When selecting a pump motor, it is vital to consider not only the upfront cost of the equipment, but also the long-term operating expenses. Single-phase pump motors may have a lower initial price tag, but the energy savings of a three-phase pump motor will generally begin to yield a return on your investment within a year.
Three-phase motors are known for their reliability and long operating life, extending the pump replacement interval. They use up to 90% less power to do the same work as a single-phase motor. In the long run, the life cycle cost difference between three-phase and single-phase motors could save your organization thousands of dollars.
Three-phase pump motors are more efficient in general than single-phase motors. Pound for pound, they use less energy at the same load, partly because they create less friction and partly because they can turn over the same amount of water at a lower pump speed. Fewer revolutions per minute translates to reduced energy usage whenever the pump is running. However, the bulk of the energy savings from three-phase motors comes from soft start afforded by their variable frequency drive (VFD) control system.
Advantages of Soft Start Technology
Single-phase motors have a “hard start”, requiring a considerable in-rush of power to overcome inertia, up to 5 or 6 times the current required for normal operation. This has a significant impact on the efficacy of the piping system and components and your organization’s power bill.
Energy companies add a demand charge to the power bills of industrial and commercial facilities. This surcharge is based on the peak demand of your business, as the energy company must generate the capability to provide you with the maximum power you may need at any given time.
If they are accounting for enough energy to be able to power a hard start at any moment, the bill might be rather steep. In some instances, the demand charge outstrips the cost of actual energy expenditure.
A VFD control system eliminates this problem by facilitating a gradual “soft start,” which requires only around 1.5 times the normal operating current. The energy effectiveness of a soft start means a much smaller demand charge on your power bill every month.
Reduction in Maintenance Expenses
The lower start-up current needed for a soft start also means less wear and tear on the pump, piping, and components, further reducing operating costs by decreasing the maintenance and repair requirements for the entire system. The lower pump speed and reduced friction of three-phase motors also produce less stress and cooler temperatures for other components.
Additionally, three-phase motors produce less vibration in the system than single-phase motors, reducing the stress on pipes and their supports. Three-phase power provides a smoother, more balanced motor operation.
Excess vibration from single-phase motors can loosen joints and cause cracks in welds. Some of the vibration is a result of an excess of fluid energy that builds up when the flow rate of a single-phase motor far outpaces the need of the system. A VFD control system solves this problem, decreasing the need for repairs and replacement parts.
Efficiency and Flexibility of VFD Control Systems
With single-phase, pumps, sizing the pump to the specific application is absolutely critical for efficiency. This almost never happens perfectly, especially in the pool industry. A single-phase pump is usually a little oversized for the actual hydraulic conditions on-site, so the operator must produce artificial backpressure by valving down to get the desired flow rate. You are then constantly using max horsepower and simulating the need for that power by causing more total dynamic head in the system.
With a VFD control system, you can reduce energy use to match your need. Our three-phase pumps are designed to always use the least amount of horsepower to maintain the system design flow rate. This translates into ongoing energy savings and a reduced load on the pump, leading to longer pump life and lower maintenance requirements.
On top of this, VFD controls give you options not available with single-phase pumps. For instance, if you have a three-phase filter pump in a commercial pool, you can slow the pump down to a minimum speed at night to reduce your energy usage even more. The VFD control system is programmable, so you can set a schedule for the pump that optimizes energy savings and is ideally suited to the operating hours and particular needs of your organization.
Except for a few specialty pumps, single-phase motors will soon be eliminated from the pool industry. The energy sector is increasingly requiring variable-speed pumps because soft starts are so much better for the electrical grid. They are also requiring more efficient motors, leading to a radical decline in the production of single-phase motors above 3 hp.
The cost of single-phase pump motors has therefore almost tripled, shrinking the amount of additional investment required to upgrade to a three-phase motor. Check with your local energy company. Your organization may be able to recoup some of its investment with a utility rebate if you choose a three-phase, variable-speed pump.
To Learn More
Our VFD-controlled three-phase pump motors minimize system maintenance requirements and maximize energy efficiency. For more information about the energy savings afforded by three-phase pumps, contact Com-Pac Filtration of Jacksonville, Florida. With over 100 years of combined industry experience, the professionals at Com-Pac would be happy to answer your questions and help you select the pump that will best meet the needs of your organization.