# Installing 240V Circuit



## tblake1984 (Mar 12, 2015)

I have a Ridgid R4512 table saw that is rated at 13A. Doing the math and assuming a 70% efficiency on the motor, that means I am getting 1.5hp max out of this thing. I bogged it down and tripped the breaker cutting some raised panels with it two weeks ago and it freaked me out a bit. My question is this; If I convert it to 240V, does the amperage go down to maintain the same wattage or will I actually get more power out of the saw? Basically, I figure the equation would then be (240*13)-30%=2184W=2.9hp. Is that right?

If so, I want to run it on 240v. Here are the options I am considering for the circuit.

[1] Hire an electrician to install a dedicated 240V 15A circuit. This is obviously the smartest way to go but also the most expensive. I have a basement shop (aka, a concrete cave with unfinished walls) so installing a dedicated outlet box and conduit is a PITA.

[3] Install the circuit myself and replace a pre-existing 1-gang 120v outlet box with a 2-gang outlet box so I can have a 120V and a 240V outlet in the same box (I would also use the pre-existing conduit as well with 12-3 NM wire and a 15A breaker). This would be much cheaper and seems easy enough to do on my own but I'm not sure if running 120 and 240 in the same conduit is a good idea.

I will be replacing the whole cord assembly on the saw with something longer as well. Also, what are your thoughts on making this a 20A circuit despite Ridgid's recommendation of 15A?


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## OggieOglethorpe (Aug 15, 2012)

I LOVE Internet discussions on electric questions!


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## Parabola (Dec 31, 2015)

For your motor power question:
A motor is built for a specific power output. Doubling the voltage will divide the current in half. (P = I*V)
Many motors will show the amperage draw for both voltage configurations and they always reduce the current when you up the voltage.

I won't speak to the electrician questions as my answers may not be correct.


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## MadMark (Jun 3, 2014)

To get both 110vac and 220vac you'll need two hots, a neutral, and a ground. A cordset would require a NEMA14-20 connectors. Do NOT try to use the ground as a neutral. Put a 20A breaker in line (no point in doing all this for 15A)

If you are in a basement run your wiring thru the first floor joists. If the ceiling is finished put a NEMA14 on the wall next to the existing breaker panel and run a cordset to where you need it.

220vac is actually two 110vac lines 180° out of phase. so yeah, you can mix 110vac and 220vac in the same box / cable.

M


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## CharlesA (Jun 24, 2013)

I think your equation should read:

(240*6.5)-30%=1092W=1.46hp


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## SirIrb (Jan 12, 2015)

Took me 6 tries to get through college algebra with a 74. I will choose to not add anything to a discussion on math. You need @TheFridge, resident electrician.


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## Cato (May 1, 2009)

I think your HP will basically remain the same just draw less amps.


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## CharlesA (Jun 24, 2013)

Some folks argue that a 240v setup is more efficient than 120, but it would be in the single digits %, not 100%.

I have a Craftsman that is very similar to the Ridgid. Some thoughts: use a thin kerf blade, make sure you keep it sharp, and feed particularly hard or thick wood more slowly.

I've cut 8/4 Jatoba without much trouble. The only lumber I'be had a hard time with is 2×12 floor joists (I ripped in strips to make my work bench), and it would curve back together and squeeze the blade.


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## dhazelton (Feb 11, 2012)

You'd have to look at your local electrical code to see if you could put both circuits in the same box. The conduit would also have to be large enough so things aren't tight or bunched up in it. I would keep them separate myself. If the only thing keeping you from doing it yourself is the concrete get a Ramset or buy some masonry screws or anchors. Screws work best in green concrete, so I might go with the Ramset. You can also just drop a large piece of wood down from a ceiling or rim joist and attach your box to that.


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## clin (Sep 3, 2015)

Just another confirmation that yes, going from 120 V to 240 V, will cut the current draw in half.

