PLUMBING


strategy in each building. Multiple boilers and a series of smaller circulators in a secondary loop would transfer warm fluid from a primary loop to the individual system loops. This included: 1) low-temperature water for the radiant heating and snowmelt systems; 2) high- temperature water for the hot water unit heaters warming the two


“vacuum buildings” and 3) an indirect water heater supplying the carwashing equipment. (The indirect unit was subsequently eliminated as unnecessary.) The number of circulators in all of these loops totaled 39, all fixed-speed models. Even while bidding the project,


McMullen pondered an alternative approach to the pumping. Upon winning the contract, he met with MDM sales representative Todd Sisson to revisit the pump strategy. The team thought they could shrink the circulator total to 19 by changing the piping layouts from primary- secondary to a direct supply-and-return. The new pumps would be somewhat larger and with more horsepower, but reducing the number of pumps from 39 to 19 and eliminating all of those electrical connections would cut costs substantially. (The final savings turned out to $12,368.) Reducing the number of


circulators by 20 would inevitably have lessened ongoing maintenance hours and costs, of course. But PJ’s believed that their new approach could also shrink the airport authority’s monthly electric bills by a substantial percentage. “Just looking at the total wattage of the 20 circulators we were eliminating, we thought we could cut power consumption by half at least,” says McMullen. “At least” is the key phrase here. PJ’s not only wanted to halve the


number of pumps but also to introduce a new, power-saving technology into the mix, ECM (electrically commutated motor) variable-speed circulators. As already noted, all the pumps in the original design for the carwash were constant-power — that is, “fully on no matter how much power is actually required,” explains Erik Chidester, a PJ’s field supervisor who oversaw the installation. “We recommended a


relatively new type of circulator that automatically adjusts its speed according to current demand, instead of maxing out every time it came on. We figured this variable-speed technology could cut power consumption by up to 70%.” The circulators that PJ’s


ultimately recommended were the 115-volt Alpha and the 230-volt Magna, made by Grundfos Pumps USA and supplied by MDM. Both feature a permanent magnet motor design to cut power consumption dramatically and both are equipped with proprietary logic circuitry — trade- named AUTOADAPT™ — that automatically varies circulator speed to match system demand. The Magna is the larger


of the two circulators, with a flow range of up to 170 gallons per minute (gpm) and a head range up to 42 feet. Six of these units were ultimately installed to control the movement of warm water from the boilers to PEX loops in the snowmelt slabs outside the three buildings. Five of the smaller ALPHA circulators (22 gpm, 19 feet of max head) were subsequently used for the radiant slab heating system inside the carwash facility, one for each of five zones, each with a different load. Rounding out the pump


23


says Chidester. “Variable speed pumps like the


ones used on the Gallatin project eliminate the margin of error for friction calculations traditionally used to size pumps,” adds David Weiel, P.E., the mechanical designer on the project. Reputable engineers


Pat and Erik have become huge fans of variable-speed circulator technology. Says McMullen: "I have never come across a circulator that works so easily and efficiently with so little power” as the Alpha and Magna models made by Grundfos.


use the best tools and techniques available to them to calculate friction losses. But not every situation is ideal, and piping layouts often change in the course of construction. As a result, projected head losses from calculated design parameters don’t always match what occurs in the real world once a system has been built.”


Field supervisor Erik Chidester inspects one of the circulators, whose one-touch, button-type interface permits the user to toggle quickly and easily among seven different hydraulic operating modes, including the AUTOADAPT setting. Five of these ECM variable- speed circulators were used for the radiant heating system inside the car wash facility.


package at Gallatin are four Grundfos UP26-99 circulators (115-volt) and four Grundfos UPS26-150 circulators, all used at fixed speeds to manage boiler-loop circulation. “Thanks to AUTOADAPT,


we were able to use the same Alpha circulator in all five zones in the carwash building, despite their differing loads,”


Other cost savings The switch to variable-speed


circulators enabled PJ’s to trim installation costs in two other important areas: • No need for circuit setter


balance valves. The original engineering drawings called for circuit setters to be installed with


e Continued on p 24


phc january 2011 www.phcnews.com


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