Abstract:

The California Investor-Owned Utilities (CA IOUs) analyzed the applicability and effectiveness of the National Electrical Manufacturers Association (NEMA) MG 1 Part 34 Test Procedures for Totally Enclosed Air-Over (TEAO) motors. TEAO motors are a specific type of motor used in heating, ventilation and air conditioning (HVAC) systems and other applications where cooling is provided by an external airflow. Given the widespread use of TEAO motors, it is crucial to have standardized and reliable test procedures that can accurately measure their efficiency and performance. The evaluation focuses on understanding how well the NEMA MG 1 Part 34 Test Procedures (“Part 34”) measure the performance and efficiency of these TEAO motors. The study involves a detailed analysis of two different test procedures provided by Part 34 (“Test Procedure 2” or “TP2” and “Test Procedure 3” or “TP3”) to determine their repeatability, reproducibility, and accuracy. Accurate efficiency measurement is critical for ensuring energy conservation and compliance with regulatory standards.

The primary objectives of this study were to answer the following research questions:

Objective 1: Does Part 34 Test Procedure 2 generate representative and repeatable measured efficiency results?

Objective 2: Can repeatability be enhanced by refining aspects of Part 34 Test Procedure 2, such as requirements related to airflow, blower characteristics, blower placement, and temperature measurement?

Objective 3: Are Part 34 Test Procedures 2 and Test Procedure 3 functionally equivalent in practice? Does either method introduce unique bias or result differences?

Key findings from the study were:

1. Results from TP2 were repeatable. Two measurements each of individual motors produced results within measurement uncertainty for 95% of motors for total losses and for 100% of motors for full load efficiency, counting all motor groups.
2. While tests of individual motors were repeatable, performance sometimes varied among different motors within a motor group. 
3. Tested motor efficiency was generally below NEMA Premium efficiency. Note that TEAO motors at this time were not required to meet NEMA Premium, and often may be using hardened environment seals with performance impacts. 
4. Sealed bearings are associated with significantly higher losses compared with open bearings for these test samples, resulting in different efficiencies. 
5. Variations in blower outlet size, distance, and blower angle significantly changed test results. Additional specification in Part 34 may be beneficial.
6. Temperature rise is an important driver of test results.
   1. Default temperatures based on insulation class may not correspond well with actual operating conditions. 
   2. If the nameplate temperature rise is inconsistent with typical operating conditions, then efficiencies from tests at the nameplate temperature rise may not provide accurate guidance to consumers about actual performance.
7. TP2 and TP3 are not functionally equivalent; 
   1. Significant differences in test result losses were observed between TP2 and TP3. TP3 was biased toward higher losses.
   2. Differences were in the no-load portion of testing, where TP3 had a stator temp 20 °C higher than TP2, nearly an insulation class (i.e., 25 °C).  
   3. Temp difference estimated to be fan on versus fan off during that test section.
   4. TP3 changed the motor losses by a NEMA band (10% of losses) for 7% of motors, and by 0.5 NEMA band for 26% of tested motors. 
   5. The difference between mean efficiencies for TP2 and TP3 for each motor group was smaller than the lab measurement tolerance for efficiency.  

Based on this research, we recommend certain improvements to the test procedure and for motor labeling and testing to ensure accurate representation of motor efficiency in the field.

The California Investor-Owned Utilities (CA IOUs) analyzed the applicability and effectiveness of the National Electrical Manufacturers Association (NEMA) MG 1 Part 34 Test Procedures for Totally Enclosed Air-Over (TEAO) motors. TEAO motors are a specific type of motor used in heating, ventilation and air conditioning (HVAC) systems and other applications where cooling is provided by an external airflow. Given the widespread use of TEAO motors, it is crucial to have standardized and reliable test procedures that can accurately measure their efficiency and performance.