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Operating Motors in Wet/Damp/Hazardous Conditions

Posted by WE Electric Motors on 3/20/2015

Operating Motors in Wet or Damp Environments


“When electric motors are installed in wet or damp areas, the life of the motor is almost always shortened from what would be expected in a dry situation. However, there are several cautions and suggestions that can extend the life of motors in these less than ideal situations."

-Baldor Motors & Drives-


Open Drip-Proof Motors

  • Not suitable for wet environments; however, there are situations where an equipment manufacturer chooses the open drip-proof motor (most likely due to lower initial cost) for use where a totally enclosed motor would have been a better and longer life choice.

  • Tips to extend life of open drip-proof motor in such conditions:

    • Motor should be shielded from the direct impact of precipitation

      • Do not restrict air flow to and around the motor

      • Motor Shelter must be well-ventilated or louvered so that hot air is not trapped inside

    • Motor should be rotated to put the louvers in the proper position to fend off rain rather than funneling it inside



Totally Enclosed Fan Cooled

  • Increased adaptability to outdoor and high moisture areas and work well (with some caution)

  • Tips to extend life of totally enclosed fan cooled motors:

    • Make sure the weep holes are at the bottom-most part of the motor

      • “Weep holes” are at the bottom of the end housings of these motors; these fittings are put there to allow condensation or other accumulations of moisture to drain

  • Where motors run continuously, the heat generated in the motor by normal operation can keep windings dry; however, when a motor is used infrequently, it is subject to large swings in temperature.

    • Two methods which can be used to reduce the susceptibility to failure caused by this accumulated moisture:

      • 1. Use of heater within the motor

      • 2. “Trickle heating”- Source of low voltage single phase power is applied to the three phase motor windings when the motor is at rest

        • Results in a low energy, single phasing condition that produces heat in the windings, rotor, and indirectly in the shaft and bearings of the motor




Hazardous Location

  • Due to explosion proof design requirements, gaskets cannot be used

  • These motors are difficult to protect in wet and damp environments

  • Tips to extend life of Hazardous Location motors:

    • Breather drain devices- allow moisture to drain from the motor while still retaining the explosion proof integrity

      • Breather drain must be at the lowest point on the motor to allow moisture to drain

    • Install heater to keep internal temperature of the motor above the outside temperature during idle periods

    • Shelter from direct precipitation

      • Do not restrict air flow to and around the motor from outside



Being cautious and using the tips provided can help increase the life of your motor in non-ideal circumstances.