Wiring for 3HP 220V (for Laguna Tools 18|Bx)

I recently purchased a Laguna Tools 18|Bx 3HP 220V 18″ Bandsaw, specifically a MBAND18BX2203, and needed to wire a 220 Volt outlet. I’ve done a fair bit of electrical work (both low and high voltage), but I had a couple questions.

Just for the record, I enjoyed this video to make sure everything was setup correctly and this unboxing video was helpful. Also, here is the manual. The instructions weren’t great, but the wiring digram in the manual was helpful. YouTube and web forums are incredible for learning how to do new things like this. This article, Understanding 240V AC Power for Heavy-Duty Power Tools, was super helpful.

The 18BX2203 has a 12-amp 3 HP 220 volt 1 phase Leeson motor, with a 20 Amp recommended breaker. (Engines use more current on startup. Why not more Voltage?). 220V is a somewhat outdated nomenclature for the US system, but tools like this have adequate tolerance to take 240 without problems.

Laguna made this confusing since their website for the 18BX, differed from the manual. The website recommended a 20 amp breaker, while the manual recommend 15.

mismatch

The machine’s wiring diagram showed me a couple important things. First, I have no need for a neutral wire and the saw has a NEMA 6-15 plug.

wiring

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.

This diagram cleared everything up for me:

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”.)

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.

wire thickness

How many wires?

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. I like this reference on wires.

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 will have the same purpose. (The neutral is connected to the ground in the panel.)

What receptacle do I use?

The bandsaw came pre-wired with a 220V NEMA 6-15 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.

For this setup, I needed a NEMA 6-20.

By the way, I learned that due to an exception in NEC, I’m allowed to plug 15A-plugged loads into either a 15A or 20A circuit. Further, a 20A circuit is allowed to have 15A sockets on it (as long as there are 2 or more sockets, e.g. the above NEMA 6-15 will suffice).

I decided on 20 Amp Commercial Grade Double-Pole Single Outlet, White which has two connections for hot and one ground wire and is a NEMA 6-20R, 2P, 3W.

Breaker

This is the most simple part. I need two 20 amp breakers that connect to different leads to get both parts of the split phase. This one will work.

One thought on “Wiring for 3HP 220V (for Laguna Tools 18|Bx)

  1. This is way above my head. Hard to believe Steve & I could have such a brilliant son. Proud of you, Tim!

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