Understanding Panel Loads
Proper panel load calculation is essential for safe and efficient electrical systems.
- Connected Load Total amperage of all connected circuits.
- Demand Factor Adjustment for simultaneous usage patterns.
- Phase Balance Distribution of loads between phases.
- Circuit Types Different circuits have different load characteristics.
Load Analysis
- Demand Factors Lighting: 0.7-1.0. HVAC: 0.65-0.8. Receptacles: 0.5-0.7. Motors: 0.75-0.85. Kitchen: 0.65-0.75. Process: 0.8-0.9.
- Diversity Factors Commercial: 0.5-0.7. Industrial: 0.6-0.8. Residential: 0.4-0.6. Data center: 0.8-0.9. Healthcare: 0.7-0.85. Education: 0.5-0.7.
- Load Characteristics Power factor: 0.8-0.95. THD: <15%. Crest factor: 1.4-1.7. Load balance: ±10%. Harmonics: 3rd-11th significant.
Panel Specifications
- Electrical Ratings Bus bar: 100-1200A. Short circuit: 10-100kA. Voltage: 120/240-480/277V. Ground bus: 100-200%. Neutral bus: 100-200%.
- Physical Requirements Enclosure: NEMA 1-4X. Working space: 30-48". Mounting height: 48-72". Ventilation: 100-200 CFM. Heat dissipation: 3-5W/circuit.
- Circuit Allocation Space factor: 80% max. Spare capacity: 20-30%. Future expansion: 25%. Multi-wire branch: 2-3 poles. GFCI/AFCI: 20% circuits.
Protection Coordination
- Overcurrent Devices Breaker types: thermal-magnetic/electronic. Trip curves: B-K. Interrupting rating: 10-65kA. Selective coordination: 0.1-0.4s. Ground fault: 30mA-1A.
- Surge Protection SPD type: 1-3. Voltage protection: 330-800V. Response time: <1ns. Energy dissipation: 40-200kJ. Status indication: visual/remote.
- Arc Flash Protection Incident energy: 1.2-40 cal/cm². PPE category: 0-4. Boundary distance: 18-72". Working distance: 18-36". Flash protection: boundary marked.
Monitoring Systems
- Metering Functions Power quality: Class 0.2-1.0. Energy accuracy: ±0.5%. Demand window: 15-30min. Data logging: 30-90 days. Communication: Modbus/BACnet.
- Alarm Parameters Overload: 80-95%. Voltage deviation: ±10%. Current unbalance: >20%. Temperature: 60-80°C. Ground fault: >30mA.
- Maintenance Indicators Operation count: 1000-5000. Contact wear: 70-90%. Temperature rise: ΔT 30-50°C. Insulation resistance: >1MΩ. Torque check: annual.
Design Considerations
Future Expansion
Allow 20% capacity for future additions.
Load Types
Consider continuous and non-continuous loads separately.
Circuit Protection
Ensure proper breaker sizing for each circuit.
Code Compliance
Follow NEC requirements for load calculations.