a stainless steel rotor can and react to the magnetic forces created by electromagnetic poles in the stator. A microprocessor, which “sits on board” the pump, reverses the polarity of the stator poles rapidly (within milliseconds) forcing the rotor to be rotated in the proper direction. The faster these poles reverse their polarity, the faster the rotor spins, meaning the faster the impeller spins. ECM circulators can provide four times more starting torque compared to a permanent split capacitor (PSC) wet rotor pump. This additional starting torque pretty much eliminates the concern of a pump experiencing a stuck rotor after a summer shutdown. These ECM pumps incorporate a microprocessor that has software on board, allowing the pump to perform many functions. For example, one application may call for a constant pressure differential where the building is zoned with zone valves. Normally as valves close, the pump would develop additional head pressure across the remaining open zones, causing an increase in flow rate through these zones. This wastes energy as well as potential noise problems due to increased velocity. With this constant differential in pressure capability, as valves close, the pump momentary senses an increase in differential pressure and quickly slows down the pump’s speed to eliminate the change in pressure. The result is no change in flow rate through the remaining open zones, no wasted energy and no velocity noise problems. Another application that the microprocessor can control is called proportional differential pressure. The circulator control is set for a specific design head loss for a system. Now when the zone valve (or valves) closes, once the pressure differential starts to climb, the circulator reduces its motor speed. The difference here is with proportional control, instead of maintaining a set differential. It will lower the speed and thus pressure differential proportionally to the reduction in flow rate. The result is an increased reduction in energy consumption. The efficiency of these “greener” circulators is designed to meet the ever increasing efficiency standards that are slowly making their way over to North America. Their “wire to water” efficiency is higher than the current PSC wet rotor circulators, their multiple application capabilities with the on board microprocessors and their reduction in wattage use make them a very compelling alternative to the industry’s current offerings. You should become aware and comfortable with this newer technology. ICM If you have any questions or comments please call me at 1-800-423-7187, e-mail me at gcarey@fiainc.com or follow me on Twitter at Ask_Gcarey. ICM/July/August 2016 19
ICM July-August 2016
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