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Can some please explain this to me

 

Subject--table saw that can run on 110/220v. Disregarding all the hoopla of being more/less efficient etc.

 

If you have a 110v device pulling 15 amps, protected by a 20 amp breaker over a 12awg wire w/o tripping the breaker. I get the 20 amp breaker (10% over the 15 amp draw)

Everything is good so far.

 

Now I want to make the saw run on 220v.

So we now run the saw on a 20 amp breaker (or even a 30 amp breaker) on a 12 AWG wire.

Why??

why don't we run it on 10 amp breaker? (more probably a 15 amp breaker) on a 14 AWG wire

if you're splitting the load over 2 wires (red/black) the current s/b 7.5 amp per wire. 110% of 7.5 is something like 8 or 9 amps so a 10 amp breaker should do but 15 amp would be better (and more common & easier to obtain?)

 

In short, why don't we normally go to a smaller diameter wire instead of staying with the 12 AWG?

Is it b/c we just reuse the 110 wire (white & black) just to avoid pulling a new line? or is there something else involved in this?

 

If it were a completely new run I wonder what an electrician would pull as a matter of routine/habit.

 

Again for a saw not a dryer or stove/oven, welder.

 

thks

smitty

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I'm not an electrician and don't even play one on TV but the wire size/breaker size/circuit voltage may have something to do with the National Electric Code requirements.

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21 minutes ago, smitty10101 said:

Can some please explain this to me

@Artie, @Roly @DuckSoup...can you weigh in on Smitty's questions? Thanks in advance for your input.

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8 minutes ago, Artie said:

but if I ever get around to putting in some supplemental electric heat, i

 

 

On supplemental heat I already had a 30 amp breaker with 10 gauge wire for a Heat pump unit.  Wire from breaker to outlet was 16 inches.  Never had any trouble but could have easily run 12 gauge and been within code.  Better at the time seemed like an investment for later.  This past winter I bought a 220 heater that required being hardwired with 10 gauge wire to a 30 amp circuit.  But hey I already did that.  Just changed the outlet and used a Drier cord.  Having gone a tad better I made out long term.  By the way this heater works great for my 16x20 shop.  Have yet to run more than 2 hours entire winter.  Land up cutting it off when far side of the shop gets to 70Maybe an hour?

 

IMG_0768.JPG.ecfec46f4667ca881454e3303546bee1.JPG

 

As for original question have no idea really.  I have 220 for the compressor and the heater but only because they came that way.  Everything else runs off 110 with 20 amp circuits.  Bigger shop with say 100 amp service I probably would over time and budget providing upgrade to 220 machines.  My idea on this is I move machines from time to time and currently don't want to constantly run new legs of 220.  Call me lazy... :Laughing:

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15 hours ago, smitty10101 said:

If you have a 110v device pulling 15 amps, protected by a 20 amp breaker over a 12awg wire w/o tripping the breaker. I get the 20 amp breaker (10% over the 15 amp draw)

  The purpose of the breakers are to protect the wire not the equipment.

 

15 hours ago, smitty10101 said:

Now I want to make the saw run on 220v.

So we now run the saw on a 20 amp breaker (or even a 30 amp breaker) on a 12 AWG wire.

Why?? 

why don't we run it on 10 amp breaker? (more probably a 15 amp breaker) on a 14 AWG wire

if you're splitting the load over 2 wires (red/black) the current s/b 7.5 amp per wire. 110% of 7.5 is something like 8 or 9 amps so a 10 amp breaker should do but 15 amp would be better (and more common & easier to obtain?)

 

 Same size wire,#12, but different types have different ampacities.

Length of the wire run affects this as well. Longer run will normally have larger wire size to account for voltage drop.

Cost between #12 & #14 is minimal. But #12 gives you a little room to work when it comes to adding something else to a circuit.

If you were to run a saw and dust collector @ 220v you probably could run these on the same two pole breaker depending on the amperage draw. 

Like @Artie stated there are exceptions & other factors to consider. Exposing wire to its maximum rating over time can generates heat and premature failures.  

nec-wire-size-ampacity-chart_453233.png.bfb34e08f157fc9442d471ae049259f7.png

 

"If it were a completely new run I wonder what an electrician would pull as a matter of routine/habit".

As routine/habit I'm not sure there is one. Every job poses different challenges.

 If you were to run your wire in conduit and use #12 THHN you base your conduit size amongst other factors including the wire size and the amount of wires in the conduit.

