Climatic properties such as the air temperature and humidity in the environment where the electrical cubicles are installed are very important for the continuity of the system and the safety of the personnel.
The amount of water in the air is called moisture. As the temperature increases, the amount of water in the unit air increases. Sudden decreases in air temperature cause some of the moisture in it to become water, which is called a dew point.
It is determined that condensation is unavoidable in the areas where the relative humidity is above 65%. The water that is gaseous state in the hot air is not to be in the gaseous state when the ambient temperature decreases, and it converts into water droplets in liquid form. These droplets merge with the dust on the equipment such as insulators and breakers inside the cubicles, cause to short circuit or faults due to decrease the creepage distance.
The heat caused by the nominal current flowing through the electrical equipment shall be increased by an external heater to prevent this issue. The resistive heater is called “anti-condensation heater” and is used with a thermostat or a hydrostat. The temperature inside the cubicle shall be increased by 10 °C to keep the humidity in gas form. The design and type of the anti-condensation heater is more critical for this task. In order for the air to warm up against to sudden drop in temperature, anti-condensation heaters designed with stainless steel resistance material that has low resistance variation against to temperature inside an aluminum case with increased cooling surface, shall be used. Aktif brand anti-condensation heaters are designed to meet these requirements. PTC heaters are semiconductor materials manufactured based on increasing the resistor against to temperature and cannot maintain the initial power; therefore, they cannot be used as anti-condensation heaters. Pipe or coil resistors are manufactured with a low heat dissipation surface for heating liquid or solid objects and they cannot heat the air in a panel.
Anticondensation Heater Selection and Application
A heater with a capacity of 1 cm³ / W is required for providing air suitable for the panel as per international standards. In such case, a 100 W heater will be sufficient for a 1 m³ panel. This can be increased where the humidity is high. The anti-condensation heater will function more efficiently if installed to the bottom of the panel due to convection of the hot air and entering the humid air from the ventilation holes. The anti-condensation heaters shall not be closer than 10 cm to the electrical materials which can be affected by high temperature. The thermostat shall not be also closer than 10 cm to the anti-condensation heater.
- Resistance Element : Wire wound, high efficiency Cartridge Resistance
- Frame Profile : High cooling surface aluminum
- Insulation : 2 kV 50/60 Hz 1 min
- Protection Degree : IP 20
- The most efficient body surface area that can be used in the environment heating is increased extrusion and anodized aluminum. Aktif heaters’ frames have 120% more surface efficiency than stainless pipe heaters.
- MGO powder is used for insulation material. The heaters have an insulation level of 2kV 1 min. In addition, this powder increases the mechanical strength and vibration resistance of the heater.
- As the resistance element is stainless and has very low temperature coefficient been used, the power of the heater does not reduce during operation. PTC heaters cannot prevent condensation as their power significantly reduce while operating.
- Aktif heaters offer the best solution as moisture reduction performance. It is 60% more efficient than pipe heaters and 670% more than PTC heaters.
- The distribution of heat inside the cubicle is important for the Anti-Condensation Heaters in order to perform its task homogeneously. Heat dissipation at different points of the cubicle is max. 20 ºC for Aktif heaters.
- The moisture reduction rate of the Anti-Condensation Heaters shall be equivalent to the rate of fall of temperature. Otherwise, condensation cannot be prevented. Often the 6% drop in humidity eliminates the risk of condensation. Tests with Aktif heaters can reduce the humidity by 6% in 16 minutes with a 100 W heater in a 2 m³ cubicle. This speed is more than 100% compared to pipe heaters.
Usage Guidelines for Anti-Condensation Heaters
- One or more Anti-Condensation Heaters and a separate thermostat (if used) shall be used for each medium voltage cubicle.
- The thermostat shall not be used or shall set for a very large limit.
- Anti-Condensation Heaters shall be manufactured by wire winding resistance inside high cooling surface aluminum frame.
- Under normal conditions, 100 W per m³ Aktif heater (winding resistance inside high cooling surface aluminum frame) is enough. In a 2 m³ cubicle, a 100 W Aktif heater can achieve a 12% reduction in 1 hour. If this cubicle is used in a place where the humidity reaches 95% values, it is correct to increase the heater power to 150 W. In this case, the power of the heater for each cubicle shall be determined by considering the site conditions and cubicle volume.
- Anti-Condensation Heaters shall be mounted on the bottom of the cubicle at a maximum height of 20 cm from the floor due to the rise of the heated air and generally the humidity ingression from the bottom.
- The active heating surfaces of the Anti-Condensation Heaters shall be mounted so that they do not touch the cubicle construction. Because the high surface area construction reduces the temperature of the heater surface by contact, it significantly reduces the efficiency.
- In order to prevent to be switched off for any reason, a control can be established to monitor the heater circuit.
- Since the Anti-Condensation Heater surface temperature is high, it must be installed at a minimum distance of 10 cm from the materials to be affected by the temperature.
- A common misconception is that the heater is installed in the cubicle and the thermostat is installed in the LV cabinet. Since the thermodynamic values between these two environments is different, the thermostat and the heater shall be in the same environment.
We also provide panel thermostats for use with the panel heaters.