240 Plug/Receptacle choices?

[Patrick Whitehorn]

All,
I have two machines who need their 240V plugs replaced. One is my new-to-me 8" Delta 37-315 which is currently plugged with a NEMA 6-15. The second is my new-to-me Delta Unisaw 34-461 which is currently plugged with a NEMA 5-20. Eventually I will have other machines that will be on 240V as well and so I am considering my options with respect to which plug and receptacle to use.

I have decided that I will pull one or more 12/3 circuits with double-pole 20A breakers for the machines. That gives me a few options: NEMA 6-20, L6-20, 14-20, and L14-20. Regardless of what I pull, I will likely use a double-pole, double-throw switch (center-off) to allow me to run the 240V outlet or one/two 120V branch circuits. I like the fact that I can run a separate ground wire to the machine with the [L]14-20 choices, though I know that none of what I have now has that need (nor cord - I would need to replace the power cords with SJOOW 12-4 to manage that).

So, without suggesting that I pull 10/3 and use 30A capable plugs/receptacles, which do you consider the correct plug and receptacle combination? Do I go with the locking or do I go with straight? Three-way (hot-hot-neutral) or four-way (hot-hot-neutral-ground)?

Thanks!

[John Lankers]

I'm not familiar with your Delta equipment but I do know that breaker, wiring and receptacles have to be sized to match- saying you can not install a 30 Amp receptacle in a 20 Amp circuit. The wire has to be sized for the breaker and for the length of run. All this together is the installation that should be approved by an inspector. If you decide to plug in a machine that requires 20 Amp into a 30 Amp outlet you're fine but not when it's the other way around.
Also standard 240 Volt wiring is Hot Hot Ground and Never Hot Hot Neutral!!! However if the 240 Volt circuit is also used to power 120 Volt systems then the Neutral is needed but only then, think clothes dryer or kitchen range.

[Dan Friedrichs]

Whoa, whoa, whoa....

Lots of things wrong, here, first, before we even get to plug choices.

Regardless of what I pull, I will likely use a double-pole, double-throw switch (center-off) to allow me to run the 240V outlet or one/two 120V branch circuits.

....huh?

Do I understand that you want both 240 and 120 receptacles, but only want to run one wire from the breaker box? That is doable without this switch that you're proposing. I would suggest abandoning that idea, entirely - it's very unconventional.

I like the fact that I can run a separate ground wire to the machine with the [L]14-20 choices, though I know that none of what I have now has that need (nor cord - I would need to replace the power cords with SJOOW 12-4 to manage that).

No. There is no "separate" ground. There is a single ground, which you need to run to the machine REGARDLESS of the plug you choose. The locking plugs have 4 contacts, which allow you access to ground, hot1, hot2, and neutral. Your 240v machines do not require neutral, so the 4th position is not needed (nor do you need to change the cord on the machine).


To select plug ampacity, size the plug to the load, size the receptacle to match the plug, size the wire to match the receptacle, and size the breaker to match the wire. So if your loads are <20A (which they certainly are), use 6-20 plugs and receptacles, 12AWG wire, and 20A double-pole breakers. If you want locking, use the L6-20.


Many people get confused on the presence of the neutral on 240V circuits. The neutral is to provide access to 120V. Thus, things like ovens or electric dryers which use 120V light bulbs have that available. Your power tools have no such additional loads - once you rewire the motors to run at 240V, you no longer need 120V, and thus, the neutral is not required.


All that said, personally, I'd reconsider using 240V, unless you have some equipment that cannot be run on 120V. A properly-sized 120V circuit will provide equal performance to a properly-sized 240V circuit. When people claim that 240V improved the performance of their tools, what they really mean is, "The new, dedicated, properly-sized 240V circuit I just installed performs better than the undersized, shared 120V that I was using, previously".

[Rick Potter]

I will let others more knowledgeable comment on the wiring, but I have two types of 220 receptacles in my shop.