Once you start adding more circuits into the conduit the amperage rating goes down while the conduit size goes up.

 

cth4Q.png.2ebdd0f86fc101a729b797eba0ed6ef3.png

 

 There is no easy explaintion.

 

 

  

 

Edited by DuckSoup

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It has been pretty will covered but like Artie I never run less than 12 ga and  a 20 amp circuit. The cost is minimal.   Roly

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When the Electrician wired my shop,he used all #12 wire and 20a breakers. There is a 110 4 plex every 8" @ 4'off the floor , and every 8' in between a single 30a. 220v. outlet.

I run the RAS on 220v, 14" band saw 220v. 12" TS 220v, and 3hp DC 220. Everything else is 110v.

I found on the TS, if I ran it on 110v that it would bog down and burn on cuts over 3/4" thick. Since I wired it to 220v. It doesn't bog down even @ full height rips.

Herb

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@Artie I am glad you chimed in,Artie. I know less than @Gene Howe about electricity,except that sometimes one wire is white and another black and green  and once in awhile there is a red one thrown in, along with the purple,brown blue and yellow.

But I did see a difference in the table saw between 110v. and 220v., I was always blowing the breaker ripping wood larger than 3/4" thick, and leaving burn marks from the saw bogging down and stalling. Now on 220v it just eats right through the board,not even slowing down.

 

Herb

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1 hour ago, Artie said:

Tomorrow we will talk about lightning strikes, class LOLOLOLOLOL. 

I will talk about Lightning strikes as that is what burned down my last shop and house. Lightening hit the power line and back fed into my garage shop and burned the shop and the house. At least that is what the State electrical inspector determined was the cause. It blew all the breakers out of the panel and the line voltage was feeding directly into the panel like an arc welder.

Herb

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Lightning just doesn’t obey the rules of physics. On one job, the customers had attached a 10 foot piece of steel rigid conduit, across the joists of the roof rafters, for a clothes hanger. Not connected to anything, not grounded, just 3 clips holding it to the rafters.  A lightning bolt went through the roof, and basically incinerated the conduit, also created a pretty bad fire. The scaredest I’ve ever been was when I had the boat, and we waited a little too long to leave, even though we had been watching the clouds come in. (What can I say, the fish started jumping on our lines). We got to where the mooring field for the sailboats was, in a HURRY.  Wound up putting the canvas up during the torrential downpour. It’s funny now, but I don’t think my drawers were clean, then LOL. I got to see a water spout off of Cape Cod once, that was cool.  To get back to electrical, one of the bigger boats lost all their electronics from a lightning strike that didn’t hit the boat, just the water, but close enough to fry anything with a transistor in it. I can’t remember the price tag, but it was more than I paid for my boat. 

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3 minutes ago, Artie said:

but close enough to fry anything with a transistor in it.

A number of years ago I was mowing what I call my upper acre...open area that had only young tree starts at the time. I had a nearly new, shirt pocket size, digital tune/display, portable radio I carried and used with ear buds. Ominous looking clouds began rolling in but I kept mowing...I saw a couple of cloud to ground lighting bolts well off in the distance...only a few more passes and I would be done...the next bolt to the ground I saw was much closer...I sorta' felt the hair raise on the back of my neck...concurrently the radio quit working which BTW allowed me to hear the thunder...I just made it to the garage as the t-storm broke loose...Apparently there was enough charge in the air from the last one to fry that radio....the digital display would no longer work. I took it as a strong warning. I finished the last few passes the next day. 

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2 hours ago, Artie said:

Lightning just doesn’t obey the rules of physics. On one job, the customers had attached a 10

I lost 2 computers to lightening strikes, and the second one I had on a surge protector.

Herb

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6 minutes ago, Dadio said:

I lost 2 computers to lightening strikes, and the second one I had on a surge protector.

 

 

Same, and the so called warranty on the surge protector was a joke.  My insurance company paid better by 250%.  

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I always like to plan for the eventualities. I may eventually want more 220 tools so plan for it. As well as the fact that that it may be less hazardous to have a higher gauge wire and breaker to reduce the chance of problems in the future. Also do not get the idea that 220 uses less electricity that has been proven wrong but a 220 motor in my opinion will last much longer. I am not an electrician but do a lot of my own 110 work.

    Thanks Artie I had not seen that about the 220 start up on motors

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