If you are going to run new wire, run the largest wire (largest amp circuit) you can. While there may be code restrictions on how much you can load your panel, I'm pretty sure there is no limit on how large a wire you can run (just how large a breaker you can put in it). The point being, larger wire allows you the option to draw more amps if you need to, even if you only want 20 A now.

Also, you may want to consider putting in a sub-panel. For example, run a 60 A circuit, and put a small breaker panel in your basement. Then you can add on more easily in the future. This way, you are running just one new set of wires (though larger), but can then expand easily.

As always you need to understand what your electric codes are, but adding a sub-panel, is actually quite easy to do.

Also, no big deal mounting conduit to block or concrete, just get the correct fasteners and appropriate drill. You may need a hammer drill for concrete.

Also, you may want to consider framing the basement wall(s) so you can easily run wire and add shelves or cabinets. I.E., rather then individually mounting things like conduit to the masonry wall, bite the bullet once and get some framing attached to them, then more easily attach to that as needed.


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## conifur (Apr 1, 2015)

Just another confirmation that yes, going from 120 V to 240 V, will cut the current draw in half.
I do believe that is per leg, not total.


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## WhyMe (Feb 15, 2014)

You need a 20A 120V circuit for that saw. Don't worry about putting in a 240V circuit. Not worth the trouble.


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## REO (Sep 20, 2012)

This is easy lol amps times volts is watts right?! The WATT is a unit of power not amps not volts! so many are correct in their statements but their conclusions are misguided! here is a real example that cant be argued.

10 amps times 110 vollts equals 1100 watts which equals 1.475 hp
5 amps times 220 volts equals 1100 watts which equals 1.475 hp
that should clear up the HP problem!
when you pay your bill for electric you pay for WATThours not volts not amps so its easy also to determine that regardless of which voltage you use the final bill will be the same because you pay for 1100 watts times the amount of hours you have the saw running AT rated HP either way


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## conifur (Apr 1, 2015)

REO,
I worked for an electric utility for 20 years, last I knew a kilo watt was 1000 watts not 1100!!!!
you pay for 1100 watts times the amount of hours you have the saw running AT rated HP either way


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## JBrow (Nov 18, 2015)

tblake1984,

As you know, changing your circuit from 120V to 240V is a lot of work and expensive. Perhaps that would solve your problem, perhaps not. I would troubleshoot the circuit and the saw first.

The breaker tripped because:

1) The circuit was getting too many amps for the 15 A breaker. You did not mention whether the table saw circuit is dedicated or whether other devices are also powered on this circuit. If the circuit is carrying load other than the table saw, the combined load when the breaker tripped caused the trip. Some shop lights (or other household load) plus the table saw on this circuit could have taken the circuit down. If the table saw circuit is not a dedicated circuit, ensuring any other devices on the circuit are off while operating the table saw will probably solve the problem. Alternatively installing a new dedicated 15 amp circuit could also solve the additional load problem.

2) The circuit breaker itself is defective. The only way I know to determine if the circuit breaker is defective is to replace the circuit breaker. If you can do the work of replacing the circuit breaker safely, this would cost maybe $10. I do not how much an electrician would charge, but his time would be minimal.

3) The saw motor is defective. I have no suggestions for troubleshooting the motor but doubt that this is your problem. If the saw normally works ok and been ok since the breaker tripped, I would think the saw is ok. Others have already suggested methods for reducing the load on the motor when making cuts.

Even though you did not say you planned to simply install a 20 amp breaker in place of the 15 amp breaker, I have a strong word of caution since this is tempting. I WOULD NOT simply replace the 15 amp breaker with a 20 amp or larger breaker. This is a REAL FIRE HAZARD. A circuit with a 15 amp breaker, in all probability, has 14 gauge copper wire somewhere in the circuit. 14 gauge wire can safely handle 15 amps. If more than 15 amps is put into 14 gauge wire, it will heat up, damage the insulation encasing the wire, and could start a fire!

