Switch Selectable Box with Two Twist-lock Receptacles

[Joe Hollis]

Hello,

I have three single-phase 240 volt machines that are equipped with twist-lock plugs, but only two wall receptacles. Is it possible to properly rig up a wooden box with two twist-lock receptacles in it so I can leave two of the machines plugged in to the box at all times, the cord running from the box plugged into the wall receptacle, and then use a switch mounted on the box to select either one tool or the other?

I don't want to risk damaging any of the tools, but I do not have the mobility I used to, and it's really hard for me to access the wall receptacle to change the machine that is plugged in there.

Thanks,

Joe H.

[Dan Friedrichs]

...I'm confused. Why is the switch required? You only use one machine at a time, right? If you had 3 receptacles, wouldn't you just plug all 3 machines in and leave them plugged in all the time?

Just buy one of these?
https://www.amazon.com/dp/B00SJESLEG/ref=asc_df_B00SJESLEG5502514/

[Joe Hollis]

Hello Dan,

I only have two wall receptacles, but three machines, so when I want to use the unplugged machine I have to access the wall receptacle and swap.

There is not enough capacity in the electrical panel (so I have been told) to add another circuit. I would like share the one receptacle by using some sort of switch arrangement if I can.

Regards,

Joe



...I'm confused. Why is the switch required? You only use one machine at a time, right? If you had 3 receptacles, wouldn't you just plug all 3 machines in and leave them plugged in all the time?

Just buy one of these?
https://www.amazon.com/dp/B00SJESLEG/ref=asc_df_B00SJESLEG5502514/

[Mark Kanof]

I think what Dan is suggesting is to have one machine plugged into one of your wall receptacles and the other two machines plugged into the y-splitter that he linked to. Then that splitter would be plugged into the second wall receptacle. That way all three machines would always be plugged in. As long as you do not turn on both of the machines connected to the splitter at the same time, you should not have any problems.

[Dan Friedrichs]

I think sometimes people have a difficult time seeing 240v circuits the same way as they see 120v circuits, but there are no special/different "rules" for 240v. Much of the world uses 240v in the way we use 120v in the US.

So: if you had 3 tools that ran on 120v, but only a "regular" duplex 120v receptacle (2 positions to plug into), what would you do? You'd just buy a power strip or splitter to turn the 2 positions into 3 or 5 or 6...

That's exactly what you need to do, here :) But just a power strip / splitter with 240v plugs+receptacles on it.

[Rod Sheridan]

Hi, just add a third receptacle in parallel with one of the existing receptacles.

I only have one 240V circuit that feeds all may machines, and a separate 240V circuit for the cyclone...............Regards, Rod.

[Joe Hollis]

Sorry Dan, I misunderstood,

Thanks a lot for this. I will order one of those cables.

Regards,

JH.


I think sometimes people have a difficult time seeing 240v circuits the same way as they see 120v circuits, but there are no special/different "rules" for 240v. Much of the world uses 240v in the way we use 120v in the US.

So: if you had 3 tools that ran on 120v, but only a "regular" duplex 120v receptacle (2 positions to plug into), what would you do? You'd just buy a power strip or splitter to turn the 2 positions into 3 or 5 or 6...

That's exactly what you need to do, here :) But just a power strip / splitter with 240v plugs+receptacles on it.

[Carlos Alvarez]

I'm about to do something like this because I have one 240v outlet. It feeds the nearby compressor, welder, and plasma cutter. OR I can plug in a 20' #10 SJ cord which runs outside to the shop space ten-ish feet away. That powers all the wood tools. I'm going to either just change out the box to two-gang and put another outlet in it, or build a pigtail to take the single connection and make two. I have the parts for all these options sitting around. Now in MY case, I might want a switch or something because the compressor is a true 5HP, using a measured 4000 watts, so there's not enough left for most of the other tools. Or I just have to remember to turn off the compressor's own switch.

Or I could stop being lazy and put in another 240 circuit. The main panel is directly behind the existing plug, just poke in and add breakers.

[glenn bradley]

I have daisy-chained a second receptacle off of one I put in during a shop remodel. I plug two unrelated machines in that are never used at the same time and have never had an issue.

[James Biddle]

My guess is the reason you want to build one is that you could not find a 240 Wye-splitter cable here in the US. I suspect it's because most 240 circuits here are considered dedicated and the UL listing for such a Wye is not possible. That said, what you're looking to do already exists, but buying a manual transfer switch would be cost prohibitive from your post. Having a qualified electrician add another receptacle to the existing circuit is the recommended procedure, because the supply wires and breakers need to be evaluated prior to expansion. Yes, many here will give you advice to go ahead, but it's not advice that takes into account your particular home. I think someone named Julie posted something about taking online electrical advice with skepticism...that was good advice.

