The Definition of Wet Location (Electrical)

Definition of Wet Location (Electrical)

In electrical safety, a wet location is any place where electrical equipment and wiring may be exposed to water or other liquids, or to saturation with moisture. Water greatly increases the risk of electric shock because it lowers the resistance of the human body and provides a path for current to reach ground.

The National Electrical Code (NEC), NFPA 70, defines three types of locations:

• Wet location: installations underground or in concrete slabs or masonry in direct contact with the earth, locations subject to saturation with water or other liquids, such as vehicle washing areas, and unprotected locations exposed to weather.
• Damp location: partially protected locations exposed to moderate moisture, such as under canopies and open porches, and interior locations such as some basements and cold storage warehouses.
• Dry location: a location not normally subject to dampness or wetness, although it may be temporarily damp, such as a building under construction.

Why Wet Locations Are More Dangerous

The current that flows through a person depends on voltage and resistance. Dry, intact skin has a relatively high resistance, but wet skin can have a resistance many times lower. Standing in water or on a wet floor also improves the path to ground. Together, these factors can turn a fault that would cause a mild tingle in dry conditions into a fatal shock.

Wet locations are common at construction sites, car washes, food processing plants with washdown areas, outdoor events, swimming pools, marinas, wastewater treatment plants, and during flooding or firefighting.

Requirements and Standards

Equipment ratings

The NEC requires equipment used in wet locations to be listed for wet locations. Enclosures should have suitable ratings, such as NEMA Type 3R or 4, or IP ratings for water ingress. Receptacles outdoors need weather-resistant types and covers that stay weatherproof while a plug is inserted.

Ground-fault circuit interrupters

A ground-fault circuit interrupter (GFCI) monitors the current in the circuit and cuts power within a fraction of a second if it detects current leaking to ground. GFCIs used for personnel protection trip at about 4 to 6 milliamps. The NEC requires GFCI protection for many wet and damp areas, including outdoors, bathrooms, kitchens, garages and crawl spaces.

OSHA

On construction sites, 29 CFR 1926.404(b)(1) requires either GFCI protection or an assured equipment grounding conductor program for 120-volt, single-phase, 15- and 20-ampere receptacles that are not part of the permanent wiring. OSHA's electrical safety-related work practices in 29 CFR 1910.334 require portable electrical equipment and cords used in highly conductive locations, such as areas flooded with water, to be approved for those locations.

Safe Work Practices in Wet Locations

• Use GFCI protection for all portable tools and temporary power.
• Choose tools, cords and lighting rated for wet use, and inspect them before each use.
• Keep cords and connections off wet floors and out of standing water.
• Use low-voltage or battery-powered tools and lighting where practical, especially in tanks and other confined spaces.
• Wear dry gloves and footwear with insulated soles when appropriate.
• De-energize equipment and apply lockout/tagout before servicing.
• Never touch electrical equipment while standing in water.

Example of Wet Location

A food processing plant hosed down its production area every night. Sanitation workers used a corded pressure washer plugged into a standard receptacle on a wall near the floor drain. One night, a worker felt a shock when touching the washer's metal handle. An electrician found damaged insulation where the cord had been dragged across a sharp edge.

The plant replaced the receptacle with a GFCI-protected, weatherproof receptacle mounted higher on the wall, switched to pressure washers listed for wet locations, and added cord inspection to the sanitation crew's pre-shift checklist. It also reviewed all receptacles in washdown areas and upgraded those that lacked GFCI protection.

Frequently Asked Questions: Wet Location (Electrical)

What is the difference between a wet and a damp location?

A damp location is exposed to moderate moisture but is partially protected. A wet location may be directly exposed to water, weather or saturation with liquids. Equipment must be listed for the type of location where it is installed.

Does a GFCI prevent all shocks?

No. A GFCI limits the duration of a shock caused by current leaking to ground, which can prevent electrocution. It does not protect against a shock from contact between two conductors when no current flows to ground.

Can I use an extension cord outdoors?

Only if it is rated for outdoor use, is in good condition and is protected by a GFCI. Keep connections off the ground and out of water.