Burning down the shop/burning out the Unisaw?

[Kurt Keeler]

Don't panic! I recently acquired a 5hp (20 amp), right tilt Unisaw from a school district and am working on wiring it up.

I have some options -
Option A - Run 10-2 romex from the 30 amp breaker to an old screw in fuse disconnect/fuse box (about 20 foot) and from that box run some 12 gauge SO (about 20 foot) to the saw and basically having it all hardwired.
I'm not crazy about using the fuse box and relying on the disconnect as it is an old box and I would feel better with a "I can see the saw is not plugged in" lock-out/tag-out method.

Option B - Run 10-2 romex from the 30 amp breaker to a L6-20 receptacle (about 20 foot) mounted on the wall and a 12 gauge SO cable (15-20 foot) with L6-20 plug from the saw to the L6-20 receptacle.
Everything I read says the 12 gauge SO should be fine for 20 amps, I'm just concerned about voltage drops and shortening the life of the 5hp motor and I would have a cord running across the floor.

Option C - Run 20-2 romex from the 30 amp breaker to a L6-20 receptacle mounted on the extension table leg and utilize the current 10 gauge SO cord to that L6-20 receptacle.
I'm not crazy about this one either as I would need to mount and affix conduit to the concrete floor to run the romex to the saw to prevent a tripping hazard.

I'd appreciate your input. I've asked a couple electricians at work and they keep saying "12 gauge is fine if it is not too far" but never really tell me what too far is.

[John Morrison60]

Kurt

I would run 10 guage the whole way, and put a 30 amp plug, outlet,
and breaker in.

My experience is that as soon as I got to 5 HP I was also at a 30 amp requirement.

I don't think that you want any 12 GA wire in the service to that saw.


Good luck.
John

[Jim O'Dell]

I agree with John, keep it all 10 gauge and 30 amp plugs. 20 amp is ok for 3 hp, but I wouldn't do 5 hp with it.
And DON'T run romex over the concrete where it is exposed!! That's a big NO NO. Run your wire to the receptacle, either in the wall, or in conduit, then use 10 gauge heavy duty extension cord type wire to run to the saw. What I used, and it's not on the floor, is about 5/8" in diameter. Not cheap, but definitely worth it. If you need to make sure it is secure and you don't trip over it, cut some wood to make a wide ramp and glue it down on either side of the cable to make a slot for the cable to be in where ever it is exposed to foot traffic. Jim.

Oh, and I'm not an electrician, nor do I know code, but this is what makes common sense to me.

[Duane Bledsoe]

If the main breaker for this is going to be a 30 amp breaker, then at no point in the system should there ever be a 12 gauge wire, from breaker to receptacle, or receptacle to machine. Not even in an extention cord.

General rule is 10 ga. wire for 30 amp, 12 ga. wire for 20 amp. If you have a 12 gauge wire that is backed up by a 30 amp breaker and for any reason it ever got hot from too much current flow (exceeding 20 amps but not 30), it would fail before the breaker would trip and could cause a fire.

The other guys are right though, 12 gauge "could" be used if it was "not too far", but how far is too far?? You'd have to calculate the resistance of the wire based on how many feet you'd need of it and resistance per foot, current passing through it, how much voltage drop you may see, and by then, to me, it's just not worth it. Best practice is just run 10 gauge and not have the worry.

[Lee Koepke]

I also utilize the disconnect upstream of the outlet, so I can visually verify that saw is off prior to swapping blades, etc. and I agree with the sticking with 10 ga wire.

[Jim Becker]

10 gage rubber coated cord is available at the 'borg by the foot and is what I use for the connections from the outlet to the machines in my shop. Don't drop to 12 gage for that portion of your installation. This is independent of any disconnect you provide for up-stream--personally, I just unplug for maintenance, even though my Euro machines have a built-in disconnect switch independent of the operational switches.

[Callan Campbell]

Most 5HP motors are rated above 20 amps for the start-up load, or if under a heavy load. Agree with everyone else that a regular 30 amp circuit with 10 gauge run the whole length is the way to go for a standard 5HP/30 amp wiring set-up. Don't use any disconnect box if you're unsure of its life left/operation. 220 volts is nothing to play around with, and I'm speaking as a person who was once thrown 6 feet away from a shorting rod type welder that had a bad case ground and 220volt as the operating voltage of the welder. I made the 'circuit' with my body, felt pretty sick afterwards, but lived to tell the tale....

[Ken Garlock]

Hi Kurt, and welcome to the Creek.

Simple fact, if you have a 30 amp breaker, then you need 10 ga. from breaker to load unless you have intervening breakers of lesser size. Remember, the breaker protects the wiring, not the load.

Who ever told you that a short 12 ga. is OK, and reports to be an electrician, should have his credentials examined.

[Dave MacArthur]

I had a long reply written here covering the special treatment in the NEC for dedicated motor circuits which allow some unexpected results. However, I decided to put it in it's own thread for future reference and just provide a link here.

http://www.sawmillcreek.org/showthre...94#post1568394

I could see how someone might arrive at 12AWG if they considered the use periodic, used table 240.22E to arrive at .85 or .9 FLA multiplier, and did not consider 75C or 60C wire termination criteria. Not what I arrived at myself though, I'd run 10AWG and a 30A breaker.

[Tom Sheahan]

Earlier this year wife came down and said electric dryer would not work. Long story short, bad connection on dryer, not where plug connects but at factory slip on connector, one leg was on and off essentially a floating ground, ended up frying wire in junction box, wire nuts and all up n smoke. been using it since I moved in some 18 years ago without a problem. Re-wired it with conduit, did it right.

There is a reason for electric codes. They prevent us from burning stuff down.

My suggestion, if machine is placed where you want it, run conduit without a splice / junction box to a good industrial lockout box, from box to saw with flexible wire the heavy rubber stuff.

That way you can lock machine out.

Never skimp on wiring, will always come back to bite you one way or another.

[Kurt Keeler]

I went ahead and did it all 10 gauge. 10-2 to the outlet mounted on the extension leg used the same plug and wiring that has been on it (I assume) for the last 12 years in the school.

This is a temporary job until I get the final positioning down and can get to a real town that has some electrical supplies. I know it's not pretty now but I'll fix it once things are set up more permanent. Luckily I live in a county that, if your out of town, there are no inspections or anything.

Thanks for all your input.

[Rollie Meyers]

If your going to need to run on top of a floor, concrete or otherwise, the Wiremold Company makes a pancake raceway that is tailor made for that application. You will have to go to a legitimate electrical supply house not a big box store.

[David Helm]

Glad to see you went with 10 gauge wire. Everyone was right about this but noone really mentioned the consequences of using too small of wire. With a 30 amp breaker and 12 gauge wire the breaker is no longer the overcurrent device; the wire is. The wire will burn through before the breaker trips . . . not a good situation.

[Chip Lindley]

10ga / 30a !! I'm happy you decided not to skimp on the wiring Kurt. After all, you got that nice big Unisaw for a mere pitance! lol! Investing in safe, adequate wiring is no waste of money.