Drains - hdbk10920102

DOE-HDBK-1092-98

4. At each entrance to an enclosure housing with an arcing or sparking device when used in Class

I Division 1 and 2 hazardous locations, seals must be as close as practicable to and in no case

more than 18 in. from such enclosures.

5. At each 2-in. or larger entrance to an enclosure or fitting housing terminals, splices, or taps

when used in Class I Division 1 hazardous locations, seals must be as close as practicable to

and in no case more than 18 in. from such enclosures.

6. Seals must be located in conduit systems when the conduit leaves the Class I Division 1 or 2

hazardous locations.

7. Seals must be located in cable systems when the cables either do not have a gastight or

vaportight continuous sheath or are capable of transmitting gases or vapors through the cable

core when these cables leave the Class I Division 1 or Division 2 hazardous locations.

NEC Section 502-5 requires the use of seals in Class II locations under certain conditions. Any

approved sealing fittings can be used to meet this requirement.

5.4.1.2 DRAINS

In humid atmospheres or in wet locations where it is likely that water can enter the interiors of

enclosures or raceways, the raceways should be inclined so that water will not collect in enclosures

or on seals but will be led to low points where it may pass out through drains. Frequently the

arrangement of raceway runs makes this method impractical if not impossible. In such instances,

drain sealing fittings shall be used. These fittings prevent accumulations of water above the seal. [See

NEC 501-5(d).]

In locations usually considered dry, surprising amounts of water frequently collect in conduit

systems. No conduit system is airtight; therefore, it may breathe. Alternate increases and decreases

in temperature and barometric pressure because of weather changes or the nature of the process

carried on in the location where the conduit is installed will cause breathing. Outside air is drawn into

the conduit system when it breathes in. If this air carries sufficient moisture, it will be condensed

within the system when the temperature decreases and chills the air. With internal conditions being

unfavorable to evaporation, the resultant water accumulation will remain and be added to by

repetitions of the breathing cycle. In view of this likelihood, it is good practice to ensure against such

water accumulations and probable subsequent insulation failures by installing drain sealing fittings

with drain covers or inspection covers even though conditions prevailing at the time of planning or

installing may not indicate the need.

5.4.1.3 SELECTION OF SEALS AND DRAINS

Different types of seals and drains are made to be used for vertical or horizontal installations and are

to be used only for the purpose for which they were designed. Care shall be taken when selecting and

installing such fittings.

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