The HVACR Advisors WICF load calculator is a fully-featured web app which allows the user to determine an accurate design heat load for a walk-in cooler or freezer so that refrigeration equipment can be appropriate sized. This web app evaluates heat loads from the following four sources:

• Transmission Load
• Infiltration Load
• Product Load
• Internal Load

More often than not, the information needed to determine these loads is not available. This WICF quick load calculator provides an estimation of the heat load using only the walk-in box dimensions and desired box temperature. The following assumptions are used to determine the average load. Many of these assumptions are also used by other quick load charts.

Transmission Load:

• Walk-ins located indoors
  • 4 inches of extruded cellular polystyrene (XPS) is used to insulate the walls, ceiling and floor having a thermal conductivity of 0.24 Btu-in/h-ft²-°F.
  • 80°F outside wall and ceiling temperature.
  • 55°F temperature underneath the floor.
• Walk-ins located outdoors
  • 4 inches of closed‐cell polyurethane is used to insulate the walls, ceiling and floor having a thermal conductivity of 0.17 Btu-in/h-ft²-°F.
  • 95°F outside wall temperature.
  • 115°F outside ceiling temperature. The 20°F increase in temperature is to account for solar effect.
  • 55°F temperature underneath the floor.

Infiltration Load:

An air change method is used. The average air changes per day is correlated to the volume of the walk-in as follows:

Volume, ft³	Cooler, > 32°F	Freezer, ≤ 32°F
200	44	33.5
300	34.5	26.2
400	29.5	22.5
500	26	20
1000	17.5	13.5
1500	14	11
2000	12	9.3
3000	9.5	7.4
4000	8.2	6.3
5000	7.2	5.6
10,000	4.9	3.8
15,000	3.9	3

• Walk-ins located indoors
  • Air at a 80°F dry bulb, 67°F wet bulb state outside of the door(s).
  • Twice the air changes listed in the average air change table.
• Walk-ins located outdoors
  • Air at a 95°F dry bulb, 80°F wet bulb state outside of the door(s).
  • The air changes listed in the average air change table.

Please note the air changes for the indoor walk-in is assumed to be twice that of the walk-in located outdoors, and will result in the infiltration load for the indoor walk-in to be much greater. The reason for this assumption is an outdoor walk-in is generally used more for storage and subject to less door openings. In addition, the indoor walkin pages provides for an additional input of the number of glass display doors. These are doors on the walls of the walk-in which allow customers to access product without the need to enter the walk-in.

If an outdoor walk-in is to be actively used like an indoor walk-in, consider having the app calculate a quick load for an indoor walk-in instead.

Product Load:

• The pounds of product loaded into the walk-in per day equals the volume of the walk-in in cubic feet.
• Specific heat of unfrozen product is 0.90 Btu/lb and 0.45 Btu/lb for frozen product.
• Freezing temperature of the product is 29°F.
• Latent heat for freezing product is 110 Btu/lb.
• Product enters the walk-in at 10°F above the design box temperature.

Internal Load:

• Lighting – one watt per square foot of floor area.
• People – one person per 25,000 ft³ of walk-in volume.
• Fan motors – one HP motor per 12,500 ft³ of walk-in volume.

A safety factor of 10 percent is applied to the load. In addition, the load is adjusted for an 18 hour/day equipment run time.

The heavy load calculation assumes the product load is 3 times greater than the average load and infiltration load is 50 percent greater than average load. All other assumptions remain the same.

Both average and heavy load calculations are displayed.

The Detail page provides a breakdown of the quick load calculations. This can be useful for applications where information is available to determine some of the loads. For example, transmission and product loads can be determined but infiltration and internal loads cannot.