The Condenser - Why Modulating?

Most actuators can fully open or fully close a unit, but some can hold in between positions. Learn more about modulating actuators in this quick Condenser article.

Actuators open and close adjustable blades on dampers and louvers. Most of them hold one of two positions, fully open or fully closed. Modulating actuators can hold positions between open and closed. But why?

Why would you need an actuator to hold the blades partially open? Let’s talk about modulating actuators and what they can do for your dampers.

A standard electric actuator is either powered or unpowered. These states correspond to the actuator’s opening and closing actions. Phrases like “PO/SC” (power opened, spring closed) explain how the actuator works in each state. In this case, the actuator will open with power and close when unpowered.

Modulating actuators can do more while powered with a controller unit. This unit will direct the actuator to hold a predetermined blade angle, then move to full open or to another semi-open angle.

With a controller, the actuator can hold several semi-open blade positions. It can also fully open and fully close the damper, like a standard electric actuator.

Why would you need semi-open? As we discussed before, balancing dampers also hold a semi-open blade angle. Balancing dampers do not close completely. In fact, their blades are locked in place and only move when they need adjustment. This helps balance air pressure in the duct and alleviate issues with heating and cooling in connected rooms.

With modulating actuators, control dampers can double as balancing dampers. By holding a semi-open position, the damper’s blade will slow incoming airflow and regulate air pressure. Technicians can adjust the damper from the controller and monitor air pressure with additional sampling equipment. This makes it easier to make the necessary adjustments.

The control damper can still provide flow control, providing full shut off as needed.

Modulating actuators add versatility to your control dampers, but they may require additional equipment for full functionality. Like all things in HVAC design, you will need to weigh your options carefully before deciding.

Always check product submittals to ensure your options will work for your project.

For more on actuators and airflow control, check out these Newsstand articles:

• The Condenser - Actuator Closure Types
• Actuators - Making Adjustments
• Four Ways to Make Efficient Airflow Dampers
• Air Performance and Control Dampers