Running 220v from breaker

[Prashun Patel]

Let me preface by saying I'm not above hiring a pro, but want to fully explore whether I can do this myself before dropping $1000 on upgrading the wiring...

I've installed breakers and home runs before - and have passed electrical inspections - but that's all been with 15A/20A single pole breakers feeding 110v circuits.

I need to run about 100ft to the breaker to feed a new tablesaw. It draws 15A at 220v.

I can't find a clear, definitive resource on this... Any help appreciated.

I was planning to run 3 x 12ga (+a bare ground) wires through EMT conduit, and I assume I need a standard 220v doublepole breaker.

Any other advice appreciated.
- shawn

[Callan Campbell]

I suspect others more qualified than me will point out that 100 feet is a long run with 12ga if the motor rating is 15 amps with no start-up load taken into account. I'd opt for 10ga, this will allow for aging of the wires.If the load goes up to 20amps or even a bit higher when the saw is first started, you're probably better off with the heavier gauge wire, even if the 20 amp breaker is never tripped during normal use. What HP is the saw motor, this will probably help with their calculations for you.

[Rick Prosser]

"I was planning to run 3 x 12ga (+a bare ground) wires through EMT conduit"

If you are just feeding 220 (no plans for 110 connection), then you would only need 2 conductors (+ bare ground). I am all for flexibility with the extra conductor in the future, but just pointing it out.

[Keith Harrell]

As Rick pointed out most TS only really need two wires and ground but I would differently run 3+ground so you could run 110 circuits off it later. A 100ft run won't cost that much for the addition wire. You may also look at 10 gauge as the run is a good bit and the 10 gauge would offer more options down the road.

[Steve Costa]

Most of my stationary tools are 220, 20A to 30A. When building our house the electrician installed #10 wire for the 220, 30 Amp circuits. None of my runs are more than 50' from the panel.

Consider a 30 Amp breaker. Search Google for some URLs that will give you the correct wire size for the run length you have in mind. If you oversize the wire & breaker it will give you additional capability for future tool enhancements.

Some table saw motors have an overload breaker that kicks in if the saw begins to draw more amps than its capacity. Check to see if yours has one.

One of the best ways to make sure you pass inspection is to take a trip to your local electrical inspectors office. Tell him what you want to do and ask him for his "suggestions". The one where I live has kept on track more than once.

[Stuart Gardner]

Definitely 10 gage for that length. And don't oversize the breaker. If you're running a 15 or 20 amp machine on a 30 amp breaker, you can wreck your machine if it starts overloading. If it's overloading and should trip a 20 amp, but the 30 amp won't trip, the motor can burn out. Pretty unlikely, but you should match the breaker to the load when possible. By the way. I'm not an electrician. That's just my opinion based on conversations with the electrician that just upgraded my service panel and ran 220 to my garage.

[Tom W Armstrong]

Shawn, Good advice so far.

I recently researched and finally installed a 50 amp subpanel and doing all EMT runs in my garage for my shop. This included several 110 and 220 (both 20 and 30 amp) circuits. I'm only a bit handy but had zero experience with electrical at the beginning. Thanks to SMC and a few other resources (Welding websites), I was able to do it all by myself with only 7 trips to the Borg. :)

I just took my time and researched every step of the way, and all works great. The point of my post is yes, this shouldn't be a big deal. Error on the side of being conservative and you'll be fine. So, as stated, use a 20 amp DP breaker with 10-2 (or 10-3 if you want) wire running through your EMT. I used 1/2" for my 12-2 and it was a pain at points. I'd maybe use 3/4" EMT for the larger wire (e.g., 10-3) in hindsight.

My two cents

[Joe A Faulkner]

Shawn, I take it you are planning on running THHN, correct? You might want to go to your local library and review the National Electrical Code, 2011 edition or as suggested talk to your local inspector. In my area, THHN spools at the home centers are close to $90, and only come in 250' spools. A 250' spool of 10-3 Romex w/Ground is about $160, so it is a cheaper alternative, but is generally only supposed to be run in conduit to "protect" the wire. There is quite a bit of debate on this topic out there in the ether on this topic; supposedly the 2011 edition of the code was going to clarify this. Some interpretted the "okay to run in conduit to protect the wire" as meaning it was okay for short runs. If you have other future uses/needs for 10GA wire, then the THHN spools may work out fine in the end. Let us know what you decide.

[Prashun Patel]

Thanks, All. THNN 10ga is about $0.40/ft here, and it works out to about the same as Romex.

However, from what I understand, you SHOULDN'T run Romex in a conduit for fear of overheating.

The original wiring in my business's plant (where the saw will go) runs indiv wires in EMT, so that's what I'll do. The electrician who came out and quoted me $1800 said that's the way to go.

(of course, the $1800 got some bells and whistles like some lights and add'l outlets).

[Bill Davis]

"... this will allow for aging of the wires.."

Will you please explain what you mean by that statement. What happens when they age?