What Is Up With Blower Amps & Watts w/ Steve Rogers

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

Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool.

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Check out our handy calculators here or on the HVAC School Mobile App for Apple and Android.

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#airflow #blower #blower motor #blower motors #current #duct design #ecm #electrical #hvac #motors #Power #power factor #PSC

Author:

Bryan Orr

Company: HVAC School

Position: Founder

Steve Rogers

Company: The Energy Conservatory (TEC)

Position: President

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In this short Q&A podcast, Bryan answers a listener-submitted question about apps for doing proper loads. Fred specifically asks about apps or charts that can help an HVAC contractor determine the insulation value of a home without assuming numbers or drilling into walls during load calculations.

Load calculations account for all the ways that BTUs can enter or leave a home: conduction, convection, and radiation. Insulation prevents heat transfer via conduction, so it’s important to the load calculation process. High-end HVAC design software like Wrightsoft and Kwik Model 3D will have these features built into them (based on the age and location of the home). ASHRAE’s handbook also has tables and data with R-values and U-factors to help you out with Manual J load calculations.

RED Calc is an app that allows you to calculate a wall’s R-value with measurements, including surface and air temperatures indoors and outdoors. This RED Calc software is available through the U.S. Department of Energy, as is REScheck. The DOE insulation fact sheet is also quite valuable, as are The Engineering Toolbox and materials straight from the insulation manufacturers.

The best way to get a comprehensive load calculation is to have a lot of tribal knowledge about how houses are built in your area, analyze energy bills, and combine tools like RED Calc with building performance tests.

RED Calc is available through the U.S. DOE at https://basc.pnnl.gov/redcalc. REScheck is available at https://www.energycodes.gov/rescheck.

ASHRAE’s resources are available at https://ashrae.org/technical-resources.

Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool.

Purchase your tickets or learn more about the 6th Annual HVACR Training Symposium at https://hvacrschool.com/symposium. Subscribe to our podcast on your iPhone or Android. Subscribe to our YouTube channel. Check out our handy calculators here or on the HVAC School Mobile App for Apple and Android.