Panelboard & Switchboard Notes

Panelboard Selection

• Amperage:
  • OCPD must be greater than the calculated load.
  • Typically load to 80% capacity.
  • Allow for future capacity.
  • Standard Amp Ratings: 100, 150, 200, 225, 250, 400, 600

MLO or MCB

• Considerations:
  • Where will OCPD be located?
  • Is a main circuit breaker needed or sensible?

Number of Poles

• Typical options: 12, 18, 24, 30, or 42 poles.

Feeder Size

• Feeder must be sized to match the selected OCPD.

Distribution Panels

• Range: 400A - 1200A.
• Mounting: Wall mounted (surface or recessed).
• Protection: Fuses or CBs, but not both.
• Configuration: MLO or MCB.
• Siemens panels: P4 & P5.
• Physical size depends on breakers.

Enclosure Dimensions

• Type 1 and Type 3R/12 enclosures are common.
• Dimensions vary based on amperage (400-800A).

Branch Breaker Selection

• Key factors:
  • Maximum Interruption Rating (KAIC).
  • Voltage (AC).
  • Trip Type (Thermal, Magnetic, Electronic).
  • Amperage.
  • Unit Space Requirements.

Switchboards/Switchgear

• Amperage: 1200A - 6000A (MCB limited to 5000A).
• Common Range: 1200A - 4000A.
• Mounting: Floor mounted.
• Configuration: MLO or MCB.
• Standards:
  • UL891 - Switchboards (requires front access).
  • UL1558 - Switchgear (requires access on all sides).
• Compartment barriers limit to 4 devices in a vertical section.

Sizing Considerations

• Continuous load: 125%.
• Spare capacity: 10% minimum.
• Order of Work:
  1. Calculate sizing load in amps.
  2. Select appropriate OCPD (local or remote?).
  3. Select appropriate panel.
  4. Select feeder size.

Load Calculations

• Example:
  • Lighting: $6233 <br /> vert 1.25 = 7791.25$
  • Receptacles (<10KVA): $10000 <br /> vert 1.00 = 10000$
  • Receptacles (>10KVA): $16100 <br /> vert 0.50 = 8050$
  • Largest Motor: $44064 <br /> vert 1.00 = 44064$
  • Misc: $5200 <br /> vert 1.00 = 5200$