The previous owner of this house disconnected the three prong 125/250 V receptacle from the wires before he left. My dryer has a 3 prong cord and matches the receptacle. I need to rewire the receptacle. The wall box has 4 wires. Red, black, white and bare copper. Which wires go to the receptacle and which one is not needed and stays unattached to anything in the wall box after I hook up the receptacle. I suspect the bare metal ground is not needed here but want to be sure. Also does it matter to which terminals I attach the remaining three wires. I suspect I attach the red and black to the w similar appearing contacts and the white to the dissimilar contact. Please help thanks. Jonathan

The most recent edition of the NEC (Electrical code) requires 4-prong range and dryer receptacles in all new installations, so this is a great opportunity to bring your receptacle up to code.

Buy a four prong receptacle and a new 4-prong cord for your dryer. It should be intuitively obvious how to wire it up, but ask the hardware store guy if you aren't sure.

Another important thing is to remove the "bonding screw" that connects the neutral wire to the frame of the dryer. (This screw was required for a 3-prong plug, but must be removed when you install the 4-prong plug)

Well a three prong recep. Would not be rated 125/250. Just wouldn't.

Usually the round pin is ground. It should be connected to the screw on the outlet first and also bonded to the box if metal.
The other two would be brass in color and they can be connected to Red or white.

White or neutral should be capped off. You should make sure this is attached to the neutral or usually the ground/neutral bus in the main panel.

Can give more help if needed.

PS: Agree with the above post. Change to 4 prong.

[QUOTE=KeepItSimpleStupid;2130138]Well a three prong recep. Would not be rated 125/250. Just wouldn't.

Old dryer and range receptacles were 3-prong, and were rated 125/250. The neutral was bonded at the appliance, and served as a ground.

According to most sources, this was written into the code during WW2 in order to save a small bit of copper. (this may be an urban legend, someone needs to check old NEC's for when this was first allowed)
In the 1990's, this was finally corrected, and all new construction requires the ground and neutral to be separated.

Quote:

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Originally Posted by KeepItSimpleStupid

Well a three prong recep. would not be rated 125/250. Just wouldn't.

Usually the round pin is ground. It should be connected to the screw on the outlet first and also bonded to the box if metal.
The other two would be brass in color and they can be connected to Red or white.

White or neutral should be capped off. You should make sure this is attached to the neutral or usually the ground/neutral bus in the main panel.

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Sorry KISS, I know Bob corrected this but I really feel the need to clear it up a bit.

Older range and dryer receptacles were "non-grounding" 125/250v with two hots and a neutral. The advice to cap off the neutral is quite dangerous. The neutral is required in these older circuits. It was the ground wire that was allowed to be omitted.

Thanks.

I can't believe someone actually said "ask the hardware store guy". Aren't hardware stores where the "guy" wires up a cord with two male ends for Xmas decorations?. sheesh