# Advantage to 230v single phase vs 115v?



## Aaron_W (Mar 28, 2019)

I have a lathe with a 1-1/2hp motor which can be wired as 115v 17 amps, or 230v 8.5 amps. It came wired for 115v. 

I'm going to get some 230v outlets installed, and just wondering if there is any reason why I would want to add an outlet for the lathe and rewire it for 230v. 

Understand many advocate for 3 phase which has some advantages, but not sure what benefit there would be to single phase 230v power. I know less amps, but does that justify the expense of a new outlet and the work involved in re-wiring the motor when it is serviceable on a standard 115v 20 amp circuit?


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## Karl_T (Mar 28, 2019)

Yep, you are still just barely OK for 110. Don't put anything else on that circuit when the lathe is running.

If you're re wiring anyway, I'd put in a 220 circuit or two. Gives you future additional capacity. A 220 circuit is real nice in a shop. lets you run mills and lathes with a VFD, allows welders, plasma cutters, more.


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## benmychree (Mar 28, 2019)

Smaller wire size is one benefit, also motor starting relays and switch gear can be of a lower amp rating.


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## projectnut (Mar 28, 2019)

The maximum sustained output on a 20 amp circuit is 18 amps.  The maximum load on 12 gauge wire is 20 amps.  By going to 220 volts the load on each wire is halved.  Thus you can use 12 gauge wire on a 20 amp circuit with not only no fear of overloading, but you can also have multiple outlets or machines on the same circuit, rather than having a dedicated circuit for each machine.

I have a number of single phase machines in the shop that can run on either 120 volts or 220 volts.  I have them wired for 220.  It's easier and less expensive to run, and terminate 12 gauge wire than to use 10 gauge wire.


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## MSBriggs (Mar 28, 2019)

For the same wire gauge, higher voltage means less current, which means less voltage drop and more power from the motor.   Possible advantage on a longer run.


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## markba633csi (Mar 28, 2019)

Several advantages: More efficient, cooler running motor, longer switch life, smaller wire diameter requirement.
220/240 is usually a good idea on any motor larger than 3/4 hp 
mark


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## Aaron_W (Mar 28, 2019)

Ok, so if a new outlet is required there does seem to be some benefit. I only have one 115v outlet at this time and need to add a 230v outlet for the mill. I was thinking about adding at least one more 230v and a couple more of 115v outlets. I just wasn't sure if it was worth the trouble to re-wire to 230v since it works as is.


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## Nogoingback (Mar 28, 2019)

If you ever decide to buy a VFD for the mill or your lathe, you'll be able to use one with single phase input and 3 phase output at 220V.


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## Bi11Hudson (Mar 28, 2019)

All in all, the prior posts cover the salient points very well. I throw in my two cents worth as an Electrical Engineer just to verify what they told you is so. Go to the web site:


			http://www.hudsontelcom.com/uploads/ShopElex.pdf
		

for a longer story about the same subject, 120 vs 240 volts.  Beside current there are a couple of finer points that cannot be covered here. And just good reading if you are curious about electricity. Go look it up, it's really a small book. The details of what you're asking start on page 8. But it's all good reading.
Bill Hudson​


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## Aaron_W (Mar 29, 2019)

The mill is 3 phase so I have already bought a VFD for it. Now I just need to line up an electrician to do the 230v outlets. The thought was to go with one or two 30 amp in the shop (the VFD can be used with a 20 amp, but recommends 30 amp) to cover potential future needs. 

A little more upfront cost, but cheaper than bringing an electrician out in the future to an upgrade. I was going to add a 40 amp outlet outside under the carport to allow the use of a welder that I don't have yet, but 40 amps seems to cover any of the welders on my list. 

The main question was to answer one or two 230v outlets in the shop, and it appears 2 is the better answer. 

Bill thank you, it is late so I just glanced through the document you linked but it looks very thorough and actually readable. I more or less get 115v, but 230v still has some mysteries for me.


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## B2 (Apr 5, 2019)

Hi Aaron,  
Simple comment and some extra thoughts:  

You are right about the lower current draw, and this is the main point.    Use the big wire and the higher voltage and there will be a smaller voltage drop along the length of the wire to the tool.  When the motor is starting up the current draw is the highest, so a larger voltage drop occurs along the wire.  Hence, the full voltage does not arrive at the load.   Likewise, when under heavy load on the motor the current required goes up, so again more voltage drop along the wire.  So in some respect the issue of using 110 or 220 single phase is determined by how long your run is from the breaker box to the outlet.  The longer it is, the more resistance in the wire and so more power goes to the wire instead of to the load.  The same effect can happen if you have poor or loose/weak/small connections or bad/loose/underrated outlets. 

Have you ever noticed how in some locations when an Air conditioner compressor turns on, the lights in the house dim?  It is because of the huge current required to get the compressor motor started and so the large voltage drop along the wires from the power line to the main breaker.  Hence, the voltage arriving to all the other circuits dips down and the incandescent lights dim.    Usually, bigger lines to the house will solve this issue, but sometimes it is the transformer out on the pole that is too small.    

I once had a 1HP air compressor, but where I was using it I only had 15 Amp service.  The compressor motor would start fine if there was not load (no compressed air in the tank), but once the tank filled and had shut off, then part of the air was drained, it could not restart because the the startup current load was too high due to the extra difficulty of working against the back pressure in the tank.    The current required to start would go well over the 15Amp breaker limit.    Motors take a lot more current to get started than to idle or even to run against a normal load.  Because of this huge amount of current a stalled motor will soon heat up and burn out!

