Total load = transmission + door infiltration + product load + internal sources. Defrost and other project loads may also apply.
In short: calculate every component in consistent units and for one realistic peak scenario.
The Frostbox calculator estimates storage capacity, not this full engineering load.
The master equation
Total heat load is the sum of four independent loads. Calculate each in watts (W), then add them:
Q_total = Q_transmission + Q_infiltration + Q_product + Q_internal
What each component is
| Component | What it is | Dominant when… |
|---|---|---|
| Transmission | Heat conducting through panels because it is colder inside than out | Large surface area, high ΔT, thin panels |
| Infiltration | Warm, humid air entering each time the door opens | High door traffic, frequent picking |
| Product | Heat removed to cool incoming goods to storage temperature | Warm product loaded fast (e.g. fresh meat) |
| Internal | Heat from lights, evaporator fans, people, forklifts | Active work rooms, packing areas |
Why each matters
Get all four right and you size the system correctly. Skip one — most often infiltration, which is invisible — and you under-size the plant. The components are independent, so a room can be transmission-dominated (large, high-ΔT freezer with little traffic) or infiltration-dominated (busy chill picking room with constant door openings).
Once you have the four totals, you sum them and add a safety margin to reach the design load — the number you carry into equipment selection. See From total load to design load.
Related articles
- Transmission load explained
- Infiltration load explained
- Product load explained
- Internal heat sources
- From total load to design load
- Using the Frostbox size calculator
The formulas above are standard refrigeration-engineering practice; product-specific U-values and Daikin unit capacities are confirmed per datasheet. For a checked calculation, use the Frostbox size calculator or contact [email protected].
