Text version of the page

A

IR

C

ONDITIONERS

Thermal Management - 13627 Air Conditioners Sizing and Selection B

efore choosing a thermal management solution, you need to carefully consider the specifics of your applica- tion in addition to the following factors:

Sizing Air Conditioners Determine internal heat load in watts.

Determine the internal heat load produced by equipment as total operating watts.1

•••• F

an packages and blowers may introduce ambient contaminants like oil mist and dust into the enclo- sure

WATT = 3.413 BTU/Hr.

H

Determine desired temperature difference in degrees F.

eat exchangers cannot cool below the ambient temperature

1°C Δ T = 1.8°F Δ T Determine the Δ T (°F), the temperature difference between the maximum temperature outside the enclosure (To) and the

C

losed-loop air conditioners (this section) can cool below ambient temperature and reduce humidity without introducing contaminants

maximum desired temperature inside the enclosure (Ti), which can be calculated as: To - Ti = Δ T for air conditioners.

S

imple ventilation devices such as louvers or grilles and filters are appropriate if maintaining a cool, constant temperature is not a critical factor

Determine exposed surface area of the enclosure in square feet.

AREA (ft
2 ) 1 M
2 = 10.76 ft
2 Calculate the exposed surface area of the enclosure in

O

nce you have determined the proper form of cool-ing equipment you need, selecting the required cooling capacity is outlined in this section.

Square Feet: AREA (ft
2 ) = 2[(H” x W”) + (H” x D”) + (W” x D”)] ÷ 144where “H”, “W”, and “D” are the dimensions of the enclosure in inches.

How to Read Air Conditioner Catalog Numbers Determine required air conditioner capacity. CR43 - 06 1 6 - 002

( WATTS x 3.413) + [1.25 x AREA (ft

2

) x Δ T (°F)] = BTU/HR.Use this formula to determine the required cooling capacity needed to maintain the desired operating temperature for your enclosure. This selection procedure applies to uninsulated, sealed, gasketed enclosures in indoor locations. All industrial air conditioners are rated at their maximum operating point. Operating an air conditioner at temperatures below maximum conditions will result in reduced cooling capacity. In other words, operating 95°F ambient and 95°F enclosure temperature results in a 10 percent to 20 percent reduction in the rated capacity. (Note: full cooling capacity is probably not necessary at lower ambient temperatures.)Air conditioners are appropriate for applications in which:The temperature inside the enclosure must be maintained at or below ambient temperatureHumidity must be removed from the enclosure Ambient air contaminants must be kept out of the enclosure•••
12345 1. Identifies the type/family of air conditioner and the approximate height (i.e., CR43 = CR family, about 43” high).2. This is the air conditioner’s listed capacity in BTU/Hr. (i.e., 06 = 6000 BTU/Hr.)3. 1 = 115 Volt or 2 = 230 Volt; 4 = 460 Volt4. 6 = 50/60 Hz or 60 Hz (depending on unit, see Design Data); 5 = 50 Hz5. Unique set of numbers for each air conditioner which identifies the accessories on a model.

Selection and Sizing Software

Designed to assist you in determining the most suitable choices of air conditioners, heat exchangers, or fans for your application. Download a free copy of our selection software by visiting our web site: www.hoffmanonline.com.

TM-2

Subject to change without notice PH 763 422 2211 • FX 763 422 2600 • www.hoffmanonline.com © 2006 Hoffman Enclosures Inc.