Expert: Master Bob - 8/6/2004

Question
I have a dryer that I purchased used.  The gal I purched it from said it was only a year old.  When I got it home it only had a 3 prong cord.  My newer home has a 4 prong outlet.  The applicance store said I could change the prong cord out to a 4 prong cord. When I took off back of dryer there were 4 wires but only 3 prongs going into back.  Dryer is a 120/240 v.  What do I do with the 2 prongs in the middle?  Put them on top of one another?  

Answer
Hi Jan,

 Just stopped by my office for lunch break...saw your question come in.

 With the new Codes...and the exceptions to them - it is hard to buy a NEW dryer that comes with the cord already attached...most manufacturers intentionally have the cord as an "optional" hook-up item so that the user can then choose to install their own 3 or 4 prong cord. IF they are installing it a new home or in new construction...then by Code - it MUST be a 4 prong hook-up (this also applies to most ranges/stoves as well..)

 It is very likely the used dryer you just bought is fairly new...but the former owner had an older home with a 3 prong hook-up so she bought a 3 prong cord....under the "grand-father" policy.

 Based on your description...your newer home is up to date electrically...and has the 4 prong receptacle outlet for a dryer. This is a good thing....so now you'll have to convert this new dryer back over to a 4 prong hook-up.

 At the dryer connections - the main difference between a 3  wire hook-up and a 4 wire is that on the 3 - the neutral and ground are one and the same....and a metal strap (or sometimes green wire) bonds the dryer's center neutral connection to the outer metal frame off the dryer.

 On a 4 wire setup...this jumper or metal srap is NOT used...the cords neutral (or white if colored) will hook to center connection and the cords green ground wire will hook to the metal frame (usually there is a factory supplied green screw on the outside frame for this ground connection) In a 4 wire hook-up....the neutral and ground do NOT want to both hook to the same connection.

 To get an illustration of the difference between a 4 wire hook-up and a 3 wire hook-up at the dryer connections, please see the 3 and 4 wire links at :

http://www.applianceaid.com/general.html#3to4

 Hope this helps...if you need more details, please follow-up.

Best Wishes,

Bob Osgood
Master Electrician

RKO ELECTRIC

www.rkoelectric.com