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Electric Dryer Wiring

Electric dryers typically require a dedicated 30-amp, 240-volt breaker.  The wire supplying power from the breaker panel to your dryer outlet will usually be a 10/3 Romex cable (Blk wire- hot, Red wire - hot, White wire - neutral, Bare copper wire - ground).

New dryers do not come with a power cord.  That's because until recently, homes were wired with two different receptacle styles: 3-prong and 4-prong.   Knowing that homes had a variety of outlet types, it didn't make sense for appliance manufactures to pre-wire the stove with one or the other.  The 4-prong plug adds a safety ground wire in addition to the two hots and neutral found on the 3-prong plug. Below are pictures of both a 3-prong and 4-prong style outlets with respective labeling.  With a voltmeter you can check for proper voltage on the wall outlet before plugging in your appliance.  You should measure 220-240VAC between lines (hots), and half of that voltage if you measure between either of the hots to neutral.

3-prong dryer outlet4-prong dryer outlet       

Installation Procedure for a New Dryer:

3-wire dryer hookup 

If wiring a newer dryer into an older home, containing a 3-wire outlet, you can do so with the diagram to the left.  The dryer will need to have a copper grounding strap between neutral and the green grounding screw. The grounding screw will connect directly to the dryer chassis or frame.  The hots (black and red) are connected as shown and the neutral wire gets tied to the center lug.

Another option would be to upgrade the 3-prong outlet in your house to a 4-prong.  Once you do that, you can follow the 4-wire hook shown below.

 

If you have a 4-wire outlet in your house and are using a 4-wire cord to your dryer you can follow the diagram to the right.  You should remove the copper ground strap between neutral and the green grounding screw.  Once that is done, the two hots (black and red) are connected to the outside lugs.  It doesn't matter which one is on the left versus right.  The neutral must be connected to the center lug and then the green wire connects to the ground lug as shown.
4-wire dryer connection 

 

History of 3-wire vs. 4-wire dryer wiring:

In all houses the neutral wire and the ground wires are connected together... but ONLY at the main panel.

Not long ago houses were being built with a 3-prong dryer receptacle, while mobile homes were required to have a 4-prong receptacle. The 4-prong receptacle has a separate prong for the ground wire, the 3-prong receptacle either didn't use the ground, or the ground was tied together with the neutral.

With the 1996 National Electrical Code revision they stopped allowing this loophole in an otherwise sensible wiring system. Now all dryers (and electric ranges) must be wired with a 4-prong outlet.

 

 

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