If you know with absolute certainty that the circuit has 12 gauge or larger wire is running throughout, then increasing from a 15 amp breaker to a 20 amp breaker would be ok. If the motor has overload protection (a reset button somewhere on the motor), the additional amperage from a larger 120 volt circuit would probably not damage the motor, since the internal circuit breaker on the motor would probably trip if the motor draws too much current. I have read manuals from various manufacturers who recommend a circuit breaker larger than the motor rating. But then these motors may have overload protection.

If you plan to replace the power cord on the saw, I would recommend a 12 gauge power cord, which is a little more money than 14 gauge power cords. This increase in size would reduce voltage drop due to resistance inherent in copper. I believe that voltage (the force pumping the current through the circuit) decreases for a given size wire as distance increases. Increasing the size of the wire for a given current (e.g. 15 amp) would increase the length of the cord before voltage loss effects the motor. Admittedly, using 12 gauge wire instead of 14 gauge wire over a short distance would only reduce the impact of voltage drop slightly. Also, unless your existing table saw power cord is small and long, I doubt that replacing the power cord would be beneficial. Additionally, I doubt the power cord has any effect on the problem of the tripped breaker.

Hope this helps and good luck!


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## roman (Sep 28, 2007)

paid to weed through the crap on my end
pending what you get paid and I suspect it isn't much : (
I'ld skip the need to explain and just plug it in and make music with dust instead of words that waste bandwidth

" I bought an air conditioner " 
"What would you do "

Its like getting a remote control for a tv, and forgetting it takes batteries


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## conifur (Apr 1, 2015)

What most people I think dont consider is the distance in there house from where the service comes in, to where there shop is. You buy anything motorized now they have an extension cord wire gauge to length of cord for just that tool. So a friend builds a ranch home about 80ft wide 26ft deep, with a 2 car garage on the north west corner, his electric service comes in on the south east corner, over a 120ft from the garage when you figure it goes vertical from the basement to the attic and then drops down into the garage, it is a 15 amp with 14ga romex, the area of his basement that he turned into a partial shop is about 80 feet of wire from the service, an other 15amp with 14ga romex, so in the basement besides lighting he has a Jet 650 DC, Delta X5 jointer and router table. In the garage is the RAS, table saw, with a very large shop vac for DC. It all was under powered when starting up and running till I ran 20amp and 10 ga romex.
Point is you have to take all into consideration, line loss, in rush, ect.


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## roman (Sep 28, 2007)

questions lead a person to believe that its not only possible but rather probable, to ask a question that so many citydiots chime in on, that were raised in a high rise chicken coop, they could suddenly understand the need to improve an electrical system intended to power something like a washing machine or an oven or a microwave or something electrically impossible and re-invent the grid

Its beyond me why anyone would buy a toaster and re-wire a room and if that is the biggest challenge a person has, my hat is off to them


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## conifur (Apr 1, 2015)

Moron,
to bad you cant spell check or proof read your statements!!!!!!
citydiots
Or are just looking for attention???


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## roman (Sep 28, 2007)

the word was spelt right
first word " city " 
second word " idiot"


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## roman (Sep 28, 2007)

"citydiots "

a term to describe a plural form of a group


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## conifur (Apr 1, 2015)

questions lead a person to believe that its not only possible but rather probable, to ask a question that so many citydiots chime in on, that were raised in a high rise chicken coop, they could suddenly understand the need to improve an electrical system intended to power something like a washing machine or an oven or a microwave or something electrically impossible and re-invent the grid
Cant read your own writing, those are copy and paste from your post!!!


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## roman (Sep 28, 2007)

take it away
re write your own electrical system
spend weeks or days or hours plugging a toaster in dude
aint my ass making you look smart


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## roman (Sep 28, 2007)

plug the saw in
whats hard about that ?


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## conifur (Apr 1, 2015)

So now you went from 2 words to a term???? What next, an abbreviation?
BTW nice bar and I think the other is a walk in/thru closet.


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## conifur (Apr 1, 2015)

> take it away
> re write your own electrical system
> spend weeks or days or hours plugging a toaster in dude
> aint my ass making you look smart
> ...


