14
Florida Pool Pro
sm
• November 2014
COMMERCIAL CONNECTION
VFD pumping applications – limitations
and opportunities
By Alvaro G. Mendoza, CES /
Over the past few years there has been lots of growth in the use of variable
frequency drives (VFD’s) on both residential and commercial applications.
VFD’s have been a popular staple in municipal water and wastewater pumping
systems and HVAC applications for many years and were a bit slow gaining
acceptance in the pool industry.
There has also been much confusion and misinformation regarding savings
and application options. We are going to try to shed some light in order to help
clear up any lingering questions.
Basics: As an over-simplification of the technology, VFD’s convert AC voltage
to DC, then back to a controlledAC signal. During this process they take control
of the Hertz (or speed) at which the motors operate (out of a possible 60 Hertz)
and thus can turn down the rate at which the motor turns.
Limitations: This process requires a 3-phase motor in order to work, and
some sites only have single-phase power. What do you do?
Options: The VFD system can convert single-phase power to 3-phase power,
given proper sizing, in order to operate a 3-phase pump.
Residential Applications: Many residential service companies have utilized a
traditional “VFD mounted directly on a pump” package. These are marketed by
the major pump manufacturers and have a sleek and sexy appearance. Under
the hood, they utilize a 3-phase motor to allow the VFD to operate as needed.
They have simple push button controls and tie seamlessly into residential pool
automation systems.
Limitations: These are available in limited sizes, normally 2 to 3 HP at a max.
Companies have complained of significant service issues due to the quality of
motors, location of VFD device, heat and vibration effect on VFD, etc. Many say
that the convenient mounting configuration makes the units difficult to service.
Options: There are alternatives to VFD-on-pumps packages that include an
industrial grade wall-mounted VFD, that will hook to any 3-phase pump, and
