I need to wire an NEMA L6-30 (220V) circuit for a 3hp table saw. Could you please explain how to wire this from panel to receptacle? Any additional restrictions if I run the circuit under part of the shop floor? Obviously, I will use UF wire. Also, this is in my “residential shop”, the panel is a 60amp subpanel. Thanks for your help.
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3hp is about 2300 watts, and such a motor would pull about 12 amps during no-load running. Start up current could go up to 25 amps. Under load, the current could go up to 15-16 amps.
A double pole 220v, 30 amp breaker should suffice in the panel. I would run solid 10 guage, 2 conductor plus ground, wire. Routing it under the sub floor should be no problem. Get the special 3 pronged 220V outlet. Some are twist lock. The one's I have are like cloths dryer outlets. Of course, the outlet has to match the plug on your saw.
PlaneWood by Mike_in_Katy
PlaneWood
Now in the panel (which is a 60amp sub-panel) does the bare copper (ground) attach to neutral bus or ground bus since they are separate (as it should be in a sub-panel).
Additional infor: the sub-panel has it's own grounding rod and it is grounded through the main panel as well.
Thanks for your help.
Over at Breaktime we get really mad at questions like this. If you need to ask, you need a sparky.
It's connected to the ground bus bar in the subpanel. A 220V-only circuit has no neutral conductor.
Be sure, in the subpanel, that the neutral and ground buses are NOT tied together. They are in the main panel, but must not be in the subpanel.
The ground rod on the main panel is OK, if not really needed. But the subpanel ground MUST be tied to the main panel ground.
B.,
I posted to you the other day... and there was one post before mine.
Both now gone.
1) Use conduit. NOT UF.
2) Pull THHN minimum of 10 Ga., Black, Red, White and Green.
3) Use either a 2-pole 20A or a 2-pole 30A dedicated circuit breaker.
Check the Saw Manufacturer's recommendation. The outlet is 30A rated, but the saw may take less amps. Go with the recommended size only.
4) Newer equipment uses 4-prong wiring for 220v. (separate "equipment ground")
Wiring:
<<SHUT OFF ALL POWER TO THE SUB-PANEL.>> Remove the sub-panel cover.
Run the conduit from the sub-panel to the saw.
Make in the conduit to the sub-panel, pull the four conductors.
Make on the receptacle box at the saw-end of the conduit.
Make the receptacle connections according to the instructions with the saw/with the receptacle.
Make the connections in the sub panel.
Green wire to the ground buss.
White wire to the neutral buss.
Install the 2-pole breaker.
Black wire to one leg of the 2 pole breaker.
Red wire to the second leg of the 2 pole breaker.
Remove the Sub-panel cover blanks for the spaces used by the 2-pole breaker, and re-install the cover.
Turn on the new circuit. Your saw should now be wired.
<<ANY PART OF THIS YOU'RE NOT COMFORTABLE WITH... GET AN ELECTRICIAN.
YOU'RE DEALING WITH A FAIR AMOUNT OF ELECTICITY, BOTH IN AMPS AND VOLTAGE.>>
-gwc
The saw manual showed a three wire circuit, so that is what I did. However, I used 10-2 UF under the floor and cased it in PVC conduit where it pierced through the floor. I later learned to my dis-belief that UF wire should not come in contact with cement. I have and know many others in my area who have used UF in contact with cement. The UF is under 5-6inches of fresh concrete, what is the harm? What is the reason for the objection? At this point would it wise although unthinkable to re-do and use conduit and pull THHN? What is the real risk? Your opinion is appreciated. Thanks, Brian
Brian, if it's in... it's in.
The way I described violates no codes, anticipates use of an equipment grounding conductor, and would allow you to pull new wire of a larger gauge should you ever buy a larger saw.
5 HP, or 3 HP with a separate scoring blade motor.
Not planning on it? Go with what you've got for now.
Personally, I never use ####XX-2 conductor for any 220V circuit.
Always use XX-3, so the neutral path is in the white wire, not the bare copper. Some inspectors will not pass a 2 wire with ground installation.
-gwc
PS: Prohibitions for direct contact with concrete? I'd guess the jacket material isn't tested/approved for it. Concrete isn't the most
friendly material in general, with a potential for freezing and heaving, putting strain on the wire encased in the concrete.
Usually, you'd bury the wire in sand, then cover the sand with the concrete, thereby cushioning the wire.
