An old timer once demonstrated good duct-seal installation as sort of an "art"—that took a little time but paid off. Start with a good product like “RectorSeal” duct-seal compound; a slang term is
monkey dung. Roll it into hotdog-/dogpoo-sized wads and pack it in to the raceway end with the hotdogs most of the way into the conduit and lateral/parallel to installed cables. Force the cables with sideways pressure into the duct seal to compress it between cables and conduit walls. It might take six or twelve wiener-shaped pieces. The raceway-wall/ductseal/cable-jacket contact area is greatly increased, and more likely to withstand flooding than a half-inch layer pressed on the conduit end. In one case, it saved a control-room-basement lake and an 800-amp transfer switch owned by a very particular customer.
Another brickhouse-grade alternative are seals like CSBG-series on page 18 at
http://www.o-zgedney.com/PDF/R1thru24.pdf —but they take some advance planning. One “gotcha” can be not solder-blocking stranded bare equipment-grounding conductors that pass through the seal.
[This message has been edited by Bjarney (edited 04-23-2003).]
