How to Choose 24V BLDC Motors to Improve HVAC Efficiency and Cut Maintenance Costs

The operating efficiency of Heating, Ventilation, and Air Conditioning (HVAC) systems is critical to modern building management. The choice of motor, specifically, the shift to low-voltage 24V Brushless DC (BLDC) motors, represents one of the most significant upgrades an engineer can make to cut energy use and decrease long-term maintenance costs.

This guide outlines the key principles for selecting 24V BLDC motors for HVAC—explaining why they outperform AC designs and how to match torque, speed, and efficiency parameters to your HVAC application.

Why BLDC is Superior to AC Induction

Engineers often face a choice between AC induction and BLDC motors in HVAC design. In most cases, BLDC motors provide superior performance and efficiency.

Their key advantages are summarized below.

Maximum Energy Efficiency

BLDC motors are inherently more energy-efficient than induction motors because they use permanent magnets on the rotor to generate motion directly. This design eliminates the energy loss caused by magnetizing current and ensures that almost all input power contributes to mechanical output.

Unlike traditional AC motors, BLDC motors maintain high efficiency even at partial loads, which is especially valuable in HVAC systems where airflow demand changes throughout the day. Their lower heat generation not only reduces wasted energy but also minimizes the cooling load on the system, allowing the HVAC unit to operate more efficiently and reliably over time. 

Enhanced Speed Management

BLDC motors are designed for smooth, precise speed modulation across a wide operating range, allowing HVAC systems to adjust airflow and capacity in real time.

Since HVAC loads vary significantly throughout the day, variable-speed operation delivers the most substantial energy savings. For instance, a motor running at 50% speed can consume less than one-eighth the energy required at full speed.

Unmatched Reliability and Low Maintenance

BLDC motors are inherently much more reliable than brushed motors. 

• No Wearable Components - This means no need to replace brushes, and newly-formed carbon dust cannot form or enter the motor and other components 
• Longer Lifespan - The weakest point of wear is usually for the bearings. Seek out motors with high-quality, sealed, and permanently lubricated bearings if you desire maximum operational life, which can often be at 20,000 to 40,000 hours or greater! 

How to Choose 24V BLDC Motors?

Once the decision is made to use a 24V BLDC motor for HVAC, selecting the correct model requires precision in sizing, voltage management, and environmental robustness.

Precision Sizing (Torque and Voltage)

Motor sizing is paramount; an oversized motor wastes money and energy, while an undersized motor overheats and fails prematurely.

Continuous vs. Peak Torque

Always calculate the continuous torque and speed needed to operate the load (e.g., the CFM required for a blower fan). Choose a motor where the continuous torque rating safely exceeds the maximum application requirement, leaving room for momentary overload or unexpected resistance. Brushless DC motors are ideal because they provide the smooth, continuous torque characteristics required for quiet, comfortable operation.

Considering 24V Limitations

Since the motors are low-voltage (24V), the current draw (I = P/V) for a given output power is much higher than in high-voltage motors. The current draw must be within a practical level for the power source and wiring. For low-power HVAC subsystems — such as smart air dampers, mini ventilation units, or embedded fan modules — compact 24V BLDC motors (typically 50–100 W, 3000 rpm) like those from Brushless.com provide high efficiency and long service life while keeping control and maintenance simple.

For high-power commercial applications, consider moving to 48V or 96V BLDC to reduce current draw and cable gauge size, and lower switching strain on the motor controller.

Depending on the application type, power, and control requirements, 24V BLDC motors for HVAC can be selected across a wide range of subsystems. The table below provides a quick reference for typical configurations:

NEMA Standards

For larger commercial applications, adhering to NEMA standard frame sizes (e.g., NEMA 34 for large central air handlers) ensures consistency and parts compatibility. NEMA standard BLDC motors offer higher power density and torque output in a compact footprint.

System Integration and Environmental Robustness

1. Noise and Vibration - Quiet operation is essential in occupied spaces. While BLDC motors are generally quieter than AC, look for controllers that offer advanced sine-wave commutation instead of basic six-step/trapezoidal methods. Sine-wave commutation minimizes torque ripple, ensuring a smoother and quieter acoustic profile.
2. Environmental Protection (IP Rating) - Always verify the Ingress Protection (IP) rating of both the motor and controller. Motors located in dusty mechanical rooms or exposed to moisture (e.g., outdoor units, coil environments) must meet at least an IP54 or IP65 rating.
3. Temperature Range - Verify that the motor can operate reliably across the full range of expected ambient temperatures without derating its performance, which would compromise system capacity in extreme weather.

Expert Recommendations for BLDC Motor Selection

To support effective motor selection, the following table summarizes expert recommendations and practical guidelines for integrating BLDC motors into HVAC systems.

For example, compact HVAC-oriented BLDC motors from Brushless.com integrate PWM and Modbus communication for easy feedback and control integration with modern HVAC systems.

Additional Pitfalls to Watch For

While the table above outlines best practices, engineers should also be cautious of a few practical pitfalls during selection and integration:

• Improper motor sizing: An undersized motor can overheat or fail prematurely, while an oversized one wastes energy and cost.
  
  
• Voltage–current imbalance: At 24 V, current rises rapidly with load—verify supply and wiring capacity to avoid voltage drop.
  
  
• Ignoring total lifecycle cost: Focusing solely on purchase price can overlook long-term savings from higher efficiency and reduced maintenance.

ROI Considerations

Although 24 V BLDC motors cost more upfront than standard AC units, their energy savings, reduced maintenance, and extended lifespan often yield full payback within 2–4 years of operation. Over a 10-year lifecycle, total ownership costs are typically 25–40% lower—making BLDC technology a sound long-term investment for efficient, reliable HVAC systems.

Summing Up

Choosing 24V BLDC motors with a focus on maximized efficiency, appropriate sizing, and built-in dependability is the clearest way to future-proof your HVAC system. By following the logical progression of Why (efficiency and reliability) and How (precision specs and environmental checks), you ensure maximum longevity and performance, significantly reducing both energy use and expensive, unexpected maintenance calls.

FAQs

What is the primary reason to choose a 24V BLDC motor over a standard AC motor for HVAC? 

The primary benefit is efficiency and speed control. BLDC motors eliminate magnetic induction losses and physical brush friction, giving them an efficiency advantage of up to 30% over similar AC motors. Crucially, they are designed for continuous variable speed control, allowing the HVAC system to perfectly match airflow to demand, avoiding the energy waste of fixed, oversized AC motors.

Why is 24V DC used instead of 120V or 240V AC for smaller systems?

Selecting 24V DC is a common, low-voltage standard for smaller commercial and residential systems because it is inherently safe, reduces electrical hazard, and is often used for control circuits, simplifying system wiring and integration.