Siemens SQN72 Series - User Manual

The Siemens SQN72... and SQN73... series are electromotoric actuators designed for precise positioning and driving of air and gas dampers in oil and gas burners of small to medium heat capacity. They also facilitate load-dependent control of fuel and combustion air. These actuators are primarily intended for original equipment manufacturers (OEMs) for integration into their products.

Function Description

The SQN72/SQN73 actuators operate by a synchronous motor driving a camshaft via a gear train. This camshaft, in turn, actuates end switches and auxiliary switches. The switching position of each end switch and auxiliary switch can be adjusted by an assigned cam disk within the running range of the actuator. Certain actuator versions incorporate electronic switching modules that provide additional functions in conjunction with the end switches, auxiliary switches, and external units such as controllers.

The controlling elements are managed based on the current burner load. This can be achieved in several ways:

In conjunction with P-PI or PID controllers, such as the RWF5 series.
Directly via various types of burner controls, including LOA, LMO, LME, or LFL.
Through 1- or 2-wire control or 3-position controllers.

The actuators are designed to offer load-dependent control of the amount of fuel and combustion air, ensuring efficient burner operation.

Important Technical Specifications

Mains Voltage: 230 V AC -15%/+10%
Mains Frequency: 50 to 60 Hz ±6%
Actuator Motor: Synchronous motor
Internal Consumption: Max. 6 VA
Positioning Angle, Usable Range: Max. 160°, scale range 0-130°
Degree of Protection: IP54 (in accordance with EN 60529:1991 + A1:2000 + A2:2013 when using the provided cable entry and plastic washers for M fixing screws). It is crucial that the drive shaft bearing is installed appropriately to protect against direct exposure to water and dust to maintain IP54 protection.
Protection Class: II according to EN 60730-1:2016 + A1:2019 and EN IEC 60730-2-14:2019
External Primary Fuse (Si): 6.3 AT (to be installed on site) according to IEC 60127-2-5
Cable Entry: Rubber grommet for a single sheathed cable with a maximum diameter of 11 mm. The opening must be adapted to the cable's sheath diameter for a tight seal.
Cable Strain Relief: Bridge with 2 fixing screws included.
Cable Connection: 2 plug-in spaces with connection terminals (Type CUM / manufactured by Stelvio). Recommended cross-sectional area for stranded wire: Min. 0.5 mm², max. 1.5 mm².
Direction of Rotation (opening facing the shaft):
- SQN72: Counterclockwise
- SQN73: Clockwise
Holding Torque: 0.7-1.3 Nm (refer to Type summary for specific models).
Running Times: 4-30 s (refer to Type summary for specific models). Specifications apply to 50 Hz; at 60 Hz, running times are approximately 17% shorter.
Pause Times at Change in Direction of Rotation: >100 ms
Lifetime: Designed for 250,000 start cycles (OFF ⇨ ON ⇨ OFF) under load with the rated torque across the entire rotation angle range. This corresponds to approximately 10 years of service life under normal heating conditions, based on endurance tests in EN 298.
Weight (on average): Approx. 500 g
Permissible On Time: 60%, maximum 3 minutes without interruption.
Gear Backlash (between actuator motor and shaft):
- Ex works: ≤1.2° ±0.3
- After 250,000 cycles: ≤1.5° ±0.3°
Switching Voltage (End and Auxiliary Switches): 24-250 V AC
Number of End Switches: 2
Maximum Permissible Current Load (cos φ = 0.9):
- Terminals 1, 2, 3, 8: Max. 0.5 A
- Terminals 4, 5: Max. 2 A (5 A short-term peak load for max. 0.5 s)
- Terminals 6, 7: Max. 1 A (2 A short-term peak load for max. 0.5 s)
- When connecting a fuel valve: Max. 0.3 A, cosφ >0.8 inductive.
Environmental Conditions:
- Storage Temperature: -20 to +60°C, Humidity: < 95% r.h.
- Transport Temperature: -50 to +60°C, Humidity: < 95% r.h.
- Operation Temperature: -20 to +60°C, Humidity: < 95% r.h.
- Installation Altitude: Max. 2,000 m above sea level
- Vibration Tests: According to IEC 60068-2-6:2008 with acceleration of 10 m/s²
- Shock Tests: According to IEC 60068-2-27:2010 with peak accelerations of 100 m/s²
- Note: Condensation, ice formation, and water ingress are not permitted, as they can damage safety functions and pose an electric shock risk.

