Actuators and motors are commonly used in the HVAC industry, but not completely understood.
So what’s the difference between and two?
In Geek Speak Terminology:
- The term “Actuator” typically refers to a device that provides linear motion… like a piston, a rod is pushed in a linear manner when voltage is applied.
- A Motor is a device that provides rotational movement, like in a toy car, the motor spins a wheel usually through gears to reduce the speed and increase the torque.
A Motor is designed to spin from the shaft, often at high speed or Revolutions Per Minute (RPM). HVAC motors are most often chosen to operate fans.
Motors are selected and classified by Horse Power (HP), RPM, and Voltage to mention a few. See NEMA Rating to view industry motor standards throughout North America!
Webster’s Definition: Horsepower – A unit of power equal in the United States to 746 watts and nearly equivalent to the English gravitational unit of the same name that equals 550 foot-pounds of work per second
An Actuator is not intended for continuous shaft rotation, but for precise positioning. Most rotating Actuators are slow to position, and do not rotate more than 90 degree in any direction.
Most HVAC Actuators are controlled using a 24 VAC power source, which uses analog positioning. Meaning the actuator is rotated according to a variable voltage or amperage. Most often a 2-10 Volt signal, or 4-20 Milliamp signal.
With the use of controls, actuators are very useful. An economizer actuator connected to a mixed air sensor, and a Temperature, or Enthalpy sensor will vary the economizer’s dampers allowing specific quantities of air to pass through.
Not all actuators use motors. Some are pneumatic, hydraulic, or vacuum. The purpose of an actuator is to move in a linear fashion, or to rotate a shaft to a specific position.
Actuators offer solutions for control dampers, air handlers, economizer units, VAV terminal units, fan coil units, fan shutters, and unit ventilators.
Actuator static load verses dynamic load?
Actuators are designed to rotate to a specific position and hold. In the case of a damper, the process of moving the dampers to a specific spot is called Dynamic Load. Dynamic, working, or lifting load is the force that will be applied to the actuator while it is in motion.
Once a specific position is obtained, an actuator must hold & maintain that position, this is called a static load. Static or holding load is the force applied to the actuator when it is not in motion.
Actuators are chosen by their torque value measured in foot pounds.
Webster’s Definition: Foot-Pound – A unit of work equal to the work done by a force of one pound acting through a distance of one foot in the direction of the force.
There are many factors to consider when choosing the proper actuator or motor for a job. It is imperative to replace a motor or actuator with the exact same product. Choosing the wrong replacement part could be costly and in some situations dangerous.