First, there are a couple 30 amp twist locks for larger machines like my 5HP drum sander. Then there are several runs, hopscotched from one circuit to another around the shop so that adjacent machines are not on the same circuit. These receptacles are 20 amp duplex, looking somewhat like a normal pair of 110's. The duplex has been very handy when I have more than one low draw 220V machine that I want to plug in there. In a couple cases there are two machines plugged in to the receptacle, but only one is on at a time. This way I don't have to constantly unplug.

Don't know what those number machines are, but my 3HP Unisaw, my DJ 20 8" Jointer, and my 3 HP Sawstop are all on their own 20 amp circuits, with juice to spare. For example, If I remember correctly, the Unisaw takes 13 amps, and the DJ20 only takes 8.

Hope this helps.

[John K Jordan]

... When people claim that 240V improved the performance of their tools, what they really mean is, "The new, dedicated, properly-sized 240V circuit I just installed performs better than the undersized, shared 120V that I was using, previously".

People who do their own wiring sometimes forget to consider the voltage drop due to the length of the run when sizing the wire. A motor performs poorly at reduced voltage.

BTW, some of the larger motors in a typical shop cannot be run on 110/120 volts. In my shop this includes the 5hp cyclone and air compressor, and the table saw, bandsaw, biggest lathe, and jointer. An for things without motors I have two welding machines that can only be operated at reduced power at 110v and others, a big welder and a plasma cutter, that spec a 50 amp 220v circuit.

JKJ

[Jim Becker]

A long time ago when I was first setting up my shop for 240v tools, I made the decision to use twist-locks for all of those connections. Yes, they are more expensive, but I much preferred the positive connection to the outlet. One other thing I did to provide easier "future flexibility" was to bring a tool circuit out to a j-box from the panel and then route to the tool location. Several times this has been quite useful when I wanted to/needed to change the location of a given tool, especially since I have both 20a and 30a tools in play, so just "switching circuits" wasn't going to play.

[Patrick Whitehorn]

Dan,

Do I understand that you want both 240 and 120 receptacles, but only want to run one wire from the breaker box? That is doable without this switch that you're proposing. I would suggest abandoning that idea, entirely - it's very unconventional.

You are correct, it is "doable", but I also want a measure of control over it, hence the switch (This https://www.amazon.com/Leviton-1286-...Leviton+1286-I) With the switch, I can set up the system to have either the 240V receptacle on *or* the two 120V branches on *or* neither on (which is great with an inquisitive toddler around). There is no chance of overloading the system because I forget and leave the TS running while I run over to the BS/MS/RAS, what-have-you. Plus I get two 120V circuits for the price of one 12/3 wire pull!

No. There is no "separate" ground. There is a single ground, which you need to run to the machine REGARDLESS of the plug you choose. The locking plugs have 4 contacts, which allow you access to ground, hot1, hot2, and neutral. Your 240v machines do not require neutral, so the 4th position is not needed (nor do you need to change the cord on the machine). ... Many people get confused on the presence of the neutral on 240V circuits. The neutral is to provide access to 120V. Thus, things like ovens or electric dryers which use 120V light bulbs have that available. Your power tools have no such additional loads - once you rewire the motors to run at 240V, you no longer need 120V, and thus, the neutral is not required.

Electrically, no there is no 'neutral' at home - they are both bonded to the same ground. That said, there is definitely a different wire. I will try to mean the neutral wire (white) when I say 'neutral' and the ground wire (green/bare) when I say 'ground'. And I have read too many times that 240V is hot-hot-ground *and* that 240V is hot-hot-neutral. Electrically (the actual electrons) it does not matter; the NEC might care, but electrically it is all the same. Thus, when I talk about running the ground wire to the machine, I mean "to the machine", not "to the motor". I want that chassis grounded through its own dedicated path for an extra bit of safety.

To select plug ampacity, size the plug to the load, size the receptacle to match the plug, size the wire to match the receptacle, and size the breaker to match the wire. So if your loads are <20A (which they certainly are), use 6-20 plugs and receptacles, 12AWG wire, and 20A double-pole breakers. If you want locking, use the L6-20.

Done. <winks>

All that said, personally, I'd reconsider using 240V, unless you have some equipment that cannot be run on 120V. A properly-sized 120V circuit will provide equal performance to a properly-sized 240V circuit. When people claim that 240V improved the performance of their tools, what they really mean is, "The new, dedicated, properly-sized 240V circuit I just installed performs better than the undersized, shared 120V that I was using, previously".

