I need to instal a receptacle in my 240VAC, 3 phase machine for a 12V, 1A adapter. Adapter is good for 120-240VAC input. I happen to have a 125V, 20A duplex receptacle on hand. Is it okay to use it because of low current or is there an insulation or gap requirement for 240V that 125V will not meet. Thanks.

  • Is this a three phase Y or Delta system? – Nate S. Feb 6 at 0:10
  • It is delta start Y, unless I have it backwards. That should not matter, I think. I use a 3 phase converter that sends L1 & L2 out as I receive if from utility. T3 that is manufactured only goes to motor. I am using L1 & L2 for this receptacle which is identical to how 240V outlets in the shop are wired, except that they are 240V outlet. This receptacle will be inside electrical cabinet oc the saw so will not be available for anyone to accidentally plug a 120V appliance. – Imran Malik Feb 6 at 0:19
  • Got it. Is there any risk of someone trying to plug something else into this outlet, or is it going to be totally enclosed in this machine? Electrical code would say that's absolutely not allowed, because if someone tried to plug in a device that expects 120V, it may well catch fire. But the electrical code is concerned with buildings, and doesn't generally apply to machine internals (though other regulations might). – Nate S. Feb 6 at 0:29
  • I updated my response but you likely answered it before. Yes the outlet is going to be enclosed in the cabinet of the machine. – Imran Malik Feb 6 at 0:38
  • @ImranMalik -- why can't you get a 12V/1A chassis-mount PSU and hardwire it in instead? – ThreePhaseEel Feb 6 at 1:52

Use a 12V/1A enclosed chassis mount (or DIN rail mount, for that matter) supply

Your problem here is that you are trying to apply a "wall wart" in an application (inside a control panel of some flavor) where you'd be provisioning a receptacle solely for the wall-wart's use. This is a waste of a receptacle, and also poses NEMA 5/NEMA 6 confusion hazards, so why not use something more fit for the job instead, such as a DIN rail mounted supply like the one shown below? (It's a CUI PDRC-24-12, BTW, and is fully cULus listed to UL508 for field application in industrial control equipment.)

PDRC-24 series DIN rail mount PSU

Of course, more traditional enclosed chassis mount supplies will work, although they don't usually carry a full UL listing the way the supply I linked does.

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    Thank you. I got same advice from my woodworking forum. I had no clue they are so cheap. So much better solution than my approach. I have DIN rail in machine so ordered one that will go on it. Thanks again. – Imran Malik Feb 6 at 19:31
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    @ImranMalik -- we thank people around here by upvoting and/or accepting their answers :) – ThreePhaseEel Feb 6 at 19:32

Putting a 120V receptacle on a 240V circuit = future guy’s fried 120V appliance when he plugs it in without the knowledge that you have that it’s actually a 240V circuit with the wrong outlet type on it.

You need at least a NEMA 6-15R or 6-20R (looks like standard 120V outlets, except the blades are sideways so you can’t plug in 120V appliances.

  • I just realized even though the wall wart is rated for 240VAC it has two flat parallel prongs. It will not fit in the 240V outlets in my shop as they have one vertical/horizontal opening and the other opening is horizontal. I was just trying to save a trip to town but unless they sell 240V outlets that have two vertical slots this adapter won’t even fit. – Imran Malik Feb 6 at 0:45
  • This outlet is inside the machine electrical cabinet with a screwed on cover. So outlet is not accessible to anyone. – Imran Malik Feb 6 at 0:48
  • OP - Above in the question you said you have a 125V receptacle that you want to install inside your machine where there is only 240V available, presumably by wiring it to available terminals or loose wires already there. Here in the comment I think you are saying you want to plug it into an existing 240V wall outlet. It would help if you clarify, in the question, exactly what you want to achieve and what your constraints are. – jay613 Feb 6 at 2:19
  • Hi Jay, Sorry for the lack of clarity. Yes only 240V in machine and wall wart that is 240VAC capable has prongs that only fit 120V outlet. When I first posted, I was only asking for convenience but then I realized that even if I were to get a 240V outlet (like i have on my shop wall) the prongs of wall wart won’t fit. As I commented below, I have ordered a DIN rail mount power supply. – Imran Malik Feb 6 at 19:37

Can't do that! The reason is keying

The whole point of having different receptacles for different voltages is to provide interlocking so the firestarting thing does not happen.

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And it may seem all clever to do this while you're the only person tending the machine. But what's your sunset plan for this? How do you plan to assure nobody else does something stupid with it? Do you earnestly plan to tear it out if you sell the machine on Craigslist, or give it to your son, or die in a traffic accident and your estate clears it out? Honestly your best plan is to say a sentence or two of words for them that they won't remember. Maybe not you, but somebody is gonna get bit by a 120V socket fed 240V.

And when someone does that, they did everything right. It'd be your fault.

The simple fact is, they make correct receptacles for this. Just use them.

And if you just won't, then OK, solder two #12 wires (none white!) onto the wall-wart prongs, gob it up with a ton of electrical tape, and land the #12 wire on terminal blocks. At least that won't be mistaken for anything other than what it is.

However, I agree with ThreePhaseEel. 12V is an absolutely generic, common voltage and they make hundreds of thousands of different models of 12V power supply that input 230/240V (since that's standard house power on every continent except North America). Just get one of them - any of them - Amazon is awash in unapproved cheap Chinese ones, even this would be better than a suicide socket... many others are RU-Recognized (UL's component certification)... and a few are UL-Listed.

  • Thanks for all responses. I got the same suggestion, of using a proper PS, from my woodworking forum, so I ordered one last night. I am an electrical engr but not an electrician. Even though, I did all my electrical in the shop I always check with knowledgeable folks because I am not familiar with the codes. In this particular case, I really wanted to know if there is a fundamental design diff that makes a 240V outlet different than 120V. If they are not then I would have been willing to take my chances as this outlet is inside my personal machine and is inaccessible due to screwed on panel. – Imran Malik Feb 6 at 19:26
  • I am new here so missed one response. The sunset comment is convincing. Even though, I planned to permanently notate the outlet, I agree it is not worth it. – Imran Malik Feb 6 at 19:42

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