This document describes the operation, installation, and specifications of the STIEBEL ELTRON CNS U, CNS UT, and CNS UE series of wall-mounted electric direct heaters.
Function Description
The CNS series appliances are designed for heating living areas. They function as wall-mounted electric direct heaters, suitable for full heating systems in bathrooms, or as supplementary and booster heaters in smaller rooms like hobby or guest rooms. The air within the appliance is heated by a heating element and then expelled through the air outlet grille at the top via natural convection. Cooler room air is drawn in through apertures at the bottom of the appliance. Once mounted and electrically connected via a permanent power supply, the appliance is ready for operation.
The CNS U and CNS UE models offer basic temperature control and operating modes, while the CNS UT models include a 24-hour time switch for scheduled heating.
Important Technical Specifications
The CNS series includes models with varying connected loads, dimensions, and weights. All models operate on a 1/N ~ 240 V 50 Hz power supply and have an IP24 rating, indicating protection against solid objects over 12.5 mm and splashing water from any direction. They belong to Protection Class II, meaning they are double insulated. All models are finished in Alpine white.
CNS 50-300 U Series:
- Connected Load: Ranging from 0.5 kW (CNS 50 U) to 3.0 kW (CNS 300 U).
- Dimensions:
- Height: 450 mm for all models.
- Width: Ranging from 370 mm (CNS 50 U) to 1040 mm (CNS 300 U).
- Depth: 100 mm for all models.
- Weight: Ranging from 3.3 kg (CNS 50 U) to 8.9 kg (CNS 300 U).
- Hole Spacing (Wall Mounting Bracket): Ranging from 121 mm (CNS 50 U) to 787 mm (CNS 300 U).
CNS 50-300 UT Series:
- Connected Load: Ranging from 0.5 kW (CNS 50 UT) to 3.0 kW (CNS 300 UT).
- Dimensions:
- Height: 450 mm for all models.
- Width: Ranging from 370 mm (CNS 50 UT) to 1040 mm (CNS 300 UT).
- Depth: 100 mm for all models.
- Weight: Ranging from 3.3 kg (CNS 50 UT) to 8.9 kg (CNS 300 UT).
- Version: All UT models feature a 24-hour time switch.
CNS 75-300 UE Series:
- Connected Load: Ranging from 0.75 kW (CNS 75 UE) to 2.8 kW (CNS 300 UE).
- Dimensions:
- Height: 450 mm for all models.
- Width: Ranging from 445 mm (CNS 75 UE) to 1040 mm (CNS 300 UE).
- Depth: 100 mm for all models.
- Weight: Ranging from 4 kg (CNS 75 UE) to 8.9 kg (CNS 300 UE).
Usage Features
General Operation (CNS U, CNS UT, CNS UE):
- ON/OFF Switch: Appliances are switched on and off via a dedicated ON/OFF switch, typically located on the right-hand side.
- Temperature Selector: The desired room temperature is set using a continuously variable temperature selector. Once the selected temperature is reached, the appliance maintains it through periodic heating.
- Frost Protection:
- CNS U & CNS UE: Activated by turning the temperature selector as far to the right as possible. The heating element switches on automatically if the room temperature drops below the frost protection temperature.
- CNS UT: Frost protection is always enabled in constant operation mode. In time switch mode, it is only enabled during the selected time.
- Limiting the Temperature Selector (CNS U | CNS UE): The temperature setting range can be fixed or limited using two pins fitted to the back of the control casing. Pins are broken out and inserted into offset holes to set minimum and maximum values or to fix a specific temperature.
Specific Features for CNS UT Models:
- Time Switch: These models include a 24-hour time switch for scheduled heating. The current time is set by turning the time switch clockwise until the black arrow points to it.
- Operating Modes (Time Switch): Tabs on the edge of the time switch correspond to 20-minute ON or OFF periods. Pushing tabs outwards activates heating, while pushing them inwards deactivates it.
- Appliance Off "0": Moving the ON/OFF switch to "0" completely switches off the appliance and disables frost protection.
Specific Features for CNS UE Models:
- Operating Mode Switch: In addition to the ON/OFF switch and temperature selector, CNS UE models feature an operating mode switch with settings for:
- Comfort mode: Maintains the selected room temperature through periodic heating.
- ECO mode (night setback): Automatically reduces the comfort temperature by 3 °C.
- Frost protection: Switches heating on automatically if the room temperature drops below the frost protection temperature.
- Automatic: If connected to an optional control device, the appliance operates in comfort, ECO, or frost protection mode based on the control device's settings. If no control device is connected, it operates in comfort mode.
Safety Features:
- Overheating Protection: All appliances have a safety temperature controller that shuts down the unit if it overheats (e.g., due to covered air outlet/inlet apertures). Operation resumes after the cause is removed and the appliance cools down.
- Child Safety: Children under 3 years old must be kept away unless constantly supervised. Children aged 3-7 may switch the appliance on/off under supervision and after instruction on safe operation, provided it's installed as described. They must not plug in the power cable or regulate the appliance. Children aged 8 and older, and persons with reduced capabilities, can use the appliance under supervision and after instruction. Children must never play with or clean the appliance unsupervised.
- Burn Hazard: Parts of the appliance can become very hot. Caution is advised, especially with children or vulnerable persons.
- Installation Restrictions:
- Never cover the appliance.
- Do not install directly below a wall socket.
- Install so control equipment cannot be touched by a person in a bath or shower.
- Must be installed on a vertical wall that is temperature-resistant to at least 85 °C.
- Maintain minimum clearances to adjacent object surfaces (e.g., furniture, curtains).
- Never operate in rooms with fire/explosion risk (chemicals, dust, gases, vapours), near flammable/explosive materials, during work like cable laying or grinding, or when using sprays/floor polish containing napsan without sufficient ventilation.
- Never place flammable or insulating objects on or near the appliance.
Maintenance Features
Cleaning and Care:
- The appliance should be cleaned when cold using ordinary cleaning products.
- Avoid abrasive or corrosive cleaning products.
- Never spray cleaning spray into the air slot, and ensure no moisture enters the appliance.
- If brownish discolouration appears on the casing, wipe it off with a damp cloth.
Regular Maintenance:
- As part of regular maintenance, it is recommended to have the control components checked by a qualified contractor no more than ten years after commissioning.
Troubleshooting:
- If the appliance does not heat up, check the temperature setting and the MCB/fuse in the fuse box.
- If the safety temperature controller has shut down the appliance due to overheating, operation will resume after the cause is removed and the appliance cools down.
- If faults persist, contact a qualified contractor and provide the serial number from the type plate to facilitate the enquiry.
- The power cable must only be replaced by a qualified contractor using original spare parts supplied by the manufacturer.
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