Greetings Lindberg,

Not really a direct answer to your question....but the fact that you were able to plug a 120v appliance into a 240 is kind of scary. They are supposed to use entirely different kinds of plugs/outlets!

Since you recently purchased this place, it makes one wonder about whether this was disclosed, and the nature of the home inspection. One might wonder what ELSE is hidden. Here's to hoping that this turns out to be a minor issue, and that you have nothing else big 'lurking' there...good luck.

Thanks K2. Yeah, it was pretty scarry when I plugged the microwave in....sparks and loud noise. I'm not looking forward to any similar future discoveries. A pre-settlement inspection was discouraged because of the real estate market here in DC, but I'm optomistic because the seller still lives in the building.

You may want to get yourself a digital multimeter that can read AC voltage or a simpler neon light multi-voltage tester available at most good hardware stores.

A standard 15-amp 120 volt socket (NEMA 5-15) will have two vertical parallel slots like this (| |) and also have a third round hole for the ground.

The wider slot connects to the white neutral conductor (grounded conductor) and the narrow slot connects to the black live (or hot) conductor.

You must make sure to preserve polarity when replacing these.

A 15-amp 240 volt socket (NEMA 6-15) will have two slots in tandem like this: - - plus a third round hole for the equipment ground conductor.

The 20 amp version (NEMA 6-20) will have one vertical and one horizontal (| -).

The colors of these wires (in the ones I've opened) are usually black and red. The green is always supposed to be used for GROUND.

Now here is where it gets confusing: The 120 volt/20 amp socket (NEMA 5-20) looks like this: (- |) - a mirror image of the 240 volt 20-amp socket.

A 120 volt socket must NEVER be used on a 240 volt circuit for just that reason - CONFUSION by an end user.

You might want to test all the outlets in your house and have an electrician replace whatever looks bogus (if you don't know how to do it).

Joe, feel free to correct me.

thanks so much sven. that's a lot of info. And, yes, I'll be calling an electrician.