I recently wired the attached 3 phase 208 motor grundfos 96402920 using an exsiting 3 phase nema size 0 contactor and thermal overloads with 120 volt control. Before landing the wires on the motor terminals I checked the voltages gound to L1, L2, L3 and t1 and t2 all 120 and then phase to phase all 206 feeling i had it right I then wired the motor up and turned it on. It has manual speed switch built in , speed 1 - 4.05 amps, speed 2 - 4.2 amps and speed 3 - 6.3 amps and can only run at one selected speed , you can't change it while it is running. Well in speed 1 it didn't run at all and pulled no amperage, it ran fine in speed 2 for about 5 minutes never pulling more than 5 amps acutally just over 4.4 or tripping the overloads internal or extrenal but it got hot so I turned it off . Speed three ran for about 90 seconds pulling 13 amps and tripping the external overloads. It is replacing a 5 hp motor and is only 3 hp but he plumber swears it was engineered correclty and that the load is not to big on it. small hotel heat yet the 5 hp backup taco motor runs great. any thoughts on what might be happening would be greatly appreciated
grundfos motor problems
- Thread starter tyba16
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hmspe
Senior Member
- Location
- Temple, TX
- Occupation
- PE
What are the voltages when the motor is running? There are really only three options: (1) it's not the right wiring diagram, (2) it's mis-wired, or (3) the motor and/or the speed control is defective.
Martin
Martin
the voltage while the motor is running is L1-L3-210v, L1-L2-205, L2-L3 203v. we did get it to run this morning in 3rd speed correctly by reducing the outflow of the water the motor is pushing and we could regualte the amperage the motor pulled by opening or closing the outflow valve - opening the valve made the amperage go up and it went down as we closed the valve. Which indicates to me that the pump is undersized for the application . still never got speed 1 to run. Of course the plumber doesn't agree
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