240 Volt Wiring

[RI Chevy]

Good point Kevin.

 

[Moparmyway]

Good point Kevin.

Jeefus,
What point am I getting credit for, I’ve only asked 3 questions ?

 

[RI Chevy]

What makes you believe that his third wire is a neutral ?

Take a circuit with 10 receptacles in it, nothing plugged in, do you believe that the neutral has current

Have you ever measured 120v on a neutral in an operating circuit ?

This

 

[Larry B]

If you want to wire an outlet for a generator backfeed it should be with 4 wires. L1,L2,N,G. most newer generators come with 4 wire twist lock receptacles. If you are using a generator that puts out 220V and has a 3 wire receptacle the 3rd wire treated as a neutral. NEC does not allow for a ground conductor to be a current carrying conductor. The only place the G and N are connected is at the main panel by code. The frame of the generator should be grounded by either a earthing ground rod or a separate wire to building ground. Also, NEC requires a UL listed manual or automatic transfer switch to connect a generator to the electric service.

 

[RI Chevy]

Is a 3 wire generator outlet rated at 30A and the 4 wire generator outlet rated for 50A?

 

[Larry B]

Depends on the generator. The generator should come with a receptacle at least as high as the generator output. My 2600 watt generator has a 30A 4 wire twist lock. Individual outlets on a generator should have breakers suitable for the outlets. Ie, 15A breaker for a 110V 15A outlet

 

[RI Chevy]

Yes sir. I have an older Honda 3500 gen. I think it has a 3 prong twist. But now you got me thinking. It may be 4 prong. 30A I think.

 

[Moparmyway]

Is a 3 wire generator outlet rated at 30A and the 4 wire generator outlet rated for 50A?

You can get configurations of both, and just about everything in between, but small generators are rated by their power output, expressed in watts.

 

[Larry B]

220/110V generator with a 3 wire 220V outlet converted to 4 wire.

 

[Larry B]

Yes sir. I have an older Honda 3500 gen. I think it has a 3 prong twist. But now you got me thinking. It may be 4 prong. 30A I think.

If only 3500 watts is it 220/110 or just 110? At 220V only about 15A.

 

[RI Chevy]

I believe it is 110/220v. I have only ever used 120v during hurricane season. But I do believe it is 220v.
Is there an advantage to 4 prong vs. 3 prong? More Amps?

 

[Larry B]

No. Just makes it meet code for backup use. Can be wired to a transfer switch and then a panel and meet code. 220V backup generator needs to have the neutral connected to building neutral and the metal frame connected to building ground. Most 3 wire generators connect the generator frame and the neutral together which works for a portable generator but not for backup use. Making it 4 wire makes it safer.

 

[RI Chevy]

OK. Makes sense. I will see if I can grab a photo of the business end of my generator tomorrow and post it.
We use Reliance Gentran setups when we wire them to houses. Pretty simple and safe for homeowners to use.

 

[Larry B]

doing some work on my setup. Going to add another transfer switch as the one doesn't have enough circuits.

 

[RI Chevy]

Nice. Looks busy there. Lol

 

[thedude74]

Running a neutral on a 240volt circuit allows you to also run 120volt. L1-l2=240 volt. L1-neutral or l2-neutral is also 120 volts. Of course this would require a subpanel and the correct receps. The ground should never be used to carry current(yes, I've seen plenty of people do it). If your not going to run any 120v on that circuit a neutral is pointless. 2-#10 and ground (insulated or bare #12 or larger) meets code for a residential 30 240v (single phase) amp circuit.

Anyway, before my career as a firewood hack I was a mechanical contractor. Had both hvac and electrical licenses.

 

[Larry B]

Nice. Looks busy there. Lol

Yeah. The house has 2 200amp panels. The left one is most of the 220 stuff. Between the 2 panels there are 11 220 breakers plus the 220 subpanels in the barn and shop.

 

[AVB]

Just remember on long runs you need to run heavier cable just to prevent voltage drop and cable heating. My little 110v Miller Cricket work much better when using a 25 ft 12 Ga extension cable then the 100 ft 14 Ga even through the 14 Ga is rated for 15 amps. Of course use the welders at max current setting too.

 

[Larry B]

You can use any of the wire manufacturer's calculators to find out what ga. Wire you need for a certain run.

https://www.southwire.com/calculator-vdrop

Of course these are for installed wiring. They assume no voltage drop from old oxidized extension cord contacts.

 

[Marshy]

I will have to revisit this post and read the rest of the comments. Thanks for all your inputs. I'll likely be changing it out to a 3 wire sooner than I realize because I'm about to buy a 240 v welder. The 2 wire worked fine for the generator in emergency use but I'll be using the welder much more often and will want to meet code. I'll keep the 2 wire pig tail I made for the generator but the rest will be updated.