Siemens Burner Servomotor SQN70.224A20

The Siemens SQN75 series consists of reversible electromotoric actuators specifically designed for the control of gas and air dampers on burners of small to medium capacity. They are distinguished from the SQN70/71 models by their completely black housing (both the gear train and the cover) and are often used as direct replacements for older Conectron or Berger actuators. 1. Key Performance Specifications Feature Specification Rotation Direction Clockwise (CW) Nominal Torque $1.5\text{ Nm}$ to $2.5\text{ Nm}$ (depending on the model) Holding Torque $0.7\text{ Nm}$ to $1.3\text{ Nm}$ Running Time $4\text{ s}$ to $30\text{ s}$ for $90^\circ$ (at $50\text{ Hz}$) Mains Voltage AC $230\text{V}$ (suffix A21) or AC $110\text{V}$ (suffix A11) Power Consumption Approx. $6\text{ VA}$ Protection Class IP40 (upgradable to IP54 with specific cable entries) Angular Adjustment Max $160^\circ$ (Factory setting $90^\circ$) 2. All SQN75 Models & Specifics The SQN75 series uses a modular "Circuit Diagram" numbering system. The middle digits (e.g., .294 or .424) define the running time, torque, and internal relay/switch count. Model Reference Running Time (90∘) Torque Aux Switches Relays SQN75.224A21 $4\text{ s}$ $1.5\text{ Nm}$ $4$ $2$ SQN75.244A21 $4\text{ s}$ $1.5\text{ Nm}$ $2$ $3$ SQN75.254A21 $4\text{ s}$ $1.5\text{ Nm}$ $2$ $1$ SQN75.294A21 $4\text{ s}$ $1.5\text{ Nm}$ $2$ $1$ SQN75.424A21 $12\text{ s}$ $2.5\text{ Nm}$ $2$ $2$ SQN75.436A21 $12\text{ s}$ $2.5\text{ Nm}$ $3$ $0$ SQN75.624A21 $30\text{ s}$ $2.5\text{ Nm}$ $2$ $2$ 3. Design & Features Housing: Made of impact-proof and heat-resistant plastic. The black color indicates it is part of the SQN74/SQN75 branch of the family. Motor: Reversible and locking-proof synchronous motor. Geartrain: Maintenance-free with a manual disengagement mechanism (Pin K). Pressing this allows the shaft to be rotated by hand for commissioning. Adjustment: Switching points are set via color-coded adjustable cams. Some models include fine-adjustment screws that can be turned with a standard screwdriver. Potentiometer: Special versions are "ready-prepared" for fitting a potentiometer for position feedback ($1000\ \Omega$ or $5000\ \Omega$). 4. Selection Tip: SQN74 vs SQN75 While both are black-housed actuators: SQN74: Rotates Counter-clockwise (CCW). SQN75: Rotates Clockwise (CW). Installing the wrong rotation direction will cause the burner to fail its pre-ignition safety check.