These are single-phase motors running off of a DC power signal (rectified, if running off of an AC power source) that use an electronic method of switching power to alternating coils around the rotor in order to induce a rotating magnetic field. (More information available here).
They are much more efficient than traditional electro-mechanically commutated motors, and local utilities offer rebates for their use. But ECM's also provide additional benefits on heat pump applications.
Because the motor speed is controlled by the speed at which the magnetic field rotates around the shaft, and that speed is controlled by the electronic switching of the ECM, these motors are inherently variable speed devices. When applied in equipment, this variable speed capability is either used directly, providing a variable speed capability on the fan, or, more commonly on packaged refrigeration equipment, as a self-balancing mechanism to provide a fixed discharge airflow, independent of external static pressure.
Additionally, the electronic switching in these devices allows for more torque to be delivered to the rotor, allowing for greater static pressure capability on the fan it is driving.
Florida Heat Pump has capitalized on these advantages by offering ECM motors on their heat pump products. FHP ES and GS series heat pumps are supplied with ECM fan motors for efficiency, ease of air balancing, and unmatched static pressure capacity.
Let's consider those last two further. FHP uses the ECM to self-balance their units to a set leaving air flow (low, medium and high settings controlled by jumpers on the control board) regardless of external static on the fan (within a given range). Let's look at the fan table for these units (2 1/2 ton ES030 shown):
(click for larger image)
You either get 850, 1000 or 1150 CFM at anywhere from 0.10" to 1.2" of external static pressure. All you do is set the jumper to the flow rate you want to see and then the fan motor will automatically adjust itself to provide the airflow desired.
But look at that range of static pressure! Typical heat pump fans might only provide three tenths of an inch or so external static. Having over an inch available (smaller units offer about 0.80" external) is a game changer, making it very possible to have improved filtration (LEED® points) or air side economizers (energy code requirement) on these inherently efficient heat pump systems!
And these advantages are above and beyond the improved energy efficiency that is realized by using the more efficient fan technology.
ECM motors improve WSHP efficiency, reduce balancing labor and widen the applicability of these already efficient systems.
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