Panel Schedule Calculator
Professional electrical panel schedule tool for creating detailed load distributions, calculating circuit loads, balancing phases, and ensuring NEC compliance for electrical distribution panels.
| # | Description | Load (VA) | Voltage | Phases | A | B | C | Breaker | Type | Actions |
|---|---|---|---|---|---|---|---|---|---|---|
Panel schedules are essential for electrical system documentation, load analysis, and NEC compliance. Proper load calculations ensure safe operation and optimal system performance.
Load Calculations
I = P ÷ V (single phase)
I = P ÷ (√3 × V) (three phase)
Demand = Connected Load × Demand Factor
Apply NEC demand factors per load type
Continuous Load × 1.25 + Non-continuous Load
NEC 210.20(A) requirement
Phase Balance Analysis
Imbalance = (Max Load - Min Load) ÷ Max Load × 100%
Should be less than 20%
In = √(IA² + IB² + IC² - IAIB - IBIC - IAIC)
For unbalanced loads
Balance % = 100% - Imbalance %
Target: > 90% for optimal performance
NEC Article 408 - Panelboard Requirements
Construction Standards
- 408.34: Classification - lighting and appliance branch circuit panelboards
- 408.36: Overcurrent protection requirements
- 408.40: Grounding requirements for panelboards
- 408.41: Panelboard identification and circuit directory
Installation Requirements
- 110.26: Working space clearances (3 feet minimum)
- 240.6: Standard ampere ratings for overcurrent devices
- 210.11: Branch circuit required calculations
- 220.40: General lighting load calculations
Example Panel Calculation
200A main panel with mixed loads:
• Lighting: 12,000 VA (continuous) × 1.25 = 15,000 VA
• Receptacles: 8,000 VA (non-continuous) = 8,000 VA
• HVAC: 15,000 VA (continuous) × 1.25 = 18,750 VA
• Total demand load: 41,750 VA
• Current at 208V 3φ: 41,750 ÷ (208 × √3) = 116A
• Panel utilization: 116A ÷ 200A = 58% (good loading)
How to Create a Panel Schedule: Step-by-Step
A panel schedule organizes all circuits in an electrical panel, showing breaker assignments, loads, and phase balance. It is required for permits and essential for troubleshooting.
Step 1: List All Circuits With Their Loads
Document every circuit that will connect to the panel. Include the description (e.g., "Kitchen Receptacles"), breaker size, wire gauge, and the calculated VA load. Group similar circuits together for easy reference.
Step 2: Assign Circuits to Breaker Slots
Place 240V circuits (double-pole breakers) first since they span two slots. Then fill in 120V circuits. Odd-numbered slots connect to Phase A and even-numbered slots connect to Phase B.
Step 3: Balance the Phases
Distribute 120V loads evenly between Phase A and Phase B. Aim for less than 10% difference between phases. Unbalanced panels cause neutral overloading and uneven voltage at receptacles.
Step 4: Sum Loads and Calculate Demand
Add up all connected VA per phase. Apply appropriate NEC demand factors. The total demand determines whether your panel has adequate capacity for the loads.
Step 5: Verify Main Breaker Rating
Divide total demand VA by 240V to get the required amps. This must not exceed the main breaker rating. A 200A panel can handle up to 48,000 VA total demand (200A x 240V).
Formula
Total Panel Load (amps) = Sum of All Circuit Loads (VA) / 240V
Where: Circuit loads are measured in VA (volt-amperes), 240V is the line-to-line voltage for single-phase residential panels
Worked Example
Scenario: Create a panel schedule for a 200A residential panel with 24 circuits.
- Step 1: Circuits include: Range (8,000VA), Dryer (5,000VA), AC (5,000VA), Water Heater (4,500VA), 6 lighting circuits (1,800VA each), 4 receptacle circuits (1,800VA each), 2 kitchen circuits (1,500VA each)
- Step 2: Range, dryer, AC, and WH get 240V double-pole breakers (slots 1-8). Remaining circuits fill slots 9-24
- Step 3: Phase A = 22,100 VA, Phase B = 21,900 VA (balanced within 1%)
- Step 4: Total connected = 44,000 VA. After demand factors: approximately 33,000 VA
- Step 5: 33,000 / 240 = 137.5A. Well within the 200A main breaker
Result: The 200A panel handles all 24 circuits at 137.5A demand, leaving 62.5A of spare capacity for future loads.
