There isn’t really anywhere in the National Electrical Code that specifically covers ants, rodents, snakes, scorpions and other pests invading your home’s electrical equipment. However, as someone who has worn many hats and worked as an electrical contractor and insurance investigator, I’ve had some strange calls about pests entering homes and commercial and industrial buildings.
Ants in the receptacle
Recently, I received an email from a very good friend with a picture showing an ant invasion in and around a weatherproof ground-fault circuit-interrupter receptacle mounted externally to her home. She was going to plug in an electric pressure washer, but due to the massive number of ants, she decided not to.
A wise choice for the ants, and an astute choice for her as well, since she couldn’t know the extent of the ant invasion or what damage could occur from an electrical arc. I can see the Hollywood horror movie now: “Invasion of the Formicidae.”
In this case, as long as the arc was between the ungrounded conductor and the neutral conductor, the GFCI would not necessarily trip. The arc could obviously damage the receptacle and any internal insulated conductors. The arc could act as an electrical bug zapper.
Never spray insecticide or any other canned spray on electrical equipment since it could be ignitable and harm the system.
Holding back the army
With an ant infestation, I would look for some type of contaminant in the box or receptacle that would attract them. Ants leave an invisible trail for other ants to follow, and you will often see a line of ants demonstrating this. That trail can be obstructed with salt, coffee grounds, baby powder and similar materials, or your local bug exterminator can also offer a solution.
For new and existing installations, use an approved caulking for spaces around any electrical boxes cut into the outside walls, floors and ceilings. Use duct seal or fireproofing materials (based on NEC Section 300.21) around conduit penetrations into outside walls, floors and ceilings.
Scorpions are no joke
Here in the desert areas of the Southwest, we have a real problem with scorpions entering homes.
A scorpion sting is very painful for anyone, including pets, and can be extremely dangerous to very young children and older people. About eight years ago, I was walking in the hall inside my home without my shoes and felt a scorpion sting the instep of my foot. The pain lasted for about six hours.
Ants can enter a building though the tiniest opening. Scorpions, though obviously much larger, can enter through even very small openings such as ceiling exhaust ducts, under door jambs and though electrical box and raceway penetrations in outside walls.
Extermination is difficult and may require a professional. I have heard of amateur solutions, such as installing a filter in the ducts, to fix the entrance problem. A black light can be used to find scorpions in the dark since they glow in that light. Sealing around any electrical penetration from outside to inside will keep scorpions and other pests from gaining access.
Section 110.12(A) of the NEC states, “Unused openings, other than those intended for the operation of equipment, those intended for mounting purposes, or those permitted as part of the design for listed equipment, shall be closed to afford protection substantially equivalent to the wall of the equipment.”
Other NEC sections require sealing raceways and other wiring methods. Section 225.27 for outside branch circuits and feeders and 230.8 for services require raceways to be sealed as follows: “Where a raceway enters a building or structure from outside, it shall be sealed in accordance with 300.5(G) and 300.7(A). Spare or unused raceways shall also be sealed. Sealants shall be identified for use with cable insulation, conductor insulation, bare conductor, shield, or other components.” Again, use a sealant that will not damage conductor insulation and components.
Panelboards, switchboards, meter sockets, luminaires and other enclosures mounted outside that have raceways or cables that enter the home can be an entrance for all kinds of pests. Take a walking tour of any home or building and count the number of penetrations. Make a point of sealing around these areas at the time of installation. The small amount of time it takes to do these simple applications can save the owner problems in the future and will be proof of the electrical contractor’s professionalism and thoughtfulness.