to do just that.

[cheetah1]

Thank you for the explanation as it clears things up greatly. Unfortunately, I am not removing/replacing all the aluminum wiring currently in the trailer as all fixtures and outlets work great. I also looked at all the connections behind the wall plates and found no corrosion or "burn" signs. I used the proper 'Alumiconn' aluminum to copper lug connections at the old breaker box to extend the aluminum wiring there into copper wiring into the new breaker panel. I am not running these two additional circuits any great length, it seems prudent just to use the stranded copper wire. Thank you for your advice!

[cheetah1]

Trailbob - thank you for that link on the marine stranded wire!

[jdalrymple]

The factory has used Romex 12-2 with ground for years.

In standard nomenclature, 12-3 Romex has four conductors: black and red for line, white for neutral and bare for ground.


THHN is intended to be installed inside conduit.



Regards,

JD

[cheetah1]

Thank you to all for your insight and your suggestions. Based on your input and given that these two wire runs I am going to do are approx 15' and 25' from the breaker box to the outlet, I am going to use the Romex 12-2 with ground for these two runs. These are both going to be surface runs snaking under the twin bunks and kitchen sink / counters. From all of our comments, I did learn to secure the wire to the walls to reduce the up and down flexing/bouncing. Worse case scenario, should one of these two wires break some time in the future, they will be easily accessible. Thank you again for all of your input! Very Much Appreciated!!

[Boxite]

You'll do fine. You have already indicated you know to use correct connectors and fixtures for mixing aluminum and copper wiring. I'd only add to use a bit of Ox-gard electrical grease to each to insure against corrosion.

Purists are correct to recommend stranded/tinned wiring in vehicles and boats/aircraft/etc. But Airstream has used residential Romex for decades and had no issues with it, likely because there is very little-to-no actual movement of the wire looms once the trailer is assembled..... the Romex is only used for 120V and is in the lower walls and floor where little movement can occur. (Notice that AS correctly used stranded in tail lights, clearance lights and 12v circuits however.)

[cheetah1]

Bauxite, Thank you for your reply. I truly do appreciate your insight. I did decide to use the romeo for these two short runs. Thanks again!

[David F]

Originally Posted by Boxite

You'll do fine. You have already indicated you know to use correct connectors and fixtures for mixing aluminum and copper wiring. I'd only add to use a bit of Ox-gard electrical grease to each to insure against corrosion.

Purists are correct to recommend stranded/tinned wiring in vehicles and boats/aircraft/etc. But Airstream has used residential Romex for decades and had no issues with it, likely because there is very little-to-no actual movement of the wire looms once the trailer is assembled..... the Romex is only used for 120V and is in the lower walls and floor where little movement can occur. (Notice that AS correctly used stranded in tail lights, clearance lights and 12v circuits however.)

All the 12v circuits in my '67 are solid aluminum "romex" conductors.