Adjusting a Variable Frequency Drive (VFD) to Over Speed a HVAC Centrifugal Pump

Norm Hall
August 28, 2017
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The R. L. Deppmann Monday Morning Minutes from a few weeks ago discussed the option of a small amount of over speeding on B&G pumps in HVAC applications. Several of you have asked how one would do that in the VFD. This week we have a short instructional video on how to change the maximum speed on Bell & Gossett and Danfoss VFD drives. The photo below shows the startup screen on a Bell & Gossett Technologic VFD.

Bell & Gossett Controller

In past articles, we wrote about the ability to over speed an HVAC B&G pump to achieve a little more capacity. Just how simple is this to do in the B&G or Danfoss VLT drives? In this video, our Startup and Warranty expert Mike Belanger shows you how to do this.

Safety First Please…

If you are going to adjust or work on any piece of equipment including VFDs, make sure you are wearing the correct safety equipment and have read the owner’s manuals. Visit the B&G website for the B&G technologic operation manuals and the Danfoss Download Portal for more information.

How to Over Speed the B&G Technologic and Danfoss VLT Variable Frequency Drives (VFD)

When operating a drive, motor, and pump above the rated RPM, make sure you have enough horsepower on the pump and the drive is rated for the expected amp draw. Never operate the B&G pump more than 5% over the rated speed without contacting the pump representative or manufacturer to verify how much over speeding would be allowed with your pump and application.

The last few R. L. Deppmann Monday Morning Minute posts have helpful information.  In addition, if you have any specific questions or concerns, contact your local B&G representative.

Next week, the R L Deppmann Monday Morning Minutes will look at sump pumps and the elevator codes in Michigan and Ohio.