Part of my job is to investigate fires and electrical damage. I've seen a case in a residence where a fire supposedly started in the area of an empty receptacle, and the building neutral connection was bad, resulting in all sorts of voltage fluctuations between the phases. That leads me to ask this question.

I understand that UL 498 involves testing receptacles for withstand of voltages over 1000 volts, but that this test is only for a limited number of cycles. Is there test data out there for 120 volt receptacles exposed to 240 volts for weeks at a time?

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    \$\begingroup\$ There is very little difference between 120 and 240V receptacles. I can't answer your question, but find myself skeptical. Look at a nema 6-15 vs a nema 5-15 receptacle. \$\endgroup\$ – mkeith Jun 1 '17 at 20:03

I would advise you to satisfy your question through some tests that you could do. The basis for your question is an "empty receptacle" which is one where no load is connected and no current flows.

Start with a new receptacle of a similar type. Using a Meg-Ohm Meter at 500 v and 1000v measure the resistance from Hot to Nuetral and Hot to any metal surfaces on the device (ground).

Source a simple step up transformer such as this https://www.digikey.com/product-detail/en/thomas-research-products/120-277-275VA/120-277-275VA-ND/7318416

Connect the transformer to 120 v and the secondary of the transformer to the hot and neutral of the receptacle.

Disconnect the receptacle and re-do the megger tests at intervals of a day/Week/2 Weeks.

I doubt that the result of your experiment will result in any breakdown of the resistance of the receptacle.

Now if the case of your fire was the result of a load being connected to the receptacle and it wasn't empty - as in you are being lied to - that would bring up an entirely different set of questions and cause for failure.

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