WireCalc vs Transformer Calc NEC

The NEC wire sizing calculator that works where you work -- even with no signal. WireCalc gives electricians, contractors, and apprentices instant access to NEC 2023 wire sizing, voltage drop calculations, and conduit fill tables. No internet required. No subscription. Just accurate answers on the job site. STOP OVERSIZING WIRE. STOP GUESSING. Enter your load and run length. Get the correct wire gauge per NEC 310.16 in seconds. Check voltage drop. Verify conduit fill. Solve Ohm's law. All based on NEC 2023 (NFPA 70) tables. FEATURES: - Wire size calculator -- sizes by both ampacity AND voltage drop per NEC - Full NEC Table 310.16 ampacity reference (interactive, searchable) - Voltage drop calculator (single-phase and three-phase) - Conduit fill calculator with NEC Chapter 9 data (EMT, IMC, RMC, PVC) - Ohm's law calculator (V, A, Ohm, W -- enter any two, get all four) - Copper and aluminum conductor support - 60°C, 75°C, and 90°C temperature ratings - THHN, THWN, XHHW, TW, THW insulation types - Pass/fail indicators with NEC-compliant thresholds WHY ELECTRICIANS CHOOSE WIRECALC: - Works 100% offline -- designed for job sites with zero signal - No subscriptions, no ads, no account required - One-time purchase -- yours forever - NEC 2023 compliant tables and calculations - Large text and tap targets -- usable with work gloves Based on NEC 2023 (NFPA 70). Note: This app is a calculation tool and reference guide. It does not replace professional judgment or code compliance verification. Always verify calculations and consult local codes and amendments.

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 - Next-standard-size-up applied only where Note 1 permits (125% cells); 167%/250%/300% treated as ceilings - All standard OCPD ratings per NEC 240.6(A), including fuse-only ratings 1, 3, 6, 10, 601 for small transformers - Conductor sizing from NEC Table 310.16 (75°C column, printed code values) - Copper and aluminum conductor support - 40 standard kVA ratings: 0.05–500 kVA single-phase, 3–2500 kVA three-phase - 7 voltage presets: 120V, 208V, 240V, 277V, 460V, 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 (printed Table 450.3(B)): - Primary Only, 9A or more: 125% maximum — next standard size up permitted (Note 1) - Primary Only, 2–9A: 167% maximum — ceiling, no round up - Primary Only, under 2A: 300% maximum — ceiling, no round up - Primary + Secondary: primary 250% maximum (ceiling); secondary 125% (Note 1) for 9A or more, 167% ceiling under 9A 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.