
Electrical Load Calculation Validator
Validate electrical load calculations and demand factors against NEC code before construction
What You Can Do
You can submit your electrical load calculations, appliance schedules, and circuit designs to this skill, and it will validate total connected loads, demand factor applications per NEC Article 220, feeder/service sizing, OCPD ratings, voltage drop compliance, transformer utilization, three-phase load balancing, and special load classifications. The skill identifies specific sizing errors, code violations, and optimization opportunities with remediation guidance, ensuring your designs are compliant and cost-effective before they reach permitting or construction.
Features
checks arithmetic accuracy and identifies missing or double-counted loads
confirms correct NEC Article 220 factor application by load type and occupancy classification
validates wire gauge, ampacity, and protection against calculated loads
ensures branch (≤3%) and combined (≤5%) voltage drop compliance with distance and wire sizing
checks kVA loading, utilization percentage, and spare capacity alignment with design intent
identifies phase imbalances, calculates penalties, and flags design corrections needed
validates demand factors for motors, HVAC systems, EV chargers, and dedicated circuits
generates compliance rationale for design review submittal and permitting authority communication
Example Output
Example 1: Undersizing Detection
Issue: Branch circuit to kitchen receptacles undersized
- Calculated demand load: 4.2 kW
- Applied demand factor: 50% (residential small appliance branch)
- Resulting demand: 2.1 kW → 10 AWG wire selected (30A)
- Problem: 10 AWG only rated 30A; actual available ampacity ~24A at 60°C
- Violation: NEC 210.19(A)(1) requires wire sized for full load after demand applied
- Fix: Use 8 AWG (40A) or reduce connected load on circuit
Example 2: Demand Factor Compliance
Validation: Multi-family residential feeder load
✓ Individual unit loads: 5.5 kW each (12 units) = 66 kW connected
✓ Demand factor applied: 45% per Table 220.84 = 29.7 kW
✓ Feeder conductor: 2/0 AWG (95A @ 75°C) accommodates 30A equivalent
✓ Voltage drop: 1.8% (within 3% limit for feeder)
✓ Service entrance: 100A adequate with 15 kW spare capacity
Result: Design compliant; documentation ready for review
Example 3: Transformer Utilization
Finding: 75 kVA transformer at 62% utilization (46.5 kW demand)
- Current spare capacity: 28.5 kW
- Recommendation: Acceptable for current load with HVAC expansion buffer
- Alternative: Downsize to 50 kVA at 93% utilization if no future growth expected (cost savings: $2,400)
- Tradeoff analysis: 50 kVA viable if load growth excluded; verify with building owner
What's Included
- SKILL.md instruction file: prompt framework for structured load calculation validation
- NEC Article 220 demand factor lookup table: reference matrix for residential, commercial, and special loads
- Load calculation validation checklist: systematic verification steps covering summation, demand factors, sizing, and compliance
- Voltage drop calculator worksheet: tool for checking branch and feeder voltage drop against distance and wire gauge
- Three-phase load balancing template: phase allocation worksheet with imbalance penalty calculations
Who It's For
- MEP/Electrical Engineers — validating own load calculations and designs before construction document issue
- Consulting Engineers — peer-reviewing colleague calculations on multi-discipline projects
- Electrical Contractors — catching design errors during preconstruction and submittals
- Code Officials and Plan Reviewers — verifying consultant-submitted calculations for permit compliance
- Building Owners/Facilities Managers — understanding load sizing decisions during renovation or capacity expansion planning
Best For
- Load calculation verification — checking total connected loads, demand factors, and feeder sizing before permitting
- NEC compliance audits — identifying code violations in existing or proposed designs
- Design optimization — comparing sized options to balance compliance, cost, and spare capacity
- Voltage drop analysis — validating branch and service voltage drops across distance and conductor sizes
- Special load handling — validating demand factors for motors, HVAC, EV charging, or dedicated circuits







