A standard free-standing MCC enclosure with 600 W of internal losses — checked against its own natural-convection dissipating capacity, which turns out to fall well short, forcing a forced-air fan sizing calculation.
| Enclosure dimensions | 2000 mm (H) x 800 mm (W) x 600 mm (D), free-standing |
| Internal component losses | 600 W |
| Ambient temperature | 35°C |
| Maximum allowable internal temperature | 45°C |
| Natural convection coefficient | 5.5 W/(m²·K) — bare/unpainted steel |
A free-standing enclosure counts its top, both sides, front, and back (a wall-mounted enclosure would exclude the back face, which sits against the wall).
| Check | Requirement | Actual | Status |
|---|---|---|---|
| Natural convection capacity vs. internal losses | ≥ 600 W | 334.4 W | ✗ FAIL |
| Required forced-air fan flow | n/a (this is the corrective sizing result) | 186 m³/h | ✓ PASS |
Key insight: Natural-convection cooling capacity scales with surface area and allowable ΔT, while internal losses scale with the equipment actually installed inside — a physically large enclosure doesn't automatically have enough surface area for a densely-packed, high-loss equipment layout. This is a genuinely common design trap: an enclosure sized generously for physical equipment fit can still be thermally undersized for natural convection alone, which is exactly why this check exists as a distinct step from simply confirming the equipment fits inside the box.
Every input in this example is editable in the live calculator — free, no signup.
Open Panel/MCC Enclosure Cooling calculator →A larger enclosure (more surface area), a painted rather than bare-steel finish (painted steel has a somewhat higher convection coefficient, roughly 6–7 vs. 5.5 W/(m²·K)), relocating or upgrading components to reduce total internal losses, or active air conditioning for enclosures in high-ambient or dust/moisture-sensitive environments where simple filtered forced-air ventilation isn't appropriate — the right choice depends on the ambient environment and how much of a shortfall needs to be covered.
A wall-mounted enclosure's rear face sits directly against the wall it's mounted to, blocking airflow and convective heat transfer from that face entirely — the calculator excludes the back face from the effective area for wall-mounted units, which means a wall-mounted enclosure of identical dimensions has meaningfully less natural-convection capacity than a free-standing one and may need a fan sooner for the same internal losses.