Twist-lock connections - what to do?

[Jon Endres]

I am starting to plan electrical connections for my new garage and I am somewhat perplexed about how to deal with 220v circuits. In my current basement "shop" I have several machines that use 220v power. My table saw is the largest at 3hp, and my bandsaw is the smallest at 1 hp. All the rest are 1-1/2 or 2 hp motors (dust collector, RAS, jointer). I will be adding more 220v machines at some point - probably a planer and a lathe. All of them currently share a pair of 220v receptacles. Both receptacles are NEMA L6-20R twistlocks. However, the breakers for each receptacle (they are on two different circuits) are 15 amp. Each receptacle has an extension cord plugged into it using an NEMA L6-20P plug. At the other end of each cord is a NEMA 6-15R receptacle, and each machine has a NEMA 6-15P plug, regardless of amperage draw or size of motor. As I use each machine, they are plugged into the extension cord, and at the end of use, they are unplugged for safety.

I am not sure what to do in the new shop. I have all of my machines mobile now, and most of them will stay that way, although the radial arm saw is not going to move and the dust collector will probably get a permanent home. WI am considering converting all of the machines to twistlocks right on the machine cord, and putting several receptacles around the perimeter of the shop at 6-8' spacing, so that I can pretty much use any machine anywhere. I'm also going to install some ceiling drops with strain relief cords. What I don't know is what configuration these should be? Alternately, I could fit up all my receptacles as 6-20R's and be able to use either a 6-15P or 6-20P cord, but that eliminates the twistlock strategy.

Looking for advice from those of you who have several 220v machines and what you do in your shop to power them up.

[Ken Fitzgerald]

I have multiple 220 vac receptacles on all the walls of my shop. They all use twist lock receptacles. All my 220vac tools have twist lock plugs on the cords of the machines. I can reposition the tolls as needed or desired.

In the mid-70's I worked air traffic control maintenance in the Navy. Having had to repair a radar system that experienced a nearby lightning strike that ran into the radar on buried ac power lines, I unplug all my tools when I leave on extended vacations. In fact, I unplug all my tools when not in use.

There are those who will tell you to hardwire them.

It's really a matter of personal preference.

[Wade Lippman]

First of all, it is 240v, not 220v.
Second, 15a is certainly marginal for a 3hp motor. What cable size is used? If #14, you might have a problem. If #12, than you probably want to upgrade everything to 20a.
You can't have a 20a outlet on a 15a circuit.
I've never used a twistlock and have never had anything accidentally disconnect. YMMV.

[Ole Anderson]

Unless you are hanging them from the ceiling, I don't see the need for 240v twistlocks either, any more than 120 v twistlocks.

[Mike Heidrick]

I use l6-30r and plugs on all my 220 1ph tools. I have about 12 circuits of them running around the new shed. I buy Levitons in bulk on ebay, usually used like new pulls from a datacenter. I like P&S plugs. All mine are 10/2 romex and on 30amp 2pole breakes. None in the ceiling yet but planning to add some soon.

[Marty Tippin]

I've got a single 20A 240V circuit fed with 12/2 Romex with about 6 outlets along two adjoining walls and 3 outlets in the ceiling. All use 20A twist lock receptacles. All machines have matching twist lock plugs in them.

For the ceiling outlets, I made up extension cords using 10/3 SJOOW cord. I use Kellems grip for strain relief, attached to an eye bolt on the ceiling.

If I had to do it over again (and I wish I could), I'd run 10/2 Romex and make the circuit 30A for future needs. I might also run 2 circuits instead of one, but I only run one machine at a time so that's not totally necessary.

The ceiling outlets have come in handy as they let me put my jointer, planer and table saw out in the middle of the shop with the cord running down to them.

[Brian Hood]

Hi John,
I use straight blade plugs/receptacles for everything, but cut off the original ones and install right-angle plugs so the cord falls flat to the wall instead of sticking out and then down. I'll never use a twist lock for machine-to-wall, I save them for hanging cords.
One fact you haven't shared is the wire size is connected to the 15 amp breakers. It could be #14, to small, or #12 which is fine, or #10 which is just right. I'm wired with #10 from 20 amp breakers which is the deluxe option.

[Scott Dorrer]

My old shop is wired with #10. Every 8' there is a 240 outlet with 6-20r receptacle. My band saw is 5hp and has never been an issue.

I've toyed with the idea of going twist lock, L5-20r , in the new shop I'm building but will probably just stay with the tried and true 6-20r. I plan on a couple ceiling drops and will probably make a short cord to reach from the drop to the floor with a twist lock on the upper end and a straight blade once it reaches the floor..... maybe.