The conduit through the concrete was a good idea.
George,
He does not need the white (neutral) conductor. The table saw is a 220V-only device. As such, it only needs the 2 hot leads; a neutral connection is not needed.
You seem to be confusing this with a 220/110 circuit, which supplies both 220V and 110V to a device that needs them, such as a stove or a kitchen range.
For the table saw, 10-2 with ground is OK. If a romex-style sheathed cable is used and one of the conductor is white, it can simply be marked with red tape at either end.
As for type UF, it is OK for direct burial in ground. It is NOT permitted to be encased in aggregate or concrete; the concern is that the rock may damage it. Even with the direct burial in ground, the inspector will make you put it in conduit if the soil is very rocky. But as was said, it's already in place.
Under my concrete floor, I ran 1" PVC conduit. Cheap, and flexible. I just moved my router table over near the table saw, and was able to just run another couple of wires for a new 110V circuit through the conduit.
Barry, not confused, only Inspected. Three-wire w/ground is acceptable... ground gets made into the metal 4-square box; black, and red are the two hot legs, with white being made-in as the neutral.
Wiring since '86, in three different States with Electrical Inspections. So far, so good.
-gwc
PS, if I wired for 110v/220v, I'd be using two breakers, and running
separate conductors.
110v: Black, white and green. Or romex two wire w/ground.
220v: Black, red, white and green. Or romex three wire w/ground.
In conduit, I'd need to pull seven conductors in five distinct colors. White, and green stay for both circuits,
the 110v hot leg would have to be another
"hot" color. Blue/Yellow/Orange... something, but not white or green.
George, first off I'm no electrician but in all the 220 stuff I've ever done, (and on a rare occasion with a permit and inspection I might add). I've always run the white neutral just incase someone plugs something in that needs 110 for a switch relay or something. If nothing else it sure saves a lot of time going back and re-pulling 10/3 when you only pulled 10/2 the first time. And if you don't use it pull it anyway so you'll have it. I always remember that if I don't use it, the industry standard is to use RED tape on both ends so the next person that works on it knows that it could be hot.
On that rare day when I did get my inspection signed off, (without knowing about the obligatory liter of whiskey, christmas party donation). The inspector never questioned my logic, in fact he was happy to see that I had gone the extra mile.Steve - in Northern California
Steve, seems we agree. Stick with the standard wiring schemes as defined in the NEC and you've fewer problems down the road.
-gwc
"Inspected" or not, you told BHACKFORD he needed to run a white neutral conductor. This is simply incorrect. He needs to wire up a NEMA L6-30R receptacle. Well, an L6-30 has no neutral connection. And his 220V-only table saw has no need for one.
Perhaps you're thinking of a NEMA L14-30 receptacle, a 4-pole receptacle for 110/220V circuits.
Note there are two types of "220" circuits. Those that supply 220V-only, as is needed here for the saw, and those that supply both 220V & 110V simultaneously, referred to as 110/220.
I'm not sure, but yoyu seem to be under the impression that all "220" circuits are of the 110V/220V variety. The wiring you've describd for 110V/220V is in fact the wiring for two separate circuits, one a 110V-only, and the other a 110V/220V. Note also that in the conduit case, there'd be no need to pull 2 green conductors. One, sized for the larger of the two circuits according to the table for equipment grounding conductors in the NEC, would sufice. Also, if mixing up the two neutrals could cause a problem (say one of them is connected to a GFCI), then one of them should be grey.
--Barry (electrical engineer for the past 20+ years).
Barry, I think he described it correctly. You are right too. You don't need that neutral unless you have a need for 110/220 like an oven or maybe a dryer. However, some saws do have 110 relays in their switches so maybe that was the reason he mentions the neutral. Of course you're correct about the L6-30 but if you run 10/3 and leave the neutral taped off, (red tape is what I was taught to use), on both ends of the run then its there if you ever have the need for the L14-30. I do it just for that reason. My dad has an old Rockwell table saw that some where down the line had the switch replaced. The switch uses 110v relays (no I'm not kidding) so we wired his with a L14-30 and used the neutral. Fortunately the 220 was a homerun to this receptacle and was already 10/3 so it saved us a lot of work.
Inspectors seem to like it when you think proactively and consumers definitely enjoy it when they find out how inexpensive the change over is compared to what it could have cost them.
Steve - in Northern California
Edited 4/11/2002 4:50:56 PM ET by Steve Schefer
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