In the field... Robert O'Brien Technical Heating Co. Mt. Sinai , New York ECM Circulators: what are they and why are they important? ECM stands for electronically commutated motor. ECMs have been around in the U.S. for close to 10 years but really are just starting to gain some serious traction. What are they? They are pumps with permanent magnets that are electronically controlled and usually variable speed; they also convert the incoming alternating current (AC) to direct current (DC). It uses much less electrical energy and makes the pump speed completely variable. The majority of existing small wet rotor circulator pumps are permanent split capacitor (PSC) designs, commonly called PSC motors, and work just fine in most cases, with a couple of shortcomings. The PSC motors use a fair amount of power—typically about 90 watts—and are usually single speed or have three manually selected speeds that when selected converts the “three speed” pump into a single speed, which may or may not be the right speed. Why switch to ECM pumps? What are the benefits for the contractor and customer? Number one, for both, is the reduced electrical consumption with an ECM pump—it’s anywhere from 50-75% reduction in power consumption. This creates substantial savings on a percentage basis, but how much is that in dollars? The run hours vary nationwide but are generally between 1,800-3,000 hours in the U.S. In the New York area, the number is 2,000 hours—we pay about 23 cents kilowatts per hour (kWh) or about $37 per year to operate a PSC circulator. Half of that is an $18.50 savings per year, not a lot by itself but, when considering the incremental cost to upgrade to an ECM, not a bad return on investment at all—about 45 times better than a money market account. Even better, the 45 watts consumption of an ECM pump is at full speed, and these are variable speed pumps. How do they vary speeds? Some of the pumps are Delta T pumps and vary speed based on supply and return temperatures to maintain a constant Delta T, usually 20°F in most systems. These pumps provide a benefit way beyond the electrical savings. How many systems run at the theoretical 20°F Delta T? Very few, usually due to over-pumping. The circulator is just too big and the flow rate too high, which lowers Delta T and increases boiler cycling. The reduction in boiler cycling will yield savings far beyond the electrical cost savings. The other common style is Delta P pumps—these maintain a constant pressure by varying the speed in response to increased or decreased resistance to flow. On a zone pump application, the Delta P pump will never change speeds and the system head never changes. However, on a thermostatic radiator valve (TRV) or zone valve system, resistance to flow will vary as valves open and shut and the pump will change speed to maintain a constant pressure. The variable nature of these pumps adds up to 25% to the electrical savings over a conventional PSC pump. Should every new pump be an ECM pump? Probably most of them, but certainly not all pumps. It may not make economic sense on a zone pump system in rarely used zones, where there aren’t enough run hours to justify the increased cost or in areas with very low cost electrical costs. The formula is as follows: (Run Hours) x (Watt Reduction) x (Cost per Watt) = Annual Savings Watts are Kw divided by 1000. What’s in it for the contractor to reduce consumers’ electrical consumption? Put yourself in the customer’s shoes—would you like to do business with a contractor who is forward looking and concerned about the consumers best interest, striving to install and maintain the most modern, comfortable and efficient systems possible or a company that is happy with doing things the way they were always done with initial cost as the only consideration? Fuel costs vary widely, but electrical costs are much less flexible and are very slow to change, making electrical bills stubbornly high while fossil fuel costs have come down from their highs quite a bit. Electrical costs will remain an issue of importance to consumers. Why not be the guy who is offering the circulator equivalent of the LED bulb instead of the incandescent bulb guy? ICM ICM/March/April 2017 17
ICM March-Apri 2017
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