How to choose the right size Cooler?

Sizing a Residential Cooler

Follow the steps below to properly size your residential cooler or use our new TruKalc sizing program.

  1. Consult area zone map to find correct zone.
  2. Consult table to find correct “Minutes per Air Change” for your zone.
  3. Determine area to be cooled in cubic feet (building length x width x height).
  4. Divide cubic feet (step 3) by minutes per air change (step 2) to determine Cooling Feet per Minute (CFM).
  5. Refer to the Specification Charts in the cooler brochure for the units CFM ratings and expected static pressure to select a cooler model. If CFM falls between models, choose the larger model

*Interior Heat Load: High means places with unusual heat sources from hot equipment or processes, crowded conditions, etc. Normal means no unusual heat sources – typical home or office. *Exterior Heat Load: Exposed means walls, roof exposed to sun, poor insulations, etc. Insulated means walls and roof well insulated and/or shaded. Example – A house in Bakersfield, CA, 40 feet long by 30 feet wide with 8-foot ceiling. Well insulated, no unusual heat sources.

  1. 30 x 40 x 8 = 9,600 cubic feet
  2. Zone 2
  3. Minutes per Air Change = 3
  4. 9,600 (divide by sign) 3 = 3,200 CFM
  5. Referring to the CFM inside the Champion Residential brochure, cooler model 4001DD with a ½ h.p. motor is indicated, assuming a typical static pressure of 0.2″.

Sizing a Commercial/Industrial Cooler:

  1. Determine your design conditions:
    – Outdoor Dry-Bulb Temperature (DB)
    – Outdoor Wet-Bulb Temperature (WB)
    – Desired Indoor Dry-Bulb Temperature (DT)
  2. Determine the Design Sensible Heat Load (SHL) in BTU/H
  3. Calculate the leaving air temperature (LAT) of the cooler:
    LAT = DB – [(DB - WB) * Ef]
    Where Ef is 0.8 for most coolers & 0.9 for coolers with 12″ rigid media
  4. Determine the Total CFM required:
    CFM = SHL / [1.08 * (DT - LAT)]
  5. Determine the cooler(s) required. Refer to the Specification Charts in the cooler brochure for the units’ CFM ratings.

Notes: The design temperature (DT) you choose will greatly affect the overall CFM required. Choose a temperature that would feel comfortable. Remember that an evaporative cooler is different than an air conditioner. You can have the temperature a few degrees higher than you would an air conditioner and feel very comfortable because of the added cooling effect of the movement of moist air over the skin.

Contact a local HVAC engineer or your Sales Engineer if you need help approximating the Sensible Heat Load in the building. Alternate Sizing Method If the heat load is not known you may use this method to approximate the total CFM you will need. It assumes a commercial / light industrial environment with normal heat loads. If you have unusual heat loads, you should use the previous method to determine size.

  1. Determine the volume of area that is to be cooled (ft^3).
    – If the workspace has high ceilings, you should consider only the worker
    environment – normally up to about 10 feet above the floor.
  2. Determine the approximate air change rate (min. per air change)
    – Air change rate = (DB – WB) / 10
  3. Determine the required CFM
    – CFM = Volume / Air Change Rate
  4. Determine the cooler(s) required. Refer to the Specification Charts in the cooler brochure for the units CFM ratings.