WilTec SKD-2 Pressure Switch (50611, 51247)
The WilTec SKD-2 Pressure Switch is a crucial component designed to automate the operation of various pump systems, ensuring efficient and safe water management. This device, identified by item numbers 50611 and 51247, integrates a pressure switch and a water flow switch to intelligently control pump cycles based on real-time water demand and system conditions. Its robust design and comprehensive safety features make it suitable for a wide range of applications, from domestic water supply to more demanding industrial setups, provided the technical specifications are met.
Function Description
The core functionality of the SKD-2 Pressure Switch revolves around its ability to monitor both water pressure and flow, thereby determining when a pump should be activated or deactivated. This intelligent control system prevents dry running, ensures consistent water supply, and protects the pump from potential damage.
The operational logic is based on the interplay of two switching states:
- Water pressure switch actuated + water flow switch not actuated: This combination signals a normal switch-off condition. After a delay of approximately 3–8 seconds, the pump will turn off. This scenario typically occurs when a tap is closed, and the system pressure has reached its set point.
- Water pressure switch not actuated + water flow switch actuated: This state indicates a demand for water, prompting the pump to turn on. This happens when a tap is opened, causing a drop in pressure and an increase in flow.
- Water pressure switch not actuated + water flow switch not actuated: This critical combination triggers a switch-off due to dry running and activates a fault indication. After a delay of 8–15 seconds, the pump will shut down, preventing damage from operating without water. This safety feature is paramount for the longevity of the pump.
The device is equipped with a test valve to protect the piping system from pressure loss, further enhancing its reliability. The controller is designed to be oriented upwards, following the direction of the arrow indicated on the unit, to ensure proper functioning of the water flow switch.
Important Technical Specifications
The SKD-2 Pressure Switch is engineered to handle specific electrical and hydraulic parameters, ensuring compatibility with a broad range of pump systems.
- Input Voltage: 220-250 V / 50 Hz / max. 10 A. This indicates its suitability for standard European electrical grids and its capacity to manage pumps with a maximum current draw of 10 Amperes.
- Max. Pressure: 10 bar. The device can withstand and operate effectively within systems generating up to 10 bar of pressure, making it suitable for various domestic and light commercial applications.
- Max. Temperature: 60°C. The maximum permissible temperature of the pumped liquid is 60°C, which is important for continuous operation and prevents damage to internal components. For continuous operation, the temperature of the pumped liquid should not exceed +35°C.
- Connections: 32.89 mm-33.25 mm external threads. These standard thread sizes ensure easy integration into existing plumbing systems.
- Protection Class: IP 65. This high ingress protection rating signifies that the device is dust-tight and protected against low-pressure water jets from any direction, making it suitable for outdoor or damp environments.
- Fuse Protection: At least 10 A. Proper fuse protection is essential for electrical safety and to prevent damage to the device and the pump in case of an electrical fault.
- Pump Inlet Pressure: The automat is factory-set to an inlet pressure of 1.5 bar. For optimal performance, the pump inlet pressure should normally be 0.5 bar higher than the starting pressure, meaning at least 2 bar.
The device is designed to control pumps up to 1.1 kW for single-phase 220 V systems directly. For single-phase pumps over 1.1 kW or three-phase 400 V pumps (also over 1.1 kW), control is achieved via a 2-phase or 3-phase relay (contactor), respectively. The selection of the relay depends on the pump's performance and capacity.
Usage Features
The SKD-2 Pressure Switch offers several features that enhance its usability and integration into various pumping systems:
- Automatic Pump Control: Eliminates the need for manual pump operation, providing convenience and ensuring water availability on demand.
- Dry Running Protection: A critical safety feature that automatically shuts off the pump if no water flow is detected, preventing costly damage to the pump motor and seals.
- Flexible Installation Options: The controller can be installed directly on the pump or between the pump and the first tapping point. However, specific considerations apply for installations where the water column between the pump and the highest point of the pipe exceeds 15 meters. In such cases, the device must be installed at a height where the overhanging water column is shorter than 15 meters (e.g., if the water column is 20 m, the machine must be installed at least 5 m above the pump).
- Recommended Connection: It is recommended to connect the pump control to the house water pipe via a flexible hose for easier installation and vibration dampening.
- No Intermediate Extraction Points: To ensure accurate flow detection, no extraction points should be placed between the pump and the switch.
- Pre-Start Checks: Before starting the machine, it is crucial to check the suction hose and the pump filling to ensure proper priming and prevent airlocks.
- Safety Valve: Includes a safety valve to prevent water leakage if the diaphragm bursts. Users are explicitly warned not to work on or change this valve.
- Liquid Compatibility: The pump must not be used for flammable, gas-forming, or explosive liquids, nor for motor fuels, cleaning agents, or other chemical products. It is strictly for water within the specified temperature range.
Maintenance Features
While the SKD-2 Pressure Switch is designed for reliability, understanding potential issues and their resolution is key to maintaining its performance:
- Visual Inspection: Before each use, a visual inspection of the device is recommended to check for any damaged or worn safety devices. Safety devices should never be disabled.
- Troubleshooting Common Errors:
- Pump does not start: This could be due to a damaged board, missing voltage, a defective pump, or interchanged cables.
- Pump does not stop: Possible causes include a damaged board, a flow detector stuck in the upper position, a blocked reset button, insufficient pump pressure, or a leak with more than 0.6 l/min loss.
- Pump operates intermittently: This may indicate a damaged board, insufficient pump pressure, or a leak with less than 0.6 l/min loss.
- Addressing Blockages/Contamination: If the pump control switches off with a fault indication despite successful previous operation, and a reset only temporarily resolves it, the water pressure switch might be blocked. Cleaning with clean water or cleaning the housing of the pressure switch (where sand or other sediments might have deposited) can resolve this.
- Correcting Installation Position: If the pump control remains permanently switched on regardless of whether the tap is open or closed, it could be due to an incorrect installation position that prevents the water flow switch from resetting. Correcting the installation position is necessary.
- Cleaning the Water Flow Switch: A permanently actuated water flow switch at the pump control input can be caused by contamination, calcification, or a foreign body. An optical check can confirm this, and cleaning can correct the problem.
- Professional Repair: In case of a damaged cable or plug, or if the device fails, repair work must only be carried out by a qualified electrician. The operator is responsible for compliance with local safety and installation regulations and should consult a qualified electrician if necessary.
By adhering to these guidelines, users can ensure the safe, efficient, and long-lasting operation of their WilTec SKD-2 Pressure Switch and the associated pumping system.
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