Code Change Summary: Changes made to address Design B Premium Efficiency motors.
Design B premium efficiency motors are motors with a higher level of energy efficiency than the Design B energy-efficient motors referred to in Section 430.52 of previous editions of the NEC® (see below Table 3.3 History of Motor Efficiency Improvements from the U.S. Dept. of Energy Premium Efficiency Motor Selection and Application Guide).
Design B premium efficiency motors have largely replaced energy-efficient motor installations throughout the United States due to government regulations on energy conservation of specific electrical equipment dating back to 2010 in Title 10, Chapter II Subchapter D, Part 431 of the US Code of Federal Regulations.
In the 2023 NEC®, Section 430.52(C) as well as Table 430.52(C)(1) have been updated to include Design B Premium efficiency motors (see NEC® Table 430.52(C)(1) below).
Prior to this code change, when determining the maximum rating or setting of motor branch-circuit short-circuit and ground-fault protective devices, the values in previous Table 430.52 for Design B energy-efficient motors were also applied to Design B premium efficiency motors even though the table did not specifically mention Design B premium efficiency motors.
Table 3.3 History of Motor Efficiency Improvements (full-load efficiency in %) |
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HP |
1944 |
1955 U-Frame |
1965StandardEfficiency |
1980StandardEfficiency |
19941StandardEfficiency |
20042EnergyEfficiency |
20123PremiumEfficiency |
7.5 |
84.5% |
87% |
84% |
-- |
85.5% |
89.5% |
91.7% |
15 |
87% |
89.5% |
88% |
86.5% |
86.6% |
91.1% |
92.4% |
25 |
89.5% |
90.5% |
89% |
88% |
89.3% |
92.4% |
93.6% |
50 |
90.5% |
91% |
91.5% |
90.4% |
91.3% |
93.2% |
94.7% |
75 |
91% |
90.5% |
91.5% |
90.8% |
91.7% |
94.1% |
95.4% |
100 |
91.5% |
92% |
92% |
91.6% |
92.3% |
94.5% |
95.4% |
Table 430.52(C)(1)Maximum Rating or Setting of Motor Branch-Circuit Short-Circuit and Ground-Fault Protective Devices |
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Percentage of Full-Load Current |
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Type of Motor |
Nontime Delay Fuse1 |
Dual Element (Time-Delay) Fuse1 |
Instantaneous Trip Breaker |
Inverse Time Breaker2 |
Single-phase motors |
300% |
175% |
800% | 250% |
AC polyphase motors other than wound-rotor |
300% |
175% |
800% |
250% |
Squirrel cage — other than Design B energy-efficient — and Design B premium efficiency |
300% |
175% |
800% | 250% |
Design B energy-efficient and Design B premium efficiency |
300% |
175% |
1100% |
250% |
Synchronous3 |
300% |
175% | 800% | 250% |
Wound-rotor |
150% |
150% | 800% | 150% |
DC (constant voltage) |
150% |
175% |
250%
|
150% |
Based on the 2023 NEC, which of the following is true?
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