Electrical equipment generates heat under load, which can prevent condensation buildup. However, when the equipment stops working and cools down, it gradually adapts to the ambient temperature, causing the cabinet temperature to drop below the dew point. This triggers the need for radiant heat. Heaters prevent condensation formation by raising the electrical cabinet temperature a few degrees above the ambient temperature.
- Anssin’s heater series covers a range from 8W to 1200W.
- A wide range of heater accessories are available: thermostats, Hygrostat controllers, pressure relief compensation devices, etc.
Semiconductor heater HGK016
What is a Heater
Anssin heaters include semiconductor heaters and fan heaters, which serve the same purpose: to protect control cabinets, cabinets, switch boxes, and other equipment from water droplets, maintain temperature balance, and prevent rust and corrosion.
Working principle of heater
Semiconductor heaters use PTC ceramic elements for heating. This material is characterized by “self-limiting temperature”: when the ambient temperature rises, its resistance automatically increases, reducing current flow and thus lowering the temperature, automatically maintaining a stable operating temperature.
Fan heaters, on the other hand, are based on semiconductor heaters but incorporate a fan. They can achieve faster heating within enclosed spaces through fan conduction. These heaters are primarily used in electrical distribution cabinets.
How to choose a Heater
Prerequisites for Calculation:
- Dimensions of the electrical control cabinet (length, width, height)
- As is customary, the placement of the electrical control cabinet (e.g., single cabinet, row cabinet) and the effective surface area of the cabinet must be known.
- Heat exchange coefficient (W/m²K) of the cabinet material (e.g., metal, plastic)
- Temperature difference ▲T(K) between the set temperature Ti (°C) inside the cabinet and the outside temperature Tu (°C) (e.g., day-night, summer-winter, climate change)
- Heat dissipated by the electrical equipment inside the cabinet (e.g., transformers, relays, and frequency converters) during operation.
Selecting Parameters for Calculation
1.Calculate the surface area based on the cabinet dimensions
Formula for calculating the surface area of the electrical cabinet: A (m²) (H (height), W (width), D (depth))
2.Placement of Electrical Cabinets
Single unit with open sides: A = 1.8 x H x ( W + D ) + 1.4 x W x D
Single unit against a wall: A = 1.4 x W x ( H + D ) + 1.8 x D x H
First or last unit in a row, with the rest open: A = 1.4 x D x ( H + W ) + 1.8 x W x H
First or last unit in a row, against a wall: A = 1.4 x H x ( W + D ) + 1.4 x W x D
Middle unit in a row, with open back: A = 1.8 x W x H + 1.4 x W x D + D x H
Middle unit in a row, against a wall: A = 1.4 x W x ( H + D ) + D x H
Middle unit in a row, against a wall with top covering: A = 1.4 x W x H + 0.7 x W x D + D x H
Example: The electrical cabinet is open on all sides, 2000mm high/800mm wide/600mm deep, then A = 1.8 x 2.0 x (0.8 + 0.6) + 1.4 x 0.8 x 0.6 = 5.712 m².
3.Electrical cabinet material and its heat transfer coefficient K (W/m²k)
Painted steel plate 5.5W/m²k
Stainless steel plate 4.5W/m²k
Aluminum plate 12W/m²k
Double-layer aluminum plate 4.5W/m²k
Plastic plate 3.5W/m²k
4.Temperature difference between inside and outside the cabinet △T (K)
△T = Ti – Tu Formula for calculating the required heat output (heater)
Required heat output P (W) = Electrical cabinet surface area A (m²) x Heat transfer coefficient K (W/m²k) x Temperature difference △kT (K)
Example: W = 5.712m² x 5.5W/m²k x 15K = 471.24W
Result: A heater with a heat output of 500W is required to meet the requirements. If the electrical cabinet is outdoors, the required heat output of the heater needs to be doubled. Selection should be based on the following empirical diagram.
5.If the electrical equipment inside the electrical cabinet generates heat during operation, the heat generated by the electrical equipment must be subtracted when calculating the heat output of the heater.
Filter Fan Selection
Select the appropriate cooling equipment based on the following empirical chart:
Select the cooling equipment (filter fan) using the calculation formula:
Required airflow V (m³/h) = [[Heat output to be processed PV / Temperature difference between inside and outside the cabinet ΔT (K)] x Air constant [3.3 m³K/h]
Example: V = [600W 15K] x 3.3 m³K/h = 132 m³h
Air constant value range:
PV(0-100) = 3.1 m³K/h
PV(100-250) = 3.3 m³KNh
PV(250-500) = 3.3 m³K/Vh
PV(500-750) = 3.4 m³K/Vh
PV(750-1000) = 3.5 m³K/h
