3 blade dryers
Updated: Apr 21, 2020
You may have just purchased a home (let's pick a nice city like Sunnyvale) and brought your own dryer to hook it up. But as you attempt to plug the dryer in, you see that the receptacle for the dryer has 3 slots while the plug on your dryer cord has 4 prongs. What in the heck is that all about?
It is a pretty common scenario that I come across in many home inspections. 240 volt receptacles with 3 slots were the standard for houses built prior to the mid 90’s. These receptacles accepted older style dryer cords that had 3 blades (2 hot wires and 1 neutral wire). The neutral wire was then grounded to the metal chassis of the dryer. In 1996 the National Electric Code updated the requirements for dryers, and started to require a separate ground wire in addition to that neutral wire (grounding was shared by the neutral wire prior to the new code). Thus, these new requirements for a separate ground wire gave birth to the 4th prong on dryer plugs, in addition to that 4 slot receptacle.
The main reason for this is now any current that ends up on the metal chassis of the dryer has a dedicated low-resistance wire to take that current back to the panel and transformer and thus open the breaker which shuts off the power. Although neutral conductors are bonded to ground at the main panel, they are not current carrying conductors and not intended for ground fault protection.
The solution is an easy one. You’ll need to replace your 3 prong power cord with a new 4 prong cord to fit that receptacle. Just remove the metal jumper at the chassis and screw the dedicated ground wire onto that threaded stud.
There are many helpful videos on Youtube that will walk you through the process.
Keep those clothes dry and we’ll see you soon!