I've noticed a profound flow of air coming in through my main house electrical panel. I've traced it to the main pipe that comes from the outside meter through the house and to the panel. My question is can I legally spray foam insulation around the main electrical wires inside the pipe?
The original installer failed to meet the requirements of the NEC when your panel was put in. The conduit should have been sealed at that time. The typical product used is called "Duct Seal" (generic name) This is the recommended product, just work it in & around the wires until the air flow stops.Do this on the indoor side of the conduit.