Electronically Commutated Motors (ECMs) have become a game-changer in HVAC and industrial applications, offering increased efficiency, variable speed control, and intelligent operation. However, monitoring their performance requires more than just a standard current sensor due to their lower and more dynamic power consumption. That’s where the RIBXGTA-ECM comes in—an adjustable current sensor specifically designed to detect whether an ECM motor is operating correctly. In this blog, we’ll break down how ECM motors work and how pairing them with the RIBXGTA-ECM can enhance system reliability and efficiency.
Setting a Current Sensor
If a standard 3-phase fan is blowing at any significant amount of CFM, the current drawn when the fan is on will reach many amps greater than when it is off. This gives a field operator setting an adjustable current sensor's trip point a lot of leeway. Just set it to two amps and call it a day. ECM motors draw much less current so that trip point needs to be a little bit more thoughtful. The RIBXGTA-ECM has LEDs on it which guide the operator, making setting a trip point of as small as 0.25 amps a breeze. Careful - be sure the current being set really is the intended operating point.
Where ECM Motors Differ
One distinction between 3-phase motors (or PSC motors) and ECM motors is the fact that the ECM motor has a control board. Traditional motors are dumb, ECM motors are smart. With a traditional 3-phase motor, it will reach full current draw for the application within seconds. That's the normal current draw. Any deviation from that current is a problem. When setting a current sensor, simply turn on the motor and adjust the trip point based on the current it is drawing.
ECM motors, on the other hand, aren't just fully on or fully off. They can be programmed to slowly ramp up or ramp down the speed of the motor over the course of several minutes. They can operate at a specific CFM leading to unintuitive changes in current when there are changes in pressure in the HVAC system. There is also the standby current. The control board in the ECM always draws a bit of current which means the current sensor trip point can't just be set to zero.
Setting an RIBXGTA-ECM
So how do we set a current sensor monitoring an ECM motor?
Set your ECM motor to the lowest intended operating speed. Once you've confirmed it has settled at that speed, attach the RIBXGTA-ECM and set the current threshold with the help of the LEDs on the current sensor. That's it!
About Functional Devices, Inc.
Confidence and Peace of Mind in Every Box
At Functional Devices, Inc., we have been designing and manufacturing high-quality electronic components in the USA since 1969. Our mission is simple: to enhance lives in buildings and beyond by delivering reliable, innovative solutions for the building automation industry. Our product lineup includes RIB® relays, current sensors, power controls, power supplies, transformers, lighting controls, and more—each designed to meet the highest industry standards.
We test 100% of our assembled products, ensuring an exceptionally low failure rate—less than 1 in 16,000 in the field. This commitment to excellence means you get products that perform reliably, reducing downtime and increasing efficiency. With every Functional Devices product, you receive more than just a component—you gain confidence and peace of mind knowing your systems are built on trusted, field-proven technology.