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True Variable Speed ECMs versus Constant Torque Motors
What are the main differences between True Variable Speed ECM and the popular X13 Constant torque motor? This is a question we get all the time, so we have decided to dedicate a blog to this exact topic. Knowing the difference between the two will help you not only educate customers and staff members, but also understand the pros and cons of both types.
Both motors are considered ECM or “electronically commutated motors” which basically means they both are driven by DC three phase permanent-magnet motors. The main difference between the two is that True Variable ECM motors are constant airflow motors, and X13 motors are, as their name refers, Constant Torque motors.
What is Special About True Variable ECM?
What is Special About True Variable ECM?
True Variable ECM is often used with the highest efficiency systems and are up to 80% more efficient over a standard PSC motor. Unlike constant speed and constant torque ECMs, these are designed as a true variable speed. These motors are programmed to a specific piece of equipment. In the case of the ECM 2.0 and older, or in the case of the new 3.0 motors used in some of the Allied and Daikin equipment, these new motors use the program stored in the main PCB of the equipment.
Static Pressure and True Variable ECM
Static Pressure and True Variable ECM
Each equipment manufacturer would use a specific static pressure profile for that specific piece of equipment. As static pressure changes in the system, the load on the blower changes. If the filters or evaporator coil gets dirty, for example, the static pressure would increase. This would restrict air resulting in less air movement and less load on the motor. The True Variable ECM would increase its speed to make up for the loss of air.
What About Constant Torque ECMs?
What About Constant Torque ECMs?
A constant torque ECM performs more like a PSC motor. There are taps from the motor that provide different programmed torque values, not unlike a three or four speed PSC. When 24 volts is applied to the blower, the different taps will result in different speeds. As static pressure changes, the load to the motor changes. With a constant torque ECM, the output torque of each tap remains the same or constant. As the load changes, the actual operating speed of the motor will change resulting in a lower CFM output.
The Issue of Bad Ductwork Design
The Issue of Bad Ductwork Design
The one true problem that variable speed ECM motors have working against them is ductwork. Poorly designed ductwork, where either the supply or the return have too much static pressure, will be loud. This happens because the ECM tries to increase the airflow rate to make up for the increased static pressure. High airflow in undersized ductwork is loud.
The Issue of Replacement Cost
The Issue of Replacement Cost
One other thing that is worth taking note of is that True Variable Speed motors are considerably more expensive than Constant Torque motors. This might not look like a problem when purchasing a new furnace or air handler, but when the warranty of that system expires, end users can expect to pay a lot more to replace a true Variable Speed ECM than to replace a constant torque motor.
Shop with RSL
Shop with RSL
With 18 branches spanning across Western Canada and over 75 years of experience, you can trust that RSL has the capability to fulfill you HVAC/R needs. If you are interested in purchasing a True Variable Speed ECM or a Constant Torque Motor, you can do so in our online store. If you haven’t already, you can create an RSL account on our Sign Up page.
Contact Us
Contact Us
For any further enquiries into ECMs or constant torque motors, you can contact your local branch to ask any questions you may have. Alternatively, you can email the RSL Online Sales team, and your query will be passed on to the relevant department.