Cabinet Coolers 11510 Goldcoast Drive • Cincinnati, OH 45249-1621 • Phone (513) 671-3322 FAX (513) 671-3363 • E-mail: [email protected] • www.exair.com 219 To Calculate Watts: 1. First, determine the approximate Watts of heat generated within the enclosure. 2. Then, calculate outside heat transfer as follows: a. Determine the area in square meters exposed to the air, ignoring the top of the cabinet. b. Determine the temperature differential between maximum surrounding temperature and desired internal temperature. Then, using the Metric Temperature Conversion Table (below), determine the Watts/m2 for that differential. Multiplying the cabinet surface area times Watts/m2 provides external heat transfer in Watts. 3. Add internal and external heat loads for total heat load. Sizing Guide - Let us do the work On the following page, EXAIR provides a simple guide to fill in and send to us so we may do the heat load calculations for you and specify a Cabinet Cooler system. You may e-mail the information to [email protected], call 1-800-903-9247, fill out an online form at exair.com/sizing, use our new calculator at https://exair.co/cccalc_ca or fax the information to 1-866-329-3924. How To Calculate Heat Load for Your Enclosure If you would like to determine the correct model for your enclosure without our assistance, it is first necessary to determine the total heat load to which the control panel is subjected. This total heat load is the combination of two factors – heat dissipated within the enclosure and heat transfer from outside the enclosure. Example: Internal heat dissipation: 471 Watts or 1,606 Btu/hr. Cabinet area: 40 ft.2 Maximum outside temperature: 110°F Desired internal temperature: 95°F The conversion table (above) shows that a 15°F temperature differential inputs 5.1 Btu/hr./ft.2 40 ft.2 x 5.1 Btu/hr./ft.2 = 204 Btu/hr. external heat load. Therefore, 204 Btu/hr. external heat load plus 1,606 Btu/hr. internal heat load = 1,810 Btu/hr. total heat load or Btu/hr. refrigeration required to maintain desired temperature. In this example, the correct choice is a 2,000 Btu/hr. Cabinet Cooler System. Choose a Cabinet Cooler model by determining the NEMA rating of the enclosure (type of environment), and with or without thermostat control. To Calculate Btu/hr.: 1. First, determine the approximate Watts of heat generated within the enclosure. Watts x 3.41 = Btu/hr. 2. Then, calculate outside heat transfer as follows: a. Determine the area in square feet exposed to the air, ignoring the top of the cabinet. b. Determine the temperature differential between maximum surrounding temperature and desired internal temperature. Then, using the Temperature Conversion Table (below), determine the Btu/hr./ft.2 for that differential. Multiplying the cabinet surface area times Btu/hr./ft.2 provides external heat transfer in Btu/hr. 3. Add internal and external heat loads for total heat load. Example: Internal heat dissipation: 471 Watts Cabinet area: 3.7m2 Maximum outside temperature: 44°C Desired internal temperature: 35°C The conversion table (above) shows that a 9°C temperature differential inputs 17.6 Watts/m2. 3.7m2 x 17.6 Watts/m2 = 65.1 Watts external heat load. Therefore, 65.1 Watts external heat load plus 471 Watts internal heat load = 536.1 Watts total heat load or Watts of refrigeration required to maintain desired temperature. In this example, the correct choice is a 586 Watt Cabinet Cooler System. Choose a Cabinet Cooler model by determining the NEMA rating of the enclosure (type of environment), and with or without thermostat control. Temperature Conversion Table Temperature Differential ºF Btu/hr./ft.2 5 1.5 10 3.3 15 5.1 20 7.1 25 9.1 30 11.3 35 13.8 40 16.2 Temperature Conversion Table (METRIC) Temperature Differential ºC Watts/m2 3 5.2 6 11.3 9 17.6 12 24.4 15 31.4 18 39.5 21 47.7 After picking which NEMA integrity you need, choosing your options and calculating your heat load -go to page 222-224 to specify a model number. See page 226 for HazLoc Cabinet Coolers. See page 228 for ATEX Cabinet Coolers. Contact EXAIR and we’ll walk you right through it. OR Cabinet Cooler® Systems
