Wiring for Laguna Saw - 1 phase or 2?

[Tim Booher]

I recently purchased a MBAND18BX2203, Laguna Tools 18|Bx 3HP 220V 18" Bandsaw and need to wire a 220 Volt outlet. The spec sheet describes the saw as: "3HP, 220V, 1 Ph. 12 Amp."

I think I know what I need to do, but I have one question: I was confused by the breaker since the saw was described as one phase, but the breaker I selected will connect to both leads, each at 180 degree offset in phase. I am guessing that this ensures that one of the 110/120 volt connections is active at any one time, but wouldn't this make the wiring 2-phase?

Just to verify, I any thoughts on the rest of the setup below would be greatly appreciated:

Wiring diagram:

The 18BX2203 has a 3 HP 220 volt 1 phase Leeson motor. I have residential 2 phase wiring and was confused if I needed to some each 120 from the same phase or from different phases.
The manual recommended that I connect the bandsaw to a 15 amp breaker but I wanted to provide myself some additional margin for a future tool but was also aware that tools use more power on startup. I initially was going to use 12/2 wire, but I decided on schedule 40 conduit with Thermoplastic High Heat-resistant Nylon-coated THHN wire.
Another question I had was the number of wires connecting to the outlet. I initially thought I would need to have 4 wires (a 12/3 wire), both a neutral and a ground in addition to two hot wires. After thinking about it a little bit, it made sense two use three wires total, since I was setting up a dedicated circuit and the ground and the neutral would be the same wire
What receptacle do I use?

The bandsaw came pre-wired with a 220V 3-pin plug. I used this page to make sure I used the correct outlet. One of the decisions I had to make was if I wanted to use a twist lock plug, but I didn't consider the benefit worth the extra work to re-wire the saw.

I decided on 20 Amp Commercial Grade Double-Pole Single Outlet, White which has two connections for hot and one ground wire.
Breaker




What about the wire?

In setting up a 20-amp circuit, I had to make sure this worked with my setup. Per the table in the manual, I need at least 14 guage wire, so I went with 12 guage which I needed for the 20-amp breaker anyway.

[Jamie Buxton]

I agree with you: the standard American residential feed should be called 2-phase. It has two hots. They each are 115 volts with respect to neutral. They are 180 degrees away from each other. However, nobody in the US calls this feed 2-phase. Everybody calls it single phase. If everybody calls it single phase, that's its name.

[Bruce King]

It’s often called a “split-phase”, or “split single-phase” system, but never “two-phase”, as there is only one primary winding, and one electrical system phase supplying it. The phase shift is obtained by using a center tapped secondary wiring feeding the house(s). That breaker and receptacle is the most common way to install that circuit. Some jurisdictions may require the breaker to have a GFI feature. Use the 12 ga cable too. I recommend that you get an electrician for this.

[Matthew Hills]

1 phase between the two hots.
(common is not used with a 1ph/220V motor)

Matt

[Malcolm Schweizer]

That outlet always makes me think of a guy that just got punched in the eye.

[Tim Booher]

Thank you so much for your comments. I get it now. The single phase motor will need at least 12-amps of continuous current at 240V (hot 120V + hot 120V) plus a ground. Here in the US, we have 240V single-phase residential, with a center tap. The center tap is called neutral. This is called "Split-phase" since you can grab the outer "phase" wires (hot-hot) or grab one phase and neutral for half the voltage.

Where I found myself confused was on the "single-phase", if a "normal" outlet grabs one phase, and a neutral for half the voltage, wouldn't a 240V setup have two phases? There actually is a 2-phase, but it's weird as heck. It was basically two single-phase circuits set 90 degrees apart, and requires 4 wires instead of 3 but only carries about 14% more power for 33% more wires. Needless to say it wasn't popular.


This diagram cleared it up for me. The amplitude of 120V on each leg adds to 240V at the same frequency. The current doesn't add since the flow remains the same. A 240V-only piece of gear connects to two hot legs and a ground (no neutral), so if it pulls 20A, that 20A has to be going in one hot leg and out the other hot leg -- there's nowhere else for it to go! (In other words, it draws 20A, period -- the legs do not "add together".)

[Matthew Hills]

In the 240V/3-wire case, the ground is typically there for safety purposes, and not carrying current in normal usage.
The 4-wire case is used by some appliances where one of the hot leads and neutral is used to provide a 120V supply to other circuits (E.g., a light)

[Charlie Velasquez]

You were right to go with the 12awg wire. 14awg is allowed to be protected by a 20A breaker on a dedicated circuit for a specific motor, but many inspectors interpret dedicated to mean it is hard-wired and there is no possibility of something drawing 20 amps being plugged into it.

[Bill Dufour]

Two phase is an obsolete power distribution system. You have two separate phases, normally 90 degrees apart. It requires four wires to work. Three phase only requires three wires, single phase is one or two wires.
Bil lD

[Rod Sheridan]

There is only a single current path, it is therefore a single phase load and source.

2 phase power has a 90 degree phase angle, 3 phase has a 120 degree phase angle....Rod

[Rod Sheridan]

Two phase is an obsolete power distribution system. You have two separate phases, normally 90 degrees apart. It requires four wires to work. Three phase only requires three wires, single phase is one or two wires.
Bil lD

I was taught that one conductor is properly called an open circuit....Rod

[Frank Pratt]

I was taught that one conductor is properly called an open circuit....Rod

You were taught wisely my son.

[Bill Dufour]

Look at the wires on the pole for 240 volt single phase there are only two hots. Either one to ground is 120. Neutral is created at the service entrance by tying a white wire to a ground rod and pretending it is not ground from then on.
Bill D

[Bruce King]

The neutral comes from the power company transformer. The system will operate without the ground rod. The ground rod or other means of earth ground is to help smooth out spikes and harmonics. Since the power company neutral is not always a good earth ground they want to add in more poor grounds from each house to help out. Real earth ground is attempted only near some very high voltage equipment and is sometimes 200 ft deep.

[Bruce King]

For those that have added panels, usually incorrectly called sub panels, the feed should be 4 conductors. The white neutrals in your panel only connect to the feeder white wire on a terminal bar. It should not connect to the metal box via screw or anything. The bare copper wire in the feeder only connects to a terminal bar that only has copper ground wires or green wires on it. Also a green screw should connect this ground bus to the metal enclosure. If your panel is very close to the main service panel you can skip the 4th conductor if approved. Older houses with 3 wire feeds to “sub panels” are not required to be changed unless some issue comes up that is outside the point of this post. Metal conduit can replace the ground conductor only when installed with approved methods.