Why do some fittings require taping to be Underwriters Laboratories (UL) listed ?

Raceway systems such as EMT and rigid conduit are permitted by most codes to be embedded in concrete. The solid exterior of these conduits eliminates the possibility of concrete entrance, however, the termination with the connector or coupling can be susceptible to concrete entering the raceway.

Included in the UL testing procedure is assembly of the connector or coupling to the conduit, pouring of Portland-type concrete over test samples enclosed in form box, vibrating the concrete surface, and after concrete drying examine the connections for concrete entrance.

Although compression style connectors and couplings pass these tests in all trade sizes because of gland ring design, set screw type may have difficulty conforming to UL requirements. When the set screw is tightened onto the conduit, the fitting material will "yield", or stretch, enough to create an opening at the conduit/fitting connection.

Set screw fittings in the smaller (1/2", 3/4", and 1") trade sizes are less likely to stretch to the point that would permit entrance of concrete. However, 1-1/4" and larger size fittings will yield enough so that concrete can enter the raceway. UL will accept product carton marking that specify "Concrete-Tight When Taped" on fittings that cannot pass the fore- mentioned testing since the tape prevents entrance of concrete into the raceway. The taped joint must completely encircle the conduit/fitting connection.

Always use Bridgeport's UL listed Set Screw Connectors or Set Screw Couplings.




Note: Above comments are not an interpretation of the National Electrical Code or local regulations. Always consult your local electrical inspector for requirements in your area.


Please send your comments and questions to attn: Engineering at Bridgeport Fittings, Inc., Phone 203.377.5944, Fax: 203.381.3488 or email:eng@bptfittings.com