For the past three weeks, I’ve been writing about variable speed drives (VFDs) and the benefits they offer beyond constant pressure. While delivering constant water pressure is still the most recognized benefit of these systems, their potential far exceeds that one application. This week’s examples are more regional in nature, but hopefully they will help you start thinking about other ways VFDs can solve problems.
In many parts of the western US, wells are frequently pumped faster than they can recharge, making some type of dry run protection necessary. As a result, these installations have Pumptec or a similar type of dry run (underload) protection. However, VFDs already have this protection built into them. In addition, not only do they have protection by design against underload, most also have overload (bound pump) protection built in, as well as undervoltage and overvoltage protection. In cases where you know that an installation may face challenging conditions, for a small incremental cost—remember, besides a Pumptec, you also need control box in a conventional system—you can use a VFD such as SubDrive for even better protection of the pump and motor.
Another niche application for variable speed systems is operating installations where fire codes are in effect. Particularly in dry areas of the country, local fire codes dictate the minimum size pump required for fire protection. In the majority of cases, the GPM the pump is required to deliver in case of fire far exceeds the output required for regular daily residential usage. Continue reading