Choosing a Control Panel Cooling unit
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How to choose a model in the ENC series
1. How to select a control panel cooling unit [indoor installation]
The cooling capacity required to maintain the inside of the control panel at the desired temperature can be calculated by the following equation.
Required cooling capacity [W]
= (1) Total heat generated inside the control panel [W] + (2) heat transfer coefficient [W/m2 °C] × ((3) maximum ambient temperature [°C] － (4) desired temperature inside the panel [°C]) × 5) control panel effective surface area [m2]
(1) Total heat generated inside the control panel
Total amount of heat generated by the devices stored inside the panel.
*Refer to the heat generation list by device for the amount of heat generated by each device.
(2) Heat transfer coefficient
The heat transfer coefficient represents the proportion of heat trying to penetrate inside the panel from the outside.
It varies depending on the type and thickness of the sheet metal, but in steel plates with a thickness of 2 mm, it is about 5 [W/m2· °C].
(3) Maximum ambient temperature
Temperature that is expected to be the highest in the installation environment.
(4) Desired temperature inside the panel
Desired temperature inside the panel (recommended temperature is 35 °C).
(5) Effective surface area of control panel
Total surface area of all the surfaces in the target control panel that are in contact with the atmosphere (for autonomous panels, this is the surface area excluding the bottom surface).
２． How to select a control panel cooler [outdoor installation]
For outdoor installation, the model is selected by adding the amount of the energy from sunlight to the figure of the control panel cooler selected for indoor installation that is calculated in (1) How to select a control panel cooler [indoor installation].
Required cooling capacity [W]
= Total solar radiation penetration heat + cooling capacity required for indoor panel (Refer to Section 1. How to select a control panel cooler [indoor installation])
How to determine the total solar radiation penetration heat
1) Calculate the amount of penetration heat due to solar radiation.
The amount of solar radiation depends on the installation location, date, time, and orientation.
★Solar radiation sample data of each surface (Tokyo area, July 22 weather clear) Unit: W/m²
| Sky side | North side | East side | South side | West side | |
|---|---|---|---|---|---|
| 11 o’clock | 1026.7 | 302.8 | 302.8 | 305.1 | 77.3 |
| 12 o’clock | 1064.0 | 78.3 | 78.3 | 325.9 | 78.3 |
| 13 o’clock | 1043.0 | 78.8 | 78.8 | 310.1 | 307.7 |
| 14 o’clock | 980.2 | 79.1 | 79.1 | 261.7 | 523.3 |
| 15 o’clock | 872.1 | 80.7 | 80.7 | 179.8 | 715.3 |
Therefore, the required solar radiation penetration heat will be the sum of all the values calculated for each side. The solar radiation amount of each side is determined by the following formula.
olar radiation on each side [W/m²] ×
Description of terms
- “Heat transfer coefficient (W/m²・ °C)” ... When there is a temperature difference between the ambient temperature (temperature rise on the housing surface) and the desired temperature, the opposing surface area ratio of the penetration (or dissipation) heat due to heat transfer varies according to the plate thickness and material of the control panel but this is defined as 5 to 6 W/m²・ °C by the Thermal Solution Equipment for Cabinet Technical Association.
- Housing external heat transfer coefficient (W/m²・°C) ... This value is believe to be about 10 W/m² °C when there is no wind, and about 15 W/m² °C at a wind speed of 1 to 2 m/s. The higher the wind speed, the greater the heat transfer rate.
- “Temperature rise on housing surface (equivalent outside air temperature rise)”... Equivalent rise in the air temperature due to sunlight.
From the above, it can be seen that the value varies depending on the installation area, color and condition of the panel surface, condition of the outer walls of the panel (thickness, double structure, installation of sunshade, etc.), condition of the wind flowing over the panel and so on.
As an example, we’ll try to calculate it with the control panel under the following conditions.
