3 Phase Single Phase Wiring

[schwalby]

I have been researching 3 phase for awhile and I my head is spinning. I don't have the electrical know how to totally understand it so I want to just try and get the basics down. I know that some tools / equipment have to have 3 phase and some have it as an option. I know that you either need to get 3 phase from the street or have a converter. Correct me if I am wrong on any of this.

What I want to know, how does the wiring differ? Budgets being budgets I will end up doing all of my wiring well before having all the tools I will be using and won't really know where I want them. Most likely I would end up moving things around even if I did know where I want them the first time. So would the same wiring be used if I was doing a 3 phase outlet or a 220 outlet? Idea being I can run some wiring to different locations and then wire the outlet for the tool as needed.

Hope that made sense.

 

[mypov]

The wiring mostly differs at your service hook up and the wire from the service hook up to your panel. If you are a diyer, or a backyard mechanic looking to have basic tools (no large electrical motors, or utilities) then single phase will be more then adequate. 3 Phase power is useful for large electric applications, hoists, and other larger demanding power users (however, you can get 240/220 hoists that are more than fine using single phase). 3 phase power users tend to be a more simplistic design, and are longer lasting, this is why industrial applications tend to be 3 phase.

In saying all this you can have a single phase hook up and convert to 3 phase for the desired application, but this can cause more wear on the machine, and is generally not desirable.

In short, it all depends on your desired use for your shop. Hope this helps.

 

[spy604]

3 phase wiring is useful for electric motors. It works like this. The motor spins because there is an magnetic field created by the electric current. In single phase motors, the field alternates 180° apart, so imagine there is a pulse at the top, then a pulse at the bottom. Before the motor starts spinning, these pulses dont do anything to help it start, since they just fire directly across from each other. 3 phase motors self start becuse there are 3 'pulses' 120° apart, so that can 'push' the motor to start.

Imagine having 2 cyl engine. you put cyl 1 at TDC and cyl 2 at BDC. The cylinder is already compressed with air/fuel. If the spark plug fires, the engine wont turn, it doesnt have anything 'pushing' it around in either direction. Now take a 3 cyl engine with 3 cyls 120° apart, that engine will start spinning on its own, depending on which order you fire the cylinders.

 

[schwalby]

Thanks for this info, it is helping. This is bring it more down to my level of electrical knowledge.

My main question is would the wires from the panel to an outlet be the same for a single phase 220 outlet as it would be for a 3 phase hook up? Or would I be better off just running conduit from the panel to the outlet location. Then pull whatever wires I need as I need them?

 

[spy604]

There would be 3 hots, not 2. The whole problem is that you would need 3 phase service, its not a simple 'upgrade'. You can buy a phase converter, that would generate 3 phase power for you at the machine.

I forgot to mention, in my analogy, the 3 cylinders can be smaller, since you have 3 cylinders instead of 2 to do the work. (smaller wires)

 

[930dreamer]

Hello, what do you want to power with three phase?

 

[schwalby]

The whole problem is that you would need 3 phase service, its not a simple 'upgrade'. You can buy a phase converter, that would generate 3 phase power for you at the machine.

I know it isn't cheap to do 3 phase but I want to know what issues there would be down the road since I can't wire everything in at once. Basically when the drop from the street is done I would decide then if I was going 3 phase or not. If it would be a major hassle later to run the wiring and locate the equipment that needs 3 phase that would make an impact on my decision to have 3 phase brought in.

The garage is going to be a 60x40 so it isn’t huge but plenty big enough to do the fab work I want and I will be “renting” out space to friends that also do fab work so the ability to run 3 phase equipment will be nice to have.

Again thank you for the info.

 

[schwalby]

Hello, what do you want to power with three phase?

Milling machines, CNC plasma cutters... Going to be fabbing custom roll cages, custom bumpers and drive line mounts. Rock crawling rigs.

 

[930dreamer]

I know it isn't cheap to do 3 phase but I want to know what issues there would be down the road since I can't wire everything in at once. Basically when the drop from the street is done I would decide then if I was going 3 phase or not. If it would be a major hassle later to run the wiring and locate the equipment that needs 3 phase that would make an impact on my decision to have 3 phase brought in.

