How to visually tell an ODP motor from a TEFC motor?

How to visually tell an ODP motor from a TEFC motor?

ODP stands for an Open Drip Proof motor.  Here drip proof part of the abbreviation is not important for our discussion—it just means that any nothing can drip out of the motor enclosure.  ‘Open’ is the main characteristic of this type of motor.  Here ‘open’ refers to the motor winding—open as in open to air stream.  In this type of motor, winding is cooled down by air freely entering the enclosure where the winding is.  If the air can freely get in the winding space, so can all air borne dust, and in extreme conditions even water can get in.

ODP is a less expensive motor in comparison to TEFC and can be used indoors where dust or water is not a concern.

TEFC is an abbreviation for totally-enclosed-fan-cooled motor.  In fact the real name of this type of motor should be TEFC-DP, or totally enclosed fan cooled drip proof motor, as this motor too is drip proof.  But the main difference between this type of motor and the open type--or the ODP motor--is that here the motor winding is totally enclosed in a chamber—air cannot get into the chamber.  So how do you cool the motor when it is totally sealed?  Easy!  The metal enclosure housing the winding gets hot--you put fins on the motor enclosure and blow air over it using a fan.  So, in fact you are not directly cooling down the winding (as you do in ODP), but you are cooling the motor enclosure.

How can you visually tell a TEFC from an ODP?  Look for the fins on the motor enclosure.  If the enclosure has fins, it definitely has a fan too that is blowing air over the fins—it is a TEFC motor.  You don’t see any fins—it is an ODP.

ODP motor image courtesy of http://www.fastenal.com

TEFC motor image courtesy of http://www.wegelectricalmotors.com

Supply and Return air ducts in ceiling space.