Engineering tools
Control Panel Heat Calculator
Calculate component heat losses, assess the natural heat-dissipation capacity of a control-panel enclosure and estimate the airflow required where forced ventilation is needed.
Build a traceable heat-loss schedule, configure the enclosure dimensions, material and installation arrangement, and produce a calculation report for engineering review.
All calculations run locally in the browser. Calculation data is not uploaded to a server.
Project and document information
Calculation engine: CP-heat v1.0
Calculation summary
Connected, diversified and allowance losses are derived from trusted included rows.
Component heat-loss schedule
Enter maximum manufacturer heat losses. Invalid and excluded rows do not contribute to trusted totals.
| ID | Qty | Manufacturer | Part number | Description | Max temp °C | Unit loss W | Diversity | Connected W | Diversified W | Included | Actions |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 12 | 12 | ||||||||||
| 4.5 | 4.5 | ||||||||||
| 0.42 | 0.42 | ||||||||||
| 0.315 | 0.315 | ||||||||||
| 0.21 | 0.21 |
Allowances and additional losses
Diversity is applied once. Detailed conductor-loss entry is deferred; enter its calculated total here.
Terminal 0.1682 W · Cabling 0.1682 W
Enclosure and environment
Material coefficients are workbook/project assumptions, not certified universal values.
Enclosure preview
Normalized isometric preview of enclosure proportions and installation constraints.
Against a wallAmbient 26.0 °C
Internal 31.5 °C · Pass — natural cooling
Painted Carbon Steel enclosure, 400 mm wide, 500 mm high and 210 mm deep. Against a wall. Ambient 26.0 °C, predicted internal 31.5 °C. Pass — natural cooling.
Natural cooling results
Natural heat dissipation is based on effective surface area, coefficient and allowable temperature rise.
Forced ventilation
Airflow is an idealized minimum estimate; allow for filters, pressure loss, derating and real fan curves.
Natural cooling is adequate; forced ventilation is not required.
Warnings and review items
Resolve errors before relying on trusted totals.
No calculation warnings.
Calculation report
Preview the immutable engineering report before opening the browser print dialog.
How the control panel heat calculation works
The calculator totals diversified component heat losses, applies terminal and cabling allowances once, adds manually calculated conductor or other internal losses, and compares the result with the estimated natural heat-dissipation capacity of the enclosure.
Component losses should come from current manufacturer data at the intended operating conditions. A diversity factor may be used only where the maximum credible operating state justifies it. Equipment mounted outside the enclosure can contribute to electrical load without contributing all of its losses to the internal thermal calculation.
Temperature rise and natural heat dissipation
The natural temperature rise is estimated as panel heat loss divided by the product of the enclosure heat-transfer coefficient and its effective exposed surface area. The permitted rise is the difference between the maximum internal and maximum ambient temperatures. The arrangement matters because a wall, adjacent enclosure or covered surface reduces the area available to reject heat.
Natural dissipation capacity is the heat-transfer coefficient multiplied by effective surface area and permitted temperature rise. A positive margin indicates that the estimate remains within the selected temperature limit; a deficit means additional cooling or a design change is required.
Required ventilation airflow
Where panel losses exceed natural dissipation, the calculator applies the workbook relation airflow = 3.1 × excess heat ÷ permitted temperature rise. The result is an idealised minimum in cubic metres per hour. Select a real fan using its duty at the expected system resistance, allowing for filters, grilles, contamination, ageing and maintenance.
Worked example
Consider a 400 mm wide, 500 mm high and 210 mm deep painted-carbon-steel enclosure against a wall. Its effective surface area is approximately 0.587 m². With a coefficient of 5.5 W/m²K, ambient temperature of 26 °C and maximum internal temperature of 35 °C, its estimated natural capacity is about 29 W.
If the calculated internal loss is 80 W, approximately 51 W remains after natural dissipation. At the permitted 9 K rise, the idealised minimum airflow is about 17.6 m³/h. The selected fan should provide more than this at the installed operating point; the result is not a catalogue selection or a substitute for thermal verification.
Assumptions and limitations
This is an engineering thermal estimate based on the supplied calculation workbook. It is not a complete IEC TR 60890 or IEC 61439 temperature-rise verification.
Final design must consider manufacturer derating, local hot spots, air paths, filter pressure loss, solar gain, cable and busbar losses, altitude, contamination, maintenance requirements and applicable project standards.
Related design resources
- Use the control panel load calculator to separate supply sizing from enclosure heat loss.
- Review the BS 7671 guide for design engineers for the wider electrical design and verification context.
- Browse the electrical design and control systems topic hubs.