The garage is going to be a 60x40 so it isn’t huge but plenty big enough to do the fab work I want and I will be “renting” out space to friends that also do fab work so the ability to run 3 phase equipment will be nice to have.

Again thank you for the info.

If your future shop doesn't have three phase power, but it's available on the pole that's one thing. If you want the power company to add another transformer on the pole and a wiring involved, safe estimate would be 10-15K.

 

[Steve from Socal]

A phase converter will NOT cause wear to a machine!

The first place to start is at the site you plan to use, is this residential, commercial or ag property? If it is residential you most likely wont be able to get utility three phase, if it is commercial you will pay a higher rate for three phase service than single phase and, if you are in a rural area you MAY be able to get three phase for a reasonable rate.

In general lets consider the location with single phase power service. To run three phase equipment you will need one of these devices, a rotary phase converter, a static phase converter or a VFD/inverter drive. For small machines with one three phase motor a VFD is the best bang for the buck. For machines with several three phase motors WITHOUT regenerative braking a rotary phase converter is best. For some CNC equipment you will need either utility power or a special rotary phase converter known as a "phase perfect"

The wiring from the panel would be a little different with three phase as there are three conductors to each machine. Most shops with three phase have a single phase and three phase panel so this would add some cost as well.

For loads under 10 HP single phase service is going to be the most cost effective over time, even though three phase motors are more efficient the higher charges for all power make three phase a bad choice in a situation like this.

Steve

 

[theoldwizard1]

If your future shop doesn't have three phase power, but it's available on the pole that's one thing. If you want the power company to add another transformer on the pole and a wiring involved, safe estimate would be 10-15K.

In general, 3 phase is only available in "commercial" areas.

 

[eriksalo]

It's great that you're thinking about this stuff early. I have a looked into 3 phase shop power at some depth and have built my own rotary three phase converter for my milling machine. Overall, I don't think it's worth it to try and accomodate native 3 phase power in a residential shop but that's up to you, I can help you out with some information. There are some things that are (likely) true for you:

1) Three Phase probably isn't available: Unless you live in an industrial area, you might not be able to get three phase power from your electric utility at all. This is easy enough to figure out if you have overhead power lines coming to your house. If there are three main wires (and a ground) on the pole, then there is three phase power available at your pole. At my house, there's only one main wire (called single phase) so I couldn't get 3 phase power if I wanted it. Power plants (mostly) generate 3 phase power and all the big power lines are high voltage three phase. However, as the branch circuits split up into neighborhoods, they are often/usually split into three separate single phase lines. If three phase power is available on your nearby pole, it probably isn't wired into your service. It will be pretty expensive to get the 3 phase power to your shop.

2) Do you think you will need 3 phase power? Due to the difficulty of getting 3 phase power in residential applications, most home shop tools run on single phase power. It's true that single phase electric motors are more complex, less efficient, larger, more expensive to wind and use more current per unit horsepower. Today, the practical limit for single phase electric motors is 7.5hp. A few decades ago, even small motors were most often 3 phase. I have a 7.5hp Speedair compressor (single phase) and a 5.0hp planer (single phase) that run just fine on regular power. It's only the big stuff and the old stuff that uses three phase power. Some examples:

• Most big milling machines and VMC's
• Most old milling machines and lathes
• Electric motors larger than 7.5hp
• Some of the older transformer based welders (big ones, 200-400 Amps)
• Industrial woodworking and metal working machines with large electric motors (again larger than 7.5hp)
• Older woodworking and metal working machines (ex: My 1960's Delta Unisaw is a 3 phase motor)
• I'm sure there are more but that's what comes to mind

3) It's not that hard to make 3 phase power. I have two applications that require 3 phase power and I make it for each of them.