[Dan Friedrichs]

James, the Amazon link I posted above is a UL-listed 240v wye splitter...

There is nothing about 240v that requires dedicated circuits. Much of the world uses 240v for general-purpose convenience use the way we use 120v. Nothing to be skeptical about :)

[James Biddle]

I stand corrected about the splitter, but I still don't think it's a good idea to seek electrical advice here. Also, it's because we use 120 as our general purpose voltage that makes our 240volt circuits more unique and typically dedicated, unlike the rest of the world.
James, the Amazon link I posted above is a UL-listed 240v wye splitter...

There is nothing about 240v that requires dedicated circuits. Much of the world uses 240v for general-purpose convenience use the way we use 120v. Nothing to be skeptical about :)

[Carlos Alvarez]

I never even thought about buying a splitter, simply because I have the parts and knowledge to make my own. But then I realized that I think I may have some down in one of the server rooms, unused, because they aren't uncommon in that environment.

[Don Bullock]

I have one 220 floor plug. My jointer and table saw needed to be plugged into it. The “Y” connector that Dan linked to works perfectly since I only run one machine at a time. It’s good quality as well.

[joseph mansker]

I don't disagree with James on his point regarding electrical advice if you do not do further research. Most building codes require separate circuits for 240v applications such as your dryer, electric range/oven, water heater, etc. Even your circuits for your refrigerator, freezer and dishwasher are dedicated circuits although they are normally 120v. I use dedicated 240v circuits in my shop because its my choice to do so and its good practice. Although, I have to say that I rarely have two machines running at the same time. But I am a conservative guy. Safety first.
Joe

[Carlos Alvarez]

There's nothing unsafe about splitting an outlet, and code doesn't apply to things you plug into an outlet. It's about things that are hard-wired. Even if you overload the circuit, you just trip the breaker.

[Matt Mattingley]

I just built this power bar splitter this past weekend. It wasn’t cheap, just over $300. Each receptacle(wiring device) has a 30 amp rating and the cord is only 14 gauge, But it has only 6amp fuses prior to it. If I counted each plug that went into that power bar and the receptacle for that Power bar it would be pushing $500. Each female cost $48 each male $38. L17–30’s. All Hubbell.

387626

[Doug Dawson]

I don't disagree with James on his point regarding electrical advice if you do not do further research. Most building codes require separate circuits for 240v applications such as your dryer, electric range/oven, water heater, etc. Even your circuits for your refrigerator, freezer and dishwasher are dedicated circuits although they are normally 120v. I use dedicated 240v circuits in my shop because its my choice to do so and its good practice. Although, I have to say that I rarely have two machines running at the same time. But I am a conservative guy. Safety first.
Joe

To be even more explicit, the current NEC code (in the United States) requires that each 240V receptacle be on its own breaker. If you violate this, and something happens to your house (fire?) even if it has nothing to do with your plugs, insurance companies are always _gleefully_ looking for ways to deny claims.

[Carlos Alvarez]

And to continue the explicitness, that's for hard-wired receptacles, not extension cords or multi-outlet cords. Per our home inspection people, the multi-outlet SJ cords I have laying on the ground going to a single outlet are not covered by any code requirements. The key is whether they are "permanent." In our area, commercial facilities have a 30 day limit on "temporary," but they said nothing like that applies to residential.

States and regions may vary.

[David L Morse]

To be even more explicit, the current NEC code (in the United States) requires that each 240V receptacle be on its own breaker.

Are you sure about that? Please point to the specific statement in the code that you think requires that. My understanding of the code is that there is no difference between 120V and 240V circuits.

[Van Huskey]

To be even more explicit, the current NEC code (in the United States) requires that each 240V receptacle be on its own breaker.


Please cite the applicable NEC section.


Edit: Consider this. What difference is there in a 240v 4 wire circuit and a 120v multi-wire branch circuit inside the walls?

[Carlos Alvarez]

I should clarify my post... I didn't mean to suggest that he's right about the 240 dedicated breaker requirement, but that despite that, if true, plug-in cords aren't covered. I've never found anything that says you must have one breaker per receptacle, but it's so hard to prove a negative. In any case, cords are not prohibited.

[Dan Friedrichs]

Doug, where does it say that?

