Emergency and standby generator sizing, transfer switch design, fuel system specification, and CEC Section 46 compliance for life safety and critical power.

How do I know what size generator I need?

Generator sizing is NOT simply adding up all connected loads. You must account for motor starting inrush (typically 6× running current), non-linear load derating (1.5-2× for UPS/VFD loads), and sequential loading strategy. Undersizing causes voltage collapse on motor starts; oversizing causes wet stacking on diesels (minimum 30% loading required).

Key Deliverables

• Load classification (life safety, critical, optional) per OBC/CEC S.46
• Generator sizing calculation (running kW + starting kVA analysis)
• Motor starting voltage dip analysis (≤20% threshold)
• Automatic Transfer Switch (ATS) specification and design
• Single-line diagram (normal + emergency distribution)

Open transition vs closed transition ATS?

Open transition (break-before-make) has a brief power interruption during transfer, acceptable for most loads with short ride-through capability. Closed transition (make-before-break) provides seamless transfer with no interruption and is required for sensitive loads like data centres. Closed transition requires utility approval for momentary parallel operation.