# Rewire to 220v



## Froglips (May 29, 2012)

I am wondering how one can determine if a power tool can be rewired for 220v. My new shop is turning out to be a bit more amperage limited than I had hoped. My electrician has told me that 220v equipment draws half the amps of 110v. I understand Ohm's Law so that makes sense but it does seem like I am getting something for nothing. Nevertheless, I wonder if any of my power tools could be switched over to 220v and how I would determine this.
Thanks!


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## Huxleywood (Feb 24, 2012)

You don't get something for nothing, you will still be using the same amount of watts, which is the way we pay for electricity.

Just look at the plate on the motors, it will indicate if it is a dual voltage motor. In the end unless one has a specific reason due to power available in a specific part of the shop switching voltage gains you nothing other than a very small reduction in the time it takes the motor to reach full speed. Anyone who says they see an increase in performance by switching a dual voltage machine to 240V from 120V is experiencing a placebo effect.

One possible monetary advantage to going 240V is IF you are wiring the shop ground up, this would give you the ability to run smaller gauge wire for the 240V circuits compared to the 120V circuits for the same motors since the required ampacity of the circuit would be cut in half.


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## tvman44 (Dec 8, 2011)

Look at the Plate on the motor, if it is marked 120/240 volts you are good to go. If only 120 volts it would require a different motor.


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## knotscott (Nov 8, 2007)

Huxleywood said:


> .... In the end unless one has a specific reason due to power available in a specific part of the shop switching voltage gains you nothing other than a very small reduction in the time it takes the motor to reach full speed. Anyone who says they see an increase in performance by switching a dual voltage machine to 240V from 120V is experiencing a placebo effect...


In theory, there's not supposed to be a difference in performance, but there are also a lot 120v circuits that aren't up to snuff and starve a given tool for amperage at peak times, which deprives it of it's full capability. A 220v (aka 240v) line often cures that, as would an _adequate_ 120v line (in theory). I noticed a big difference in my Cman 22124 hybrid saw when I switched, and it was more than wishful thinking. Less so with my GI contractor saw...it really depends on the individual circuit and the individual motor involved....they're all different. If we didn't know any better, the sluggish performance would be "normal" to us. Faster startups don't mean a thing during cutting, but faster startups also mean faster recovery from lugging the saw which definitely helps and is easily noticeable....in truth, with the 220v circuit, the saw is just doing what it should have been doing all along, but wasn't due to shortcomings of the 120v line. 

In general, 220v lines suffer less voltage loss than 120v, and they help distribute the amp load more evenly. If you've got a 220v available, there's no harm in trying it, and there might be some performance benefits if the 120v line was choking the motor. If there are zero issues with your 120v circuits, it's probably not worth putting in unless you plan to use motors that are 2hp+.


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## woodnthings (Jan 24, 2009)

*agreed*

Lets start at the breaker box or power panel. 
Let's say your panel is rated at 100 amps and has 12 slots for breakers. 
Each 220 V breaker takes up 2 slots, regardless of the amperage, whether 20 or 40 AMPs..... and each 115 V breaker takes up 1 slot regardless of the aperage whether 15, or 20.
Let's say you have 3 - 220 V, 20 amp tools, and 1 - 30 amp tool, you have used up 8 slots. You have 4 slots remaining for 115 V circuits. This is a reasonable shop set up in my opinion and similar to what I have in my small shop.
You haven't reduced the power requirements of any of the tools only reduced the size wire need to power them. A tool wired on 220 V will only need 1/2 the AMPs needed to operate it on 115 V and therefore a smaller size wire can be used. We still haven't saved much money only on wiring. :laughing:
Tools seem to run more efficiently on 220V than 115 V , but that is often debated. Some large motors, 3 HP and up, can only be run on 220v so that's a given. Some motor 1 3/4 HP and under can be wired either on 115V or 220V and I would choose 220V ....unless you have run out of slots on your panel. :blink::thumbdown: 
So when installing a panel always go for one that has the most slots for a given total amperage. My 100 AMP panels have 24 slots if I recall. I completely filled one 100 AMP panel with many 220V and 115 individual circuits to each separate tool.
I also recommend using EMT or thinwall tubing since circuits can be moved or added since you can' go back inside the drywall and run more wires easily. :no: bill


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## cabinetman (Jul 5, 2007)

Froglips said:


> I am wondering how one can determine if a power tool can be rewired for 220v. My new shop is turning out to be a bit more amperage limited than I had hoped. My electrician has told me that 220v equipment draws half the amps of 110v. I understand Ohm's Law so that makes sense but it does seem like I am getting something for nothing. Nevertheless, I wonder if any of my power tools could be switched over to 220v and how I would determine this.
> Thanks!


 





 
To answer you question simply, it has been stated it should tell you right on the motor if is a dual voltage motor.










 







.


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## jigs-n-fixtures (Apr 28, 2012)

What voltages a motor will operate at, and the amp draw at that voltage, are printed on the motor name plate, along with the type and form factor. Just in case you should want to replace it. 

Once again everybody jumps in and doesn't read the post. 

