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.
Installation Procedure for a New Dryer:
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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.
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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.
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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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