Explosion Proof Seal Fitttings

[Dale Hayes]

For conduit or tubing nipples less that 24" in length, does the 60% fill rule apply for Class 1, Division 1 and 2 explosion proof seal fittings that normally require a 25% fill?

This question is based upon infromation obtained from NEC Chapter 9 Tables (4) Where conduit or tubing nipples having a maximum length not to exceed 600 mm (24 in.) are installed between boxes, cabinets, and similar enclosures, the nipples shall be permitted to be filled to 60 percent of their total cross-sectional area, and 310.15(B)(2)(a) adjustment factors need not apply to this condition.

Dale Hayes

 

[Rockyd]

501.15(C)6 The 25% fill for seal-offs came out about two code cycles back. I like the fact that the fill was reduced from 40% because it was near impossible to pack a seal in a manner as to comply with 110.3(B).

You must comply with the 25% fill for Seal-offs.

So how do you avoid running up the cost with all these seal-offs?

Use an RE to upsize your seal-off coming in, and RE going out(make sure that you get the the right RE's).

You may want to read 501.15(A)3 on two or more boxes, where it discusses nipples.

Seals are about stopping flame propogation, and containing an explosion within, or from outside, the raceways and equipment. A lot of C1D1 and C1D2 is per engineer's specs, sweet the amount of change orders that go with classified space work!