Created Date: July 17,2003

Created by: dougcampbell81

I'm searching for information on large scale radiator cooling with multiple fans controled by a PLC. Here's our problem.

A 12MW diesel engine power plant is cooled by 2 radiators. One has two 7.5HP fixed speed fans, and the larger radiator has two 20HP fans, one fixed speed, the other on a VFD.

With 3 fixed speed fans and 1 fan on a VFD, the PLC controls the return temp off the two paralled radiators.

The existing PLC program does not work well. The fixed speed fans would start and stop every few minutes to maintain temp.

I'm persuing a better control design, which may include a VFD, on all the motors. I do not want to reinvent the wheel here. Does anyone know of a working design that has stable fan operation?

Thanks,

Doug

Created Date: July 17,2003

Created by: Tech Guy

The problem probably lies in a slow loop response. By the time your thermocouple senses the water is cooled the engine, too much cool water has been produced and vice versa.

Diesel engines are notoriously hard to tune the cooling loops on. I don't have a really good method to tell you to use, but I can suggest using thermocouples on both the temp from the engine and temp from the radiator. A least then you can watch the difference in temperature and do predictive fan control.