Usage Features

Housing: Impact-proof and heat-resistant plastic housing (dark gray lower housing, light gray cover).
Electrical Connections: Plug terminals for easy wiring.
Gear Train: Maintenance-free and can be disengaged manually using a pressure pin for easy setup or adjustment. Automatic reset feature.
Position Indication: Internal position indication for monitoring.
Switching Point Adjustment: Easy-to-adjust end and auxiliary switches with fine adjustment for precise setting of switching points via rotating cam disks. Scales adjacent to the cams indicate the angle of the switching point.
Mounting: Front of gear serves as a bearing surface, with fastening via through holes.
Shaft Design: Burnished steel, fixed on one side at the front of the gear, available in different versions.
Potentiometer Installation: Some actuators are factory-prepared for potentiometer installation, requiring only the separate order of the potentiometer itself. Detailed mounting instructions are provided.
Safety: Safety-relevant applications are only available with Siemens burner controls. The connection terminals must have adequate touch protection, and the housing cover must be screwed tight to prevent electric shock. Static charges should be avoided to protect electronic components.

Maintenance Features

Maintenance-Free Gear Train: The gear train does not require regular maintenance.
Unit Replacement: When replacing an actuator, it is essential to check and correct the connection to the basic unit and the assignment of functions.
Designed Lifetime: The actuator has a designed lifetime of 250,000 start cycles. After reaching this lifetime or corresponding usage time, the actuator must be replaced by authorized personnel. This designed lifetime is not a warranty period.
Disposal: The unit contains electrical and electronic components and must be disposed of according to local and currently valid legislation, not with domestic waste.

Mounting and Installation Notes

Compliance with national safety regulations and standards (e.g., DIN/VDE 0100, 0550, 0722, EN 60730, EN 60335) is mandatory.
The actuator must not be exposed to direct solar radiation.
The connection between the actuator drive shaft and the controlling element must be form-fitted and backlash-free.
Additional axial and radial bearing loads are not permitted during mounting.
The correct mounting sequence must be observed: first fit and secure the actuator, then connect the drive shaft to the controlling element via a coupling pin.
The drive shaft bearing must be protected from direct exposure to water or dust to ensure IP54 protection.
For shaft/hub connections, flattened shafts with corresponding counterparts are recommended. Compensating couplings with no mechanical play (e.g., metal bellows couplings) are recommended to avoid inadmissible bearing loads from rigid hubs.
The shaft connection should be overdimensioned by a factor of 2 compared to the rated torque due to potential higher torques during operation and impulse loads from mass moments of inertia.
The connection between the actuator and burner/controlling element must be very rigid (no bending), especially with column-mounted structures.
Electrical wiring must comply with national and local regulations.
Strain relief for connected cables must comply with relevant standards.
Spliced wires must not contact neighboring connections; use suitable ferrules.
Unused SQN72/SQN73 terminals must be protected by dummy plugs.
The 230 V AC range must be strictly separated from other voltage areas to prevent electric shock.
Only plastic cable glands may be used.
Before any work in the connection area, disconnect all poles from the power supply and ensure the plant cannot be inadvertently switched on.
After any work, check that wiring is in an orderly state.
Devices must not be put back into operation after impact or shock, even without visible damage, as safety functions may be impaired.
Ensure that any external torque on the controlling element (e.g., from a burner fan) is less than the actuator's zero-current state self-holding torque.
The burner's mechanical design must prevent inadmissibly high external torque from leading to critical burner operation. For example, if airflow moves an air damper in the OPEN direction, it leads to excess air, which is less critical than a lack of air.