3 Phase Wiring

[DawgPaw]

I am about to run the wiring for my basement wood shop. I am going to run 220 to several machines.

One day it is possible that I could get some 3 phase equipment and maybe run it off of a phase converter. Would it be possible to run lines in preparation for that equipment?

I know almost nothing about that process, and it would be down the road. In my head I was thinking a larger phase converter that could handle several pieces of equipment would be in a utility closet near the breakers, and then run lines to the machines. I don’t know what would be required to convert the lines for 3 phase. I’ll have to get an electrician’s help connecting it, but if I could go ahead and get the wire run then I could close the wall up.

 

[Terry D]

I don't understand the advantage of this. I know sometimes you can pick up used 3 phase equipment cheaper. But if you are buying new equipment, just get single phase. At least the phase converters that I have looked at needs twice the input power as the output. It all depends on what the machines are and how many are running at the same time. VFD's might be a better option

 

[DawgPaw]

A 12 or 16” jointer is $2-3000 to get an old heavily built but 3 phase machine. New they start at $8,000 and go up very quickly. Planer, lathe, bandsaw, air compressor, etc are all similar. VFD’s are a solution that some use. As are motor swaps, but I was trying to have options.

I am certainly no expert, but I believe that on higher HP machines, especially those that do not benefit from variable speed, many people opt for rotary phase converters.

 

[Walkers]

I have a 3 phase system in my shop connected to my rotary phase converter. Just run 3 wires and a ground in a conduit to wherever you want the equipment and the RPC.

The advantage of 3 phase equipment is its low cost. I can pick up a 10 horse 3 phase motor for a hundred bucks, or a single phase motor for a thousand. 3 phase equipment sells much cheaper because of the lack of 3 phase to most hobby shops. Once you have an RPC and one piece of equipment you will start to run into lots more. My current list is an Ironworker, milling machine, lathe, pyramid roller. My last 2 post lift was 3 phase, as was a big abrasive saw. I have most equipment on twist lok plugs for easy access.

 

[nadogail]

There are ways to build your own Rotary Phase Converter, Basically all you are going to need is a large 3 phase motor and bunch of Capicators

 

[Steve from Socal]

Three phase motors are smoother in machine tools than single phase. To the OP while a large phase converter is possible any thing less than a 5 HP motor can be run using a single phase input inverter/VFD. That would be a better option IMHO, the cost per unit is rather low and the efficiency is quite high.

Rotary phase converters have their place but today small motor loads are better served by VFD's in most situations. The rotary is going to require monitoring and capacitance changes for varying loads and once optimized for a particular load a number of additional capacitors will be required to change that for other load schedules.

Starting from scratch the VFD's make more sense. Your single phase panel and breakers are used, the VFD supplies overload and starting parameters for the motor that include soft start and braking when desired.

I have had both phase converters and single phase machines in my garage in the past. They predated the small single phase VFD's that are common today. I have a 5HP milling machine that I put a single phase motor in when I had it in my garage, I would have saved money and had better results with a VFD Vs changing the motor.

Steve

 

[mogandave]

It should be easy and pretty cheap to run the extra wire in the conduit.

Three-phase motors start better under load and are easy to reverse.

Also, assuming you have three-phase service, they will balance your load and keep your peak usage down.

 

[wyliesdiesels]

You just need 3x ungrounded conductors and 1 EGC....

 

[matt_i]

If you are going RPC with some open-ended detail a pretty good plan is to run a conduit "trunk line" either down the center or a perimeter configuration with extra tees put in where you potentially want drops or drop-legs. Not much penalty to putting in tees later up until the wires get run.

If you are running NM wires to your RPC room you can use something #8 awg and then fuse to a lower output amperage.

Size? I'd run 1-1/4 or 1-1/2 which has plenty of room for expansion in the future.

The nice thing is even if you only ever run 240vac single phase you still can use the wireway that you built.

As always I highly recommend maintaining an "as built" drawing and use wire-number-labels to keep track of what goes where. It might be crystal clear today but in 5 years might be as clear as mud. The grey matter is an imperfect storage device at the end of the day.

 

[jar944]

I don't understand the advantage of this. I know sometimes you can pick up used 3 phase equipment cheaper. But if you are buying new equipment, just get single phase. At least the phase converters that I have looked at needs twice the input power as the output. It all depends on what the machines are and how many are running at the same time. VFD's might be a better option

There is a practical limit on single phase motor horsepower.

As already stated 3ph motors are less complex and more reliable. Used commercial / industrial equipment is normally cheaper and 3ph.

OP for just one or two machines a VFD usually makes more sense.

 

[kmacht]

Seriously look at VFDs. Getting one for each machine may be cheaper than buying and running a rotary phase converter. I have a 3 phase Bridgeport mill running off a VFD I bought for about $100. The advantage of a VFD besides being easy to install is that they come with all sorts of other features. Mine has an instant e stop button, a switch to change the motor from forward to reverse and a rotary knob that lets me adjust the ROM to any setting I want.

 

[ycgoat]

Have you solicited your electrical service provider for a 3 phase service to your shop?

 

[930dreamer]

Basement shop I'm guessing means "home shop" so probably not three phase practical from the local utilities. I have a Clausing drill press on a vfd, hydraulic press, air compressor and grinders on a self built rotary phase converter.

 

[slowtwitch73]

Do what Walkers said, then it's there if you want to use it no matter what route you go.. only outlay is wire cost and some time. It wont go unused one way or another.

 

[My Old Tools]

If you plan to run multiple 3 phase machines of off an RPC, plan to set a small 3 phase breaker panel. All your branch circuits should be breaker protected just like 110 and 220 circuits. Set it right beside your shop breaker panel as it will need 220 from there to power the RPC.

 

[My Old Tools]

Three phase motors are smoother in machine tools than single phase. To the OP while a large phase converter is possible any thing less than a 5 HP motor can be run using a single phase input inverter/VFD. That would be a better option IMHO, the cost per unit is rather low and the efficiency is quite high.

Rotary phase converters have their place but today small motor loads are better served by VFD's in most situations. The rotary is going to require monitoring and capacitance changes for varying loads and once optimized for a particular load a number of additional capacitors will be required to change that for other load schedules.

Starting from scratch the VFD's make more sense. Your single phase panel and breakers are used, the VFD supplies overload and starting parameters for the motor that include soft start and braking when desired.

I have had both phase converters and single phase machines in my garage in the past. They predated the small single phase VFD's that are common today. I have a 5HP milling machine that I put a single phase motor in when I had it in my garage, I would have saved money and had better results with a VFD Vs changing the motor.

Steve

Not really. I've been running an RPC for 20 years with all kinds and combinations of machines and have never changed the capacitance of the system even once. VFD's for 5 HP and up motors get expensive for good ones. Planers, jointers, heavy table saws don't care about soft start or braking. A VFD makes sense for a single machine or where you need variable speed...drill press, bandsaw, mill, lathe.

 

[u2slow]

Get machines first, wire them once you have them in place.

Trying to exhaustively pre-wire a utility/industrial space is expensive, time-consuming, and usually misses the mark.