One of the most common write-ups on inspection reports are ungrounded, three-slotted outlets. Grounded outlets have been required by the National Electric Code (NEC) for a number of years. The purpose of grounding is to improve the safety of a home’s electrical system. I want to talk a little about these grounded and ungrounded outlets
Three-slotted outlets are the outlets with three slots (as opposed to two-slotted outlets which only have two slots). Please note that just because an outlet has three slots does not mean that it is actually grounded. In order for it to be grounded, a three-slotted outlet must have three wires attached to it: a hot (black), a neutral (white), and a ground (bare, no insulation). (See the photo below.) In other words, a two-slotted outlet cannot be grounded, and a three-slotted outlet can be either grounded or ungrounded
Two Types of Grounding
Grounded outlets improve the safety of the electrical system in a couple of ways. There are two types of “grounding” and these terms are often confused. (See my post about the difference between Grounding and Bonding for a more detailed discussion.)
The first type of grounding is provided by the home’s grounding system. This provides a safe path for an electrical surge (such as one caused by a lightning strike) to be safely discharged into the ground via the ground rod which is buried in the ground. Without grounding, a dangerous electrical arc and serious damage could occur in the home due to a voltage spike caused by a lightning strike or other electrical surge.
The second type of grounding refers to grounded outlets. Grounded outlets allow an electrical fault to be cleared (a breaker to be tripped) if a loose hot wire comes into contact with the outer metal frame or body of something such as a refrigerator or washing machine. Without grounding, the circuit remains live, and someone who touches the appliance (with a hot wire touching the frame) could receive a dangerous (often fatal) electrical shock.
On a grounded outlet (see picture above), there are three slots. The more rounded slot is the grounding slot. The wire (the equipment grounding conductor) that is connected to this slot goes back to the electrical panel. When things are operating properly, there is no voltage or current on this wire. However, when a fault occurs, this wire provides a return path for the current to return to the panel. Since the wire has almost no resistance, the current will be very high, thus tripping the breaker and shutting off power to the faulty equipment such as a washing machine or refrigerator. In this way, the risk of shock or electrocution has been removed, so no one will be hurt if they touch the piece of faulty equipment.
Why Are Grounded Outlets Safer?
When everything is operating properly, there is no difference between a grounded and an ungrounded outlet. Also, if the device that you have plugged into the outlet (even a three-slotted outlet) only has two prongs, then there is no difference between a three-slotted outlet and a two-slotted outlet. The problem with ungrounded outlets is when there is a faulty piece of equipment plugged into the outlet. As discussed above, a grounded outlet will immediately cause the breaker to trip when the fault occurs or as soon as the faulty equipment is plugged in. This tripping of the breaker will remove the shock or electrocution hazard from the device. Ungrounded outlets have no such protection, so the faulty equipment will remain energized and will continue to be shock or electrocution hazard to anyone who touches it
Are Ungrounded Outlets Unsafe?
That being said, are ungrounded outlets unsafe? They can be, but many items only have two prongs, so the grounding slot is not even used when these two-pronged devices are plugged into them. However, plugging an item with three prongs into an ungrounded, three-slotted outlet or into a two-slotted outlet by using an adapter creates a situation that is not as safe as plugging the item into a grounded outlet – if the item is damaged or faulty. (NOTE: An ungrounded, two-slotted outlet is not against code, but an ungrounded, three-slotted outlet is a violation of code.)
In order to improve the looks of their homes, many homeowners buy new, clean three-slotted outlets and install them where there was previously only a two-slotted outlet. This should not be done since it can give people a false sense of security by making them think it is a grounded outlet.