Up To Speed: Is A Clean Air Filter Really That Important?


Up To Speed Graphic Thin VersionUp To Speed is a concise, technical blog compiled by industry veteran Mark Reeder. It provides an interesting fact, answers a thought-provoking question, or offers a cliffhanger from an actual site visit by one of our world-class Field Service Engineers.

“This week’s post comes from a recent site visit to a large dairy operation by one of Franklin Electric’s Field Service Engineers.

The reported issue was with a Franklin Electric P-Series Variable Frequency Drive that had only recently started to 2017 Permanent Magnet Motor Video Shoot Trip 252underperform. In the case of a water system, underperforming almost always means ‘we’re not getting enough water’. Troubleshooting over the phone had already been attempted to no avail. The system was still delivering water, but when the system was installed, the dairy operation was getting a lot more. So, the mystery was, what changed? Had the well water level dropped? Had the pump become damaged somehow? Was there a restriction in the system?

The answer turned out to be none of the above. Nothing had changed, including operation in a very dusty, windy environment from the beginning.

Most mechanical things need cooling. Your truck engine needs so much cooling that it has a separate system (radiator) just to keep it cool. Electric motors and variable frequency drives are no exception and many are air cooled with one or more fans. To keep dust and dirt out of the drive, there’s an air filter. At this point, you probably have guessed that the issue was a very dirty, clogged fan filter.

Here’s the Good News…

The P-Series, like most drives, protects itself when it comes to heat. Much like you and I, if it gets too hot, it slows down. That’s exactly what this unit was doing. Over several days, the drive had backed itself down to 55 Hz (about 3100 RPM) versus its regular 60 Hz (about 3400 RPM). When a drive protects itself like this, it greatly reduces the amount of current in the unit and therefore the amount of heat that is internally generated. So, the system was still delivering some water, but at the same time, protecting itself from heat damage.

Here’s an example where everything was working just as it should. The filter was doing its job, the drive was doing its job, and pump and motor were doing their job. Everything was just running slower. Once the filter was cleaned, everything worked just like it did at the initial installation.

In the end, something did change … performance was restored and the dairy’s operations supervisor now checks and cleans the filter once a week.”

Now, you’re up to speed.