I have a 1960's Delta Unisaw that has a 3 phase motor. The motor is only 3hp but at that vintage, those size motors were often three phase. I had the choice to buy a 3hp single phase motor (they are commonly available today) or to generate my own three phase power for the motor. I chose to buy something called a "VFD" (Variable Frequency Drive). The VFD uses a rectifier to take single phase power and slice and dice it up to any sort of 3 phase power. The advantages of the VFD are that it can generate any frequency of power you want (utility power is always 60Hz). This means I can run the motor an any speed I like. The VFD also has soft start and fast stop features so the motor just runs better on a VFD. I got my VFD from eBay and it cost less than a new single phase motor

The other application I use three phase power for is my large Okada VM500 milling machine. I chose to make my own 30hp, 3 phase rotary converter. A degree in electrical engineering and a good oscilloscope really helped but neither is critical. There are many good write-ups and tutorials available on the internet and they are easily found with a bit of help from google. The phase converters don't make "perfect" 3 phase power but in practice, it's good enough for even today's sophisticated CNC machines. If you have a big beast of a milling machine, I would look at buying a rotary converter. I don't recommend the "static" converters as they are really a cheat that doesn't approximate 3 phase close enough (this is just my considered opinion, others may disagree). A good rotary converter will be a few thousand dollars, likely much less than paying your local utility to string 3 phase to your shop.

In both cases the cost of the converter was much less than the cost of even a small amount of dedicated wiring would have been. The only reason I would have full native 3 phase (assuming I could get it which I can't) is if I had a large number of 3 phase machines that all needed to be running at the same time. In my case, I'm just a one man shop and it's no bother to run one machine at a time.

Getting native 3 phase power is expensive and you also have to pay your utility both a monthly fee and a usage fee for the service. I would recommend asking yourself if you really anticipate such a need. If your requirements are like mine, specific and sporadic then it's probably a better deal to forget about native 3 phase and just make 3 phase power for a particular machine if you happen to need it in the future.

I hope this helps.

 

[Charles (in GA)]

We have three phase in lots of areas around here, along the main roads, in towns, but of course they don't run it down the side roads and subdivisions.

If you have one wire on an insulator on top of the pole, and one wire further down the pole, probably not on insulators, thats single phase service.

If you have three wires all on insulators across a cross bar on the pole

o--o--o

Or three wires one above the other

o
|
o
|
o

Or sometimes in a triangle configuration, and in all cases, have a fourth wire, not on insulators, below these three, then you have a typical three phase service at the street.

It is expensive however, because they have to install THREE transformers on the pole to feed you, and it all costs alot of money, with little payback for the power company.

Charles

 

[TWX]

Not that it's important, but there are some residential parts of Mesa, AZ that are wired for three-phase because the city used to have a law requiring three-phase if one had an air conditioner. That law is gone now, but ripping wire out isn't worthwhile, and as these older parts of town are also interspersed with some businesses it makes sense that some of it remains.

 

[kursplat]

make sure all the 3-phase equipment you end up getting is the same voltage your going to end up with. for example,flavors available here in L.A. are 120v/208v, straight 240v, 480v/277v, straight 480v, 480v with a corner ground.
good luck

 

[cnc-me]

Your best bet is to run conduit as you need it.
Its hard to anticipate everything your likely to acquire in the future.
We were extremely lucky, in the mid eighties to have 3 phase power installed
for free. Line power is still the best.

 

[Norcal]

make sure all the 3-phase equipment you end up getting is the same voltage your going to end up with. for example,flavors available here in L.A. are 120v/208v, straight 240v, 480v/277v, straight 480v, 480v with a corner ground.
good luck

The voltages in bold may only be avail. to existing customers, as is the case w/ PG&E, & since SoCal Edison is subject to the CA PUC rules like Pacific Graft & Extortion is, suspect it may be the same. This only applies to CA, the PoCo rules vary elsewhere....

 

[StaggeringGoat]

My main question is would the wires from the panel to an outlet be the same for a single phase 220 outlet as it would be for a 3 phase hook up?

Three phase power requires a five pole outlet, not 3 or 4 pole like 240v.

 

[Steve from Socal]

Three phase power requires a five pole outlet, not 3 or 4 pole like 240v.

Huh;

Excluding some oddball device three phase service is three conductors and ground, vary rarely would a neutral be used. In most three phase equipment that has low voltage controls, lighting etc a transformer is used to provide the low voltage single phase power.

240 is a voltage by the way; it can be either single phase or three phase.

