System and Duct Design November 7, 2023, 6:48 pm

November 7, 2023

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HVAC School – For Techs, By Techs

Real training for HVAC ( Heating, Ventilation, Air Conditioning and Refrigeration) Technicians. Including recorded tech training, interviews, diagnostics and general conversations about the trade.

Bryan Orr and Steve Rogers dive deep into measuring power consumption in HVAC blower motors, particularly focusing on the differences between PSC (Permanent Split Capacitor) and ECM (Electronically Commutated Motor) technologies. The discussion stems from a question raised at an educators’ conference about the accuracy of clamp-on meters in measuring blower motor watt draw, as specified in the ACCA Standard 310.

Steve shares insights from extensive testing conducted with different types of motors and power meters. The tests compared PSC motors with constant torque and constant airflow ECM motors across various static pressure conditions. One key finding was that two out of three field-available clamp-on meters tested were capable of accurately measuring true power at levels expected in residential blower motors. However, one meter showed significant inaccuracy at low power levels, highlighting the importance of carefully reviewing meter specifications before use.

The conversation delves into the concept of power factor and its crucial role in understanding the true power consumption of ECM motors. Steve explains that ECM motors often have a low power factor (around 0.6), which can lead to misconceptions about their efficiency if only the current draw is measured. The discussion emphasizes the need for proper measurement techniques, including simultaneous voltage and current readings with the blower door on, to accurately assess motor efficiency.

Key topics covered in the podcast:

Differences between PSC and ECM motor technologies
Importance of power factor in measuring true power consumption
Accuracy of field-available clamp-on meters for power measurement
Impact of static pressure on motor performance and efficiency
Misconceptions about ECM motor efficiency and longevity
Proper measurement techniques for assessing blower motor watt draw
Relationship between duct system design and motor efficiency
Implications of ACCA Standard 310 for HVAC installations
Challenges in comparing constant torque and constant airflow ECM motors
The role of control algorithms in ECM motor performance
Importance of understanding meter specifications for accurate measurements

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