How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manufactured and modular homes
When was it first required that 240-volt receptacles for a clothes dryer and range be four slot (equipment ground connection)?
Sunday, January 13, 2019
The requirement for 4-slot receptacle outlets and 4-prong cord plugs began with the 1999 edition of the National Electrical Code (NEC), primarily affecting residential electric ranges and dryers. An older 3-slot receptacle can continue to be used when an old appliance is replaced with a new one, although the cord may have to be changed out if it comes with a 4-prong plug. But often the cord is sold separately from the appliance.
The older 3-slot receptacles provided connections for two hot wires and a neutral, but the 4th slot adds a separate connection for any current to ground.
When installating a new or replacement cord, it’s important to also use a strain relief clamp at the hole where the cord enters the appliance. See our blog post Why is a strain relief clamp necessary for the cord connection to some electric appliances?
The latest edition of the NEC has to be “adopted” by each local building department before it becomes effective in their jurisdiction, and that sometimes happens more than a few years later than the cover date. For more on this, see our blog post Is the latest edition of the National Electrical Code (NEC) the standard used for the electrical system of new homes?
• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •
To learn more about electrical wiring, devices, and receptacles, see these other blog posts:
of Blog Posts
Top 5 results given instantly.
Click on magnifying glass
for all search results.
Buying a home in North/Central Florida? for a team inspection by two FL-licensed contractors and inspectors. Over 8,500 inspections completed in 20+ years. In a hurry? We will get it done for you.