# What gauge wire?



## Ray Newman (Mar 9, 2009)

Colleagues: getting a new piece of equipment and need to determine wire size needed to hook up.

Breaker is 40 amps, 220v. 

Outlet to saw will be about 30 feet -- up and over DC system. Concrete floor so cannot go under slab. 

Have 45 feet of 12/3, but I do not think that is the right gauge.

Thanks.


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## CharleyL (Feb 28, 2009)

You will need 8 gauge wire for 40 amps. I would go to 6 gauge if you go to 100' distance, but you said 30' so 8 gauge is the good number. 12 gauge is only good for 20 amps up to 100', so not nearly heavy enough for this application.

Charley


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## DaninVan (Jan 1, 2012)

Ray; just work backwards from #14 = 15A
12 = 20A
10 = 30A
* 8 = 40A*
6 = 60A

3 = 100Amp

Assuming Copper wire!


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## kp91 (Sep 10, 2004)

My reference has 8- 10 ga depending on the wire type. The big question is what is the requirement of the consumer? Wire ain't cheap, it might be a better solution to reduce the size of the breaker and run a cheaper wire. a 5 HP saw is only in the 20 amp range, so you could go with a 30 amp circuit. Depending on the wire type, 10 or 12 works for 30 amp. I would probably pick 10 gage for a 30 A circuit.

big thing is the type of wire. Power cable versus Romex, stranded versus solid core, and the insulation rating. 

Of course, your local code may vary depending on application.


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## Herb Stoops (Aug 28, 2012)

Is this TO the 40amp breaker? or to the saw? If you are running 40amps to the saw, it must be a hellva saw. 

If you are installing a 40 amp branch panel and have 15-20-30 amp breakers then size the runs to the machines according to what the machine draws/breaker sizes.

Herb


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## Stick486 (Jan 4, 2013)

knowing the total electrical requirements for the new equipment...

what is your amp draw for it...


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## Ray Newman (Mar 9, 2009)

Stick: new saw is 3HP/13amps/220 volts.

I should have expressed my problem clearer: What I am trying to determine is what gauge wire I will need for a 25-30 foot wire run from the wall outlet to the saw connection.

Actual straight line distance from the saw position to wall outlet is about 10', but I need to run it up the wall, over the DC system, then to the saw to have clear floor space for a wheelchair.


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## Stick486 (Jan 4, 2013)

Ray Newman said:


> Stick: new saw is 3HP/13amps/220 volts.


a *15AMP 14GA* wired circuit will work but be marginal at best...
you'll experience nuisance trips...
a *20AMP 12 GA* wired circuit will be the be the better/safer way to go...
use stranded wire and tip the scales in your favor...

BTW... that *40AMP* breaker is way too big...
you could overload *(from FLA draw during use)* your motor and cook/burn it up while never knowing you were doing so till it's too late...
a dulled blade, feed rate, amount of cut ''bite'', material hardness, type of blade, lack of chip evacuation will all contribute to overloading and elevated amp draw...
the name of the game here is ''PROTECT'' your new saw and yourself...

*NOTE:*
The amp rating indicates the electrical current load the tool is capable of carrying for a theoretically indefinite amount of time without degrading the motor insulation system or other electrical components.....

the bigger breaker will allow higher amp draw while under load w/o ''tripping''...
and things will go south in a hurry...
not to mention the possibility of causing/starting a fire...


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## DonkeyHody (Jan 22, 2015)

Ray,
The 12 gauge wire will carry the 13 running amps your saw requires just fine. That's what I would use for your saw because it's cheaper and MUCH easier to pull than even #10 wire, and especially #8. But, you normally can only use a 20 amp or smaller breaker with 12 gauge wire. 

You MAY have a problem with the saw tripping a 20 amp breaker on startup because the starting current is often about 3 times the running current depending on the motor. However, the heavy load is very brief, and the breaker may carry it without tripping. 

I would run the #12 wire on a 20 amp breaker and see if it ever trips on startup. If not, you're golden. If it trips, it's time for plan "B".

There is a little-known special provision in the National Electric Code which allows you to go 1 step higher, to a 30 amp breaker on #12 wire if certain conditions are met:

1. The load on the circuit must be an electric motor which has its own overload protection (yours will have a thermal overload protector on the motor).
2. There must be NO other loads on that circuit.

The idea is that overload protection is provided at the motor, and a dead short would trip the breaker, even if it is slightly oversized. 

