 Failed Duct Putty Seal |
Customers may be skeptical of claims that FST Foam is superior to duct putty and canned foams for sealing interior conduit ends. Fair enough. After all, users are familiar with these mature, simple, inexpensive, readily available products from reputable companies. They're excellent choices for many uses ... but not for sealing interior conduit ends. What does the literature say? This example of Canned Foam Literature describes an insulating foam for small gaps "to minimize drafts and insect infestation for gaps, cracks and holes less than 1 inch" with a "water-resistant bond." There's no mention of ducts, conduits, or cables. The vast majority of electrical and telcom ducts to be sealed are larger than 1" ID. And seals must be watertight, not "water-resistant." These seals must be plugged airtight, not stuffed to "minimize drafts." Testing and field experience prove conclusively that porous, open-celled canned foams make ineffective conduit sealants. Water and gases go right through. An example of Duct Putty Literature describes a soft compound used "to seal around junction boxes, flashings, and service mast entries." Sealing a 1/4" gap around a duct/wall penetration is different than sealing the 4" ID of said duct. Duct putty is air and watertight ... until it sags and pulls away from the conduit wall, creating a big opening. Air and water don't have to go through--they just go around. The literature lists a sag test, saying duct putty: "will not slump when shaped into a 2-inch cylinder 4 inches tall and placed in an air-circulating oven at 400° for 1 hour." But as the experienced craftsperson knows, it will eventually slump in a hot duct sometime after 1 hour. Again, there's no mention of conduits. The term "duct putty" refers to sealing the outside of HVAC ductwork. Putty fails as a conduit sealant. Use this literature to sell FST. Aerosol foam and duct putty manufacturers make no specific claims about suitability for conduit sealing; they don't market their products for such use. End users have adopted them as a low-cost, short-term fix to meet nebulous code requirements. Effective alternatives were rare--until the advent of FST Foam Sealant. |
