Using automotive primary wire for 30a outlet

[fofobraselio]

Ok, so I feel like I initiated a bit of a storm here..

I am planning to use primary wire - the stranded wire that seems to be used for 12v applications, the same wire I have used to wire everything in my trailer, different gauges for different applications, 14g for LED LIGHTS, 12g for 12v fridge and so on.

Understanding that 30A is considerably powerful and requires at least 10g wire, I am opting for 8g wire just to be on the safe side.

Starting from outside to in, I have a 20 amp male to 30 amp female extension cord connector that will twist lock to the 30 amp male inlet on the outside of the trailer.
On the inside of the trailer, the female portion of the inlet, I will strip and insert the 8 gauge wire to the ground, neutral and hot ports and lead them to the 110v ground bar, neutral bar and 30a circuit breaker in my converter respectively. (This ground bar is not the same as my 12v ground bar FYI)

I know that for such a short range (less than 3ft) using 8 gauge wire is more than enough for 30A draw especially if this wire is rated for 200°C and 600V.

I am wondering if it is OK to use this wire for this application as opposed to the ridgid wire used in houses (which is harder to work with)

As long as the wire is rated for 30a, 110v and a high temperature does it matter if its the flexible stranded stuff or the ridgid household wire?

Am i pulling hairs here?

Ps, you guys rock

[Borrego Dave]

Mark, probably the biggest reason for using stranded over solid wire in an RV is the stranded is flexible and will hold up better in the rolling earthquake environment of RVs with out breaking. Stranded is a lot easier to use in close quarters. Although in the real world I'm sure it's been done many times without a problem because of the wire but more to a connection loosing up. From my own experience with any house or vehicle, any wiring problem was always from a loose connection and fortunately never a fire. YMMV

[John in Michigan]

Mark, I don't understand your statement "Starting from outside to in, I have a 20 amp male to 30 amp female extension cord connector ...". Can you explain this?

[steve dunham]

You are making this far more complicated then needed

1) Your home is wired in NM (Romex ) because it is the least expensive code approved wiring method ( Romex is not allowed in many applications )
2) If you buy a spool of # 10 wire that is stranded you will pay 10% more than # 10 solid cause it costs more to manufacture
3 ) Stranded wire works better than solid in areas of high vibration ( flexibility)
Stranded wire is also easier to pull in conduit and often doesn’t require 2 men
4) There is no need to use #8 wire ‘, the wire run is only 3 ft and your breaker is 30 Amp —— Look in the NEC and you will find that a #10 is good for far more than 30 amps but is only limited by a FPN



The things I would worry about

1) Proper Grounding
2 ) Proper Polarity
3) Proper wire size and color code
4) Proper terminations and strain relief
5) Mechanical protection of the conductor
6) Cutting the correct size hole in the FG

[Raspy]

Originally Posted by steve dunham

You are making this far more complicated then needed

1) Your home is wired in NM (Romex ) because it is the least expensive code approved wiring method ( Romex is not allowed in many applications )
2) If you buy a spool of # 10 wire that is stranded you will pay 10% more than # 10 solid cause it costs more to manufacture
3 ) Stranded wire works better than solid in areas of high vibration ( flexibility)
Stranded wire is also easier to pull in conduit and often doesn’t require 2 men
4) There is no need to use #8 wire ‘, the wire run is only 3 ft and your breaker is 30 Amp —— Look in the NEC and you will find that a #10 is good for far more than 30 amps but is only limited by a FPN



The things I would worry about

1) Proper Grounding
2 ) Proper Polarity
3) Proper wire size and color code
4) Proper terminations and strain relief
5) Mechanical protection of the conductor
6) Cutting the correct size hole in the FG

Steve's points clear this up very nicely. Follow these and everything will turn out just fine. Use THHN or similar, stranded house wire for line voltage (600 volt rated) from the back of your wall plug and keep the sun off the wires with conduit or tube of some kind, as needed. A dab of no-lox grease will prevent corrosion where dampness might get to the back of the plug.

Don't tin or solder the bare connectors before clamping them into the plug. Just strip them and clamp them. No-lox is optional.

If you really want to get carried away, you can get tinned and fine stranded wire designed for marine use. This is probably the very best and comes in both single conductor and romex style. But these are not necessary in trailer use.

I don't like using any single strand conductors around trailers.

[fofobraselio]

Originally Posted by John in Michigan

Mark, I don't understand your statement "Starting from outside to in, I have a 20 amp male to 30 amp female extension cord connector ...". Can you explain this?

https://www.amazon.ca/gp/aw/d/B07BB8...?ie=UTF8&psc=1

Thanks Dave for confirmation and Steve for the thorough explanation.
I'm going to stop overthinking this 'type of wire' shenanigans.
Glad I can use the flexible stuff.
🥂

[ntsqd]

I cringe when I see NEC type wire, even the stranded stuff like THHN, recommended for use in a vehicle. Yeah, it is stranded, but no it is not terribly flexible. The strand size is still rather large and subject to fatigue failure due to vibration. BT, DT, got to fix the mains feed wire on a THHN wired dune buggy literally in the middle of the Mojave Desert because the wire failed from fatigue. This was a wire that was supported about 6" from the terminal that it failed in.