(It doesn't)

Moreover, what exactly is the risk? If you overload a 120V circuit, the breaker trips and prevents potential danger. If you overload 240V circuit....the breaker trips and prevents potential danger.


As I said earlier, people seem to lose their minds (and their logic) when talking about 240V...

[Matt Mattingley]

Doug, I think that’s only for home appliances. You can’t have your dryer on the same circuit as your AC unit. Or your welding plug in your garage on the same circuit as your stove. Do you have the NEC reference number?

[Van Huskey]

Doug, I think that’s only for home appliances.

That is likely the source of the confusion. Most homes have nothing but dedicated 240V circuits because they only have 240V circuits for appliances that are required to have dedicated circuits.


Note one ALWAYS has to check local codes and there are some that require dedicated circuits for ALL (120 or 240) runs over a certain ampacity, usually, this is 20 amps.

I go back to my illustration using the 120V multi wire branch circuit. Many modern kitchens will have them in order to economically meet the requirement for 2 circuits to the kitchen countertop. You have the same 240v potential there as in a 240v circuit.

[Carlos Alvarez]

As I said earlier, people seem to lose their minds (and their logic) when talking about 240V...

That is SO true, but I'd extend that to anything outside of normal household circuits. I had a long conversation with a friend about powering his travel trailer (120v 30a) at home. He just couldn't wrap his head around any of the current requirements, what can run from a 15a, 20a, or 30a outlet, etc etc. Normally he just gets it. This happens to me often.

[Matt Mattingley]

That is SO true, but I'd extend that to anything outside of normal household circuits. I had a long conversation with a friend about powering his travel trailer (120v 30a) at home. He just couldn't wrap his head around any of the current requirements, what can run from a 15a, 20a, or 30a outlet, etc etc. Normally he just gets it. This happens to me often.
As I posted (post #17) L17–30 splitter cord... add a little bit a three phase and 600 V and the confusion gets a little more. That little cord will run almost 15 hp of machinery. It’s restriction is the cord. It could run up to 30 hp of machinery if the supply, the fused disconnect, fusing and wiring were all adequate.

There are guys who run 20 hp 3p in their single phase shops.

I believe under the NEC the feeder line is only allowed to be 250% of device load potential.

[Doug Dawson]

Are you sure about that? Please point to the specific statement in the code that you think requires that. My understanding of the code is that there is no difference between 120V and 240V circuits.

I went to look at the nfpa.org document that I was using before, and it is currently a giant pile of dysfunction, i.e. unreadable on my laptop. What is up with those guys.

I wanted to do what some of y'all are doing, or at least have it as an option, and it was a nogo re passing inspection, with the argument as I stated. I understood why, and I agree. What I will do is print out all the replies to my post, and present them as proof to the code inspector that everything should be okay. That should be sufficient. Thanks!

Ugh, I can't see as well as I used to. Don't ever get old. Somebody come over here and help old Uncle Cletus.

[John Lanciani]

NFPA70 2017 table 210.24 lists the acceptable number of taps on 15, 20, and 30 amp branch circuits as 14 regardless of voltage. There is no rule mandating only one outlet on a general purpose 240 volt branch circuit.

[Rod Sheridan]

I just built this power bar splitter this past weekend. It wasn’t cheap, just over $300. Each receptacle(wiring device) has a 30 amp rating and the cord is only 14 gauge, But it has only 6amp fuses prior to it. If I counted each plug that went into that power bar and the receptacle for that Power bar it would be pushing $500. Each female cost $48 each male $38. L17–30’s. All Hubbell.

387626

Wow Matt, next time use straight blade devices...........Rod.

[Van Huskey]

There is no rule mandating only one outlet on a general purpose 240 volt branch circuit.




This is almost certainly the source of the confusion. A home would rarely have a general purpose 240v circuit in it.

This certainly doesn't rule out that Doug's AHJ doesn't take a different view of the matter based on local code. I am guessing much higher than 95% of new homes in the US use NM cable for the majority of their wiring, but not in Chicago.

[James Biddle]

The point of contention would be whether the AHJ will consider the circuit(s) to be for motor control or general purpose. Article 430 covers motor circuits and has very different requirements than for general purpose covered in Article 210 (and others). Our inspector allowed them in our shop because we showed that we had dedicated circuits for all equipment except for mobile equipment with under 5hp motors. Plus, we had multiple general 240 volt circuits to alleviate other his other concerns. I used that same methodology on my home basement and garage circuits. This is not advice, but an alternate viewpoint.