Panel Schedule Questions & Answers
What information must be included on a panel schedule?
NEC requires circuit identification, load in amps or VA, circuit breaker size, and wire size. Best practice includes circuit description, phase assignment, and calculated loads. The inspector needs to see that each circuit is properly protected and that the panel isn't overloaded. Missing or incomplete panel schedules are a common cause of inspection delays.
How do I balance loads across phases?
Try to keep each phase within 20% of the others. In a 200A panel, if Phase A has 160A, Phase B should be 128-192A, and Phase C should be 128-192A. Unbalanced loads cause neutral current, voltage variations, and inefficient operation. Large 240V loads (like water heaters) help balance since they use two phases equally.
Can I exceed the panel's main breaker rating?
The total connected load can exceed the main breaker rating, but the calculated load (with demand factors) should not. A 200A panel might have 300A of connected load, but after applying NEC demand factors, the calculated load is 180A. This is normal and acceptable - not everything runs at full load simultaneously.
What's the difference between connected load and calculated load?
Connected load is the sum of all circuit breaker ratings - if you have 40 circuits at 20A each, that's 800A connected. Calculated load applies demand factors from NEC Article 220. Those same circuits might only be 400A calculated load after demand factors. You size the panel feeder for calculated load, not connected load.
How many circuits can I put in a panel?
It depends on the panel's physical spaces and load capacity. A 200A panel might have 40-42 spaces but can't handle 40 circuits at 20A each (800A total). The calculated load is the limiting factor, not the number of spaces. Most residential panels max out on load before running out of spaces.
What's the 80% rule for panel loading?
Continuous loads (3+ hours) must be calculated at 125% of their rating, which means you can only load a breaker to 80% for continuous loads. A 20A breaker can handle 20A non-continuous or 16A continuous loads. This applies to individual circuits, not the entire panel. The panel itself can be loaded to 100% of its rating.
Do I need AFCI and GFCI protection on every circuit?
AFCI is required on most 15A and 20A branch circuits in living areas per NEC 210.12. GFCI is required in bathrooms, kitchens, outdoors, basements, garages, and other wet locations per NEC 210.8. You can use AFCI/GFCI breakers in the panel or GFCI outlets downstream. Mark these protection types on your panel schedule.
How do I handle multi-wire branch circuits?
Multi-wire circuits use a shared neutral between two hot conductors on different phases. They must be on a common trip breaker or have handle ties per NEC 210.4(B). On your panel schedule, show both circuits and note they're part of a multi-wire branch circuit. The neutral carries only the unbalanced current between the two phases.
What spare capacity should I include?
NEC requires 25% spare capacity in dwellings per 210.11(C)(3). For a 200A service, plan for 150A of connected loads max. This gives room for future additions without service upgrades. Commercial buildings don't have this requirement, but 10-20% spare capacity is good practice for future flexibility.
Can I use tandem breakers to add more circuits?
Only if the panel is listed to accept them. Check the panel label - it will say something like "Maximum 30 circuits, 20 single pole" which means 10 tandems are allowed. Don't exceed the maximum circuit count even with tandems. Some panels don't allow tandems at all, especially in certain positions.
What's the difference between a panel schedule and a load calculation?
A load calculation determines the total electrical demand to size the service and main panel. A panel schedule shows how that load is distributed among individual circuits. You do the load calculation first to determine panel size, then create the panel schedule to show how circuits are arranged and loaded within that panel.
What's the most common panel schedule mistake?
Not updating the schedule when changes are made. I see panel schedules from 1995 on panels that have been modified 20 times. Circuits are mislabeled, loads are wrong, and new circuits aren't documented. Keep the schedule current - it's required by NEC 408.4(A) and makes troubleshooting much easier for the next electrician.
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