Electrical enclosures
in the sun
Updated:
Why solar radiation determines the cooling outdoors, and the five measures you can take to keep the heat out of the enclosure.
Solar load: the underestimated heat source
When it comes to cooling an electrical enclosure, most people think of the power loss of the equipment. Outdoors there is a second source: solar radiation. It heats the enclosure surface far above the air temperature. Part of this heat travels inwards and has to be removed as well.
For this, engineers calculate with the sol-air temperature: a notional outside temperature that combines air temperature and radiation. It depends on the radiation intensity, the colour (absorptance) and the heat emission of the surface.
Five levers against solar heat
- Light colour: RAL 7035 (light grey) absorbs significantly less radiation than dark shades. Dark corporate colours noticeably increase the solar load — more in the guide to RAL colours.
- Double wall with rear ventilation: the air layer between the outer and inner shells carries the heat away by convection before it reaches the equipment. For double-walled SZD enclosures, our cooling capacity calculator uses a heat transfer coefficient of around 3.5 W/(m²·K).
- Sun shield roof: a projecting roof with an air gap shades the top — the surface that receives the most radiation at midday.
- Site and orientation: use shade from buildings or trees, and if possible do not face the door side south or west.
- Cooling with reserve capacity: the solar load belongs in the sizing — otherwise a fan is sufficient in spring and fails in July.
Calculate instead of estimating: the cooling capacity calculator takes solar radiation, colour and wall design into account and recommends a fan, heat exchanger or cooling unit. The outdoor enclosures of the SZD series are double-walled as standard.
Frequently asked questions about sun protection
How much does the sun heat up an electrical enclosure?
Direct sunlight can heat the surface of an enclosure far above the air temperature. How much of that reaches the inside depends on colour, wall design and ventilation.
Does a light colour help against solar heat?
Yes. Light colours such as RAL 7035 absorb significantly less solar radiation than dark ones. If you need a dark corporate colour, allow for the additional solar load when sizing the cooling.
What are the benefits of a double-walled outdoor enclosure?
The rear-ventilated air layer between the outer and inner walls carries away a large part of the solar heat before it reaches the equipment. This significantly reduces heat transfer compared with a simple sheet-metal wall.
Enclosure in blazing sun?
Tell us the site, colour and power loss — we will design the wall construction and cooling.
Request a quote Calculate cooling capacity