Lineworker Reference

Construction Standards

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Fuse Calculator
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Enter values above
Enter values above
Load Calculator
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Calculates 100%, 200%, and 250% load amps per phase.
Enter values above
Voltage Tolerances
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Range A (±5%) enforced at meter. Range B for extreme conditions.
Nominal Range A Range B
120 V 114.0–126.0 104.4–127.2
208 V 197.6–218.4 181.0–220.5
240 V 228.0–252.0 208.8–254.4
277 V 263.2–290.9 241.0–293.6
480 V 456.0–504.0 417.6–508.8
Single Phase Fusing
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All Single Phase Fuse Rating @ 150% Min.
25 kVA ÷ 7.97 kV = 3.14 A
× 1.5 = 4.7 A → 6K Fuse
kVA 2400V 7970V
5 6K 3K
10 10K 3K
15 10K 6K
25 20K 6K
37.5 30K 10K
50 40K 10K
75 65K 15K
100 80K 25K
167 100K 40K
Three Phase Fusing
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@ 200% Min (<225 kVA)
@ 100% Min (≥225 kVA)
kVA 4160V 13800V
15 6K 6K
30 10K 6K
45 15K 6K
75 20K 10K
112.5 30K 10K
150 40K 15K
225 40K 15K
300 50K 25K
500 65K 25K
750 100K 40K
1000 140K 40K
1500 N/A 65K
2500 N/A 100K
Vertical Clearances
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At mid-span (lowest sag). NESC 232/234.
Surface Sec Pri
Pedestrian 12 ft 14 ft
Res. Drive 12 ft 16 ft
Commercial 16 ft 16 ft
Public Roads 18 ft 18 ft
Highways 22 ft 22 ft
Over Roof 10 ft 14.5 ft
Pole Clearances
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NESC 235 – Vertical at pole. Primary above secondary.
Pair At Pole Mid-Span
Pri → Sec 40 in 30 in
To Neutral 12 in 12 in
Sec → Drip 12 in N/A
To Guy/Arm 6 in —