Transformer Calc NEC

NEC Art.450 kVA & OCPD

$0.99 · In‑App Purchases · Designed for iPad. Not verified for macOS.

Transformer Calc NEC - professional NEC calculator for electricians. Offline, permit-ready. NEC transformer overcurrent protection calculator for electricians, apprentices, and electrical engineers. Size primary and secondary OCPD per NEC Table 450.3(B), calculate full-load amps (FLA), and select conductors from Table 310.16 - all per NEC 2023 (NFPA 70). Works 100% offline on the job site. Whether you're sizing overcurrent protection for a 75 kVA, 480-to-208V three-phase transformer, or checking if primary-only protection requires 125% or 300%, this calculator gives you accurate NEC-compliant results in seconds. Use it as your go-to transformer protection reference - from kVA rating to OCPD and conductor selection. TRANSFORMER CALCULATOR FEATURES: - Primary overcurrent protection per NEC 450.3(B) - 125%/167%/250%/300% rules - Secondary overcurrent protection per NEC 450.3(B) - 125%/167%/250% rules - Primary-only and primary+secondary protection methods - Full-load ampere (FLA) calculation: single-phase and three-phase - Automatic next-standard-size-up per NEC 240.6(A) with Note 1 logic - All standard OCPD ratings from 15A to 6000A per NEC 240.6(A) - Conductor sizing from NEC Table 310.16 (75°C column) - Copper and aluminum conductor support - 12 standard kVA ratings from 3 kVA to 1000 kVA - 5 voltage presets: 120V, 208V, 240V, 480V, 600V - Single-phase and three-phase support - NEC article references for every calculation result NEC REFERENCES INCLUDED: - NEC Table 450.3(B) - Transformer overcurrent protection (600V or less) - NEC 450.3(B) Note 1 - Next-size-up rule for primary-only protection - NEC 240.6(A) - Standard overcurrent device ratings - NEC Table 310.16 - Conductor ampacity at 75°C PROTECTION METHOD RULES: - Primary Only (≤9A): Maximum 167% primary OCPD - Primary Only (≥9A): Maximum 125% primary OCPD (next size up per Note 1) - Primary Only (any): Maximum 300% if 125%/167% doesn't correspond to standard size - Primary + Secondary: Maximum 250% primary, plus 125%/167% secondary OCPD CALCULATION RESULTS INCLUDE: - Primary full-load amps (FLA) with formula - Secondary full-load amps (FLA) with formula - Primary OCPD size (standard rating per NEC 240.6(A)) - Secondary OCPD size when applicable - Primary and secondary conductor sizes with ampacity - Applicable NEC percentage rules and references - Protection method notes and explanations PRO FEATURES (one-time purchase): - No ads - clean interface for professionals - Save transformer calculation history with labels - Export calculations as PDF reports for permits and records - Dark theme support HOW THE TRANSFORMER CALCULATOR WORKS: 1. Select phase type (single-phase or three-phase) 2. Choose kVA rating from standard sizes 3. Select primary and secondary voltage 4. Choose protection method (primary only or primary + secondary) 5. Select conductor material (copper or aluminum) 6. Get OCPD sizes, conductor recommendations, and NEC references instantly BUILT FOR ELECTRICIANS ON THE JOB SITE: This transformer calculator is designed by electricians, for electricians. Enter your transformer parameters, get the correct OCPD size and conductor recommendation instantly - no complicated menus or unnecessary features. One-hand operation, instant results. PERFECT FOR: - Licensed electricians sizing transformer protection daily - Electrical apprentices studying for journeyman exams - Electrical engineers and designers - Electrical contractors bidding jobs - NEC code exam preparation - Journeyman and master electrician exam study OFFLINE & PRIVACY: - Works 100% offline - no internet needed on the job site - No account required - No data collection - your calculations stay on your device Simplify your transformer protection sizing on the job site.

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Version 1.0.7

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Information

Seller
  • Rizvan Adzhoian
Size
  • 31.1 MB
Category
  • Utilities
Compatibility
Requires iOS 13.0 or later.
  • iPhone
    Requires iOS 13.0 or later.
  • iPad
    Requires iPadOS 13.0 or later.
  • iPod touch
    Requires iOS 13.0 or later.
  • Mac
    Requires macOS 11.0 or later and a Mac with Apple M1 chip or later.
  • Apple Vision
    Requires visionOS 1.0 or later.
Languages
  • English
Age Rating
18+
In-App Purchases
Yes
Copyright
  • © 2026 Rizvan Adzhoian
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