Enclosure Classifications
General and Motor

General

NEMA
Type

Definition

1 Indoor General Purpose
3 Outdoor, Rainproof Dusttight.  Protection against windblown dust, rain, sleet, and external ice formation.
3R Outdoor, Rainproof.  Protection against falling rain and external ice formation.
4 Indoor or Outdoor. Protection against windblown dust and rain, splashing water, hose-directed water, and external ice formation.
4X Indoor or Outdoor. Protection against corrosion, windblown dust and rain, splashing water, hose-directed water, and external ice formation.
6P Indoor or Outdoor.  Protection against the entry of water during prolonged submersion at limited depth, and external ice formation.
7 Indoor use for areas classified as Class I, Groups C&D as defined in the NEC.
9 Indoor use for areas classified as Class II, Groups E, F and G as defined in the NEC.
12 Indoor Dusttight Industrial Use.  Protection against dust, falling dirt, and dripping non-corrosive liquids.
13 Indoor Oiltight.  Protection against dust, spraying of water, oil, and non-corrosive coolant.
Motor

NEMA
Type

Definition

Standard (smaller) NEMA Frame Sizes

TEFC Totally Enclosed Fan Cooled.  Offers best protection from the environment because the air does not pass freely through the motor.  An external shaft driven fan circulates air over the finned frame housing.
ODP Open Drip Proof.    Air from the environment is circulated through the motor for cooling.  Lowest enclosure cost.  Inlet and exhaust openings are protected from dripping water at an angle of 15 degrees.  Should be used in a relatively clean, weather protected area.
XPFC Explosion Proof Fan Cooled.  These motors have special enclosures and conduit box certified for use in hazardous environments.  Care must be taken in specifying the proper motor for the environment and temperature.
Larger NEMA Sizes
WPI, Type I Weather Proof, Type I.These are a version of an open motor where air circulates from the environment through the motor.   Outlet vents have louvered covers and screens.  It offers light weather protection.  From some vendors this is just an ODP with rodent screens.
WPI, Type II This is a further upgrade to the WPI by adding a protective hood which changes the air flow into the motor by three 90 degree bends.  The hood also slows the air flow to less than 600 CFM and adds weep holes to drain moisture away from the entry to the motor.  This is the most rugged open type and is suitable for outdoor use in severe weather.  Air filters are available and insulation can be added to create a "low noise" motor.  This may require a larger motor for the application since the cooling air flow has been lowered.
TEBC Totally Enclosed Blower Cooled.  These are similar to TEFC motors except that the cooling is provided by a separately powered axial fan.   These motors are often used in variable speed applications where a wide speed range is desired.