# 10/3 or 10/4 wire?



## mixpat (Dec 26, 2014)

Hi...Santa brought me a new 5000 watt generator, which I plan to have connected to our circuit breaker box. For safety, we'll either use a transfer switch or an interlock to a 30amp/double pole circuit breaker. Plan on using L14-30 connectors (4 prong). At 30 amps, I'll be using 10 gauge wire. My question...what is the difference (other than price) between 10/3 (which also has a ground wire) and 10/4 wire? Both have 4 wires. The only difference I see is the 10/4 wire's ground has a jacket on it and the 10/3 doesn't. Can I use 10/3 wire for this application? Thanks for any input.


----------



## Jim Port (Sep 21, 2007)

It would help to know the cable types you are asking about. I suspect you are asking about NM cable and flex cords like SOOW.


----------



## silver50032000 (Nov 30, 2014)

10-4 Backdoor.


----------



## mixpat (Dec 26, 2014)

I was planning to put the box/plug in the garage...then run Romex-like 10 gauge wire to the circuit breaker box.


----------



## Desertdrifter (Dec 10, 2009)

Running your generator outside of course?


----------



## mixpat (Dec 26, 2014)

Yes CLW1963...generator outside, with connection plug inside the garage. Then Romex-like cable to circuit breaker box


----------



## TarheelTerp (Jan 6, 2009)

mixpat said:


> My question...what is the difference between 10/3 and 10/4 wire?


First... it is a **cable** that includes several wires.
The /3 or /4 is in addittion to the ground wire.



> Can I use /3 wire for this (240V) application?


Probably. The questions of if you should or how I'm not gonna touch


----------



## micromind (Mar 9, 2008)

Typically, a cable (like the kind you'd run in the walls of a house) will have the # of insulated conductors, then usually a 'w/g'. If this cable is 10/3 w/g, then it has 3 insulated conductors plus an uninsulated ground. 

If it's a flexible cord (like an extension cord), then 10/3 means 3 insulated conductors and no ground, 3 wires only.

To connect a gen like your to a transfer switch (or breaker interlock), you'll need 3 conductors plus a ground. 

A cable would be 10/3 w/g; a cord would be 10/4.


----------



## ritelec (Aug 30, 2009)

micromind said:


> Typically, a cable (like the kind you'd run in the walls of a house) will have the # of insulated conductors, then usually a 'w/g'. If this cable is 10/3 w/g, then it has 3 insulated conductors plus an uninsulated ground.
> 
> If it's a flexible cord (like an extension cord), then 10/3 means 3 insulated conductors and no ground, 3 wires only.
> 
> ...


The 10-3 cord would probably include the ground like 12-3 
Blk wht grn

But yes. When speaking about nm cable you say the size and number of conductors. The ground is not mention but included. When speaking of cord. You say the wire size and number of conductors and include the ground in you count


----------



## ritelec (Aug 30, 2009)

Just to clarify. You want 10-3 nm cable and 10-4 so cord Both will have 4 conductors. The nm will have bare ground. The cord will have insulated grn ground


----------



## sparky90 (Aug 1, 2014)

mixpat said:


> Hi...Santa brought me a new 5000 watt generator, which I plan to have connected to our circuit breaker box. For safety, we'll either use a transfer switch or an interlock to a 30amp/double pole circuit breaker. Plan on using L14-30 connectors (4 prong). At 30 amps, I'll be using 10 gauge wire. My question...what is the difference (other than price) between 10/3 (which also has a ground wire) and 10/4 wire? Both have 4 wires. The only difference I see is the 10/4 wire's ground has a jacket on it and the 10/3 doesn't. Can I use 10/3 wire for this application? Thanks for any input.


Typically what we do is use 10-3 NM cable from the panel (if using interlock) to a connection point near the outdoors either inside the garage or a receiver box outdoors. That part of the installation is permanent. From that point to the the generator we use 10-4 SO cable. If you want to always have a temporary connection from generator to panel you can use 10-4 SO cable all the way with a plug and receptacle at the panel.


----------



## Desertdrifter (Dec 10, 2009)

There's a couple of points regarding grounding when connecting a generator to your house panel. Hopefully the pros will chime in. A couple questions 

1) Does your genny have a 120/240v outlet. Some new gennys only output 120v?

2) are you going to buy a generator inlet to connect from your genny to the panel?


----------



## micromind (Mar 9, 2008)

ritelec said:


> The 10-3 cord would probably include the ground like 12-3
> Blk wht grn
> 
> But yes. When speaking about nm cable you say the size and number of conductors. The ground is not mention but included. When speaking of cord. You say the wire size and number of conductors and include the ground in you count


Yes, 10/3 will be black, white and green. But that gives only 120, not 120/240 as the OP wants. 10/4 will be Black, White, Green, Red. 

BTW, the unwritten standard of power cord (as opposed to control cord) colors are Black, White, Green, Red, Orange, Yellow, Blue and Brown. Next would be White w/ Black stripe, Red w/Black stripe (in a power cord, there's only one ground) and so on. 

Control cord is usually Black, Red, Blue, Orange, Yellow and Brown. No White or Green. Then Red w/Black stripe, Blue w/Black stripe, etc. 

These are not an absolute standard, but if you order multiple conductor cord and don't specify otherwise, most manufacturers will use the above colors.


----------



## mixpat (Dec 26, 2014)

Sparky90...that is exactly what I was looking to do: 10-3 NM cable from connection point to the panel and 10-4 SO cable from the genny to receiver box in garage. Just wasn't clear on the lingo! Thanks everyone!


----------



## mixpat (Dec 26, 2014)

CLW1963...yes, it does have the 240v twist lock outlet (GFCI protected) and yes, was planning on putting inlet box in garage.


----------



## joed (Mar 13, 2005)

The cable is listed by the # of insulated conductors. The 10/4 cord has an insulated ground so it counts. The 10/3 NMB has a bare ground so the ground does not count in the cable description.


----------



## sparky90 (Aug 1, 2014)

mixpat said:


> Sparky90...that is exactly what I was looking to do: 10-3 NM cable from connection point to the panel and 10-4 SO cable from the genny to receiver box in garage. Just wasn't clear on the lingo! Thanks everyone!


You can save yourself about $80.00 and forgo the receiver box. If you plan on converting over to SO cord inside the garage you can use a large 1900 box and splice the 10-3 NM cable to the SO cable in it. Use a squeeze connector on the SO cable coming out of the 1900 box and strain relieve it. Put an on the wall bracket to coil up the SO cable when not in use. No use spending $80.00 on a weather proof receiver box and using it indoors unless you don't want the SO cord in sight. But you have the idea.


----------



## mixpat (Dec 26, 2014)

Sparky90...I'm not sure what a 1900 box is?? Is it a simple junction box to house the spliced wires?


----------



## sparky90 (Aug 1, 2014)

mixpat said:


> Sparky90...I'm not sure what a 1900 box is?? Is it a simple junction box to house the spliced wires?


Yes, it is a metal box or could be plastic large enough to house the spliced wires from the NM cable to the SO cable. If you use a metal box be sure to bond it to the ground of the NM cable with a green screw. This will make a hard connection from the NM cable to the SO cable. This eliminates the need for the receiver box and also the female plug on that end. So you save over $100.00 doing this. I put a hook bracket to hang the rolled up SO cord when not in use. Be sure to put a blank cover over the box as well.


----------

