New cooking top on old 200V plug - DIY Chatroom

sahucd · 08-22-2008, 02:55 PM

Hi,

my girlfriend just moved in a old Victorian house and I bought her a radiant cooking top. The current electrical stove is connected to a old 3 prongs plug (220V / 50A) that is angular like that:

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Problem is that all cable coming to that plug are black (doesn't help)

The cooking top has 3 wires: black, red (hots) and green (ground). I'd naturally think the 2 angular prongs are the 220V hots (and I can plug the red and black cables on those) but I am not sure about the bottom prong: If that's a neutral then that would not be a good idea to plug the green/ground cable on it I guess.
Shall I then just not use the bottom one? (I can try to ground the green cable on another ground somewhere).

daxinarian · 08-22-2008, 03:17 PM

There is a standard for how the outlet is supposed to be wired (but I never trust that the previous person knew what they were doing).

220 is almost always 2 hots and a ground, alternately it can be two hots, a neutral and a ground. Here is what you do. Get yourself a voltage meter and check the voltages between the prongs. The two hots will be ~220 and between a hot and ground you will get ~110.

Another option is to get a voltage detector, these beep or flash when they sense voltage. check each wire, the one that doesn't beep is your ground.

theatretch85 · 08-24-2008, 04:50 AM

220volt plugs:

When the Center pin is:
Flat Blade = 50 Amp Neutral
Right Angle Blade = 30 Amp Neutral
Round Pin (or U Shaped) = Ground

What you have is a 50 Amp 120/240 volt plug. Do you see a 4th wire in the box? If you do then its probably a ground and you should use that for the ground. However, I think you should be ok using the neutral wire as your ground, since there are no other outlets on this circuit (or at least there shouldn't be) and it should tie into the ground back at the main panel.

It sounds like you don't have a cord on this new cooktop yet; if you have the 4th wire in the box for the ground, i'd wire in the 4 wire outlet now which is the new code from the NEC, though most place won't require that to be the case for quite some time. Then just wire on a 4 wire cable to the cooktop and use the green wire (in the event your outlet box has another wire in it),

TazinCR · 08-24-2008, 08:35 AM

If there is anything 120V on the range top outlet,clock etc. you must use the neutral. It is a grounded conductor.