 

[eriksalo]

Three phase power requires a five pole outlet, not 3 or 4 pole like 240v.

With respect, I don't believe this is a strictly correct statement.

Here's a quick key to the different power feeds:

110V Single/Split Phase (3 wires): One hot, one neutral, one safety ground. Hot returns through neutral

220V Single/Split Phase (3 wires): Two hot wires, one safety ground. Each hot wire returns through the other

110V / 220V Mixed (4 wires): Combination of the above. 220V parts run as 220V and the two hot wires return each other. 110V single phase parts run from one of the hot legs and return the neural. There is a safety ground. While it's almost never true in this case that the 110V lines carry the full circuit current, NEC code says the neutral line needs to be the same gage as the hot lines. This happens often for hot tubs and air conditioners.

220V Three Phase (4 wires): Three hot wires, one safety ground. The three hot wires return each other.

220V Three Phase mixed (5 wires): Three hot wires, one neutral, one safety ground. The three hot wire return each other but you can also run 110V single phase by connecting one of the hot legs to the neutral. As above, Nec states the neutral must be the same gage as the hot wires.

There is an analogous set of configurations for 440V. But you can also get 277 by connecting two of the hot legs.

 

[StaggeringGoat]

With respect, I don't believe this is a strictly correct statement.

What country do you live in that has 110/220 volts?

 

[schwalby]

I now know a ton more than I did before. Thank you for bringing it down to my level.

I always wondered why some power lines around here only had the one insulated line. Good thing is around here you very rarely see the single line runs, everything is 3 phase. 

Most likely I think I am going to at least go with conduit instead of running any wires anywhere without a set purpose. Just going to make sure it is sized to carry the wires I may run in them. For the 3 phase / single phase question I should have plenty of time between getting price options for everything and when I will have to make the final decision. And with the new knowledge I have it should be an easy call to make.

 

[eriksalo]

What country do you live in that has 110/220 volts?

I agree you're right. I say 110 out of habit but that isn't accurate. The nominal voltage standard in the USA is 120V +/- 5% which works out to 114V to 126V at the supply. There was a time when the US standard was 110V (and also times when it was 115 and 117) at the supply but today it's 120V.

The 120V spec is the RMS (root mean square) value of the "mains" voltage. However, voltage drops between the breaker box and your outlet due to the resistance associated with pushing electrons through the wires. The "utilization" voltage or voltage at the equipment is typically 3% to 5% lower than the nominal supply voltage. If you take the bottom spec of the supply (114V) and subtract the average drop between supply and utilization voltages, you get 108V-111V (e.g. about 110V). Electrical appliances are often called "110V appliances" for this reason, hence the habit of calling 120V power 110v.

 

[theoldwizard1]

I always wondered why some power lines around here only had the one insulated line. Good thing is around here you very rarely see the single line runs, everything is 3 phase.

If 3 phase is available where your shop is locate, you definitely want that run in from the pole to your breaker box. Even a furnace blower runs more efficiently on 3 phase. Pulling 120V is just like on a residential split phase breaker panel and probably use the exact same breakers.

The problem is if you need 240V, you can not get it. Phase-to-phase is 208V (I can never remember if that is delta or wy). Some equipment that requires 240V may have a multi-tao input so that it can be run on 208V.

 

[Jim Johnstone]

The problem is if you need 240V, you can not get it. Phase-to-phase is 208V (I can never remember if that is delta or wy). Some equipment that requires 240V may have a multi-tao input so that it can be run on 208V.

Could he not transformer it from 208 to 240?

 

[schwalby]

If 3 phase is available where your shop is locate, you definitely want that run in from the pole to your breaker box. Even a furnace blower runs more efficiently on 3 phase. Pulling 120V is just like on a residential split phase breaker panel and probably use the exact same breakers.

The problem is if you need 240V, you can not get it. Phase-to-phase is 208V (I can never remember if that is delta or wy). Some equipment that requires 240V may have a multi-tao input so that it can be run on 208V.

Interesting about the furnace blower. Would the cost of the additional charges to go to 3 phase be worth it though? Or is that an impossible question without knowing the cost difference.

