Burner Servomotor LKS 120

Product Details

The Siemens LKS series consists of electromotoric servomotors designed for the control of air dampers in oil and gas burners. While the SQN and SQM series are more common in high-end modulating systems, the LKS series is frequently used in smaller, residential, and commercial burners where simple two-stage or multi-stage air control is required. 1. Popular LKS Models The LKS series is primarily divided by the type of burner (Gas vs. Oil) and the specific torque required. Model Series Application Torque Running Time (90∘) LKS 110 Oil burners (Small) $0.7\dots 1.0\text{ Nm}$ $3.5\dots 5.0\text{ s}$ LKS 120 Oil burners (2-stage) $0.8\dots 1.5\text{ Nm}$ $5.0\text{ s}$ LKS 160 Gas burners $1.5\dots 2.5\text{ Nm}$ $5.0\dots 30\text{ s}$ LKS 210 Large Oil/Gas Up to $3.0\text{ Nm}$ $5.0\dots 15\text{ s}$ 2. Technical Specifications Mains Voltage: $200\dots 240\text{V AC}$ ($+10\% / -15\%$) or $100\dots 110\text{V AC}$. Frequency: $50\dots 60\text{ Hz}$. Power Consumption: Approx. $7\dots 12\text{ VA}$ (depending on torque). Duty Cycle: $50\dots 60\%$. Angle of Rotation: Adjustable up to $160^\circ$ (Factory set to $90^\circ$). Protection Class: IP44 (Standard) or IP54 with specific cable glands. Operating Temp: $-10\text{°C}$ to $+60\text{°C}$ (standard) or $-40\text{°C}$ for specialized oil versions. 3. Key Functional Features Synchronous Motor: Ensures constant running time regardless of load fluctuations or voltage drops. Adjustable Cams: Similar to the SQN series, LKS servomotors use mechanical cams to set: High-Fire Position: Maximum air intake. Low-Fire Position: Minimum air for idle or low-stage. Ignition Position: Specific air-gap for safe lighting. Clutch Mechanism: Most LKS models have a manual disengagement button, allowing you to move the damper by hand to check for mechanical binding. Integrated Position Indicator: A visible scale on the side or top of the unit shows the current angular position of the shaft. 4. Selection and Replacement When replacing an LKS motor, you must match the Shaft Type and Running Time exactly: Shaft Types: Square: Often $8\text{ mm}$ or $10\text{ mm}$. D-Shape: Flat-sided shaft for set-screw mounting. Internal Thread: Some specialized LKS 160 models use an internal thread for direct valve mounting. Running Time: If the replacement motor is slower than the original, the burner controller may time out during the pre-purge cycle and cause a safety lockout. 5. Wiring Overview The LKS typically uses a 7-pin or 10-pin terminal block. Terminal 1/2: Power Supply. Terminal 3: Control signal for "Open." Terminal 4: Control signal for "Close." Auxiliary Contacts: Used to feed back a "Purge Complete" signal to the burner controller.