Path-Q Solar

How should refrigeration loads be included when sizing outage backup?

Answer

Include both the refrigerator's starting surge and its average energy use over the intended outage period. Because refrigeration cycles on and off, do not size it as if its compressor runs continuously, but allow for higher runtime in hot conditions and for other loads starting at the same time.

Key points

  • Use manufacturer data or measurements for running energy and compressor startup demand.
  • Account for the refrigerator's duty cycle rather than multiplying running power by the entire outage.
  • Include freezers, refrigeration equipment, and any controls or alarms that must also operate.
  • Allow margin for hot rooms, frequent door opening, aging equipment, and simultaneous starts.

What it depends on

  • Refrigerator and freezer starting and running power
  • Expected ambient temperature and duty cycle
  • Required backup duration
  • Other loads operating on the same inverter

Risks and trade-offs

  • Ignoring compressor surge can cause inverter overload or shutdown.
  • Using an optimistic duty cycle can overstate runtime.
  • Backing up refrigeration may require prioritizing it over discretionary loads.

Information you may need

  • Appliance labels, manuals, or measured power data
  • Number and type of refrigeration loads
  • Worst-case outage duration
  • Whether loads can be staggered or shed automatically

Your next step

What to do next

Measure or obtain the running and startup requirements for each refrigeration appliance and add them to a time-based critical-load estimate.

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SQ01503