By the way, there is a legal (code) and safe trick to wiring 220 and 110 from one feeding wire.  Use a double pole 220 breaker (both sides of the breaker are coupled mechanically to trip both breakers if either breaker sees its current limit) and run a 3 plus ground wire (say, for 20 amp service, the wire is 12-12-12 gauges plus ground) just as you always would for any 220 circuit.  However, at the string of outlet positions you can use either a 220 or a 110 outlet at any location.  At a 220 outlet location you wire it up just as you normally would.  However, at the 110 outlet position you use a normal 110 outlet and just hook up one side of the the 220 pair and the neutral.  The other hot does not need to be used.  So the 110 outlets have 110 voltage and the 220 outlets have 220 voltage.  In fact, if you purchase good 110 outlets you can break the tab between the two outlets and then the top outlet  cam be on one 110 circuit and the bottom outlet can be on the other 110 circuit.  You just have to purchase the more expensive wire, but you only have to run one wire and you have the option of voltage at the outlet location.  It is safe as the neutral wire is the same size as each of the hot wires.  If only one side of the two hot wire's current exceeds the current rating of the breaker both breakers will be tripped.  When the 220 is being used the current does not flow in the neutral as it goes down and back the two hot wires.  After all, the double pole 220 breaker is really just two 110 breakers mechanically connected to break if either side has current above either breaker rating.  If you happen to be drawing power from both the 220 outlet and the 110 outlet, the one side of the wire will be carrying more current, but this is still safe.  Say the 220 is using 10 Amps and the 110 is using 10 amps, then back at the breaker one side has 10amp flowing and the other side has 20 amps flowing while the neutral takes care of the imbalanced  10 amps.   The total on either side just cannot exceed the breaker 20 Amp limit or it will trip. 

What does break most cities' code (not all cities use the same code) is to use two uncoupled 110 breakers in a 220 circuit!

Have fun.

Dave


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## Truefire (Apr 6, 2019)

Everyone else has covered the topic well and this is slightly near the dugout but, I'll throw nugget into the air simply because the voltage class gets tossed around so much in everyday life fields, with such variation that it actually may make someone wonder, "What the heck man?"

When it comes to USA -- our voltage class for single phase residential dwellings of today is 120 / 240 volts.  It hasn't been 110 volts since probably 1950s.  The 230V is seen on many motors simply because we have so many international markets and those single phase motors are shipped the world over.  They're used here and they could and are potentially used there --> Britain, UK and all of eastern Europe use 230 volts..its 230 volts line to nuetral (hot to nuetral)..so they get stamped accordingly because of engineer's huddled talk to design components for world power systems.

However, NOW DAYS in the US, our single phase residential power is 120 volts (line to neutral) and 240 volts (line to line) respectively.  Quite often, depending on proximity of houses to transformers, the voltage is typically just a tad hotter than 120 or 240.  What I'm trying to convey is, its actually quite important to understand that it's not 110 or 115, that would actually signify a voltage drop which could be a potential issue, depending.

Regarding the original question-- anytime you can draw less amperage across your coils inside your motors, you are going to extend the life of your motor simply because you're creating less heat.  Less heat equates to a much longer lived motor.  Installing those 240 volt outlets is a win-win for you.


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## astjp2 (Apr 16, 2019)

I put in 6 outlets at 240v in my shop.  I daisy chained them because I only run 1 piece of equipment at a time.  I also ran 6ga wire in EMT and a 50 amp breaker.  When I moved shops, I took the wiring with me and installed it in the new shop.  The hardest part of the job was bending the EMT.  Just dont wire anything hot...oh and I never put in for a building permit...but I am cheap that way, I would rather spend money on the wire and outlets.  Now I just need to put outlets on the other side of the shop.  Tim


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## Dabbler (Apr 17, 2019)

so one of the things I didn't see in the above postings...  dual voltage motors put two sets of windings in series for 120V, and put them in parallel for 240V.  You do get a little better starting torque on choosing the 240 volt wiring.
The motor will also run cooler under load, as the current is less in the same gauge wire.

Pro tip:  make all 3 of your outlets the same:  if your max is 40 A, make them all 40 amp.  I made the mistake of having 220V 15A, 20 A, 30 A and 50A in my shop.  what a pain!


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## Aaron_W (Apr 17, 2019)

Dabbler said:


> so one of the things I didn't see in the above postings...  dual voltage motors put two sets of windings in series for 120V, and put them in parallel for 240V.  You do get a little better starting torque on choosing the 240 volt wiring.
> The motor will also run cooler under load, as the current is less in the same gauge wire.
> 
> Pro tip:  *make all 3 of your outlets the same:  if your max is 40 A, make them all 40 amp.  I made the mistake of having 220V 15A, 20 A, 30 A and 50A in my shop.  what a pain!*



Is this simply in relation to having to keep track of the allowable amps at each outlet or something more subtle. I was thinking of doing 30 amps for most as that seems to cover any of my current / potential needs, with one outside at 40amp for a welder.


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## astjp2 (Apr 17, 2019)

Aaron_W said:


> Is this simply in relation to having to keep track of the allowable amps at each outlet or something more subtle. I was thinking of doing 30 amps for most as that seems to cover any of my current / potential needs, with one outside at 40amp for a welder.


run 40, that is pretty standard and common, you may upgrade equipment someday and may need more power.  It is better to run more than you need once than have to rerun power again.


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## Dabbler (Apr 18, 2019)

If you use the same 40A connector and breakers, you can still run all your lower amperage machines,on them, but allow you to plug anything in anywhere.  I now own 3 types of extension cords because I moved most of my machines after wiring (my bad!!)


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