Distribution cabinet heater

Distribution cabinet heater

Why use an electrical cabinet heater?

Electrical equipment generating heat under load can prevent the accumulation of condensate. However, when the equipment stops working and cools down, it gradually adapts to the surrounding ambient temperature, causing the temperature inside the cabinet to drop below the dew point. Therefore, this triggers the demand for radiant heat! The heater prevents the formation of condensation by raising the temperature of the electrical cabinet several degrees higher than the ambient temperature outside the cabinet.

Rep Electric's R series heaters cover a range from 10W to 1000W.

Rich heater matching devices: temperature controller, humidity controller, pressure release compensation device, etc.

Selection of Heater

Calculation prerequisite:

1. Dimensions of electrical control cabinet (length, width, height)

2. As a convention, it is necessary to understand the placement position of the electrical control cabinet (e.g. single cabinet, row cabinet) and the effective surface area of the electrical cabinet

3. Heat exchange coefficient (W/m2K) of the material of the electrical cabinet body (e.g. metal, plastic)

4. The temperature difference △ T (K) between the set temperature Ti (° C) inside the electrical cabinet and the temperature Tu (C) outside the cabinet (e.g. day night, summer winter, climate change)

Select parameters for calculation

1. Calculate the surface area of the electrical cabinet based on its size

2. Placement of the electrical cabinet (as shown in the following figure)

Single four sided open space

Single against the wall

The front or last unit in the cabinet, with the rest empty and open

The front or last unit in the cabinet, against the wall

The middle unit of the cabinet is empty at the back

Calculation formula for surface area of electrical cabinet A (m2) (H height, W width, D depth)

A=1.8xHx(W+D)+1.4xWxD

A=1.4xWx(H+D)+1.8xDxH

A=1.4xDx(H+W)+1.8xWxH

A=1.4xHx(W+D)+1.4xWxD

A=1.8xWxH+1.4xWxD+DxHA=1.4xWx(H+D)+DxH

A=1.4xWxH+0.7xWxD+DxH

Central unit of the cabinet, against the wall

The middle unit of the cabinet is covered against the wall

Example: If the perimeter of the electrical cabinet is open, with a height of 2000mm/width of 800mm/depth of 600mm, then A=1.8x2.0x (0.8+0.6)+1.4x0.8x 0.6=5.712m23. Material and heat transfer coefficient of the cabinet body K (W/m2K)

Painted steel plate

stainless steel plate

aluminum plate

Double layered aluminum plate structure

plastic sheet

5.5 W/m? K

4.5W/m? K

12 W/m²K

4.5W/m²K

3.5W/m2K

4. Temperature difference between inside and outside the cabinet AT (K)

AT=Ti -Tu

Calculation formula for required heat generation (heater)

Required heat generation P (W)=electrical cabinet surface area A (m2) x cabinet material heat transfer coefficient K (W/m2K) x temperature difference △ T (K) Example: W=5.712m2x5.5W/mKx15K=471.24W

Result: A heater with a heat output of 500W is required to meet the requirements. If the electrical cabinet is located outdoors, the required heat output of the heater must be doubled! Select based on the following experience chart

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 generated by the heater.

Selection of filter fan

Select the appropriate cooling equipment based on the following experience chart: Calculate the required air flow rate V (m3/h) for the cooling equipment (filter fan) through a formula=[heat generation to be processed PV/temperature difference inside and outside the cabinet Δ T (K)] x air constant [3.3 m ³ K/Wh] Example: V=[600W/15K] x3.3m * K/Wh=132 m ³/h Range of air constant values:

PV(0-100)=3.1 m³K/WhPV(500-750)=3.4 m³K/WhPV(100-250)=3.3 m³K/WhPV(750-1000)=3.5 m³K/WhPV(250-500)=3.3 mK/Wh

JRQ250~JRQ200 heaters