I would love to live on 120V, but my TS is rated for 16A on 240 ... or 32A on 120V. I have no inclination to run an 8/2 wire simply so that I can use a 120V circuit to feed it (with a NEMA 5-30). That just seems silly when I can run 12/3, use [L]6-20/[L]14-20 plug/receptacle, *and* have two branch circuits that have 20A 120V outlets for other uses. And I agree that a dedicated circuit is better, though some of that performance may be realized by moving equal amounts of power using more conductors, too (two 12-gauge conductors at 20A each versus one 8-gauge conductor at 40A).


Thanks for your input!

[Dan Friedrichs]

There is no chance of overloading the system because I forget and leave the TS running while I run over to the BS/MS/RAS, what-have-you. Plus I get two 120V circuits for the price of one 12/3 wire pull!

Uhhh, that sounds very unsafe

The purpose of the breaker is to ensure you don't "overload" the system. Should you draw more current than the wire is rated for, the breaker trips. It's unlikely that you would trip the breaker, even in the situation you describe, because a when the saw isn't cutting anything, the motor only needs to draw enough power to overcome bearing friction, windage, etc (aka - very little power). So you could, conceivably, leave the TS running without adding much load to the circuit. I would not advocate that, though

That said, you still don't need the switch you propose. Look into "multi-wire branch circuits". Because each half of the double-pole breaker can trip independently, it is possible to add 120V loads. I would be VERY hesitant to use that switch. In particular, the switch is only rated to 16A for motor loads, so you're effectively de-rating the entire circuit to that.

I think you're trying to "solve" a non-existent problem with the switch idea. Install a disconnect, if you like, but I think it will quickly become a PITA to switch your receptacles on and off every time you move from the TS to the RAS, etc...

Electrically, no there is no 'neutral' at home - they are both bonded to the same ground.

While they do get connected together back at the breaker box, they are NOT the same, and there IS a neutral. The neutral carries current in normal operation, the ground only carries current in a fault situation. Because wire has resistance, the neutral may thus develop a voltage on it, in normal operation, while the ground will not.

And I have read too many times that 240V is hot-hot-ground *and* that 240V is hot-hot-neutral.

Every connection requires a safety ground. Loads that are purely 240V (motors) only require hot1 and hot2. Loads that have both 240V and 120V components (dryers, ovens) require hot1, hot2, and neutral. Both will ALWAYS require a safety ground.

I want that chassis grounded through its own dedicated path for an extra bit of safety.

Just to be clear, that is not an "extra bit of safety"; it is absolutely required. You are not proposing anything new. It is required that you have an equipment grounding conductor (aka - a non-current carrying grounded wire) connected to the equipment chassis.

I would love to live on 120V, but my TS is rated for 16A on 240 ... or 32A on 120V.

I agree. Years ago, I (foolishly) converted everything I could to 240v. I would have been better off with a few 240V receptacles for just the larger equipment. My 6" jointer does not need 240

[Art Mann]

Mr. Whitehorn, you don't know nearly as much as you think you do about AC wiring. You would do well to accept what Dan is saying in post #8. For example, there is no safe way to run a three wire circuit that supplies both 120 VAC and 240 VAC. You need 4 wires for both ground and neutral. Regardless of the fact that ground and neutral are connected at a single point only, these are separate wires and serve different purposes. If you don't understand what I just said, you should get an electrician to do your installation.

[Malcolm McLeod]

Patrick,
On you original question, I use the locking plugs. I just feel better about them in use.

I think Dan is trying to steer you in the right direction. Perhaps consider this - - imagine explaining this proposed wiring system to a potential buyer. How many will run?

Also, I'm fuzzy on the economics of this. You didn't describe your wire run distances, panel/sub-panel, available breaker space, etc., but for the cost of the DPDT switch you can buy 250ft of 12/2 wire at BORG. That's a LOT of dedicated 120V circuits, plus you still have the dedicated 240V circuit...?

