2 or 3 wire for 220

[springer]

Just moved and need to run a couple 220 lines for all my junk. In the past, I've always done 2 wire because I have all single phase machines. Here, I now have a 3 phase machine and just got my vfd in the mail.

Question is, do I need to run 3 wire to the vfd? I've tried searching and anything to do with a vfd is talking about wiring from vfd to machine. I am leaning towards not needing 3 wire, but thought I'd ask someone of more know how than me. I'm electrically challenged.

Second question, if I do run a 3 wire, can I install some 120 outlets off that same 30a breaker? I've found info saying I cant run more than 1 220 plug on a 30a, but I'm still kinda lost. I was planning to run some 120v outlets to the same area and if I could do it through the same run of wire, thatd save me a little headache and money.

Thanks in advance.

 

[tq60]

2 wire PLUS GROUND?...



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[DavidR8]

I just finished a VFD install on my mill.
The 220b feed is two wire plus a ground.
Bringing a third wire to the 220v outlet does give you the ability to run a 110v circuit using the neutral and one of the hots.
Caveat: I’m not an electrician but this is what I have done.


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[ttabbal]

For single/split phase 220, you need 3 wires. 2 hots and ground. If you have something that wants 120v as well, you include the 4th wire as neutral. One hot + neutral = 120v.

For a VFD you don't need neutral. For running the 3 phase output to the equipment, you need 4 wires. 3 hot phases, and ground.

You can run 220v 4 wire and include 120v outlets, technically. I'm not sure what the code says about that. I don't think they would care so long as everything in the chain is rated for the current. That's one thing that might trip you up. Normal 120v outlets are rated for 15A, though in most areas you can chain them with a 20A circuit. Feeding one with a 30A breaker and wire might be a problem. If there is a short, you can get 30A through the 120V outlet, which could be a fire hazard. To be safe, I would run a separate 120V 20A circuit. The fire isn't likely, but it's cheap insurance.

 

[markba633csi]

Ttabbal pretty much nailed it, 120 volt outlets are supposed to be limited to 20 A so a 30 A breaker might be a code violation
-Mark

 

[markba633csi]

My feeling is you can wire up your house any way you want, as long as you use good practices. Bending the rules is ok sometimes, as long as there isn't a shock or fire hazard.
This applies to old houses and remodels. For a new construction you pretty much have to follow the code or the inspector will have a cow, unless you are doing owner/builder interior stuff without moving walls

 

[Ulma Doctor]

hey @springer,
glad to hear you are moved! i hope it was easy

Q1:
you'll need 2 hot 240 volt wires and a ground to power up the VFD, a neutral wire is not necessary - there is no place on the vfd to wire it to

Q2:
i would run the 240v single phase to a distribution box (load center), then split into 120v circuits from the load center
from the load center you can wire the outlets and machines

 

[DavidR8]

For clarity, my 220v circuits are 20a wired with 12 ga wire and my 110v receptacles are rated for 20a.


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[mksj]

To clarify, their is no neutral in the US for using a 220V VFD, but you will often see a "N" terminal on the VFD. Do not hook this up to neutral, wire per the directions. Breakers protect the wire, there is some variations on sizing specs. of breakers relative to the a multitude of NEC codes, etc. Although it is not common to bring a neutral wire to a machine which is 220VAC, you can do it and then breakout separate sub circuits at the machine enclosure using supplemental breakers or fuses. Just remember that all the wire up to the fuse/breaker should be rated for power in breaker size (in this case 30A). On both my mill and lathe I use 4 wire cable (L1, L2, N, G), these then connect to the power disconnect switch at the machine and then to breaker/fusing if used. VFD's do provide guidance's on VFD fusing/breakers for each model, in general a 30A breaker is sufficient for either a 2 or 3 Hp single phase 220VAC VFD.

Example below, supplemental dual pole15A breakers for power supplies, second dual pole15A breaker for sockets mounted at the lathe and for DRO, and fusing for the VFD. The lathe is setup for either single or 3 phase 230VAC, but currently it is powered off of single phase. Attached enclosure diagrams give some suggestions, you need to comply with all electrical codes.

 

[matthewsx]

How much would it save you to run 12/2 vs 12/3?

$15?

Just run the 3 wire and be done with it. Money is in the labor, not the materials, make it easy for yourself or the next guy if it needs to be something different eventually.

John