How to Replace a Mismatched Dryer Cord and ReceptacleNovember 5, 2016 • By The Internet Electrician
What do you do when your new dryer cord does not match the existing receptacle in your home? This situation came up recently when some friends of mine purchased a new washer and dryer set for their home here in the valley area of Phoenix, Arizona.
During a conversation over dinner, it was mentioned that the new dryer had a 4-prong cord and plug, (NEMA 14-30R) but the receptacle outlet in the home was only a 3-prong receptacle (NEMA 10-30). What the installer chose to do was to replace the 4-wire cord and plug with a 3-wire to match the existing receptacle. The installer informed my friends that this was a good solution, and that he knew what he was doing.
This got my attention for a few different reasons, but the main concern I had was this; the person installing the appliances probably has done this many times, but isn’t likely a licensed electrician so may not be aware of what should be done in this situation, and the ramifications of not doing it correctly.
I decided to check out the installation to ensure the connection was safe. We pulled the dryer out and I opened up the outlet box to see what supply wire was there, and what type and size of cable was present.
This home was built in 1999 so I assumed the wiring should meet the code rules of the day. I found that there was a #10/3 cable with ground, but the ground wire was just tucked into the back of the box and the receptacle was connected to the red and black (hot wires), and the white neutral or “grounded conductor”.
Current electrical code regulations require that an outlet for an electric dryer must be of the NEMA 14-30R configuration, which is two hot wires, a neutral (grounded), and a ground (grounding or equipment ground) conductor.
Without that ground wire, the appliance needs to have the frame grounded so the code makes an exception. Simply put, it states that if the outlet and cable provided for the dryer connection is of the older style 30A 125/250V (NEMA 10-30), then it will allow the connection of the dryer using a 3-wire cord and plug assembly provided you follow the manufacturer’s supplied diagram for a 3-wire connection.
Upon my investigation, the installer did make the connections and the internal wiring change to accommodate this, which amounts to bonding the neutral conductor of the supply circuit to the dryer frame. His only mistake then is not checking the supply cable to see if the outlet could be changed to meet current code standards instead of changing the cord on the dryer.
The effort and cost required to do that would be equal, only that he wasn’t likely qualified to work on a home’s electrical system. What should have happened is that he enlisted the opinion and services of a qualified person to assist with this installation.
So with the decision to change the cord and receptacle back to the 4-wire type, I set out to make things right. Should you ever encounter this same situation, the video below demonstrates what should be done.
Why Was This the Best Solution?
To wrap this up, I’m going to attempt to explain why this is the best solution to this fairly common issue when connecting newer appliances to older electrical systems.
Electrical codes evolve over time, as we learn more about electricity, and how to protect ourselves from the hazards that it can present.
One of those changes was the realization of the need for, and putting into practice the use of ground wires, earthed, or equipment ground wires.
Systems function quite normally without ground wires, but the function they perform is a safety measure for when things go wrong. In a 3-wire dryer connection, you are using the grounded conductor (the neutral or white) wire for both an intended path for current flow, but also as the equipment ground conductor for the dryer frame. Sure, they are really the same as they are bonded or connected together as one common point in the main service panel.
However, the code rules of today say that is the only point that neutral and ground should be connected. Connecting a dryer in this way creates a second bond point, and without getting into the theoretical side of this, should something go wrong somewhere in the system, this can create dangerous scenarios, such as floating ground currents, or fault current finding a way to ground taking paths that it shouldn’t.
So when an appliance is connected in this way, you are trusting that the neutral connection in the panel is a good sound connection, and you’re trusting the same guy that connected the A/C to the dryer breaker, and vise-versa. (Watch the video above for the rest of the story)
Think of it this way. You have two lanes on a road, and you have a center lane that is shared for either direction to use when making left hand turns. However the road usually has a ditch that you can take if suddenly the normal traffic lanes are blocked. Connecting the appliance in this manner effectively takes away the ditch as an emergency escape route!
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