Electrical enclosure overheating?
Causes & solutions

Overheating is the most common cause of unplanned failures in electrical enclosures. Controllers crash, frequency inverters switch to protective mode and the service life of electronics drops sharply — a rule of thumb says: every sustained temperature rise of 10 °C halves the service life of electronic components. The good news: with the right climate control, the problem can be solved reliably and cost-effectively.

Calculate the cooling capacity — the free online calculator

Enter the enclosure dimensions, power loss and temperatures — the calculator estimates the required cooling or heating capacity in real time (guide value based on IEC 60890) and directly recommends the right type of solution: filter fan, heat exchanger or cooling unit.

The most common causes of overheating

• High power loss of the components: frequency inverters, power supplies, transformers and contactors give off part of their power as heat. The more densely the enclosure is populated, the more heat is generated in a confined space.
• Enclosure too small or packed too densely: a small enclosure surface can release less heat to the surroundings. Without spacing between the devices, heat builds up.
• High ambient temperature: in production halls, boiler houses or in summer, the ambient air may already be 35–45 °C — fresh air then barely cools at all.
• Solar radiation (outdoors): outdoor enclosures heat up considerably in direct sunlight. Without a sun shield roof or active cooling, the internal temperature quickly rises above critical values.
• Dirty or clogged filter mats: a clogged filter drastically reduces the air flow. Regular maintenance is a must.
• Incorrect air routing: if warm exhaust air is drawn straight back in (short-circuit flow), even a powerful fan achieves little. Air in at the bottom, air out at the top — that is the basic principle.

What overheating actually causes

• PLC and controller failures: sporadic crashes that are hard to reproduce — often caused by temperature.
• Derating and shutdown: at excess temperature, frequency inverters automatically reduce their output or shut down completely.
• Shorter service life: electrolytic capacitors, relays and power supplies age considerably faster in heat.
• Condensation and corrosion: large temperature swings lead to condensation — particularly critical outdoors.

How the calculator works — the rule of thumb in detail

Before choosing a cooling solution, you need to know how much heat actually has to be dissipated. This takes three steps:

1. Add up the power loss: add up the power loss of all installed components (figures from the data sheets, in watts). Typical guide values: frequency inverter approx. 3–5 % of the drive power (7.5 kW inverter → ~300 W), power supplies 5–10 % of the output power, contactors/relays 2–10 W, PLC 10–50 W, transformers/chokes as per data sheet.
2. Subtract the enclosure's own heat dissipation: the enclosure releases heat through its surface: Q [W] = k × A × ΔT with ΔT = internal minus ambient temperature. The heat transfer coefficient k depends on the material: painted sheet steel ≈ 5.5, stainless steel ≈ 3.7, single-walled aluminium ≈ 12, plastic ≈ 3.5 W/m²K. The effective surface area A (simplified according to IEC 60890, dimensions in metres) depends on the installation — e.g. free-standing A = 1.8·H·(W+D) + 1.4·W·D, wall-mounted A = 1.4·W·(H+D) + 1.8·D·H (W = width, D = depth); reduced areas apply to baying enclosures.
3. Difference = required active cooling capacity: the heat generated by the components, minus the passive dissipation, has to be removed actively.

Example: enclosure 2.0 × 0.8 × 0.6 m, free-standing → A ≈ 5.7 m². With a hall at max. 35 °C and 45 °C permitted inside (ΔT = 10 K): Q ≈ 5.5 × 5.7 × 10 ≈ 315 W self-dissipation. If the enclosure contains 800 W of power loss, ~485 W must be removed actively — exactly what the online calculator works out for you.

The solutions at a glance — which cooling, when?

Solution	When suitable	ZPAS component
Filter fan	Surroundings cooler than the desired internal temperature, low to medium power loss. Inexpensive and low-maintenance.	LV series: 15–930 m³/h, IP 54
Air/air heat exchanger	Dusty or humid surroundings where no outside air may enter. Separates the internal and external air circuits.	Wall-mounted or roof-mounted unit, IP 54
Cooling unit (compressor)	Surroundings as warm as or warmer than the target internal temperature, high power loss. Maintains a defined internal temperature.	Side-mounted unit CVE (310–5,800 W), roof-mounted unit ETE (330–2,700 W)
Air/water heat exchanger	Very high heat loads and an existing cooling water circuit (e.g. in data centre or machine cooling).	On request / custom build
Outdoor air conditioner / heat pump	Outdoor cabinets exposed to sunlight — cool in summer, heat in winter.	CVO (550–5,800 W), AHP 7.0 (−15 to +50 °C)

More on the relationship between degree of protection and installation site: → IP ratings explained. For high-load environments with several racks: → data centre and server room cooling. Detailed selection guide: → choosing a cooling unit for electrical enclosures & server racks.

Outdoors: sun and frost

Outdoor cabinets face two opposite problems: overheating from solar radiation in summer, condensation and frost in winter. Proven measures:

• Sun shield roof and double-walled construction against direct heating
• Outdoor air conditioner (CVO) or reversible heat pump (AHP 7.0) for active heating and cooling in one unit
• Filter fan with weather protection hood for moderate loads
• Thermostat-controlled heater against condensation and icing

Details on weatherproof enclosures: → ZPAS outdoor enclosures & outdoor cabinets.

Common design mistakes

• Power loss estimated instead of added up — the sum from the data sheets is a must, especially for frequency inverters.
• Calculated with the average instead of the maximum temperature — what counts is the hottest summer day in the hall or at the installation site.
• Solar radiation forgotten — for outdoor enclosures, allow for an additional heat load (sun shield roof, double-walled design).
• No reserve — allow a 20–25 % margin for later extensions and filter soiling.

How ZPAS finds the right cooling for you

You do not have to do the design yourself. In the electrical enclosure configurator you select climate control components directly — filter fan, side-mounted cooling unit (CVE) and roof-mounted cooling unit (ETE) are available as options. For outdoor use, the outdoor enclosure configurator offers CVO air conditioners and a heat pump. Tell us your power loss and ambient conditions — we calculate the right cooling capacity and deliver the enclosure ready for operation from the factory.