The original poster says that the electrician says the amperage to his shop is limited. This means one thing: the feeder to the shop is undersized. 

The purpose of running the tools on 220 is to lower the amp draw. Not to increase the power. 

And, whether switching to 220 results in more power at the tool, is generally dependent on whether the existing wiring was undersized for the amp draw at 110. There is an exception though; some of the older contractor grade tools had the motors wound to draw more than half the amps at 220, than they did at 110. 

This was because if you were using them as job-site tools the highest amperage 110 outlet you could expect to find find on a job-site was 15 amps, and you frequently had to use extension cords. So thy were designed to draw 13 amps at 110. 

If you set it up in a shop, on a dedicated 220 circuit, the least you could expect was a true 10 amps, and the motors were wired to pull 8.5 or 9 amps. 

Which means that the motor wired at 220 was generating about a third more horsepower than at 110.

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## knotscott (Nov 8, 2007)

jigs-n-fixtures said:


> ...Once again everybody jumps in and doesn't read the post...


Just because everyone who replied doesn't know the complete answer, or didn't provide a complete answer for the OP doesn't necessarily mean that "_everyone_" didn't read the post....we'd have to ask everyone separately to know that for sure. :shifty: Every comment was at least pertinent to the topic, and pertinent comments are encouraged AFAIK. Aside from that comment, I thought your answer was excellent and thorough.


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## woodnthings (Jan 24, 2009)

jigs-n-fixtures said:


> Once again everybody jumps in and doesn't read the post.
> *
> The original poster says that the electrician says* the amperage to his shop is limited. This means one thing: the *feeder to the shop is undersized. *
> 
> ...


Specifically he did not say "the electrician said...":no:
He said it himself, maybe based on what the electrician had told him...
Quote:
"I am wondering how one can determine if a power tool can be rewired for 220v. My new shop is turning out to be *a bit more amperage limited *than I had hoped."


Regardless, depending on the number of tools, especially 220 V only motors, the service/feed may or may not be undersized. It may simply be a panel with limited number of available slots as I suggested. A 60 amp feed will power all the tools in my shop, because they are not ever all turned on at once. But a 60 AMP panel will not have enough slots to have separate dedicated circuits to that many tools.

Your point about wiring for 220V is ...not to increase power. But then you say a motor wired for 220V generates about 1/3 more power than when wired on 110 volts. Can you explain the seeming contradiction? thanks, bill


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## Leo G (Oct 16, 2006)

I suppose by using 240v for your tools you can take advantage of the limited capacity of the wire going to your shop. Lets say you are limited to 60 amps in that wire. Voltage isn't going to change that. If you draw 60a on 120v then you will be able to access 7200 watts of power. If you change over to 240v then you will have access to 14,400 watts of power. But most likely you won't have the capacity in your circuit breaker box to access that. If you have a 60a line coming in then you will likely have an 8-12 circuit breaker box. which means 4 to 6 220v circuits. You are not getting anything for free because you pay by the kilowatt. But you can access more wattage by using a higher voltage while still drawing that same 60a (or less).

That is one of the reasons high HP motors are wired for 440v. You can deliver more power using a smaller wire. Wire costs more money as they get larger. Increase the voltage is one way to get around using bigger wire.


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## jigs-n-fixtures (Apr 28, 2012)

woodnthings said:


> Specifically he did not say "the electrician said...":no:
> He said it himself, maybe based on what the electrician had told him...
> Quote:
> "I am wondering how one can determine if a power tool can be rewired for 220v. My new shop is turning out to be a bit more amperage limited than I had hoped."
> ...


Some of the older tools were wired that way, and drew more than half the amps at 220, than they did at 110. This is not true for all older motors, but quite a few of them. I tried to explain it before. 

A horse power is about 746 Watts. And, volts multiplied by amps equals Watts. The motor on a modern Delta Contractors saw, and all the motors I've looked at on modern machines list the amperage draw at 220 as half of what it is at 110. So, the motor makes the same horsepower on either voltage. 

As I said before, to decrease the odds of burning up the motor with an under voltage condition, some of the older motors were designed to only draw 12 to 13 amps at 110-volts. So they generate about 1.9 horsepower and are nameplated by the advertising types as 2-horsepower motors. 

When the motors are wired at 220-volts they draw 8 to 9-amps. Which is about 1850-watts, or about 2.5-horsepower. This is because the designers figured that when the saw was wired for 220 it would be on a circuit that would reliably deliver 10-amps or more.

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## Leo G (Oct 16, 2006)

In order for that to happen they would need different coils inside the motor. Separate coils for 120 operation vs 240 operation. In a normal motor for 120 the coils are wired in parallel and in 240 they are wired in series.


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## Froglips (May 29, 2012)

Thanks everyone for the great replies! There is a lot of knowledge out there. My situation is that I am constructing a new shop. Originally I had intended to run new 400 amp service to the shop. The local (Colorado) electrical inspector refused to allow this because the garage/shop is connected by a breezeway to the house. His ruling meant I have to split the service from the house. The house has 400 amp service so there is 100 amps to spare. The builder is adding a 100 amp sub panel in the garage.

