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// CODE SNIPPET

608.8 Electrical System Efficiency

Green Construction Code 2012 of Maryland > 6 ENERGY CONSERVATION, EFFICIENCY AND CO2e EMISSION REDUCTION > 608 Building Electrical Power and Lighting Systems > 608.8 Electrical System Efficiency
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Electrical systems shall comply with Section 608.8.1.

608.8.1 Prescriptive Compliance

Prescriptive compliance for electrical systems shall be in accordance with Sections 608.8.1.1 through 608.8.1.3.

608.8.1.1 Transformer Efficiency

Distribution transformers installed on the load side of the service disconnecting means shall comply with the provisions of Tables 608.8.1.1(1), 608.8.1.1(2) and 608.8.1.1(3), and the Energy Policy Act of 2005 as applicable.
Exception: The following transformers are exempt from the efficiency standards of Section 608.8.1.1:
  1. Transformers not covered by the Energy Policy Act of 2005.
  2. Transformers for special purpose applications, and not used in general purpose applications.
  3. Transformers with multiple voltage taps where the highest tap is not less than 20 percent more than the lowest tap.
  4. Drive transformers, rectifier transformers, auto-transformers, uninterruptible power supply transformers, impedance transformers, regulating transformers, sealed and nonventilating transformers, machine tool transformers, welding transformers, grounding transformers, and testing transformers.
TABLE 608.8.1.1(1)
LOW-VOLTAGE DRY-TYPE DISTRIBUTION TRANSFORMERS
(Maximum 600 Volt Primary)a
SINGLE PHASE THREE PHASE
kVA Rating Minimum
Efficiency (%)
kVA Rating Minimum
Efficiency (%)
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. All efficiency values for low-voltage transformers are at 35 percent of nameplate-rated load, determined in accordance with the DOE test procedure. 10 CFR Part 431, Sub-part K, Appendix A.
TABLE 608.8.1.1(2)
MEDIUM-VOLTAGE DRY-TYPE DISTRIBUTION TRANSFORMERS
(Maximum 34,500 Volt Primary, Maximum 600 Volt Secondary)a
SINGLE PHASE THREE PHASE
kVA Rating 20-45 kV BIL
Minimum
Efficiency (%)
46-95 kV BIL
Minimum
Efficiency (%)
>96 kV BIL
Minimum
Efficiency (%)
kVA Rating 20-45 kV BIL
Minimum
Efficiency (%)
46-95 kV BIL
Minimum
Efficiency (%)
>96 kV BIL
Minimum
Efficiency (%)
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

BIL = Basic impulse insulation level.
  1. All efficiency values for medium-voltage transformers are at 50 percent of nameplate-rated load, determined in accordance with the DOE test procedure. 10 CFR Part 431, Sub-part K, Appendix A.
TABLE 608.8.1.1(3)
MEDIUM-VOLTAGE LIQUID-IMMERSED
DISTRIBUTION TRANSFORMERS
(Maximum 34,500 Volt Primary, Maximum 600 Volt Secondary)a
SINGLE PHASE THREE PHASE
kVA Rating Minimum
Efficiency (%)
kVA Rating Minimum
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
883 99.49 2000 99.46
— — 2500 99.49
  1. All efficiency values for medium-voltage transformers are at 50 percent of nameplate-rated load, determined in accordance with the DOE test procedure. 10 CFR Part 431, Sub-part K, Appendix A.

608.8.1.2 Voltage Drop in Feeders

The voltage drop in feeder conductors shall not exceed 1.5 percent at design load.

608.8.1.3 Voltage Drop in Branch Circuits

The voltage drop in branch circuit conductors shall not exceed 1.5 percent at design load.

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