When you look at buying a new HVAC system it will surely arise when the HVAC salesman or HVAC contractor who comes to give you an estimate will show an HVAC system that has a variable speed motor or the GE ECM (Electronically Commutated Motor) installed in it. These are systems that have a higher efficiency rating than the HVAC equipment that has the typical electric blower or condenser fan motor. The ECM (Electronically Commutated Motor) uses less energy than the standard PSC motor that is commonly used in air handlers and condensers to mover air. The ECM motor also offers more control which has good benefits in HVAC applications.
HVAC Motors That Save Energy
GE or General Electric and Emerson (to name a few) produces these variable speed ECM motors for the HVAC industry. The HVAC manufacturer then takes these ECM motors and installs them inside their air handlers and condensing units. Not all ECM motors are variable speed. For example, in condensers the motor has a fixed speed the same as many standard PSC motors. The reason manufacturers use the more expensive ECM motor and runs them at fixed speeds is because they use less energy than the standard PSC motors commonly used in condensing units. This allows the condensing unit to use less energy and give the HVAC equipment a higher SEER rating. Typically the ECM motors in the air handlers are variable speed but require a control board to control the speed to ramp up and down according to what the controller is calling for. The control boards can also be set to change the amount of air the ECM blower moves through the air handler. This is commonly done with dip switches and gives the manufacturer a lot of flexibility for offering a single air handler that can accommodate different air flow capacities.
How the ECM Motor Works as a Blower
Trane, Carrier, Rheem, York, and all the big HVAC manufacturers (and a few small ones also) have their own tag line for describing the ramp up and ramp down for the ECM blower motor. The air handler will turn on and ramp to 50% (or whatever percentage the manufacturer deems appropriate) and then after so many minutes as determined by the program the ECM blower will ramp to 100%. When the thermostat satisfies the motor will slowly ramp down and then stop after so many minutes. This is often referred to as soft start and soft stop. The typical PSC motor starts and immediately goes to 100% and then stops almost immediately (aside from inertia) when the thermostat satisfies. The benefit of this is it can reduce humidity in the air when the unit first starts. This is important in the summer time when humidity levels are typically high in many geographical areas. The less the humidity in the air the more cooler you will feel. A big part of air conditioning is humidity removal and the variable ECM blower motor helps humidity removal when the motor is stepped up as described.
Efficiency Ranges and Other Factors for the ECM Motor
The ECM motor (Electronically Commutated Motor) is preprogrammed to run at certain speeds as determined by the HVAC manufacture such as Trane, York, Lennox, or Carrier. The first stage in the program is usually a lower speed in the cooling cycle to remove humidity. A slower rate of airflow across the evaporator coil allows the cold evaporator coil to remove the humidity in the air. The second stage of the ECM motor is usually 100% peak speed as designed for CFM’s and tonnage of the system. From low to high speed the ECM (Electronically Commutated Motor) maintains a good efficiency range between 60% and 80% between all speeds versus the PSC motor with multiple windings getting between 10% efficiency at lower speeds to nearly 50% efficiency at higher speeds. As you can see that no matter the speed of the ECM it maintains efficiency and reduces the amount of electricity consumed to do the same thing the PSC motor does to move air. Another bonus for the ECM motor especially in cooling mode is the fact that temperature of the motor is constant and typically at or near ambient temperature whereas the operating temperatures of the PSC motor is 90 degrees F. to 170 degrees F. This means the air conditioner that uses the PSC motor must also overcome the heat generated and added to the system by the PSC motor while the heat added to the system with the ECM motor is nil to none.
Common Sense Protection for the ECM Motor
ECM motors are here and they offer a higher efficiency because they use less energy and provide benefits that the typical PSC motor cannot offer. ECM blower motors have been around for a while and have proven their reliability in HVAC applications. They are not trouble free though as with any mechanical or electrical device problems can occur. To prevent some of the problems that occur it is recommended that surge protectors be used because of the solid state controls that control the ECM motor. Surge protectors can be purchased at most electronic stores and even some HVAC wholesaler’s offer surge protectors. By purchasing the air handler or gas furnace and condenser with an ECM motor you will consume less energy when your air conditioner or heating system is running. This means lower utility bills and more money in your pocket in the long run.
This entry was posted on Monday, September 4th, 2006 at 9:34 pm and is filed under Technical Reference.
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