We recently moved into a new house with a 3 prong dryer outlet. Our
dryer is a newer model, which has a four prong cord. I bought a 3
prong cord to replace the 4 prong one and found some instructions on
how to do so. However, the one step that I am not sure about involves
the ground and the neutral. I have no problem attaching the left,
right, and center wires to the correct screws. However, our dryer
does not have a ground strap. It does have a green ground wire
running from somewhere inside the case of the dryer out to the ground
screw on the case. Is the dryer properly grounded with this wire in
place as is? From what I have read, the ground strap would have run
from the center white neutral terminal to the case. Do I need to add
something that runs from the center terminal to the case? And in that
case, what do I do with the green ground wire?
Thanks for your help.
Thanks for your question. Yes, the green ground wire has the same
size ring on the end as the other wires that attach to the three
terminals. Should I simply unhook the green ground wire from the
ground screw on the case and attach it, along with the center wire
from the cord, to the center terminal?
<< We recently moved into a new house with a 3 prong dryer outlet. >>
The smart thing to do here is replace the 3-prong outlet with a 4-prong, adding
the necessary ground wire from the service panel if needed. With all the
electronic controls and doodads on new appliances these days it makes sense to
get stray currents from static electricity or whatever diverted to a positive
ground muy pronto.
Of course, you could add a grounding wire to any handy metal plumbing if you
are sure there are no plastic piping interruptions in those lines. Your choice,
and good luck.
It is a violation of the US NEC to use water piping as the ground for a
branch circuit unless it is an underground metal water pipe of at least
ten feet of buried pipe and the connection is made to it within five
feet of were it enters the home.
"250.130 Equipment Grounding Conductor Connections.
Equipment grounding conductor connections at the source of separately
derived systems shall be made in accordance with 250.30(A)(1). Equipment
grounding conductor connections at service equipment shall be made as
indicated in 250.130(A) or (B). For replacement of non–grounding-type
receptacles with grounding-type receptacles and for branch-circuit
extensions only in existing installations that do not have an equipment
grounding conductor in the branch circuit, connections shall be
permitted as indicated in 250.130(C).
(C) Nongrounding Receptacle Replacement or Branch Circuit Extensions.
The equipment grounding conductor of a grounding-type receptacle or a
branch-circuit extension shall be permitted to be connected to any of
(1) Any accessible point on the grounding electrode system as described
(2) Any accessible point on the grounding electrode conductor
(3) The equipment grounding terminal bar within the enclosure where the
branch circuit for the receptacle or branch circuit originates
(4) For grounded systems, the grounded service conductor within the
service equipment enclosure
(5) For ungrounded systems, the grounding terminal bar within the
service equipment enclosure
250.50 Grounding Electrode System.
If available on the premises at each building or structure served, each
item in 250.52(A)(1) through (A)(6) shall be bonded together to form the
grounding electrode system. Where none of these electrodes are
available, one or more of the electrodes specified in 250.52(A)(4)
through (A)(7) shall be installed and used.
(A) Electrodes Permitted for Grounding.
(1) Metal Underground Water Pipe. A metal underground water pipe in
direct contact with the earth for 3.0 m (10 ft) or more (including any
metal well casing effectively bonded to the pipe) and electrically
continuous (or made electrically continuous by bonding around insulating
joints or insulating pipe) to the points of connection of the grounding
electrode conductor and the bonding conductors. Interior metal water
piping located more than 1.52 m (5 ft) from the point of entrance to the
building shall not be used as a part of the grounding electrode system
or as a conductor to interconnect electrodes that are part of the
grounding electrode system." Copyright 2002 the National Fire
As you can see the last sentence forbids the use of piping more than
five feet form the point of entry as a grounding electrode or grounding
Dryers are designed to work with either three or four wires, no need
to retrofit an old installation to conform to a new dryer that will be
plugged into it. (That's why they sell 3 AND 4 wire cord sets!)
You need to check the manual that came with your dryer. If you don't
have one many manufacturers make theirs available on line.
What wiring method was used to wire the dryer outlet? Is it armored
cable, non metallic sheathed cable, rigid metal conduit, or what? The
wiring method used may make it easier to convert the receptacle to four
Thanks for all of the replies. The house is ten years old, so it is
new to us, not new as far as the code requirements for a 4 prong
outlet go. I am not an electrician and do not know anything about the
wiring of the outlet. We just now found the dryer manual and it has a
section of instructions on connecting it to a 3 prong cord. So I am
going to follow those instructions. The instructions show the green
ground wire being left in place attached to the green ground screw on
Thanks for your help and comments.
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