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need help w/breaker for table saw

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Forum topic by DonEC posted 05-22-2013 08:12 AM 529 views 0 times favorited 6 replies Add to Favorites Watch
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DonEC

6 posts in 523 days


05-22-2013 08:12 AM

I just relocated and I have a table saw(3hp 12.5amp 220v). What is the max breaker that I can use?
I had a shop before and had a designated 20amp outlet just for my ts, but I don’t have that luxury now
and was wondering if I can use the 30amp outlet from our dryer(not at the same time of course).
I am new to this forum so I’m sorry if this isn’t the right place. Thanks.


6 replies so far

View Dave G's profile

Dave G

176 posts in 736 days


#1 posted 05-22-2013 09:36 AM

Hi. I’m not a licensed electrician. If I read your question correctly, you are concerned about protecting the saw with the breaker because you ask about “max” breaker? If so, electrical circuits are designed and coded to protect themselves. The breaker is sized to protect the wire and “devices” which include receptacles. Whatever is hooked up temporarily by a plug is on its own. If it burns itself up that’s too bad and allowed by the electrical code. It’s not ok by consumer safety rules and lawsuits but that’s different then the electrical circuit setup. Think of your household circuits. You could plug in 10 or more things on a 15 amp household circuit. The 15 amp breaker protects the wire and receptacle not the things. All that said, the 30 amp dryer breaker will likely trip with any short in the ts. And it’s plenty big enough to support the ts. I did that for my 220v bandsaw for years in a rented place no problems. I’m not a licensed electrician, did I say that yet? Just don’t hook up a 110v device to the 220v circuit. Note too that most existing dryer circuits are old 3 wire not newer 4 wire that does better job of grounding but lots of people are still living with the 3 wire; there’s been no effort to refit the old circuits.

Because of that 3-wire issue, you won’t find any new 3-prong plug part to fit the ts if it doesn’t already have one. You’ll have to splice a 3-prong dryer cord onto it (still available at Home Depot). It’s not advisable to replace your existing 3-prong dryer receptacle with a 4-prong receptacle without changing the 3-wire wire to 4-wire wire.

-- Dave, New England - “We are made to persist. that's how we find out who we are.” ― Tobias Wolff

View Shawn Masterson's profile

Shawn Masterson

1262 posts in 636 days


#2 posted 05-22-2013 09:58 AM

I will work fine, but if you are concerned about the machine being protected then put a fused disconnect on the machine. Then the machine is protected even if the breaker is faulty.

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Charlie

1048 posts in 974 days


#3 posted 05-22-2013 12:52 PM

The breaker protects the wiring. Not the machine. So as long as it’s WIRED (from panel to receptacle) appropriately for 30amp, then that 30 amp breaker isn’t a problem. It’s not like you’re going to push more electricity to the saw than it can use (unless there’s a short in the saw…then the SAW’S wiring has to withstand 30amps). The saw DRAWS what it needs. If there is an abundant surplus, the saw doesn’t care.

If you want to better protect the saw, you can do as has been mentioned and put a fused disconnect on the saw with lower amp fusing or breakers in it. If the saw shorts and it has a 20amp fused disconnect, it will trip that disconnect at 20 amps of draw. Without the disconnect, on a 30 amp circuit, it will draw 30amps before the breaker trips.

If I remember correctly, 12 gauge chassis wiring (saw’s internal wire for power cable-to-switch and switch-to-motor) is good for around 40 amps. Even if it’s 14 gauge it would still be good for something a bit over 30 amps (like 32 amps I think).

I’m not an electrician. I was a journeyman millright in a plant and we did everything (welding, pipe fitting, mechanical, etc) but we were not responsible for electrical. We had electricians, but the millrights worked WITH the electricians (under their supervision) for electrical issues.

Personally, I don’t see the 30amp circuit as an issue at all. As long as you use an appropriate receptacle and plug.

View helluvawreck's profile

helluvawreck

15960 posts in 1554 days


#4 posted 05-22-2013 01:49 PM

The smart thing to do is get a qualified electrician.

helluvawreck aka Charles
http://woodworkingexpo.wordpress.com

-- If a man does not keep pace with his companions, perhaps it is because he hears a different drummer. Let him step to the music which he hears, however measured or far away. Henry David Thoreau

View Fresch's profile

Fresch

21 posts in 608 days


#5 posted 05-22-2013 05:37 PM

#14awg. Is good for 15 amps #12awg. Is good for 20 amps #10awg. Is good for 30 amps
Load circuits to 80%

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DonEC

6 posts in 523 days


#6 posted 05-22-2013 08:34 PM

thank you for the help

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