Wiring 240

[Doug Donnell]

I have been trying to find the answer to this on various "electrical" sites and realized the quickest way to get a answer was right here.:o

I just bought a Grizzly GO586 8" (mini gloat) and I am setting it up. By the way, renting an engine lift for $24.40 to get it on the base is the best money I spent on the tool...;)

It comes without a plug, with a 3 wire set up (black, white, and green). It draws 14 amps at 240V per the specs.

I have a pre-wired 10-3 run I put in when I built the shop since I figured someday I would need a 240 circuit but didn't know what the amp would need to be. No receptacle or breakers.

I went to the home center and the guy in the electrical dept insisted I needed 30 amp equipment since I had 10 gauge wire (9 years ago a different guy in the same home center told me to use 10-3 and I would have any conceivable future use covered). I had always just assumed I could use just the necessary wires and smaller amp equipment if needed when the time came (as long as the outlet restricted the use to the lowest amp component), but not according to this guy. :confused:

Anyway, he sells me a 30 amp dual pole breaker, a 4 prong NEMA L14-30R 125v-250v outlet, and a matching NEMA L14-30P 125v-250v plug. When I asked him what to do about the 3 wire to four wire issue he said to just not worry about wiring the neutral pole in the plug since the motor didn't use a neutral...

Now I am normally a trusting guy and all, but I also like to consider the "price of failure" when I am dong something I know nothing about. Is what this guy told me true, and is it safe? He got that vague look about him when I started asking questions, and didn't have the air of a seasoned professional...

Any help you guys can provide would be a huge help. I really don't want to hire an electrician since this should be within my ability to do it, assuming I have decent directions. Thanks in advance!

Doug

[Dan Friedrichs]

The guy you spoke to today was wrong - you can certainly use a lower-rated breaker. 10-3 wire means the largest breaker you can use is 30A, but since the machine draws 14A, if this is a dedicated outlet for just this machine, I'd put a 20A breaker in it. (Remember, though - the purpose of the breaker is to protect your wire from getting to hot and melting in an short-circuit condition - it's not supposed to protect your equipment; that just may be a side benefit).

I don't think there is anything inherently unsafe about using the L14-30 parts with the neutral just left unconnected (maybe someone can think of a situation where doing so may be dangerous, but off the top of my head, I can't...). But the correct parts to use would be NEMA 6-20 (3-pin devices, that look just like 110V plugs, but with one blade rotated 180 degrees). These are sold at all home centers, as well - they're common for window air conditioners.

In summary: I would use a 20A breaker, and NEMA 6-20 plug and receptacle.

[Doug Donnell]

Thanks for the quick reply Dan.

I was thinking about returning the parts and going 20 amp but the guy seemed to think the wire was too large for 20 amp parts. I have not heard of that before, I always heard that you could go larger than needed on the wire, but never smaller.

I would just cap the neutral wire in the 10-3 and should I ever need a 30 amp service I could re-install 30 amp components.

The only reason I can think of to install the 30 amp equipment would be a potential need for that much draw in the future. Anyone know if any woodworking or metal working equipment (welders or plazma cutters, neither of which I have or really need right now) need a 30 amp service?

And I would really like some additional feedback on the 4 prong set up without the neutral from the motor. Like, Dan, I couldn't come up with a reason that would not work, but I'm a forester, not an electrician....

[Rod Sheridan]

I also would put a 20 ampere 2 pole breaker and a 20 ampere 2 pole receptacle.

Please, never install receptacles with unused poles. When you see a 3 pole plus ground receptacle in a 120/240 V system it means it has a neutral connected.

If you're not going to run a neutral, use a 2 pole plus ground receptacle.

Incorrectly wired receptacles can lead to problems ranging from inconvenient to fatal.

Regards, Rod

[Doug Donnell]

Ok Rod, I want to make certain I don't leave a land mine for some future electrician or unsuspecting home owner. If I cap the neutral, both in the receptacle and in the breaker box, will that be sufficient warning that the neutral isn't in use? I assume so.

Its a mute point, but if I had proceeded with the original installation I had planned to go ahead and fully wire the neutral to the receptacle and the neutral bus in the box, so the circuit would be correct for the receptacle and not a future danger to someone. My assumption (and the direction of the home center guy) was that since no neutral was coming from the motor, that the plug on the machine would be the only one "incorrectly" wired, but would use the 2 hots and the ground in the plug. Since the machine is mine I could rewire if ever sold or inform the new owner of the set up.

What I am curious about is whether that set up would have even worked, would it have been dangerous, etc.

Last clarification, no one sees any problem using 10 gauge wire on 20 amp equipment, correct? The fact the guy at the center thought so really draws into question the rest of the information I got from him... or at least his level of attention or my clarity in communication...

Thanks all...

