A wiring module is installed within an electrical box, wherein the wiring module is configured to connect to a power cable routed to the electrical box. The wiring module distributes electrical power according to a functional module that is pluggable into the wiring module. A cover is removably mounted to the wiring module so that the cover extends generally flush over an open face of the electrical box. The cover prevents plaster and other material from fouling the wiring module during wall panel installation and is removed after wall panel installation so as to plug the functional module into the wiring module.