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C405.7 Electrical Transformers

Energy Conservation Code 2021 of Colorado > 4 [CE] Commercial Energy Efficiency > C405 Electrical Power and Lighting Systems > C405.7 Electrical Transformers
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Low-voltage dry-type distribution electric transformers shall meet the minimum efficiency requirements of Table C405.7 as tested and rated in accordance with the test procedure listed in DOE 10 CFR 431. The efficiency shall be verified through certification under an approved certification program or, where a certification program does not exist, the equipment efficiency ratings shall be supported by data furnished by the transformer manufacturer.
Exceptions: The following transformers are exempt:
  1. Transformers that meet the Energy Policy Act of 2005 exclusions based on the DOE 10 CFR 431 definition of special purpose applications.
  2. Transformers that meet the Energy Policy Act of 2005 exclusions that are not to be used in general purpose applications based on information provided in DOE 10 CFR 431.
  3. Transformers that meet the Energy Policy Act of 2005 exclusions with multiple voltage taps where the highest tap is not less than 20 percent more than the lowest tap.
  4. Drive transformers.
  5. Rectifier transformers.
  6. Auto-transformers.
  7. Uninterruptible power system transformers.
  8. Impedance transformers.
  9. Regulating transformers.
  10. Sealed and nonventilating transformers.
  11. Machine tool transformers.
  12. Welding transformers.
  13. Grounding transformers.
  14. Testing transformers.
TABLE C405.7
MINIMUM NOMINAL EFFICIENCY LEVELS FOR DOE 10 CFR 431 LOW-VOLTAGE DRY-TYPE DISTRIBUTION TRANSFORMERS
SINGLE-PHASE TRANSFORMERS THREE-PHASE TRANSFORMERS
kVAa Efficiency (%)b kVAa Efficiency (%)b
15 97.70 15 97.89
25 98.00 30 98.23
37.5 98.20 45 98.40
50 98.30 75 98.60
75 98.50 112.5 98.74
100 98.60 150 98.83
167 98.70 225 98.94
250 98.80 300 99.02
333 98.90 500 99.14
— — 750 99.23
— — 1000 99.28
  1. kiloVolt-Amp rating.
  2. Nominal efficiencies shall be established in accordance with the DOE 10 CFR 431 test procedure for low-voltage dry-type transformers.
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