6/4 wire cable for 50A Inverter install

[Ozzie Cozzies]

I need to purchase some extra cable for my inverter/charger install. It is a 3000W 50A inverter. Everywhere I read or viewed on Youtube, I require a 6/4 wire, or a 6/3 with ground. I'm thinking of purchasing a VEVOR 50' RV extension cable and cutting the end plugs off. (about 7.5 metres or about 25' run from AC distribution panel to inverter.
https://www.vevor.ca/generator-exten...p_010170800091
It has a STW jacket and appears to have stranded copper wire on the 6 gauge wires. Does anyone have any views on this? Can a STW cable be installed inside an RV - I would have thought so. The SOOW cable is much more expensive. Is there any specific requirement for the outer jacket specification? What is the most economical way to buy such cable?
Any suggestions?

[rohrmann]

https://www.homedepot.com/p/Southwir...9199/204725137


https://www.homedepot.com/p/Southwir...0099/204632777


Either of these will work and you will only need to buy just what you need. If you only want 6/2 with a ground, this will work and it's less money, again you will only need to buy what you need. https://www.homedepot.com/p/Southwir...4499/204632776

[Ozzie Cozzies]

Thanks Bob for your reply but the SOOW cable you suggest equates to $410 CAD for a 50' length compared with a retail RV extension cord for $286CAD - 30% cheaper.
I was specifically asking whether STW was suitable and whether a cheaper option was available. I'll need about 50'.
Thanks for your reply.

[Daryles]

I would use 6 gauge welders cable.
6 gauge is rated for 55A.
Welders cable is very flexible and easy to work with.
Make sure it is pure copper, NOT copper coated aluminum. Aluminum is NOT as conductive as copper.

https://www.wireandcableyourway.com/...-cable-class-k

[Bourbon County]

First of all, what is the output voltage of your inverter; do you actually need 3 insulated wires? If you could post the make & model of your inverter it would help.

I'm not understanding why you need 6 gauge wire. The output of a 120 volt 3000 watt inverter is about 25 amps, which would be a 10 gauge or maybe 8 gauge if you apply the derating factors.

Everything in an RV that operates at 120 vac is wired with type NM (commonly referred to as romex) cable, it will be fine for your application. The cables you are referring to are flexible extension cords like the shore power cord for your RV. The flexible cords are highly flexible and the types that start with an S are extremely durable. The individual wires are fine strand and all conductors are the same gauge wire and individually insulated with a robust outer jacket. Type NM in all wire gauges larger than 10 will be coarse stranded wires and in a 6 gauge will likely have a 10 gauge bare copper solid ground conductor which is fine for a 50 amp circuit. There will be a thin outer jacket like the smaller gauge wires you're used to seeing. The NM cable will be much stiffer, but doesn't matter if it's not required to flex much after installation.

Before you go to a big box to buy it, I would at least call some local electrical wholesale houses and ask if they sell that size by the foot and their price on it. It's actually a common size often used for electric ranges; most small contractors prefer to buy it by the foot rather than buy a 250 foot roll. I believe you'll find a wholesale supply will be considerably cheaper than big box.

[Ozzie Cozzies]

Originally Posted by Daryles

I would use 6 gauge welders cable.
6 gauge is rated for 55A.
Welders cable is very flexible and easy to work with.
Make sure it is pure copper, NOT copper coated aluminum. Aluminum is NOT as conductive as copper.

https://www.wireandcableyourway.com/...-cable-class-k

Thanks Daryl,
These individual 6g wires will work out about the same cost as the fully enclosed and insulated STC cable. I'll keep it mind - it's an option. I've taken on board your comment on copper.

[Carl n Susan]

I don't understand why you need 50' of cable (and the associated high cost. I would think you are only going from the inverter to either a transfer switch or sub-panel? It seems those distances should be pretty minimal assuming the inverter in in the pass thru or battery compartment and the transfer switch/sub-panel. is at the back of the pass thru compartment.

What am I missing here?

[Ozzie Cozzies]

The distribution panel is at opposite the front door. I'm planning on installing the inverter on the driver side of the solid wall separating the pass through and the battery compartment towards the king pin/ nose end. Coming from the transfer switch (very close to AC panel) to compartment wall is 8', across the compartment wall is 6', down compartment wall then loop back under and connect to base of inverter is 5', giving 19'. Cable length from transfer switch to inverter plus cable length from inverter to panel about 38' - give or take a bit.
The extension cables come in 25' and 50' - that's why I chose 50'. Yes, I got a shock when I added up the measurements.

[Foldbak]

I assume you are referring to the battery cables? Just FYI, Keep the cable length as short as possible, no longer than 10 Ft (3 meters). This will keep the overall system efficiency as high as possible, and will keep the voltage drop between the battery and INVERTER to a minimum.

