Checks whether an electrical enclosure (panel, MCC, switchgear cubicle) can shed its installed components' heat losses by natural convection alone while staying within the maximum internal temperature rating, and — if not — sizes the forced-air fan flow needed to do so.
Standards followed
IEC 60890-derived enclosure heat-rise method, as widely published by enclosure/cooling manufacturers (e.g. nVent Hoffman, Rittal, Pfannenberg application notes)
What it can do
- Effective dissipating surface area from enclosure dimensions and mounting type (free-standing counts the rear face; wall-mount doesn't).
- Natural-convection heat dissipation capacity at the allowable temperature rise, using a user-adjustable convection coefficient (≈5.5 W/(m²·K) bare steel, ≈6-7 painted).
- Pass/fail check of natural convection against the installed heat losses.
- Forced-air fan flow sizing (m³/h) if natural convection alone isn't enough.
Example problem
2000×800×600mm free-standing enclosure, 600W internal losses, 35°C ambient, 45°C max internal temperature, k=5.5 W/(m²·K).
- Effective area = top (0.8×0.6) + 2 sides (2×(2×0.6)) + front (2×0.8) + back (2×0.8) = 0.48+2.4+1.6+1.6 = 6.08 m².
- Allowable ΔT = 45−35 = 10°C.
- Natural convection capacity = 5.5 × 6.08 × 10 = 334.4W — less than the 600W of losses, so natural convection alone is inadequate.
- Required fan airflow = 3.1 × 600 / 10 = 186 m³/h.
Natural convection can only shed 334.4W against 600W of losses — inadequate — requiring 186 m³/h of forced airflow.
Want the full step-by-step version?
This is a simplified, first-pass heat-rise method — it doesn't account for solar loading, altitude derating of the fan, filter/vent pressure drop, or non-uniform internal air circulation. For safety-critical or high-density enclosures, verify against the enclosure/cooling manufacturer's own sizing tool.