Circulator pump reliability in extreme conditions

On a military base in east-central Alaska — where the average winter temperature is 16° F with lows that fall well below minus 50° at times — dependable, low-maintenance winter heating systems are critical for the active-duty military families and Department of Defense civilians who live on the military post.

The company that owns and manages the on-base military housing units was faced with a challenge when renovating the base housing mechanical systems. The original heating system circulators were outdated and inefficient. In addition, many of the older circulators were the three-piece oil-lubricated type with mechanical seals that required yearly maintenance and costly part replacements.

Extreme winter temperatures demand a reliable maintenance-free circulator design, and the Grundfos portfolio of wet rotor circulators fit the bill for the frigid Alaskan climate that requires a significantly higher energy cost to run around the clock. The average residential rate in the region is 24 cents per kWh, which is double the national average. Given the high electricity costs in the region and the high system run hours, reducing the overall energy consumption played a major role in the renovation.

High-efficiency solution

Low maintenance and reliability are crucial in remote areas like this one. The building management company owners were impressed with the maintenance-free, wet rotor design of the Grundfos MAGNA circulators. The energy-efficient, variable-speed, electronically commutated motor (ECM) design convinced the company’s mechanical engineering firm and its technicians that the MAGNA circulators were the perfect choice for their heating system upgrade.

The conventional two-story townhouse units included basement mechanical rooms served by a steam-to-high temperature glycol heat exchanger that was powered by the central steam plant. The MAGNA1 32-100 distributes the desired flow to satisfy heating demands in the individual loops with a high output copper-fin baseboard and high-mass radiant floor heating. A MAGNA1 50-150 serves the main glycol loop off the heat exchanger.

MAGNA1 is a high-efficiency solution when a standard circulator pump is needed. It includes all the efficiencies of the permanent magnet motor, as well as three control modes with nine different settings that can be optimized for a particular application. The MAGNA1’s programming simplicity makes it an energy-efficient solution ideal for multi-unit residential hydronic and radiant floor applications.

For applications with extremely high or low temperatures that want to take advantage of the sophisticated wireless monitoring features, the MAGNA3 offers a premium product upgrade. The more advanced MAGNA3 has infinite settings, as well as advanced features such as AUTOADAPT, where the pump reacts and adjusts automatically to the best operating point. It also has building management system communications built-in. When connected to a BMS at one data point, a multitude of measurements can be read, such as pressure, fluid, temperature, flow rates and other crucial data that would normally require numerous devices that can be expensive to integrate into a BMS. MAGNA3 includes Fieldbus communication via CIM modules, as well as analog and digital inputs and configurable relays.

The MAGNA3 is more than just a pump. The MAGNA3 also offers an intuitive display that allows operators to connect wirelessly; the Grundfos GO app provides instant access to reports and monitoring features. The FLOWADAPT feature reduces the need for throttling valves, which cuts costs on system components.

Both the MAGNA1 and MAGNA3 are maintenance-free, thanks to the canned-rotor design. The pump and motor form an integral unit without a shaft seal and with only two gaskets for sealing. The bearings are lubricated by the pumped liquid. The robust technology of the pumps is the same, including the high-efficiency hydraulics and motor.

The wide range of temperatures for the operating fluid made this pump an ideal choice for the Alaskan application. When the unit is heating in extreme cold temperatures, it can handle up to 230°. On a cooling application, it can handle frigid temperatures as low as minus 14°.

Even with the wide range of fluid temperatures, the MAGNA pump is very stable. Some products will run into issues with their electronics where they are forced to scale down based on extreme temperatures. MAGNA provides a full range of reliable performance throughout the range of operating temperatures. MAGNA3 also has a full setup from the screen on the pump itself. It does not require an external laptop or any other equipment. MAGNA circulators include the pump, motor, and VFD — all integrated into one unit with intelligent wireless communication technology and realized savings over promised savings.

Real-world results

The large-scale renovation project on the Alaska military base has taken place over the course of several years and is ongoing. To date, more than 1,000 Grundfos MAGNA circulators have been installed. As the heating system renovation nears completion, many replacement MAGNA circulators operate at a watt level less than half of the original induction motor circulators, substantially reducing overall energy consumption and providing dependable, maintenance-free operation.

“The Grundfos MAGNA provided the reliability and energy savings the base was striving to achieve,” says Mitch Mayo, sales engineer for Pac West Sales in Alaska. “The maintenance-free design, wide performance range and ease of control selection provided the optimal solution. The new, efficient MAGNA circulators are paying dividends, saving both time and money.”