[Dan Friedrichs]

I misread your first post - I thought you pulled 10-2. Let me revise my advice:

Since you have 10-3, you have a neutral available in the box. You can wire up the L14 receptacle using all 4 wires, and have a correctly-wired outlet. Your jointer doesn't need one of those wires, so you can just not connect the neutral terminal when wiring the plug. This is not unusual or unsafe in any way. In the future, you have a properly-wired 4-wire outlet available for other applications.

You can use any breaker SMALLER than 30A on your 10ga wire. Again, the purpose of the breaker is to protect the wire, so there is technically nothing wrong with using a 30A breaker. Should something go wrong with the jointer, its internal overload should save it - should something go wrong with the wire/outlet/plug, the breaker should save it. But since this is essentially a "dedicated" outlet for this machine, there is no real advantage to using a breaker larger than necessary, so a 20A would be a better choice.

So really, you can do whatever you want :) I'd still personally use a 20A breaker and L6 plugs (just cap the unused neutral wire and stuff it in the back of the box - that way it's available if you ever do get a tool that requires it), but you can also safely use your 30A breaker and L14 parts (but connect the neutral to the receptacle so that it is properly wired).

[Jim O'Dell]

You'd be safe if you follow Dan's last post. It's pretty clear. Ipersonally used 10-2 and 30 amp breakers when I wired all of my 220 outlets. Only one so far needs it (5 hp cyclone). The others would have been fine on 20 amp. Main reason I used the 30 amp breakers is that I got a sweet deal on the 8 I needed on an Ebay auction for new breakers. Same thing on a box of 20 amp single pole breakers for the lights and outlets.
You are correct that the 10-3 wire is fine with either the 20 amp breaker, plug and receptacle, or the 30 amp breaker, plug and receptacle. I'm sure there is no price difference in the breakers, and if the difference between the plugs and receptacles is minimal, I'd stay with them and save the gas required to exchange them. Go ahead and wire the neutral in the box and the receptacle. The plug on the new tool just won't have a wire for the neutral connector. Be sure to tighten that screw down so it can't back out and fall into the plug and create a problem. That way, if you move, you don't have to remember to do anything or tell anyone anything. You also can't get dinged by the inspector if they caught a 20 amp plug on a 30 amp breaker. Jim.

[Rod Sheridan]

Ok Rod, I want to make certain I don't leave a land mine for some future electrician or unsuspecting home owner. If I cap the neutral, both in the receptacle and in the breaker box, will that be sufficient warning that the neutral isn't in use? I assume so.



Last clarification, no one sees any problem using 10 gauge wire on 20 amp equipment, correct? The fact the guy at the center thought so really draws into question the rest of the information I got from him... or at least his level of attention or my clarity in communication...

Thanks all...

Dan, I mis read the 10-3 as 10-2, I should probably wear my reading glasses more often.

10-3 is perfect for a 3 pole receptacle with ground.

Using a larger conductor is perfectly acceptable in this case.....Regards, Rod.

[Scott T Smith]

[QUOTE=Doug Donnell;1434547]

The only reason I can think of to install the 30 amp equipment would be a potential need for that much draw in the future. Anyone know if any woodworking or metal working equipment (welders or plazma cutters, neither of which I have or really need right now) need a 30 amp service?

QUOTE]

It depends upon the welding and plasma equipment. Most 240VAC stick welders require a 50A service, as do the larger plasma cutters and TIG welders.

Some lower amperage mig welders run on 30A.

You should be able to use either 20A or 30A breakers and receptacles on your 10 ga wire. If you go ahead and install 30A now, then your circuit is installed correctly for the size of the wire and you will be ready for any future equipment that requires 30A or less.

If you install the 20A breaker and receptacle now, you'll have to swap it out in the future if you upgrade to something that needs up to 30A.

[Tom Godley]

Do what you want -- but I never wire my 20amp tools to 30amp circuits.

More than likely that tool has supply wires that are 14g -- mine was and I just don't like to do it especially if it needs some type of extension cord.

My inspector indicated that it was fine to cap off the neutral on both ends of a 10/3 when I wired a straight 220 outlet - that is what I did. But you should use the correct plug/receptacle setup with three prongs.

[Brian Cover]

use the correct 20 amp plug and receptacle. They are half the price of that 125/250 plug and receptacle.

[Brian Cover]

Last clarification, no one sees any problem using 10 gauge wire on 20 amp equipment, correct?

The only problem is that you have equipment designed to run on a 20 amp protected circuit that is on a 30 amp breaker. The motor has no protection from damage. The wiring in the equipment can be severely damaged and the 30 amp breaker will not trip. I see this all the time on HVAC equipment installed with incorrect breakers. Your motor will cost several hundreds of dollars to replace. A new 20 amp breaker only costs about $15. Get the right breaker.

[Doug Donnell]

Thanks all. Went 20 amp and capped the neutral. Works like a champ.

DD

[Greg Portland]

Anyone know if any woodworking or metal working equipment need a 30 amp service?Any large table saw, planer, shaper, dust collector or bandsaw could require a 30A service. This usually means motors 3HP+ depending on the motor plate rating & local codes (percentage you can be within breaker rating).