Page 278 - Handbook of Electrical Engineering

HAZARDOUS AREA CLASSIFICATION 263

10.6.2.4 Type No. 3R: Rainproof and sleet (ice) resistant

An enclosure intended for outdoor use to protect the enclosed control against rain. These enclosures
must have provisions for watertight connectors, for locking and for drainage.

10.6.2.5 Type No. 3S: Dust-tight, rain-tight and sleet- (ice) proof

An enclosure intended for outdoor use to protect the enclosed control against windblown dust and
water and to provide for its operation when the enclosure is covered by external ice or sleet. These
enclosures do not protect the enclosed equipment from malfunction due to internal icing. These enclo-
sures must have provisions for watertight connectors, for mounting external to the enclosure cavity
and for locking. In addition, these enclosures must have the ability to support the additional weight
of ice and to withstand the removal of ice by a hand tool to permit access to the enclosure interior.

10.6.2.6 Type No. 4: Water-tight and dust-tight

An enclosure intended for indoor use to protect the enclosed control against splashing water, seepage
of water, falling or hose-directed water and severe external condensation. These enclosures must have
provision for watertight connectors and for mounting external to the enclosure cavity.

10.6.2.7 Type No. 4X: Water-tight, dust-tight and corrosion-resistant
Same as Type No. 4 with corrosion-resistant construction.

10.6.2.8 Type No. 5:

Superseded by Type No. 12

10.6.2.9 Type No. 6: Submersible, water-tight, dust-tight and sleet-(ice) resistant
An enclosure intended for use indoors or outdoors where occasional submersion is encountered. The
enclosure protects the enclosed control against a static head of water of 6 feet for 30 minutes, dust,
splashing or external condensation of non-corrosive liquids, falling or hose-directed water, lint and
seepage. These enclosures must have provisions for watertight connectors and mounting external to
the enclosure cavity.

10.6.2.10 Type No. 7: Class I, Group A, B, C or D indoor hazardous locations air-break
equipment
An enclosure intended for indoor use in the atmospheres and locations defined as Class I, Group A,
B, C or D in the National Electrical Code. The letters A, B, C or D, which indicate the gas or vapour
atmospheres in the hazardous location must appear as a suffix to the designation Type 7, to give the
complete NEMA designation.
Note: Type 7 enclosures are termed explosion proof as defined in NEMA and the National
Electrical Code.