Work out how much heat your panel gives off, how much its own walls can shed, and what is left over. The answer decides whether a cheap filter fan will do or whether you need a cooling unit — and in an Iraqi summer that answer is usually not the cheap one.
Tap the components and enter the heat each one gives off in watts. This is the power it wastes as heat, not the power it switches — a 22 kW drive does not give off 22 kW.
Size matters, but so does how it is installed. A cabinet squeezed between two others sheds far less heat than a free-standing one, because two of its sides are effectively blocked.
The gap between these two numbers is what decides everything. If the outside is hotter than the inside target, no fan on earth will help.
This is what your panel needs. Send it to us for a price on the fan, cooling unit or heater.
This calculator gives an indicative cooling requirement for budgeting and comparing quotations. It is not a design document. Final selection must be confirmed by a qualified engineer using the actual power-loss figures from every component datasheet, the manufacturer's cooling unit performance curves at the real ambient and altitude, and the temperature-rise requirements of IEC 61439. Solar gain and internal hot spots are not modelled. Mega Standard accepts no liability for decisions made on these figures alone.
Component heat figures shown as defaults are typical values, not measurements. Use the power-loss figure from each manufacturer's datasheet for a real design. Solar gain, altitude derating of cooling units and internal air circulation are not modelled here.
The instinct is to add up the outside area of the enclosure and call that the cooling surface. IEC 60890 does not, and for good reason: a face pressed against a wall or against another cabinet cannot shed heat the way an exposed one can, and the floor sheds essentially nothing.
So the standard weights each face. An exposed top counts at 1.4 times its area, because hot air rises and leaves through it readily. An exposed vertical face counts at 0.9. A blocked face — against a wall, or against a neighbouring cabinet — drops to 0.5. The floor counts as zero.
The consequence is that where you put the cabinet matters as much as how big it is. Move a panel from free-standing into the middle of a row and you can lose a quarter of its cooling surface without changing a single component inside it.
There are two ways to cool a panel, and the choice is not really a choice — it is decided by one comparison.
A filter fan pushes outside air through the enclosure and lets the hot air out the other side. It is cheap, simple and reliable. But it can only ever bring the inside down towards the outside temperature. It cannot go below it, any more than a household fan can make a room colder than the air outside.
A cooling unit is a small air conditioner. It is sealed, and it pushes heat out against the temperature gradient, so it can hold an inside temperature below ambient. It costs several times more, needs a condensate path, and needs its filters cleaned.
The comparison that decides it: is the outside air cooler than the temperature you need inside? If yes, a fan can work. If no — and in a Kirkuk or Basra plant room in August the answer is usually no — a fan is worse than nothing, because it actively imports heat. This calculator checks that first and says so plainly.
Once the effective surface is known, the rest is a straightforward heat balance:
Ae = Σ (face area × surface factor) [IEC 60890 Table 1] Q_out = k × Ae × ΔT Q_surplus = Q_inside − Q_out k = 5.5 W/m²K painted steel, 3.7 stainless, 12 aluminium, 3.5 GRP ΔT = inside target − outside ambient Filter fan airflow V = 3.1 × Q_surplus ÷ ΔT (m³/h) Cooling unit Q = Q_surplus (W)
Notice what happens to the fan formula as ΔT gets small: the airflow needed goes up steeply, and at ΔT = 0 it becomes infinite. That is the mathematical version of the same point — a fan trying to hold a small difference has to move an absurd volume of air. Below about 5 K of difference, a cooling unit is the practical answer.
It depends on one comparison: whether the air outside the panel is cooler than the temperature you need inside it. If it is, a filter fan can work and is far cheaper. If the outside air is as hot as or hotter than your target — common in an Iraqi summer — only a cooling unit can help, because a fan can never cool below ambient.
Add up the power loss of every component from its datasheet. Manufacturers publish it as power loss or power dissipation. As a rough guide, a variable speed drive wastes about 3 % of its rated power, a control transformer or power supply between 3 % and 10 %, and contactors and breakers a few watts each.
Because faces that cannot shed heat freely do not count fully. IEC 60890 weights an exposed top at 1.4, an exposed side at 0.9, a blocked side at 0.5, and the floor at zero. A cabinet in the middle of a row against a wall has most of its surface discounted, which is why installation position changes the answer so much.
Check the datasheets, but 35 °C is a common target. Most switchgear is rated for 40 °C ambient and variable speed drives typically begin derating their output above 40 °C, so leaving a margin below that protects both the equipment and its rated performance.
No. It gives a defensible figure for budgeting and for checking a supplier's proposal. A real design needs the actual power-loss figures from every datasheet, the cooling unit's performance curve at your ambient and altitude, consideration of internal hot spots and airflow paths, and compliance with the temperature-rise requirements of IEC 61439.
We supply Rittal enclosures, filter fans, cooling units and heaters across Iraq, and we will tell you when a sunshade or a bigger cabinet would beat a cooling unit. Send us the result and we will come back with a specification and a price.