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.
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.
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!
Functional Devices, Inc., located in the United States of America, has been designing and manufacturing quality electronic devices since 1969. Our mission is to enhance lives in buildings and beyond. We do so by designing and manufacturing reliable, high-quality products for the building automation industry. Our suite of product offerings include RIB relays, current sensors, power controls, power supplies, transformers, lighting controls, and more.
We test 100% of our products, which leads to less than 1 out of every 16,000 products experiencing a failure in the field.
Simply put, we provide users of our various product confidence and peace of mind in every box.