No, not worth the risk.
It is against the National Electrical Code to connect extension cord wiring through a hole or opening in a wall, inside a dropped ceiling or under flooring.
Quick Info
NEC ARTICLE 400 Flexible Cords and cables General 400.1 Scope.
This article covers general requirements, applications, and construction specifications for flexible cords and flexible cables.
400.8 Uses Not Permitted (ref. Extension Cord) Flexible cords and cables shall not be used for the following:
(1) As a substitute for the fixed wiring of a structure
(2) Where run through holes in walls, structural ceilings, suspended ceilings, dropped ceilings, or floors
(3) Where run through doorways, windows, or similar openings
(4) Where attached to building surfaces
(5) Where concealed by walls, floors, or ceilings or located above suspended or dropped ceilings
Canadian Electrical Code CEC® 4-010 (3)(a)(ii)
Flexible cord shall not be used run through holes in walls, ceilings or floors.
Misuse of extension cords is the #1 cause of household fires in the US – According to the NFPA® National Fire Protection Association
Extension cords need ventilation to prevent heat buildup, if inside a wall or enclose space, heat will cause the outer jacket to dry out over time, crack, exposing bare wires, creating a point of electrical shorting of the wires, causing a spark, resulting in a possible dangerous fire.
INSURANCE POLICY UPDATE: If a fire would result, due to improper use of an extension cord as outlined in the NEC, most home/renters insurance companies may not cover damages.
OTHER REFERENCES:
Professional Building Inspectors discussion regarding Extension Cords Click Here
FAQ
No
Extension cords are not designed or made for use inside a wall or ceiling, not even heavy-duty types, due to National Electrical Code restrictions, as listed above, specifically regarding the non-use of flexible cords cable. Extension cords sold in retail stores in North America, have labeling specifically warning not for use inside walls or ceilings.
In-wall rated extension cords do not exist, not even heavy-duty industrial type cords.
No matter what you may be told, or how long you search online, there are absolutely no type of extension cords manufactured anywhere in the world rated for in-wall use for North America.
All A/C power run through or concealed within the walls or ceilings requires use of proper code compliant in-wall rated building electrical wire, manufactured and listed by UL or CSA to meet Code compliance. Most areas of the US and Canada permit NM-type, well known brand ROMEX, for in-wall electrical power wire. Some areas require MC-type, metal clad/conduit wire.
Proper agency rated electrical connection junction boxes, J-Boxes, are also required for all wire connections and must also provide correct internal cubic inch capacity.
No. The Canadian Code and NEC specifically state extension cords shall not be concealed within walls. This includes inside conduits within walls.
No. The Canadian Code and NEC specifically state extension cords shall not be used as a substitute for permanent electrical premise wiring. his method, is not code compliant, as the extension cord is physically attached permanently to the ROMEX inside a junction box, making it a fixed wire connection, not temporary or removable.
1) Install a standard A/C outlet wired directly to the premise circuit.
2) Install a PowerBridge In-Wall Power Extension with in-wall power-wire rated for your area, safest and easiest and code compliant method of concealing power inside walls.
Extension cord cables are not made with materials fire rated to use inside a wall to connect in-wall mounted electrical devices, as referenced in the National Electrical Code for rated in-wall building electrical wire cable.
PowerBridge is installed using specific types of UL-listed in-wall rated building electrical wire, not an extension cord inside the wall.
The in-wall power wire creates a direct “power-extension” by connecting the upper PowerOUT wall plate to the lower PowerIN wall plate together, making a code compliant in-wall power extension.
Depending on your local code requirement, several types of in-wall rated power wire are used. There are several types of in-wall wire that can be used with PowerBridge.
The most commonly used type in the US is best known brand ROMEX®, manufacturer of NM-type wire, made specifically to use inside wall and ceilings to connect all of your electrical outlets, switches and lights fixtures.
The in-wall extension is the “fixed wiring extension” within the wall. The “fixed wiring” is the use of the proper type of building electrical wire installed and secured to screw terminals of the wall plates within junction boxes mounted to the structures walls as required to meet Code compliance.
PowerBridge kits include one 6-foot length heavy-duty power-connect cord to plug into the existing power outlet or surge protector then plugged directly into the PowerIN wall plate.
This is NOT a “fixed wiring substitute” use of an extension cord, as it can be unplugged easily at anytime, no different than plugging and unplugging any appliance or cord from an existing outlet.
The supplied power-connect cord is NOT installed within the wall of the structure..