[jsb5717]

Here's an option for $200

https://www.amazon.com/Mophorn-Exten...eae8f9840&th=1

[firestation12]

There seems to be some confusion about what the OP is doing. Post #7 I think is correctly asking why the large gauge wire connecting the inverter’s OUTPUT to the power distribution center (breakers), while post #9 is referring to sizing conductors from the 12 volt batteries to the INPUT of the inverter. After re-reading post #1, I too am wondering why the OP is considering #4 or #6 conductors for 3,000 watts over a distance of 25 feet, not to mention the nightmare or terminating such large wires.

[Foldbak]

If he's referring to the AC output wire from the inverter to the panel then we're way of base.

For a maximum of 50 amps, you'll need a wire gauge of 6
https://www.amazon.com/Bulk-Cable-10...830155676&th=1

[bcrvman]

Originally Posted by Ozzie Cozzies

The distribution panel is at opposite the front door. I'm planning on installing the inverter on the driver side of the solid wall separating the pass through and the battery compartment towards the king pin/ nose end. Coming from the transfer switch (very close to AC panel) to compartment wall is 8', across the compartment wall is 6', down compartment wall then loop back under and connect to base of inverter is 5', giving 19'. Cable length from transfer switch to inverter plus cable length from inverter to panel about 38' - give or take a bit.
The extension cables come in 25' and 50' - that's why I chose 50'. Yes, I got a shock when I added up the measurements.

I had to do a similar job when I installed my 3000W inverter. Mine was a little easier in that I don't have a onboard genny so no transfer switch, I just purchased by the foot SOOW as it is easy to work with. As for terminators rent a crimper either hydraulic (preferred) or a hammer and if you can't rent, then buy a hammer crimper and practice until you can create fused connections. BTW, since these are effectively outdoor damp terminations, they need to be marine tinned connectors.
As to the cable, the price of copper is insane due to world events. There is a trick you can use if you are prepared to work for it. I ran only 6/2 + G to the inverter and back, that cable had to be connected to the 2 ends of the N and the 2 ends of the black/red going to/from the inverter with the other red/black left alone. You also need to connect the 3 N's together. I used very big marine grade bus bars for the G, N, one hot.
It doesn't matter how you do it, the price of copper is insane. Buying an extension is going to cost more than by the foot unless somebody has either screwed up or it's inferior wire. If you try to save money with inferior wire, then use some of the savings for increased fire insurance and hope the insurance company does not find out you read this and are now criminally liable. If the reason for all this is to boondock, you are saving close to $50 to $100 a night in camp fees so why is this a difficult decision?
Just found this, it will work. https://amz.run/6c7m

[rohrmann]

Bought one of these, and though not the heavy duty utility grade I was used to, works very well for crimping the copper lugs. Also, much better than a rock and a hammer.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[bcrvman]

Originally Posted by rohrmann

Bought one of these, and though not the heavy duty utility grade I was used to, works very well for crimping the copper lugs. Also, much better than a rock and a hammer.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

But he needs 6AWG, those are 8-10, too small.

[rohrmann]

It's # 8 to 1/0 strand, not #10.

[rohrmann]

This is the rotating dies on the crimper. So far, I've crimped #8, #6, and #4 copper connectors with it, and it worked well.

[bcrvman]

Originally Posted by rohrmann

This is the rotating dies on the crimper. So far, I've crimped #8, #6, and #4 copper connectors with it, and it worked well.

WOW, that's impressive. I thought you needed a hydraulic crimper at those sizes. I am fairly certain I have a mechanical for up to #8, and that takes all my strength, but it is a shorter handle, so maybe that explains it. I got one to fit into a toolbox. I will never need one again, so too late to help me, but that should go into a MOC file to save everyone who needs one the extra $50+ hydraulic cost.

[jking]

for my 4x100amp lifepo battery bank and my 3000w inverter I used 4/0 welding wire. It was NOT CHEAP, but it gives me the performance and safety I want. Electricity has rules - follow them or get Burned, Literally! I work the electrical Dept at THE Big Box store, and majority of customers are pretty clueless as to what they really NEED, as well as often lackadaisical about code (which = safety). just sayin what I SEE out there.

[Bourbon County]

Originally Posted by jking

for my 4x100amp lifepo battery bank and my 3000w inverter I used 4/0 welding wire. It was NOT CHEAP, but it gives me the performance and safety I want. Electricity has rules - follow them or get Burned, Literally! I work the electrical Dept at THE Big Box store, and majority of customers are pretty clueless as to what they really NEED, as well as often lackadaisical about code (which = safety). just sayin what I SEE out there.

So if a customer walks into THE Big Box store looking for the correct size wire for a 3KW load you would sell him 4/0 welding cable? I sincerely hope you're on commission.