On the 240V issue, that means I would have to have a gas dryer and stove or source out a dryer and stove that run on 208? Thinking that might increase the cost of the appliance a lot.

I forgot to mention that there will be a 3 bedroom residence above the garage. Didn't think it would affect all of this, guess I was wrong.

Does raise another point I should have stated is that I may have solar panels so will 3 phase allow you to feed back to the service? Reverse metering. This issue may not affect anything since solar is a want but not a need. Oh and how does 3 phase affect running a generator for when there are power outages?

 

[kursplat]

The voltages in bold may only be avail. to existing customers, as is the case w/ PG&E, & since SoCal Edison is subject to the CA PUC rules like Pacific Graft & Extortion is, suspect it may be the same. This only applies to CA, the PoCo rules vary elsewhere....

yup, just pointing out he better read the motor plates to see what he's getting before buying

 

[ert01]

The short and easy answer is that for three phase wiring you need more wires going from the panel to the device. They will also be smaller (cheaper) wires then ones for a single phase installation (assuming the same motor size).

Your best bet if you are unsure of what service you want is to install conduit now. Then buy the equipment you want and then pull your wires to suit.

NOTE: if you get 3phase service installed that doesn't mean that you can't use single phase equipment anymore and that it all has to be 3phase... You can still run single phase equipment on a 3 phase system without any issues or weird wiring or anything.

I'd go for the three phase if I were you. More options are never a bad thing...

 

[spy604]

As far as the furnace blower goes, a drive motor swap would be all it takes.

 

[offroadsteve]

One other thing I haven't seen mentioned yet is that 3 phase service from the PoCo will require a 3 phase breaker panel, which is compleatly different and incompatible with a 120/240 split phase panel found in most residental construction.

On the subject of 240V appliances on 208V, some are rated to be workable on 208V, but will draw more current (watts = volts x amps, where watts will be constant). In our shop at school we had all sorts of 240V equipment wired across 2 legs of our 208V with only one problem... we had a plasma cutter that never did work right, but I'm not positive that was the cause (may have just been old and junk).

My advice, and the direction i will be going in my future garage, will be to wire for 240V split phase and use either a VFD or rotary converter for any equipment I get that requires 3 phase power.

 

[neufab]

american rotary phase converter is my vote.i would buy a converter as u need it two hard to guess what u will aquire,i would go rotary not static just me.been useing converter for 20 years now and no problem,in fact just got a transformer run off my converter to bump my 220 three phase to 480 three phase works great.

 

[nehog]

If your future shop doesn't have three phase power, but it's available on the pole that's one thing. If you want the power company to add another transformer on the pole and a wiring involved, safe estimate would be 10-15K.

As I've suggested before, one alternative for an occasional need is a diesel generator. I use a 'retired' military generator, three phase, and that provides a good solution to my needs (which are very rare need for three phase).

make sure all the 3-phase equipment you end up getting is the same voltage your going to end up with. for example,flavors available here in L.A. are 120v/208v, straight 240v, 480v/277v, straight 480v, 480v with a corner ground.
good luck

Aw, you forgot 240/416!

Huh;

Excluding some oddball device three phase service is three conductors and ground, vary rarely would a neutral be used. In most three phase equipment that has low voltage controls, lighting etc a transformer is used to provide the low voltage single phase power.

240 is a voltage by the way; it can be either single phase or three phase.

I'll choose to disagree. Many times neutral is used, either for a wye connection (what I use) or for a high leg delta...

 

[theoldwizard1]

Interesting about the furnace blower. Would the cost of the additional charges to go to 3 phase be worth it though? Or is that an impossible question without knowing the cost difference.

Likely, yes, even on a 1/2-3/4 hp motor that runs a lot. (I used to work on BIG computers; their blowers were 3 phase.)

On the 240V issue, that means I would have to have a gas dryer and stove or source out a dryer and stove that run on 208? Thinking that might increase the cost of the appliance a lot.

Maybe yes, maybe no. The transformer solution mentioned in another post would work, but it would be expensive for one large enough to run a stove and dryer.

