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When I search for replacement plugs at Home Depot or Amazon (US), all I see are plugs rated at 125V. Even plugs marketed as "heavy duty" are still only 125V. Here is one such example. The only ones I've found rated for higher voltages are the big 20-amp plugs with non-vertical prongs. Yet all kinds of devices around the house are rated for 110-220V, even ones with small, flimsy plugs.

Why are the bigger and seemingly more sturdy replacement plugs only rated at 125V? Is it just a conservative rating? I had been under the impression it was more the wire and power transformer you have to watch out for, not so much the plug.

The reason I ask is because I would like to replace a plug on a device with a 110-220V power supply, that I would conceivably take abroad some time. Of course I would use the appropriate plug adapter.

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This is a code issue. By code, certain outlets should only be used on a 120 V circuit. And a different outlet should be used on a 240 V circuit.

If the 120-V outlet were used on a 240-V circuit, somebody could plug in a device that isn't rated for 240-V. This would likely damage the device, and could cause further damage like starting a fire or electrocuting the user.

Your example plug is designed to fit the NEMA 5-15 outlets that are commonly used for 120 VAC, 15 A circuits in North America. Therefore retail vendors describe them as "120 V" plugs.

enter image description here

(image source)

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    \$\begingroup\$ I think you missed the point. The OP wants to use a device that is rated for either 120V or 220V, installing a 120V plug permanently and using a plug adapter when necessary for 220V. The OP wants a plug that is physically compatible with 120V receptacles but electrically rated for 220V use. \$\endgroup\$ – Elliot Alderson Jun 11 at 17:03
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    \$\begingroup\$ @ElliotAlderson, okay, but most manufacturers aren't going to give a rating beyond the normal use conditions (because nobody wants to over-reject product). Using this product at 240 V would be out of spec. I explained the reason why the manufacturer would market it the way they do. \$\endgroup\$ – The Photon Jun 11 at 17:06
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    \$\begingroup\$ @ElliotAlderson: There's no place to use such a plug. Physically compatible with 120VAC socket, but with 220VAC on it is an absolute NO when wiring a house. There's no point in rating the plug for 220 because you can never (by code) have anyplace to plug it in that will give it 220. \$\endgroup\$ – JRE Jun 11 at 17:42
  • \$\begingroup\$ Can I take your answer that it's a code issue to also mean, by extension, that it is probably not a physical limitation of the plugs (assuming you use the correct plug adapter for 220V countries)? Of course, I realize this is not a sweeping generalization someone can make; just looking for some guidance. \$\endgroup\$ – Anthony Jun 11 at 18:49
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    \$\begingroup\$ @JRE No, you are not getting the point. I never said that a receptacle designed for 120V would have 220V on it. And there is a point in rating a plug for 220V if it can be used with an adapter for 220V in another country. \$\endgroup\$ – Elliot Alderson Jun 11 at 18:55
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I think the answer boils down to cost. There is no real incentive for a manufacturer to certify a plug to 220V if 99.999% of the users will only use it for 120V. The situation you describe is exceedingly rare.

It might be better if you permanently attach a plug compatible with European 220V receptacles and use an adapter in the US. You should be able to easily find the plug rated for 220V, since that is its normal use case.

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  • \$\begingroup\$ What's ironic is that the reason I want to replace the plug is that the manufacturer accidentally sent me a power supply with a European cord/plug, and I thought no problem, I'll just replace the plug. \$\endgroup\$ – Anthony Jun 11 at 17:17
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The US has a ~120V residential power distribution system, with 220V available for high power applications, and other voltages and systems available for industrial and lighting applications.

Because of that, the vast majority of outlets and plugs are rated for 125VAC. Since manufacturers want to sell their products around the world, more and more devices are "universal input" meaning something like 85-264VAC.

There is a use case for US style outlet strips that are rated for higher voltage. That is when you are abroad (e.g. in Europe) and want an outlet strip for your universal input US style plug devices. Then you can use a single adapter and get a strip of US style outlets. These type of power strips exist, and you can find them online.

However, it is likely difficult to find standard US style outlets rated for 220VAC, since it could cause damage or fire if a 110VAC only device were plugged into it while powered at 220V.

As for plugs, if the device itself is rated for universal input, then it's likely that the plug and wire is fine for use with an adapter or outlet strip that converts 220V outlets to standard US style outlets. There are thousands of people that do it every day with laptop and phone chargers.

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  • \$\begingroup\$ The OP is not looking for a "US style" receptacle rated for 220V, they are looking only for a plug. \$\endgroup\$ – Elliot Alderson Jun 11 at 17:04
  • \$\begingroup\$ @ElliotAlderson Fair enough, edited to add additional comment on plugs. \$\endgroup\$ – John D Jun 11 at 17:10
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Yet all kinds of devices around the house are rated for 110-220V, even ones with small, flimsy plugs.

A big reason for this is international markets. Where I work we sell to europe and the US, so all of our products need to work for both voltages. Otherwise, it becomes confusing with the need to stock two separate products. I'd imagine that this is a big reason why your devices work for both.

Why are the bigger and seemingly more sturdy replacement plugs only rated at 125V? Is it just a conservative rating? I had been under the impression it was more the wire and power transformer you have to watch out for, not so much the plug.

In the US the standards and codes were developed around 120V. Plug width is determined by the voltage somewhat, as electricity can arc through air and a wider spacing supports higher voltages. In the products I build, If I use a higher voltage, I have to make a wider air gap between conductors. This and other factors like cost determine what plugs we use.

Normally products come with a C13 or C14 power connector on them, and then the cord determines what it can be plugged into. The devices can autoswitch between voltages. Some of our products cannot, they have a manual switch to determine the voltage. If we needed a higher amperage, we go to a C20 style, since most circuits only support 20A, you see most products supporting C13/C14

enter image description here
Source: https://www.digikey.com/product-detail/en/qualtek/703W-00%2F08/Q336-ND/1164207&?gclid=EAIaIQobChMIu_b6r_bh4gIVkvhkCh2QBgTxEAQYAiABEgI8-PD_BwE

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  • \$\begingroup\$ Note, OP's example has a dielectric withstand rating of 2000 V. I don't know if higher values are required in 240-V jurisdictions, though. \$\endgroup\$ – The Photon Jun 11 at 17:15
  • \$\begingroup\$ Your point about the gap between the prongs and the potential for arcing in the air makes me wonder if using the appropriate plug adapter when on a 220V circuit would "solve" the problem by widening the gap. In which case I would conclude that it's probably okay to use a plug rated for 125V on a 220V circuit with the right plug adapter. \$\endgroup\$ – Anthony Jun 11 at 17:24
  • \$\begingroup\$ @ThePhoton I usually go off of the listed ratings, I'd imagine most of the plastics used in plugs have higher dielectric ratings and the plugs wider gaps than what is required. \$\endgroup\$ – Voltage Spike Jun 11 at 17:29
  • \$\begingroup\$ @Anthony Most plugs are rated for 250V so they can sell them in all markets. \$\endgroup\$ – Voltage Spike Jun 11 at 17:30

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