[Jon Endres]

OK, my current workspace uses #12 wire. I was planning on using #12 in the new shop but now I'm wondering if I should just run #10. Everything will be in 3/4" EMT and will be using THHN stranded wire, so it won't be an issue to pull #10 vs. #12.

Based on your responses, I'm leaning toward reusing my L6-20R receptacles and L6-20P plugs (they'll be removed from my basement anyway and the circuits will be repurposed). Putting everything on 20-amp breakers and #10 wire? And converting all my machine plugs to L6-20P.

[Wade Lippman]

Unless you are planning on some 5hp motors there is no particular benefit to #10. No harm to it except cost and ease of pulling it; but no benefit.

[Rollie Meyers]

Twistlock® is a registered trademark & unless they are made by Hubbell, they are just locking connectors.

[Dan Hintz]

Twistlock® is a registered trademark & unless they are made by Hubbell, they are just locking connectors.

Hand me a Kleenex so I can finish with this Xerox job (though I can't say I've heard anyone call it a Xerox in quite a long time).

[Rick Potter]

The only twist locks I have in my new shop are the ones on the ceiling. On the walls I have a couple of 30A circuits for my large sander, but most 240V outlets are 20a duplex plugs. These look just like an ordinary duplex plug, but are made for either 15 or 20A, 240 volt equipment. They are available at most electrical supply houses. In my shop, they come in very handy when I have two 240V tools next to each other. This way I do not have to unplug one to operate the other.

Good timing on the question, since just yesterday I made one of my 240V, 20A, extension cords from a single receptacle to a duplex, for that very reason. It feeds my SawStop saw, and my DJ20 jointer. Making a lot of thin strips, I had to make a cut, unplug the saw, plug in the jointer and joint for the next cut, unplug the jointer and plug in the SS...wait for it to finish testing itself, make the cut, etc.

[Robert Engel]

Electrical like politics many opinions, 50% of them wrong.

Here's mine:

First off, don't waste the extra money on #10 wire. #12 @ 240V is fine for anything 3HP or below.
Great to be using EMT because you can add a run to a new outlet very easily.
I'm a big fan of armored cable like Armorlite. Its about 2X the cost of romex but worth it because so much easier then EMT.
I think 15A is too small but if you're not tripping the breaker, I wouldn't change it.

If you've got them use them, but I wouldn't use twist locks for anything but a hanging cord.


Unless you're running more than one machine at once it will never be necessary for more than one circuit.
I use standard 240V/20A *single* receptacles and have several all around the shop on one circuit. It will only pop the breaker if I have 3 machines idling running while using the planer. You can either make a 240V extension cord or extend the supply cords from your machines.

[roger wiegand]

I use 20A 240 v straight blade connectors. If something is going on with a machine that would cause it to yank its plug out of the wall I think I want it to yank the plug out ;-) No locking connectors for me.

I know some here disagree, but I've found it very convenient to run 12-3+ ground wire and use multiwire branch circuits to place 120 outlets whereever I have 240. Seems like there's always a lamp or something that needs to get plugged in. Also very convenient to be able to reconfigure any box to whatever combination of 120 and 240 I need. Things that run at the same time as other tools get dedicated circuits (eg air conditioner, air compressor), tools that get used one at a time share a few circuits. I've got outlets about every six-eight feet along the walls, on the posts in the shop, and one run under the floor to the table saw.

[Rollie Meyers]

Electrical like politics many opinions, 50% of them wrong.

Here's mine:

First off, don't waste the extra money on #10 wire. #12 @ 240V is fine for anything 3HP or below.
Great to be using EMT because you can add a run to a new outlet very easily.
I'm a big fan of armored cable like Armorlite. Its about 2X the cost of romex but worth it because so much easier then EMT.
I think 15A is too small but if you're not tripping the breaker, I wouldn't change it.

If you've got them use them, but I wouldn't use twist locks for anything but a hanging cord.


Unless you're running more than one machine at once it will never be necessary for more than one circuit.
I use standard 240V/20A *single* receptacles and have several all around the shop on one circuit. It will only pop the breaker if I have 3 machines idling running while using the planer. You can either make a 240V extension cord or extend the supply cords from your machines.


Armorlite is MC, Metal Clad cable, not armored cable, they are two different items, and each has their own NEC articles meaning different requirements, & AC cable is not very common anymore, the product sold at the big box stores is MC.

AC is covered in art 320, MC, art 330.

[Ken Kyler]

like many others, I installed multiple outlets. Every 4' around the perimeter is a single 30A 220v twist-lock and a gang of 20A 110v outlets. I put a set across the ceiling too (but not enough). Wall outlets are set at 49" above the floor.

[Erik Loza]

We've used the twist-locs from Lowes or HD (not sure of actual brand) for over ten years and no complaints. It is "the" plug you see at any industrial trade show where a quick-disconnect is needed.

Erik