I'm sure many electricians will argue the advisability of it, but the NEC allows it. For the Nay-Sayers, check out Section 430, Part D - Motor Banch-Circuit Short-Circuit and Ground-Fault Protection.
Paragraph 430-52 

Enjoy your new saw!


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## Cherryville Chuck (Sep 28, 2010)

That's the same as my unisaw. 12 gauge and 20 amps is the proper size. Distance is not an issue. Unless you are unable to walk past the end the wire comes in from then it needs to be shielded as in bx cable or run the wires through the empty bx sheath. You can't just walk on the bare wire. Truthfully to satisfy code it should be shielded as soon as it leaves the wall. The only exception would be if it was plugged in to a wall outlet via a power cord/plug-in which is not all that good an idea as the power cord will also wear.


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## Ray Newman (Mar 9, 2009)

Gents: am going to ask around about an electrician. Earlier I thought that 40 amps is way too much and Stick's comment confirmed it. 

Thanks for the information.


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## kp91 (Sep 10, 2004)

Ray Newman said:


> Gents: am going to ask around about an electrician. Earlier I thought that 40 amps is way to much and Stick's comment confirmed it.
> 
> Thanks for the information.


Good call, ask the experts when not certain!


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## paduke (Mar 28, 2010)

Cherryville Chuck said:


> That's the same as my unisaw. 12 gauge and 20 amps is the proper size. Distance is not an issue. Unless you are unable to walk past the end the wire comes in from then it needs to be shielded as in bx cable or run the wires through the empty bx sheath. You can't just walk on the bare wire. Truthfully to satisfy code it should be shielded as soon as it leaves the wall. The only exception would be if it was plugged in to a wall outlet via a power cord/plug-in which is not all that good an idea as the power cord will also wear.


 Chuck is BX legal in canada? We use MC here in the states BX the shield is the ground MC has ground wire inside shield


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## DaninVan (Jan 1, 2012)

Bill; I think the Cdn. Electrical Code designation has changed to *AC*, I presume standing for 'Armoured Cable'...a different product line than TECK cable.
http://www.southwire.ca/documents/AC90AG_Sales_Sheet.pdf
Note that the AC90 has both an armoured shield as well as a ground conductor.


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## Dejure (Jul 27, 2009)

I'm an overkill kind of guy, but I'm not so hot at seeing what the future holds, aside from that swapping a smaller gauge for a larger is no simple task, after the drywall goes up. For that reason, my 240 circuits are all ten gauge. After all, I only have to run them once, and with that, I can upgrade what's on the end.

My Unisaw would run fine on twelve. Of course, it'll run fine on ten. As such, it is on ten with a thirty amp breaker protecting the line wires (and not the machine).

Scoot over to my four bag collector and it would tax that circuit, if it were limited to twenty amps. It sucks the utilities teat to the tune of seventeen amps. That doesn't leave much buffer. Since I'm set to run up to thirty on all those circuits, I can swap places with the table saw and the collector, or the jointer, or...


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## Cherryville Chuck (Sep 28, 2010)

DaninVan said:


> Bill; I think the Cdn. Electrical Code designation has changed to *AC*, I presume standing for 'Armoured Cable'...a different product line than TECK cable.
> http://www.southwire.ca/documents/AC90AG_Sales_Sheet.pdf
> Note that the AC90 has both an armoured shield as well as a ground conductor.


Are Bx and AC considered different Dan? When I googled it I got: "BX cable, a genericized trademark term for type AC armoured electrical cable (from Bronx cable)". Seems to me that I've seen bx with a separate ground but once you connect to the outlet box(es) it's also grounded anyway.

Certainly tech cable is better stuff but it's also more expensive.


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## DonkeyHody (Jan 22, 2015)

Dejure said:


> I'm an overkill kind of guy, but I'm not so hot at seeing what the future holds, aside from that swapping a smaller gauge for a larger is no simple task, after the drywall goes up. For that reason, my 240 circuits are all ten gauge. After all, I only have to run them once, and with that, I can upgrade what's on the end.


Same here, but I was able to add several #10 circuits while my shop was stripped down to the stud walls. I don't enjoy pulling it through conduit and such.


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## Herb Stoops (Aug 28, 2012)

My shops walls were all finished drywall ,so I surface wired everything in plastic conduit with a outlet every 8 feet and it was fast and easy. I pulled single strand wires, all # 12ga. or larger. Also 4 runs full length of the ceiling for lights with a 4X4 box every 8'.

