HVAC Selection Guide: Why Slow Thermal Actuators Ruin Precise Temperature Control

When configuring Fan Coil Unit (FCU) systems, decision-makers often overlook the terminal component: the Actuator. This small device determines whether your climate control is a stable line or a fluctuating wave.

1. Understanding Temperature Overshoot

The feeling of a room being "too cold one minute and too warm the next" is rarely a fault of the chiller. It is a classic case of Control Lag, which leads to Temperature Overshoot. In control theory, lag prevents the system from stabilizing at the setpoint efficiently.

2. The Great Divide: 5 Minutes vs. 30 Seconds

Thermal Actuators: The Wax Expansion Delay

●Mechanism: These rely on heating a wax element until it expands to push the valve.

●Response Lag: It typically takes 3 to 5 minutes to fully actuate.

●The Flaw: By the time the thermostat sends a "Close" signal, the actuator still needs minutes to cool down and retract. During this delay, water continues to flow, causing the room temperature to drift far beyond the setpoint.

Saswell SA905-S: Direct Motorized Precision

●Mechanism: Utilizes a high-efficiency stepper motor for direct mechanical drive.

●Fast Response: Complete actuation occurs within 30 seconds.

●Advantage: Instant execution of commands ensures that water flow is cut off the moment the target is reached, maintaining a flat temperature curve and eliminating discomfort.

3. Integrated Systems Perspective: Why Algorithms Demand Speed

Modern Building Management Systems (BMS) utilize PID Control Algorithms that require a tight feedback loop.

4. Eliminating "Data Noise" for System Efficiency

Slow hardware creates "Phase Lag" in the data collected by the BMS. This inaccuracy forces the system to make inefficient adjustments to pump speeds and chiller loads.

The Saswell SA905-S eliminates this "dead time," allowing energy output to match real-time demand perfectly, which significantly lowers operational costs (OPEX).

5. Verdict: Don't Let Sluggish Hardware Be Your Bottleneck

For projects where climate precision is non-negotiable—such as luxury hospitality or laboratories—the choice is clear. Replace sluggish thermal actuators with fast-acting, motorized linear actuators like the Saswell SA905-S.

Fast Actuator for PID Control Systems

SA905-S Eliminate Data Noise, Boost System Stability