Some (many?) appliances are setup for a wide input voltage range, typically 200-250V. Obviously, 208 and 240 fit in that range. A lot of electronics are set up for wide range (90-140) and some can "autorange" (90-140 or 200-250). Check the owners manual.

Does raise another point I should have stated is that I may have solar panels so will 3 phase allow you to feed back to the service? Reverse metering. This issue may not affect anything since solar is a want but not a need.

I'm sure it can be done, it will just cost more money. Maybe triple ? I know that 2 OutPack Power Inverters can be "linked" into a 240V split-phase power. I would bet somehow they could take 3 of them and make 3 phase.

Oh and how does 3 phase affect running a generator for when there are power outages?

"You can get anything you want ..." if you have the money ! BIG generators do generate 3 phase, like those giant CAT generators out behind Sam's club and Costco.

 

[theoldwizard1]

american rotary phase converter is my vote.i would buy a converter as u need it two hard to guess what u will aquire,i would go rotary not static just me.been useing converter for 20 years now and no problem,in fact just got a transformer run off my converter to bump my 220 three phase to 480 three phase works great.

Rotary converters are fine for intermittent (few hours per month) use. They are big and they are inefficient. But, if 3 phase is not available, it is definitely the way to go.

 

[theoldwizard1]

One other thing I haven't seen mentioned yet is that 3 phase service from the PoCo will require a 3 phase breaker panel, which is compleatly different and incompatible with a 120/240 split phase panel found in most residental construction.

Excellent point !

This is one decision you need to make up front that would cost you a lot if you made the wrong decision !

 

[eriksalo]

A phase converter will NOT cause wear to a machine!

There are several different types of 3 phase converters. Some are better than others.

Static phase converters (converters without an electric motor) essentially run a three phase motor on single phase power. A static converter uses capacitors to buffer in the third phase for starting only. A static converter will only a allow a motor to provide between 50% and 66% of it's rated output. If the motor is fully loaded, it will heat up and eventually burn out and die if run from a static converter. In this case, the machine life is potentially shortened.

The better converters (rotary converters and VFD's) are just fine and won't cause appreciable wear over time.

 

[kursplat]

Aw, you forgot 240/416!

crazy east of the mississippi voltages...

 

[Steve from Socal]

Gee, I get slammed by not one but two, people for offering suggestions that are misconstrued.

First any three phase power converter is going to have three conductors and an earth ground, if you have a generator or utility Wye power your neutral would only be used on single phase circuits with few exceptions that probably don't apply to a small home shop. I don't recall ever wiring a neutral to a three phase machine or process line and I have installed a several big machines and process lines that include heating elements, frequency generators etc.

Next; the comment I referenced was "a phase convert will wear out a machine" how this was taken to infer that I suggested a static phase converter is beyond me? My original comment mentioned a static phase converter in passing; with my advocating either a VFD or rotary phase converter as a source of three phase power from a single phase source. The machines life has nothing to do with a motors life, I have changed plenty of three phase motors in perfectly serviceable machines due to phase loss that burnt a motor winding. I agree that a static phase converter is a dubious way to run a motor however; they do have their place, I have a small static converters on my lathes coolant pump and my band saws coolant pump. The capacitors change the phase angle, never heard it described as "buffered"

I also mentioned a three phase panel for utility power that got lost in translation I guess?

I was trying to give someone a brief overview of the options he may have, my intent was not to go into minute detail. None of what I wrote was wrong or misleading, if you want to split hairs on a something, use a valid point to argue.

I am generally pretty easy going but, these seem to be needless finger pointing. Nothing I said contradicts the NEC or good practices

Steve

 

[foolishpride]

crazy east of the mississippi voltages...

I live east of the Mississippi, and have dealt with :

345,000
138,000
69,000
34,500
13,800
12,470/7200
6600
4160
2400
480/277
240/120
208/120

But I've never heard of 240/416.

 

[hh76]

"I'm sure it can be done, it will just cost more money. Maybe triple ? I know that 2 OutPack Power Inverters can be "linked" into a 240V split-phase power. I would bet somehow they could take 3 of them and make 3 phase."

you can interconnect PV to 3phase with little to no extra cost. It won't be a factor.