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Sealing fittings must be installed at a boundary between a hazardous and nonhazardous area. Sealing fittings must also be installed at a boundary between
a Class I, Div. 1 area and a Class I, Div. 2 area.
Other NEC Requirements:
•
Splices and taps are not to be used in sealing fittings.
•
Where moisture may accumulate in system, an approved method must be provided to remove such accumulation.
•
Depth of sealing compound should be to trade size of conduit, having a minimum thickness of 5/8 of an inch.
Installation
1. Run the conductors through the fitting.
2. Pack the sealing fitting with fiber filler. In a horizontal run, place the fiber filling at both ends of the fitting (refer to Figure 5); in a vertical run, fill only
the bottom end (refer to Figure 6).
Fiber filler makes a dam that keeps the sealing compound in the chamber of the sealing fitting while it cures and hardens. The fiber dam is also used
to separate the individual conductors so the sealing compound seals around each conductor. If the electrical conductors are not properly separated,
gases can migrate through the seal, making the seal ineffective.
FIBER FILLER
Figure 5. Horizontal Fitting, Damming and Sealing
3. Prepare the sealing compound. Use sealing compound suitable for the application and follow the instructions supplied by the sealing compound
manufacturer.
4. Pour the sealing compound into the fitting.
HAZARDOUS AREA
ENCLOSURE
TO BE SEALED
SEAL MAY BE POSITIONED
ON EITHER SIDE OF BOUNDARY
ENCLOSURE TO BE SEALED
Figure 4. Sealing the Enclosures
SEALING COMPOUND
NONHAZARDOUS AREA
NO UNION, COUPLING, BOX, OR FITTING IN CONDUIT
IS PERMITTED BETWEEN SEALING FITTING AND
POINT WHERE CONDUIT LEAVES HAZARDOUS AREA
Figure 6. Vertical Fitting, Damming and Sealing
SEALING
COMPOUND
FIBER FILLER
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