Why is a safety factor added to the walk-in load?

Q: How do I calculate the refrigeration load for a walk-in cooler?

The calculator uses the standard load-per-24-hours divided by running-time method (Heatcraft / ASHRAE Refrigeration). It sums four 24-hour-average loads — transmission (U·A·ΔT through walls, ceiling, and floor), infiltration (box volume × air changes × an enthalpy factor), product (sensible plus any latent freezing heat), and internal (lights, fan motors, people) — adds the safety factor, then multiplies by 24 and divides by the daily run hours to get required capacity. Confirm with manufacturer selection software before specifying equipment.

Q: What size refrigeration unit do I need for a walk-in freezer?

Enter the box dimensions, a freezer box temperature (below 30 °F is treated as a freezer), a higher R-value such as R-40+, and a run time near 18 hours per day to allow for defrost. The tool sizes air changes at about 80 percent of a cooler and includes the latent heat of freezing the product, then reports the required capacity in BTU/hr and tons. Because it is a first-pass estimate, verify product pull-down time separately, since a fast pull-down can exceed the steady-state capacity shown.

Question

Why is a safety factor added to the walk-in load?

Accepted Answer

Component loads here are 24-hour averages, so capacity is intentionally scaled up so the equipment removes the full daily load within its run window. A safety factor (typically 10 percent, adjustable 0 to 50) pads the subtotal before the run-time scaling to cover door usage, defrost, and modeling uncertainty in the first-pass air-change and infiltration figures, which assume roughly 90 °F / 55 percent RH ambient.

Why is a safety factor added to the walk-in load?

Answers