Wire question? Compressor and welder(syncrowave)

[Scott]

I am in the process of installing a 100amp sub-panel in my garage for a compressor and welder among other things. I plan on buying around a 5hp 220v compressor and a Miller Syncrowave 200. My question is there any reason to run 4 conductor wire to these machines? 2 hots, 1 neutral, 1 ground? Or do I only need 2 hots and a ground? I am pretty sure the compressor only needs 3 conductors. For the future should I run 4 conductor in case I install something else? From the Miller website it looks like I only need 2 hots and a ground, but how do they offer a 115vsc receptical on the front of the machine with no neutral?

I am planning on using 10ga to the compressor and 6ga to the welder.

 

[rockwithjason]

It depends on how the manufacturer designs the control wiring. Most compressors use straight 240V single phase meaning two hots and a ground. As for the welder you will need to see the requirements from the manufacturer. If they have a recepticle on the front that is a pretty good indicator that you will need a nuetral. There are ways to have a recepticle with out a supplied neutral but they are rarely used. This requires a transformer and breakers or fuses. I suppose they could be using part of the welding core transformer for this but I doubt it.

 

[Scott]

Hmmm, maybe I need to call my local welding shop to find out. Maybe the machine has a separate 110v cord on the back or something. The manual does not indicate that though.

 

[Scott]

Looking at the wiring diagram, I think they create 115vac internally with a transformer. So I am pretty sure 6/2 with ground will do it for the welder and 10/2 with ground for the compressor.

 

[byrdman]

Check your startup specs on the compressor, some 5hp models might want more than #10. I downloaded the manual for my 7.5hp before I bought it, based on the chart I used #6.

 

[Charles (in GA)]

I would certainly carry a netural to the sub panel. You never know what you might want to tap off the subpanel and if You don't have a netural and want 120V you will be cussing yourself for not running the netural.

 

[Scott]

I plan on extending an unused existing circuit with 6/3 with ground romex to the subpanel from a 60amp breaker. That way I can break out my outlets in the garage from the house circuits. Currently the garage and both bathrooms share a single 20amp breaker!! ahh!

 

[drbill]

If I remember right when I wired my compressor with 220v I used 2 hots (110v each) and the common.
By the way take a look at your existing fuse box, all the commons and grounds go to the same place.

 

[Charles (in GA)]

If I remember right when I wired my compressor with 220v I used 2 hots (110v each) and the common.
By the way take a look at your existing fuse box, all the commons and grounds go to the same place.

Actually, current NEC requires an isolated netural and ground beyond the service entrance (where they do, indeed meet).

Most 240 doesn't need a netural, except for four prong dryer outlets and the like, you don't even have a prong for the netural, but if you are supplying a subpanel, you should carry the netural to it, if for no other reason than its future usefulness. From the subpanel to the device, it may not make sense or be practical to run the netural, depending on the device or appliance you are going to power.

Charles

 

[rockwithjason]

Neutral wires are REQUIRED to be run to the sub panel. The neutral is the return path for fault current and deleting it in your sub feed is very dangerous. I agree that you should run a neutral to the welder and compressor, just in case.

 

[W-Cummins]

Neutral wires are REQUIRED to be run to the sub panel. The neutral is the return path for fault current and deleting it in your sub feed is very dangerous. I agree that you should run a neutral to the welder and compressor, just in case.

The Grounded conductor ( the "Neutral") is NOT required UNLESS your using a 120v or 277v load. No 120V or 277v loads no grounded conductor is required. The Requirement for the 4 wire 240V to range and dryer outlets is becuse thouse applications MAY have a 120 volt load in them. The function of the grounded conductor is to complete the circuit on 120V or 277v loads.

 

[Scott]

4 wire to the panel, 3 wire to the compressor and welder, check! Thanks guys!

 

[sberry]

Now how we figure this? If its a sub it would be fed 4 wire and the N wouldnt have anything to do with a line to case fault. You could run only 240 to a panel many single breaker panels used as disconnects are wired this way as is a one armed bandit for a water heater.

 

[bassman]

No neut. to the loads unless the nameplate data tags or mach lit. reguires one. Neut has nothing to do with a fault to gr. thats what the grounding cond. for.

 

[EricVonHa]

Ground and neutral are the same point and carry the same potential. If it's within the same building (i.e. "ground", think about it), anything wired off the main needs to be the same potential.

 

[bassman]

They are not the same in the slytest way. The neut. is NOT common to the metal surface of the mach. Its only there as the GROUNDED cond. to operate 120V loads. The GROUNDING cond. is common to the metal frame and all metal parts of the mach. or appliance to conduct a safe path to ground in case of a fault to ground. . The ONLY place the connect is at the service entrance.