Herb


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## DaninVan (Jan 1, 2012)

Charles; I'm still using the remaining spools of BX I had left over from projects 12 yrs ago. I must remember to have a look at the label on the spool to see what the Code designation was back then.
I think this is the same issue as when 'Loomex' was categorized officially as NMD90. That was when the heat rating went from 60deg. C to 90degC.
That was the same time as the change to thermoplastic sheathing came in if I remember correctly(?)...
Early 70's? I missed the fabric and tar sheathing...but not for long!


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## smitty10101 (Oct 15, 2004)

Ray two questions/thoughts

If I read your question correctly you are running a wire from an OUTLET/RECEPTALE ??
What is the gauge from the service panel to the outlet?? you will need at least the same or equivalent size gauge 

smitty


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## Cherryville Chuck (Sep 28, 2010)

Dan I used the just the sheathing well after that and was inspected and passed. I remember the fabric well. Someone told me that the fabric contained arsenic to discourage mice from chewing on it and if you pulled on it all day long it would cause sores. It won't meet code anymore because that squiggly ground wire was 16 gauge instead of 14.

At least finding that quote let me know what the BX stands for (*B*ron*x* cable). I've been wondering that for years.


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## Herb Stoops (Aug 28, 2012)

Cherryville Chuck said:


> Dan I used the just the sheathing well after that and was inspected and passed. I remember the fabric well. Someone told me that the fabric contained arsenic to discourage mice from chewing on it and if you pulled on it all day long it would cause sores. It won't meet code anymore because that squiggly ground wire was 16 gauge instead of 14.
> 
> At least finding that quote let me know what the BX stands for (*B*ron*x* cable). I've been wondering that for years.


What about Romex?

Herb


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## Cherryville Chuck (Sep 28, 2010)

Loomex here. Same stuff as far as I tell.


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## DaninVan (Jan 1, 2012)

'ROMEX' and 'LOOMEX' are both brand names for *non-metallic sheathed cable*. Lots of other lesser known brand names for the same stuff.
Didn't know that about the Arsenic, Charles.


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## firstmuller (Aug 28, 2014)

If you are worried about the start up load, use a 20 amp high magnetic trip breaker with the 12 gauge wire. We use them at work when we have toridal transforms to turn on.
Allen


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## RainMan 2.0 (May 6, 2014)

I'm late . I had 12Gauge 3 wire put in for my tablesaw with a 30 amp dual throw breaker(15 amps per side) . In theory I could have gone with a 40 amp dual breaker because each 12 gauge strand is rated for 20 amps . 
Your fine with 12 gauge ,and I think the breaker your reffering to is a dual one, 20 amps per side for a total of 40. I don't see a problem with your design , well unless this 40 amp breaker is actually 40 amps per side for a total of 80 amps .
Pic of the breaker ?


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## Stick486 (Jan 4, 2013)

TheCableGuy said:


> I'm late . I had 12Gauge 3 wire put in for my tablesaw with a 30 amp dual throw breaker(15 amps per side) . In theory I could have gone with a 40 amp dual breaker because each 12 gauge strand is rated for 20 amps .
> Your fine with 12 gauge ,and I think the breaker your reffering to is a dual one, 20 amps per side for a total of 40. I don't see a problem with your design , well unless this 40 amp breaker is actually 40 amps per side for a total of 80 amps .
> Pic of the breaker ?


you need to reread what you wrote....
editing or rewiring is in order...
both????


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## RainMan 2.0 (May 6, 2014)

Stick486 said:


> you need to reread what you wrote....
> editing or rewiring is in order...
> both????


Well this is what I'm using , a breaker made for 240V , 20 amps a side for a total of 40 amps capacity . This is connected to 12 gauge wires feeding my table saw . 
It's a bit of overkill as I could have gotten by with a 240 volt breaker with 15amps a side , but I like the extra headroom for inrush current . 




I don't think Ray was going to use a 40 amp per side breaker , or maybe I'm misunderstanding something here


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## Cherryville Chuck (Sep 28, 2010)

Rick if your saw is rated 3 hp then you need 12 ga/20 amp. That's what the 3 hp Unisaws, Generals, and Powermatic 66s all require. While a 15 amp breaker might work, the chances are that heavy loading would cause it to trip. Any breaker that keeps getting tripped will eventually weaken and won't handle its rated load anymore.

When talking about dual voltage breakers (220-240) you don't add the load together. It's understood that it's rated 20 per side.


