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Every device in a panel produces some power loss, and that loss becomes heat. If the enclosure surface cannot reject it, the internal temperature rises: drives derate, contactor coils and electronic boards lose life. Many of the 'unexplained stoppages' seen in summer are exactly this.
Step 1 — Add up the power loss
Drives typically dissipate 3-5% of their rated power; for a 22 kW drive that is roughly 700-1100 W. Power supplies, transformers, contactors and terminal blocks are added from catalogue data. No climate control decision is sound before the total loss (Pv) is known.
Step 2 — Subtract the enclosure's own capacity
A sheet-steel enclosure rejects heat naturally through its surface. The effective surface area (A) is multiplied by the inside-outside temperature difference (ΔT); around 5.5 W/m²K is used for sheet steel. Whatever remains must be removed actively.
Step 3 — Is a fan enough, or is cooling needed?
- If ambient is at least 5 K below the target internal temperature, a filter fan is enough. Required airflow is roughly V = 3.1 × Pv / ΔT (m³/h).
- If the environment is hot, dusty or oily, a fan is not the answer; move to a closed-loop cooler or a panel air conditioner.
- If outside is hotter than inside (boiler room, foundry) a fan makes things worse.
- If a fan is chosen, the outlet grille and filter must go into the maintenance plan; a clogged filter equals no fan at all.
Frequently asked questions
What should the panel thermostat be set to?
A common practice is to start the fan around 35 °C and run the heater at 5-10 °C to prevent condensation. The exact value follows the operating limit of the most sensitive device in the panel.
Should the fan be at the top or the bottom?
Fresh air is drawn in low through the filter fan and hot air leaves through the outlet grille at the top. The reverse layout fights natural convection and reduces effectiveness.
What is a panel heater for?
It prevents condensation on internal surfaces in cold, damp environments. Condensate causes corrosion and leakage on electronic boards; a small heater controlled by a hygrostat or thermostat prevents it.
Are a closed-loop cooler and a panel air conditioner the same?
Neither mixes inside air with outside air. A heat-exchanger loop is enough when ambient is below the internal target; when ambient is hot, a panel air conditioner with a refrigeration cycle is required.