If your application is installed in an environment with high ambient temperatures, oil and dust exposure, and you have high splash proof requirements (NEMA / IP), then it becomes absolutely necessary to prevent the ambient air from entering the enclosure. A cooling system with closed loop cooling normally consists of 2 loops; one loop closes the ambient air off and cools and circulates clean air into the enclosure. The second loop uses the ambient air or water to dissipate the heat. For these applications cooling units and air/water heat exchangers are normally used.

General rules:

• the only method to reduce enclosure temperature below ambient temperature (using cooling units and air / water heat exchangers)
• suitable for NEMA /IP requirements
• during planning you need to take the ambient temperature and the generated power loss into consideration. For outdoor applications, please also consider the solar load.(check the performance charts of the product you want to use to ensure that your system temperature is properly maintained)

The right selection of a cooling unit is determined by the following criteria:

1. required cooling capacity in Watt
2. max. ambient air temperature and desired enclosure air temperature
3. mounting requirements (wall, recessed or top mount)
4. dimensions of cooling unit and enclosure
5. mounting location (indoor, outdoor, shading, etc.)

The following simple formula calculates the necessary cooling power:

Pk = Pv - Pr
Pk [W] = Cooling capacity of the unit
Pv [W] = Power loss (thermal power generated inside an enclosure by the dissipation loss of components)
Pr [W] = Radiant heat gain/loss (heat transfer through the outer body of the enclosure)

The following formula calculates the heat gain/loss:

Pr = k x A x ≜T
k [W/m²K] = Coefficient of heat transmission
A [m²] = Enclosure surface area
≜T [K] = Temperature difference between ambient air and internal enclosure air

Important information when utilizing cooling units:

1. The enclosure should be sealed to prevent the inflow of ambient air.
2. The NEMA /IP rating of the cooling unit and the enclosure should be the same.
3. Use a door contact switch to prevent operation with open doors and consequent excessive accumulation of condensation.
4. Ensure that the air inflow and air outflow in the external circuit are not obstructed which would prevent proper heat exchanging at the condenser.
5. It also must be ensured that components with a high level of self-ventilation do not direct the air into the cold air outlet of the cooling device.
6. Ensure the unit stands straight.
7. Setting the temperature to the lowest is not always the best solution. The pre-set value of +35°C is a good compromise ensuring long life of electrical components, efficient operation and minimum condensation. This might also vary depending on the application.