CFR > Title 10 - Energy > CHAPTER II—DEPARTMENT OF ENERGY > SUBCHAPTER D—ENERGY CONSERVATION (parts 400 to 491) > PART 431—ENERGY EFFICIENCY PROGRAM FOR CERTAIN COMMERCIAL AND INDUSTRIAL EQUIPMENT > SUBPART K—Distribution Transformers (§431.191 to §431.198) > 431.196—Energy conservation standards and their effective dates.

431.196—Energy conservation standards and their effective dates.

(a) Low-Voltage Dry-Type Distribution Transformers. The efficiency of a low-voltage dry-type distribution transformer manufactured on or after January 1, 2007, shall be no less than that required for their kVA rating in the table below. Low-voltage dry-type distribution transformers with kVA ratings not appearing in the table shall have their minimum efficiency level determined by linear interpolation of the kVA and efficiency values immediately above and below that kVA rating.
Single phase Three phase
kVA Efficiency (%) 1 kVA Efficiency (%) 1
15 97.7 15 97.0
25 98.0 30 97.5
37.5 98.2 45 97.7
50 98.3 75 98.0
75 98.5 112.5 98.2
100 98.6 150 98.3
167 98.7 225 98.5
250 98.8 300 98.6
333 98.9 500 98.7
750 98.8
1000 98.9
1 Efficiencies are determined at the following reference conditions: (1) for no-load losses, at the temperature of 20 °C, and (2) for load-losses, at the temperature of 75 °C and 35 percent of nameplate load.
(Source: Table 4-2 of National Electrical Manufacturers Association (NEMA) Standard TP-1-2002, “Guide for Determining Energy Efficiency for Distribution Transformers.”)
(b) Liquid-Immersed Distribution Transformers. The efficiency of a liquid-immersed distribution transformer manufactured on or after January 1, 2010, shall be no less than that required for their kVA rating in the table below. Liquid-immersed distribution transformers with kVA ratings not appearing in the table shall have their minimum efficiency level determined by linear interpolation of the kVA and efficiency values immediately above and below that kVA rating.
Single-phase Three-phase
kVA Efficiency (%) kVA Efficiency (%)
10 98.62 15 98.36
15 98.76 30 98.62
25 98.91 45 98.76
37.5 99.01 75 98.91
50 99.08 112.5 99.01
75 99.17 150 99.08
100 99.23 225 99.17
167 99.25 300 99.23
250 99.32 500 99.25
333 99.36 750 99.32
500 99.42 1000 99.36
667 99.46 1500 99.42
833 99.49 2000 99.46
2500 99.49
Note: All efficiency values are at 50 percent of nameplate-rated load, determined according to the DOE Test-Procedure. 10 CFR Part 431 , Subpart K, Appendix A.
(c) Medium-Voltage Dry-Type Distribution Transformers. The efficiency of a medium-voltage dry-type distribution transformer manufactured on or after January 1, 2010, shall be no less than that required for their kVA and BIL rating in the table below. Medium-voltage dry-type distribution transformers with kVA ratings not appearing in the table shall have their minimum efficiency level determined by linear interpolation of the kVA and efficiency values immediately above and below that kVA rating.
Table I.2—Standard Levels for Medium-Voltage, Dry-Type Distribution Transformers, Tabular Form
Single-phase Three-phase
BILkVA 20-45 kVefficiency(%) 46-95 kVefficiency(%) ≥96 kVefficiency(%) BILkVA 20-45 kVefficiency(%) 46-95 kVefficiency(%) ≥96 kVefficiency(%)
15 98.10 97.86 15 97.50 97.18
25 98.33 98.12 30 97.90 97.63
37.5 98.49 98.30 45 98.10 97.86
50 98.60 98.42 75 98.33 98.12
75 98.73 98.57 98.53 112.5 98.49 98.30
100 98.82 98.67 98.63 150 98.60 98.42
167 98.96 98.83 98.80 225 98.73 98.57 98.53
250 99.07 98.95 98.91 300 98.82 98.67 98.63
333 99.14 99.03 98.99 500 98.96 98.83 98.80
500 99.22 99.12 99.09 750 99.07 98.95 98.91
667 99.27 99.18 99.15 1000 99.14 99.03 98.99
833 99.31 99.23 99.20 1500 99.22 99.12 99.09
2000 99.27 99.18 99.15
2500 99.31 99.23 99.20
Note: BIL means basic impulse insulation level.
Note: All efficiency values are at 50 percent of nameplate rated load, determined according to the DOE Test-
Procedure. 10 CFR Part 431 , Subpart K, Appendix A.
(d) Underground Mining Distribution Transformers. [Reserved]

Code of Federal Regulations

[70 FR 60416, Oct. 18, 2005, as amended at 71 FR 24997, Apr. 27, 2006; 72 FR 58239, Oct. 12, 2007]