Sounds like a bit of miss directed anger on NY eve, thinking about the divorce?


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## roman (Sep 28, 2007)

sorry
i just viewed your gallery
its empty so with this might I wish you a happy new year with abundant blessings surrounded with good food, people you love, and the fixing to make 2070 a good page


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## conifur (Apr 1, 2015)

Going back to the original post, so you bogged it down, may have been the wood tension pinching the blade, is it a thin kirf blade that is recommended for lower HP saws? Do you have a riffing blade on the saw to prevent blade pinching?
As mentioned earlier, bad breaker. I had a client that had a breaker trip all the time, not running machinery on it, the screw was a bit loose that held the hot lead on it.


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## conifur (Apr 1, 2015)

Yes you may Moron, same to you for 2016, kinda new here still learning about all the features here. It was a fun jesting!!!!


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## conifur (Apr 1, 2015)

Yes you may Moron, same to you for 2016, kinda new here still learning about all the features here. It was a fun jesting!!!!


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## roman (Sep 28, 2007)

indeed
some dream in tecknocolour
my fear is that never dies
wink wink 
the pencil you put to ink
people suddenly shut up 
oh no
some one forgot : )


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## roman (Sep 28, 2007)

2015lessons
always look into eye
and find the target
putting a deer in yr freezer is a one shot op ?
growing yr own veggies
no brainer 
Organic is nothing more then a word called :lazy:


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## Knothead62 (Apr 17, 2010)

14 ga. wire is too light for shop circuits. The only thing 14 ga. is used for, in my experience, is for ceiling lights. I worked in the electrical/lighting department at Lowe's. We always recommended using 12 ga. for all wall outlets and ceiling lighting in the house. Why buy two different wires?
I ran a line in my basement/shop as I only had one outlet for my power tools. I used 12 ga. wire and a 20 amp breaker.


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## WhyMe (Feb 15, 2014)

> 14 ga. wire is too light for shop circuits. The only thing 14 ga. is used for, in my experience, is for ceiling lights. *I worked in the electrical/lighting department at Lowe s. * We always recommended using 12 ga. for all wall outlets and ceiling lighting in the house. Why buy two different wires?
> I ran a line in my basement/shop as I only had one outlet for my power tools. I used 12 ga. wire and a 20 amp breaker.
> 
> - Knothead62


You're a brave man throwing that out there as electrical credentials.


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## TheFridge (May 1, 2014)

14/2 is cheaper, easier to run, easier to make up.

How about we talk about 15A receptacles on 20A circuits 

Yes, you can run as many circuits as you want in one pipe. If you wanted to add a circuit in the box for 240v, it would have to be a 12/4 if you're putting only one cable. I'd just run 2-12/2s. It's probably cheaper.


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## REO (Sep 20, 2012)

conifer I hope you have a great year. when the fog clears re read the post. I first gave an example of ohms law: I X E=P in garage mechanic form. the second part was clarifying that the unit paid for was the watt not volts or amps. technically Kilowatt hours which would be as you have stated 1000watthours or KWhours. Frequently similar posts come up, some of them become lengthy concerning the same thing. they get prolonged because people don't understand and every one takes a shot at telling how one voltage is better then the other or not as good. I was just trying to explain that regardless of what people may have been told a watt by any other name is still a watt! There is one consideration for higher voltage: the cost of materials they break about even for the breaker and wire the difference would come in termination , a required tamper proof gfi in an outbuilding or garage or a standard 220 outlet. in an industrial situation the higher voltage wins out because there can be a significant savings running the smaller wire and in cases the conduit size.

On the point of running two diferent voltages in one box. I just got my shop electrical final and I ran 110 piggybacked on the 220 and three phase in the same box.(three phase is on another circuit. If the double breaker trips it will take out everything. I am a one man shop and don't see that happening . Ran the old shop that way for 25 years with two people and had a trip maybe three times.


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