[Erik Loza]

A long time ago when I was first setting up my shop for 240v tools, I made the decision to use twist-locks for all of those connections. Yes, they are more expensive, but I much preferred the positive connection to the outlet...

+1 ^^^...

Can't comment on your electrical situation but as far as the plugs and outlets go, Twistlocs are the only kind I use.

Erik

[Robert Engel]

Wow, you've made a very simple situation very complicated (+1 on what Art ^ said).

You asked for advice and mine is "Call an electrician".

[Malcolm McLeod]

I have decided that I will pull one or more 12/3 circuits with double-pole 20A breakers for the machines.

Patrick,
Sorry if this seems like piling on, but something was bugging me and it took a few minutes to register. If you pull 12/3 wire (H-H-N-G) from the panel and are operating in 120V mode on your switch with the 2 resulting 120V circuits each pulling 20A (:: 2 tools running), the breaker will support this just fine. However, the neutral WILL be conducting and trying to carry 40A. And the neutral does NOT have current protection on it.

I realize you may feel you'll never load the circuit like this, but it will never meet code, pass inspection, or be safe. I strongly recommend you do not pursue this option.

--Malcolm

[Patrick Whitehorn]

Mr. Mann,
Thank you for your input - please post your bona fides as to why I should take you seriously instead of simply being insulted by your response. I am here to learn and grow; if you would like to help me with that in a respectful manner, I would appreciate your help. If not ... good day.

[Patrick Whitehorn]

Dan
I fear that I might not have been quite as clear as I thought I had been - I have drawn up a quick diagram (excuse the MSPaint) that might show it better. One of the reasons that I want a DPDT switch is because, even though I could use two SPDT (effectively 3-way switches) to do what I want, if I don't trip both switches, one leg of the 240V outlet would be hot ... and that toddler I mentioned before might get curious and jam something into that hot leg in a moment of inattention on my part. The DPDT ensures that both legs are on (and hopefully in use behind a locking plug) or both legs are off.

These two things confuse me, however:

While they do get connected together back at the breaker box, they are NOT the same, and there IS a neutral. The neutral carries current in normal operation, the ground only carries current in a fault situation. Because wire has resistance, the neutral may thus develop a voltage on it, in normal operation, while the ground will not.

... and ...

Just to be clear, that is not an "extra bit of safety"; it is absolutely required. You are not proposing anything new. It is required that you have an equipment grounding conductor (aka - a non-current carrying grounded wire) connected to the equipment chassis.

... if these are both true ... then why do my 240V machines' power cords only have three conductors? (hot, hot, and not-hot <- to avoid the neutral versus ground issue) If the neutral does carry current (return voltage) and the ground does not ... and the ground is required ... but we only have one ... doesn't that mean that the ground (as you said before hot-hot-ground) is effectively carrying current? And then cannot be used to 'ground' the chassis? <scratches head>

The purpose of the breaker is to ensure you don't "overload" the system. Should you draw more current than the wire is rated for, the breaker trips. It's unlikely that you would trip the breaker, even in the situation you describe, because a when the saw isn't cutting anything, the motor only needs to draw enough power to overcome bearing friction, windage, etc (aka - very little power). So you could, conceivably, leave the TS running without adding much load to the circuit. I would not advocate that, though :)

That is totally fair and something that I had not really considered. Good point!

That said, you still don't need the switch you propose. Look into "multi-wire branch circuits". Because each half of the double-pole breaker can trip independently, it is possible to add 120V loads. I would be VERY hesitant to use that switch. In particular, the switch is only rated to 16A for motor loads, so you're effectively de-rating the entire circuit to that.

True, though that is the draw required for my Unisaw ... I had noticed that but I am unsure of how much an issue it might cause. I emailed Leviton to find that switch; I will email Leviton to query them on that point (afterall, what good is a 20A switch that is only really 'good' to 16A?)

I think you're trying to "solve" a non-existent problem with the switch idea. Install a disconnect, if you like, but I think it will quickly become a PITA to switch your receptacles on and off every time you move from the TS to the RAS, etc...

Might do, yes. That said, I can simply remove the switch and have everything hot constantly if it becomes a pain.

Again - thanks!