---
title: "Transformer Calc NEC - Reviews, Revenue and Downloads in South Africa | Apple App Store"
description: "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 s"
---

# Transformer Calc NEC — South Africa
> NEC Art.450 kVA & OCPD

![Transformer Calc NEC App Icon](https://is1-ssl.mzstatic.com/image/thumb/Purple211/v4/08/1f/7f/081f7f61-dad7-242e-40f7-3b3e5ee7d025/AppIcon-0-0-1x_U007emarketing-0-11-0-85-220.png/434x0w.png)

**Developer:** [Rizvan Adzhoian](https://apptail.io/developer/rizvan-adzhoian-zsuKac)
**Category:** Utilities
**Rating:** N/A (0 ratings)
**Price:** 19.99 R
**Bundle ID:** com.electools.transformerCalculator
**Store:** Apple App Store
**Country:** South Africa
**Version:** 1.0.10 (released 2026-07-10)
**Original Release:** 2026-04-24
**Languages:** English

**App Store Link:** [Download on Apple App Store](https://apps.apple.com/za/app/app/id6763311943)
**AppTail Page:** [https://apptail.io/app/transformer-calc-nec-AReA/south-africa](https://apptail.io/app/transformer-calc-nec-AReA/south-africa)

## Transformer Calc NEC Description
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.

## Transformer Calc NEC Screenshots
- [Screenshot 1](https://is1-ssl.mzstatic.com/image/thumb/PurpleSource221/v4/c5/5a/aa/c55aaafb-07cc-9b45-ec7a-383e5137955c/01_main_default.png/1290x2796.png)
- [Screenshot 2](https://is1-ssl.mzstatic.com/image/thumb/PurpleSource221/v4/00/a7/23/00a723d3-de9f-75d6-49e6-a8699b38392a/02_main_filled.png/1290x2796.png)
- [Screenshot 3](https://is1-ssl.mzstatic.com/image/thumb/PurpleSource211/v4/38/54/b4/3854b470-0cb9-64e1-7616-0e5af529d1a7/03_history.png/1290x2796.png)
- [Screenshot 4](https://is1-ssl.mzstatic.com/image/thumb/PurpleSource211/v4/59/66/c1/5966c1db-2ab4-2dc8-9ada-5d75565ed200/04_settings.png/1290x2796.png)



## Transformer Calc NEC In-App Purchases
| Item | Price |
|------|-------|
| Pro Unlock | 59.99 R |




## Transformer Calc NEC Available In
- [Nigeria](https://apptail.io/app/transformer-calc-nec-AReA/nigeria)
- [Poland](https://apptail.io/app/transformer-calc-nec-AReA/poland)
- [South Africa](https://apptail.io/app/transformer-calc-nec-AReA/south-africa)

---

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