Although I have a lot of power tools I am just a hobbyist. In most situation I would be running the dust collector and one other tool. I am purchasing a larger dust collector for this new shop so I will probably buy a 3hp 240v system to support a large fixed duct system. My current Delta system is 1.5hp on a trolley with a flex hose.

All the wiring is new in the garage/shop. I am not so concerned about saving money on the wiring as I am about not having enough power to run the shop.


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## Leo G (Oct 16, 2006)

That' enough for nearly 30HP. I think you'll manage.


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## woodnthings (Jan 24, 2009)

*My shop panels*

I took some shots of the power panels I have, a 175 AMP main in the big shop with a 100 AMP sub panel breaker to the garage.

The color coded 100 AMP panel is the small upstairs wood shop.
By using colored electrical tape on the breakers and the corresponding color on the receptacles, I can immediately determine which breaker controls that circuit. The 220 V douple pole breakers go to dedicated receptacles. There is one 30 AMP, color code red/white, for a heater at each end of the shop, where ever I choose to locate the heater. The 3 HP motors are on 220 V - 20 AMP circuits, like the planer, dual drum sander etc. All the wall circuits are 120 v - 20 AMPs and the lighting is on 15 AMP breakers. Keep the lighting and power tool outlets on separate circuits, so if you trip a breaker on a tool you can still see what you are doing..... :laughing:

A tip: Use 4 outlets per box if you can as you see there's a plug coming out of each outlet on the right hand side in the bottom photo. You can't have too many outlets. :no:


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## Froglips (May 29, 2012)

woodnthings said:


> There is one 30 AMP, color code red/white, for a heater at each end of the shop, where ever I choose to locate the heater. The 3 HP motors are on 220 V - 20 AMP circuits, like the planer, dual drum sander etc. All the wall circuits are 120 v - 20 AMPs and the lighting is on 15 AMP breakers.


Thanks! This is really a great suggestion. I have in floor heating so no need for heaters but plan for a dust collector so you have...

heater 30amp
3hp motors 20amp
wall plugs 20amp (x 2?)
lights 15amp

Anyway, I am counting breakers in your sub-panel and there look to be lots more than five. Do you have over 100amps in breakers?


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## woodnthings (Jan 24, 2009)

*Heck Yes!*



Froglips said:


> Thanks! This is really a great suggestion. I have in floor heating so no need for heaters but plan for a dust collector so you have...
> 
> heater 30amp
> 3hp motors 20amp
> ...


You can have as many AMPS in breakers as you need for your circuits...more than the panel size as long as there is a Master Breaker of 100 AMPs inside the panel itself and act as a disconnect.

The theory is that you won't overload the panel with circuits all running at the same time, and if you draw more than 100 AMPs in any combination, the Master will trip and prevent the feed wires from overheating. On a 100 AMP sub like that one there is also a 100 AMP breaker in the Main panel to feed the sub.  bill


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## Froglips (May 29, 2012)

*Less concerned about amps now*

Thanks for all the info and suggestions.

Woodnthings, why bolt three table saws together, other than you can?

I have a Craftsman 12" radial arm saw from my dad (from the 50s!). It is built like a tank. I also have his old Craftsman table saw of the same vintage with two cast iron wings it is 60" wide. The stamped metal base is completely inadequate for the weight of the saw. I would love to convert it to a cabinet base but not sure it is worth the effort.


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## woodnthings (Jan 24, 2009)

*I started with only 2*

2 saws, a bare table, and 2 extensions...years ago. The wider the saw table and rip fence capacity the better. Then I scrapped out an older 10" Craftsman saw, so I had one more table.
Then I added a Bench Dog Pro router table. Then I found another 12" Motorized Craftsman saw on Craigs List... just for parts... but where should I keep it. Well, just bolt it onto the rest of them for safe keeping. 

Why? Because they were there, like the chicken crossing the road. :laughing:
But actually a dedicated dado set up (the right hand saw) is so time saving and not having to change blades for ripping (the left hand saw 24 Tooth Diablo TK rip blade) and the center saw is the most used with a 40 Tooth Diablo TK combo blade. I've got a few RAS around as well. They are so cheap, you may as well have several if you have the room. Crosscutting a long board is so easy with a long table on the left side of the blade....if you have the room. I used to have the room, but now not so much. Too many saws. :laughing: Too many tools, too much lumber... There are worse additions.
I only drink when I'm alone or with someone, I have never smoked or done any drugs, so it may as well be tools.:clap:
There is one member here with a wider table who chooses to remain anonymous.


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## pittendrigh (Jun 29, 2017)

*220 vs 110 for a ten inch table saw*

I have a Delta Industrial saw. It's a step up from the contractor's saw and a step down from the Unisaw.

I had to rip some 1/4" inch by 2" strips from 4 quarter white oak yesterday. At 110 the saw slowed down and choked with the slightest tweak on the board.

I rewired it (two hours ago) to 220 and ripped my boards without hassle. The difference was substantial. I have a sub-panel in my shop and good 12 guage cords.


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