◎Height 2000 mm, width 1000 mm, depth 500 mm ◎ door surface facing south ◎Tokyo district, July 22, weather clear, 14 o’clock, windless ◎thickness 2 mm, paint color: light beige, single structure wall surface
| Position of face | Solar radiation (W/m²) |
Solar absorption rate | Outer surface of housing Heat transfer rate (W/m²・℃) |
Equivalent outside air Temperature rise (℃) |
Heat transfer coefficient (W/m²・℃) |
Surface area(m²) | Solar radiation heat(W) |
|---|---|---|---|---|---|---|---|
| Sky side | 980.2 | 0.5 | 10 | 49.01 | 5 | 0.5 | 122.5 |
| North side | 79.1 | 0.5 | 10 | 3.955 | 5 | 2 | 39.6 |
| East side | 79.1 | 0.5 | 10 | 3.955 | 5 | 1 | 19.8 |
| South side | 261.7 | 0.5 | 10 | 13.085 | 5 | 2 | 130.9 |
| West side | 523.3 | 0.5 | 10 | 26.165 | 5 | 1 | 130.8 |
| Total solar radiation penetration heat | 443.6 | ||||||
CautionSince the absorption rate changes when the surface of the panel becomes dull together with use over the years, it is therefore necessary to select a model with the safety factor in mind.
3) Select the model by applying the required cooling capacity above to the capacity characteristic graph of each control panel cooler.
<Notes on selection>
- Note that the amount of heat generated varies greatly depending on how the inverter and servo amplifier are used and the motor torque etc.
- For inverters with a rated output of 50 kw or more, check with the manufacturer as the amount of heat generated varies greatly depending on the manufacturer.
- When selecting a model, select one that exceeds the required rating capacity and cooling capacity.
- Note that the capacity calculated by the above formula is just an estimate and not an absolute value.
- Be extra careful because the expected cooling capacity may not be obtained depending on the sealing of the control panel, position relative to the heating element, and the air flow inside the control panel.
- Carry out regular maintenance as dirty filters, deterioration of the fan motor etc. may lead to a drop in the cooling capacity.
List of calorific values by equipment
1. Power supplies and transformers
| Storage devices inside panel | Calorific value (recommended value) | Remarks | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Small transformer | Rated capacity
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| Large transformer (Single phase) |
Rated capacity
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| Large transformer (3-phase) |
Rated capacity
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| Voltage regulator | About 10% of the rated capacity | |||||||||||||
| Large resistor | About 1/3 of the rated capacity | |||||||||||||
| Constant voltage power supply | Rated capacity
|
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| Uninterruptible power supply (UPS) |
Output capacity
|
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| DC stabilized power supply (Switching regulator) |
About 20-30% of the rated capacity |
|
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| Low voltage capacitor | About 0.2-0.3% of the rated capacity |
|
2. Amplifiers
| Storage devices inside panel | Calorific value (recommended value)Remarks | Remarks | ||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| AC servo amplifier | Rated capacity
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| Inverter | Rated output
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| AC reactor (200 V system) |
Rated capacity
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| AC reactor (400 V system) |
Rated capacity
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| DC reactor (200/400 V system) |
Rated capacity
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| Braking resistance and control unit (200/400 V system) |
Rated capacity
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| Thyristor (Single phase) |
Rated current
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| Thyristor (3-phase) |
Rated current
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3. Wiring equipment
| Storage devices inside panel | Calorific value (recommended value)Remarks | Remarks | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Circuit breaker for wiring (MCCB) |
Rated capacity
|
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| Electrical leakage circuit breaker (ELCB) | Rated capacity - 225A MCCB + About 5 W - 400A MCCB + About 30 W (electrical leakage circuit unit, etc.) |
|
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| Electromagnetic contactor | Rated capacity
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| Thermodynamic overload relay (Themal) |
Rated current
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| Electromagnetic relay | About 5 W per unit |
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4. Control equipment
| Storage devices inside panel | Calorific value (recommended value)Remarks | Remarks | ||||||
|---|---|---|---|---|---|---|---|---|
| Small relay |
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| Solid state relay (SSR) |
Load current value×approx. 1.8 W | |||||||
| Temperature controller | Current consumption is considered to be the amount of heat generated. | |||||||
| PLC | Compact PLC AC power type
Approximately the power consumption of a standard PLC power supply unit |
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| PC | Approximately the power consumption of the power supply | |||||||
| LCD monitor | About 20 W per unit | |||||||
| Touch panel | About 100 W per unit |
5. Others
| Storage devices inside panel | Calorific value (recommended value)Remarks | Remarks | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Fan motor |
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Caution The above-mentioned heat generation materials by equipment that are based on materials issued by the Thermal Solution Equipment for Cabinet Technical Association contain additional materials that have been independently investigated by Apiste.
If you would like to determine the exact amount of heat generated, please contact the various equipment manufacturers as the amount of heat generated by each device is just an estimate.
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