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?
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.
Go back to the beginning. Your dryer was designed for four, give it what it was designed for! Be safe. Change the OUTLET not the dryer cord. You may or may not need to run a new wire to the outlet.
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 the following: (1) Any accessible point on the grounding electrode system as described in 250.50 (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 Protection Association
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 conductor.
Robert 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 wire.
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?
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 the case.
Following the instructions with that dryer should be safe. It would not be a good idea to assume the same instructions would work safely with another dryer.
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!)
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