Duct seal putty for exterior use9/25/2023 ![]() What kind of wire do you use for outdoor conduit? Expanding spray foam without carefully planning can damage electrical wiring.Īccording to the National Electrical Code, you can have 4 12/2 nonmetallic sheathed cables through a single bored hole that is fire- or draft-stopped using thermal insulation, caulk, or sealing foam, or where proper spacing is not maintained for more that 24 in. So, if you were wondering whether expanding foam damages wiring the answer is yes. It also requires sealants to be compatible with cable jackets and other components as referenced in the sections below. ![]() The NEC states that conduits and raceways should be sealed to prevent moisture, hazardous gases and vapors from entering buildings. Does underground conduit need to be sealed? What is the better solution? Also… duct seal (mostly used for sealing electric panels and such from water infiltration) is very similar to plumber’s putty but never dries out. The idea is to stop water from going behind the box and around the conduit into the wall. There should be holes inside the box or external ears for mounting. ![]() What you need to do is apply a paintable silicone acrylic or silicone caulk to the back of the box and around the entry hole before you screw the box to the wall. How do you seal outdoor electrical conduit? Use caulk, gaskets, or spray foam (note that spray foam degrades in sunlight). Don’t find the Electrical Inspector requesting that you remove either product.Seal all wiring holes through the exterior walls of the house, such as holes for electrical wiring, security system wiring, television and telephone cables, porch light fixtures, and exterior electrical outlets. Neither foam nor duct putty should be used for construction purposes other than those originally intended. It doesn’t fully cure in thick layers or enclosed spaces. It creates a lightweight, open-cell structure that allows water and moisture to pass through, much like a sponge. Bottom line is duct putty fails.Ĭanned foam is designed for crack and crevices. Putty holds minimal water head pressure, compresses under large cable weight and typically had no test reports showing cable jacket compatibility. When used in conduits it sags over tine and creates openings in seals when cables and wires move. Duct putty is intended to seal around junction boxes and flashings. The most widely used product to seal conduits is duct putty. FSTTM sealant is chemically resistant to gasoline, oils, dilute acids and bases, and most unsaturated hydrocarbons. Polywater® FSTTM is superior to both duct putty and aerosol cans of foam because it has been tested for cable compatibility holds 22 feet of water head pressure continuously and up to 90 feet intermittently prevents gas from passing through does not sag will not dry out and is re-enterable. Polywater® FSTTM Foam Duct Sealant meets and exceeds the NEC section requirements for sealing conduit systems. Informational Note: Presence of hazardous gases or vapors may also necessitate sealing of underground conduits or raceways entering buildings. Conduits or raceways through which moisture may contact live parts shall be sealed or plugged at either or both ends. Sealants shall be identified for use with the cable insulation, shield, or other components. Spare or unused raceways shall also be sealed. Where a service raceway enters a building or structure from an underground distribution system, it shall be sealed in accordance with 300.5(G). Where a raceway enters a building or structure from an underground distribution system, it shall be sealed in accordance with 300.5(G). ![]()
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