Other Factors to Consider

Dielectric UnionAre all the lines going into alarm or just one?

  • If only one line is going into a DPLLD Comm Alarm, then the issue could be caused by a bad transducer or another device on this line. Start by swapping transducers with another line. If the issue follows the transducer, replace it.
  • If the issue stays on this line, or all lines are going into alarm, installing a dielectric union will help isolate the transducer. Dielectric unions help isolate the transducer from the STP and can reduce or eliminate DPLLD comm alarms. Dielectric unions can be found at plumbing supply stores.

Is the Comm Alarm activating at a specific time each day?

  • Alarms may be triggered by devices that turn on at the same time every day, such as canopy lights.
  • Once the device is found, try to duplicate the problem.
  • LED lighting, neon signs and refrigeration units are known as a cause of electrical noise interference. 

If all DPLLD lines are going into the Comm Alarms, then this issue could be caused by the ATG or wiring.

  • Check the console’s grounding. Make sure the console has two isolated grounds. For variable speed STPs, confirm that a 3-phase motor is installed.
  • Check the motor windings and refer to the manufacturer’s service manual for correct ohm readings. On a 3-phase ump, the ohm reading will be the same on all three legs.

Note: There should also be no capacitor on a 3-phase motor.