8 ga. is both unnecessary and shooting yourself in the foot. Odds are good that a wire of that size will not fit into the terminals of the receptacle. Trimming strands to make it fit is a bad idea. If you do the math you'll find what a 10 ga. wire can really carry over a 3 foot length and quit worrying about it. Also, odds are poor that you can buy an 8 ga. extension cord to plug into the receptacle, so the overkill serves no purpose other than pulling weight out of your wallet and putting it in your trailer.


I'd suggest using something like this wire: 10/3 AWG Marine Grade Wire Triplex AC, Tinned Copper USA Made Boat Wiring

[Ken Max]

For a cost differential of under 50 bucks - the entire trailer can be wired with
# 12 TINNED MARINE WIRING - AVAILABLE ONLINE OR FROM WEST MARINE
RESULTING IN FEWER - IF ANY - ELECTRICAL PROBLEMS - FOR THE NEXT 20 YEARS --

WELL WORTH THE FEW BUCKS METHINKS !

Ken

[steve dunham]

Originally Posted by ntsqd

I cringe when I see NEC type wire, even the stranded stuff like THHN, recommended for use in a vehicle. Yeah, it is stranded, but no it is not terribly flexible. The strand size is still rather large and subject to fatigue failure due to vibration. BT, DT, got to fix the mains feed wire on a THHN wired dune buggy literally in the middle of the Mojave Desert because the wire failed from fatigue. This was a wire that was supported about 6" from the terminal that it failed in.


8 ga. is both unnecessary and shooting yourself in the foot. Odds are good that a wire of that size will not fit into the terminals of the receptacle. Trimming strands to make it fit is a bad idea. If you do the math you'll find what a 10 ga. wire can really carry over a 3 foot length and quit worrying about it. Also, odds are poor that you can buy an 8 ga. extension cord to plug into the receptacle, so the overkill serves no purpose other than pulling weight out of your wallet and putting it in your trailer.


I'd suggest using something like this wire: 10/3 AWG Marine Grade Wire Triplex AC, Tinned Copper USA Made Boat Wiring

In my 40+ years of working as an electrician I have installed thousands of feet of THHN stranded building wire ( 19 & 37 strand ) on machinery that vibrates .
( Concrete crushers , printing presses , large trash compactors , die casting machine , hammer mills , iron ore crushers , oil refining equipment etc etc .
These machines run 24 /7 and I can count the number of times that the wires have failed on the fingers of one hand.
IMHO If your trailer vibrated so much that it caused the wires to break then you would be seeing considerable damage to other parts of your trailer and a broken wire is the least of your worries .

[ntsqd]

In my 45+ years of working on various vehicles ranging from swathers & combines thru vintage touring cars to desert race cars, with a couple Airstreams, a Barth, and a GMC motorcoach mixed in, I've had three memorable wire fatigue failures. The THHN on the dune buggy, a fusible link that had been shortened to the point of being tensilely loaded on a Cummins Turbo-Diesel (talk about vibration!), and an ACVW that I think someone in it's past must have thought was a U-Boat because all of the wire was excessively corroded between the strands.

In my 20-odd years working in various production industry its been my experience that industrial machines tend to vibrate as a whole. Rarely is there much in the way of relative vibration where one part or sub-assembly is vibrating significantly differently than the rest of the machine. It happens, but it is much less common than it is in ground vehicles.

If THHN were suitable for vehicles the automotive OEMs would be using it because it is easier and simpler to make (read: less costly) than is the finer stranded wiring used in production vehicles. I use automotive wire or preferably marine wire for its tinned strands on ground vehicles, and I specifically use marine "romex" for any 120 VAC wiring on vehicles.

[fofobraselio]

8 ga. is both unnecessary and shooting yourself in the foot.

It may be overkill, but it does fit nicely in the outlet I'm using. No doubt it is more expensive, but it is more affordable if you have some kicking around instead of going to buy some 10g.

Sent from my ONEPLUS A3000 using Fiberglass RV mobile app

[John in Santa Cruz]

true enough, if it fits the fittings, its the right stuff to use. especially if you have it.

otoh, heavy gauge wiring adds up, and is a good way to bloat the curb weight of these trailers if you go too overboard. like, LED lighting is fine with 16 awg or even thinner, even the brightest lamps are just a couple watts, a few 10ths of an amp at 12V.

[Borrego Dave]

Originally Posted by John in Santa Cruz

otoh, heavy gauge wiring adds up, and is a good way to bloat the curb weight of these trailers if you go too overboard.

John, thanks for the last chuckle for the day .