Heat Dissipation in sealed electrical enclosures

heaT DissipaTion in sealeD elecTrical enclosures

The accumulation of heat in an enclosure is potentially damaging to electrical and electronic devices. Overheating can shorten the life

expectancy of costly electrical components or lead to catastrophic failure.

enclosure maTerials

The following discussion applies to gasketed and unventilated enclosures. Higher temperature rises can be expected with unfinished

aluminum and unfinished stainless steel enclosures due to their material's less efficient radiant heat transfer. Non-metallic enclosures

have similar heat transfer characteristics to painted metallic enclosures, so the graph can be used directly despite the difference in

material.

enclosure surface area

The physical size of the enclosure is the primary factor in determining its ability to dissipate heat. The larger the surface area of the

enclosure, the lower the temperature rise due to the heat generated within it.

To determine the surface area of an enclosure in square feet, use the following equation:

Surface Area = 2[(A x B) + (A x C) + (B x C)] ÷ 144

where the enclosure size is A x B x C in inches.

This equation includes all six surfaces of the enclosure. If any surface is not available for transferring heat (for example, an enclosure

surface mounted against a wall), that surface's area should be subtracted. Note: Enclosure volume cannot be used in place of surface area.

enclosure heaT inpuT

For any temperature rise calculation, the heat generated within the enclosure must be known. This information can be obtained from the

supplier of the components mounted in the enclosure.

enclosure TemperaTure rise (ΔT)

research has shown for every 18 f (10 c) rise above normal room

temperature 72 - 75 f (22 - 24 c), the reliability of electronic

components is cut in half.

The temperature rise illustrated by the curves in the Sealed

Enclosure Temperature Rise graph is the temperature difference

between the air inside a non-ventilated and non-cooled enclosure

and the ambient air outside the enclosure. This value is described

in the graph as a function of input power in watts per square

foot. In order to predict the temperature inside the enclosure,

the temperature rise indicated in the graph must be added to the

ambient temperature where the enclosure is located