8. Electric Panel Design
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Thermal Design
Altus equipment is designed to work at an ambient temperature of up to 60 °C (except where
specified). Therefore, this should be the maximum internal temperature of the cabinet. The following
precautions should be observed in panel design:
Size cabinets with enough internal volume for a good air circulation
Provide forced ventilation or air exchangers with the external environment, if necessary, in order to
avoid over temperature. In critical cases, it is recommended the use of refrigeration, to keep the
equipment operating within the levels of operating temperature.
Distribute homogeneously heat sources inside the cabinet.
Consider the dissipation in the cables leading higher currents to avoid internal overheating into the
gutters.
ATTENTION:
For maximum dissipation of each module of the Nexto series, see the Technical Characteristics
document for the specific module.
A method to calculate the internal temperature of the panel depending on their power dissipation is
explained below.
Heat dissipation in an electrical panel
Each electrical panel dissipates, through its surface, an amount of heat for a given difference in
internal and external temperature. To calculate the heat dissipation in cases where the temperature
difference between the inside and the outside of the panel reaches 50 °C, the following values should
be considered:
Effective dissipation surface of the panel; calculated according to DIN-VED 0660 chapter 500, as
indicated by the type of installation
The dissipation constant for steel sheet painted in W/m² °C
Panel ventilation conditions (installation location)
Degree of inner panel occupation (inside air flow impedance)
For the values mentioned above, only the value of the panel surface can be calculated exactly.
Calculation of the effective surfaces of dissipation A (m²) for the panel:
The calculation of surface "A" is done as directed by DIN-VDE, depending on the type of installation
of the panel:
Installation type according to DIN-VDE 0660/500
Formula for calculation of A (m²)
All side free panel
A = 1.8 * H * (L + P) + 1.4 * L * P
Pane with the rear surface obstructed
A = 1.4 * L * (H + P) + 1.8 * P * H
Panel with a lateral surface blocked
A = 1.4 * L * (H + L) + 1.8 * L * H
Panel with a lateral and rear surface obstructed
A = 1.4 * H * (L + P) + 1.4 * L * P
Panel with both sides obstructed
A = 1.8 * L * H + 1.4 * L * P + P * H
Panel with the two sides and the rear surface obstructed
A = 1.4 * L * (H + P) + P * H
Panel with the two sides and the rear and upper surface
obstructed
A = 1.4 * L * H + 0.7 * L * P + P * H
Table 8-2. Calculation of Effective Surface of Dissipation
L = width (m), H = height (m), P = depth (m)
In the case of panels built with painted steel sheet, for the still air around them, the heat dissipation
constant can be considered 5.5 W/m2² °C.