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## RainMan 2.0 (May 6, 2014)

Gotcha Charles


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## DaninVan (Jan 1, 2012)

"When talking about dual voltage breakers (220-240) you don't add the load together. It's understood that it's rated 20 per side."
-Charles

Oops; I think what Charles meant was _two pole _. If you're using it for 2-110V ccts...say a split receptacle on a kitchen countertop...then it's not additive. Each side is a separate cct, with the shared neutral conductor. (And the handles tied if it's a dual breaker)

If I've misquoted/misunderstood you, Charles, please sort me out.


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## Cherryville Chuck (Sep 28, 2010)

Yep. 2 pole=dual voltage= 2 times 110-120 volt and of opposite phase. Our kitchen counter plugs are 2 separate 110-120 volt circuits but they must be using the same side of the panel, i.e. the same 110-120 volts (same phase). The first time I wired a split duplex plug I made the mistake of drawing current from both sides of the panel which put 220-240 volt phase coming back on the return wire (neutral).

I don't think this is a code requirement in the US so a brief explanation. Our kitchen counter plugs must be wired so that each plug socket on one receptacle is wired to a separate 15 amp breaker. You can then run a wire to one more receptacle and join it to the first one in the same way. You have to use 14-3 to wire them. There is a small tie bar on the receptacle between the two screws on each side that can be broken off which isolates one plug from the other. You break the load side tie bar off but leave the neutral side one connected. The two breakers must be side by side and the handles tied together so that if one breaker trips, so does the other. I don't agree with the theory behind doing it but it's code so we don't have a choice.


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## Dejure (Jul 27, 2009)

Based on first hand experience, I like having the breakers tied. Years [and then some more] ago, my dryer quit drying, but not working. It really made me scratch my head. Only after a lot of troubleshooting, the hard way (disassembly) did I find one of the two breakers tripped. Reassembled the unit, turned it on and tried drying something and it was fine.

Then there is the "I tripped "the" breaker, then it still knocked me on my butt."




Cherryville Chuck said:


> The two breakers must be side by side and the handles tied together so that if one breaker trips, so does the other. I don't agree with the theory behind doing it but it's code so we don't have a choice.


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## DaninVan (Jan 1, 2012)

What Kelly said.
If one side trips or is turned off intentionally, and the handle tie doesn't trip the other side, then there's still a hot lead in the junction box wherever that's located. Nasty surprise awaits.
I'm guessing some serious incidents led to the Code requirement.


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## Cherryville Chuck (Sep 28, 2010)

Sorry. That wasn't the theory I meant. I fully agree with both breakers tripping otherwise half the plug in is still live.

When I asked my electrical inspector the reasoning behind splitting the plug into 2 separate circuits this is what he told me. "The idea is that when a housewife plugs a microwave into a socket, if she also plugged in a toaster the breaker would trip." Sounds logical right? Except that when wired properly, the top of that plug in is supposed to be connected to the bottom of the next plug in and the bottom to top. So if she walks over to the next plugin and plugs the toaster into the wrong socket the breaker still trips. 

My argument was that it would be much easier to train my significant other that she could only plug one major appliance into any outlet and dedicate the entire plug receptacle to one 15 amp breaker. Much easier to remember in my opinion. And of course I got the standard answer: "I don't make the rules, I just have to enforce them."


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## DaninVan (Jan 1, 2012)

I agree that the two split receptacles on the same two pole breaker is a dumb idea, Charles. I've always insisted on each plug point being on an independent cct. ie a run of 14/3 to the split receptacle...two pole breaker...and that's the end of the cct.
Lots of arguments with electricians; "That's not what the code requires." 
Me; "The Code is the _minimum_ required, and I'm paying for this."
The inspectors love to see the dedicated ccts.


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## Cherryville Chuck (Sep 28, 2010)

I also agree that a dedicated circuit per kitchen plug is good policy but splitting the plugs in two doesn't make sense IMO. If I can get away with it I do it my way and not their way. I also agree with the code requirements. Code says one outlet every 12' of wall space. The last thing I want is to have to run extension cords inside my house so I went every 6'. I was doing the work and the extra cost was minimal. I'm able to use the power cord on the appliance and reach a plug in no matter where the wife decides she wants it located.


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## RainMan 2.0 (May 6, 2014)

Your also allowed to run a 12 gauge 20 amp circuit to your kitchen without split plugs . You can have two outlets on the same circuit total (GFI)


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