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High humidity and quick temperature changes (example: day/night) in electrical rooms often as they generate condensation on metallic and plastic surfaces. This condensation is very dangerous when left on insulation materials, as it increases the risk of current leakage. Ultimately, it can generate short circuits or internal arcs. To ensure Blokset works within the high room humidity and quick temperature changes, it is often necessary to maintain the temperature inside the cubicle above the dew point (Tr: water vapor condensation temperature) when switchboard is shut down (maintenance, normal stop, etc.). In order to perform this, cubicle heating (using space heaters) is necessary.
For details on space heaters calculations, refer to the "5.8. Blokset - Heating resistor calculation", in the technical transfer file. This calculation must be done whenever changes in temperature and humidity are noticed. If calculation sheet mentions a space heater is necessary, then this device must be installed.
Space heaters installed in Blokset must fulfill the safety requirements of IEC61439-1/2, which Blokset is complaint with:
1. Where is the advised location for installing space heater to have effect to all compartments?
- The heater should be installed at the bottom of the column (as cold and humid air enters in the switchboard from the bottom).
- It is better to install the heater in the rear side as this will be better to avoid unintentional touch during the maintenance.
- It should be installed far from the plastic parts or electronic components or cables as the local heating by the heater may affect them.
- The heater should be protected by IP2X metallic cover to avoid unintentional touch during the maintenance.
- The heater with high wattage can be divided into two small heaters to avoid local heating. For example, instead of 500 Watt heater, 2 heaters of 250 Watts can be installed in the same column.
- The heater has negligible effect when a column has a lot of compartment and partition as Blokset Mw2. Hence, it is not required to install heater in such column. In fact, such column has very less air flow and if the humidity is increased any point of the day, the effect of the humidity inside a drawer also will be less. For example, in Blokset Mw2, it is better to install the heater inside cable compartment instead of feeder compartment.
- The heater can be installed inside the bottom frame as shown below to avoid any interference with the plastic part or cables.
2. How to manage the temperature of parts around the heater which exceed the limit temperature allowed for accessible part?
The best way to install a heater is to connect it to a thermostat and hygrostat. By this way, when humidity level goes up, the hygrostat can switch on the heater and when the required humidity is achieved, the heater can be switched off. Additionally, the thermostat can monitor the inside ambient temperature of the column and if the temperature reached to the preset ambient temperature, it can switch off the heater.
3. How to avoid control cables, customer cables and busbar from overheat?
- The heater should be installed far from the plastic parts or electronic components or cables as the local heating by the heater may affect them.
- The heater with high wattage can be divided into two small heaters to avoid local heating. For example, instead of 500 Watt heater, 2 heaters of 250 kW can be installed in the same column.
- Heater ON/OFF should be controlled by thermostat and hygrostat.
4. If the condensation is happened, is the recommendation to switch on the heater 24 hours still applicable?
Please choose the heater capacity as per the “Blokset - Heating resistor calculation”. Heater ON/OFF should be controlled by thermostat and hygrostat. Please check in the Universal Enclosure catalogue to find this thermostat + hygrostat combined device.
For details on space heaters calculations, refer to the "5.8. Blokset - Heating resistor calculation", in the technical transfer file. This calculation must be done whenever changes in temperature and humidity are noticed. If calculation sheet mentions a space heater is necessary, then this device must be installed.
Space heaters installed in Blokset must fulfill the safety requirements of IEC61439-1/2, which Blokset is complaint with:
- Parts with possible hand touching < 70°C
- IP2X minimum on live parts
1. Where is the advised location for installing space heater to have effect to all compartments?
- The heater should be installed at the bottom of the column (as cold and humid air enters in the switchboard from the bottom).
- It is better to install the heater in the rear side as this will be better to avoid unintentional touch during the maintenance.
- It should be installed far from the plastic parts or electronic components or cables as the local heating by the heater may affect them.
- The heater should be protected by IP2X metallic cover to avoid unintentional touch during the maintenance.
- The heater with high wattage can be divided into two small heaters to avoid local heating. For example, instead of 500 Watt heater, 2 heaters of 250 Watts can be installed in the same column.
- The heater has negligible effect when a column has a lot of compartment and partition as Blokset Mw2. Hence, it is not required to install heater in such column. In fact, such column has very less air flow and if the humidity is increased any point of the day, the effect of the humidity inside a drawer also will be less. For example, in Blokset Mw2, it is better to install the heater inside cable compartment instead of feeder compartment.
- The heater can be installed inside the bottom frame as shown below to avoid any interference with the plastic part or cables.
2. How to manage the temperature of parts around the heater which exceed the limit temperature allowed for accessible part?
The best way to install a heater is to connect it to a thermostat and hygrostat. By this way, when humidity level goes up, the hygrostat can switch on the heater and when the required humidity is achieved, the heater can be switched off. Additionally, the thermostat can monitor the inside ambient temperature of the column and if the temperature reached to the preset ambient temperature, it can switch off the heater.
3. How to avoid control cables, customer cables and busbar from overheat?
- The heater should be installed far from the plastic parts or electronic components or cables as the local heating by the heater may affect them.
- The heater with high wattage can be divided into two small heaters to avoid local heating. For example, instead of 500 Watt heater, 2 heaters of 250 kW can be installed in the same column.
- Heater ON/OFF should be controlled by thermostat and hygrostat.
4. If the condensation is happened, is the recommendation to switch on the heater 24 hours still applicable?
Please choose the heater capacity as per the “Blokset - Heating resistor calculation”. Heater ON/OFF should be controlled by thermostat and hygrostat. Please check in the Universal Enclosure catalogue to find this thermostat + hygrostat combined device.
Released for:Schneider Electric Vietnam
