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  • New item   -150.56€Two-speed fan transformer speed controller day/night | TK | 7.5A | 230VAC | surface-mounted | IP54 | Sentera Controls | SC2A1-75L25
    New item   -150.56€Two-speed fan transformer speed controller day/night | TK | 7.5A | 230VAC | surface-mounted | IP54 | Sentera Controls | SC2A1-75L25 1
    New item   -150.56€Two-speed fan transformer speed controller day/night | TK | 7.5A | 230VAC | surface-mounted | IP54 | Sentera Controls | SC2A1-75L25 2
    New item   -150.56€Two-speed fan transformer speed controller day/night | TK | 7.5A | 230VAC | surface-mounted | IP54 | Sentera Controls | SC2A1-75L25 3
    New item   -150.56€Two-speed fan transformer speed controller day/night | TK | 7.5A | 230VAC | surface-mounted | IP54 | Sentera Controls | SC2A1-75L25 4

    Two-speed fan transformer speed controller day/night | TK | 7.5A | 230VAC | surface-mounted | IP54 | Sentera Controls | SC2A1-75L25

    Code: SC2A1-75L25
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  • Product description

    Two-speed fan transformer speed controller day/night | TK | 7.5A | 230VAC | surface-mounted | IP54 | Sentera Controls | SC2A1-75L25

    SC2A1-75L25 – Sentera Controls two-speed fan transformer speed controller for single-phase 230 VAC voltage-controllable motors up to 7.5 A. It has TK terminals for motor thermal protection, remote switch-on inputs, an alarm output and restarts automatically after a power failure.

    Key idea:
    Two preset speeds – high and low – are switched by an external timer or thermostat (day / night), and the motor is protected against overheating via the TK contacts. This is a complete fan control unit without additional relays.
    What it is for SC2A1-75L25:
    This model is intended for high-power fans (up to 7.5 A) – industrial fans in production halls, warehouses, farm buildings or a larger group of fans.
    Max. motor current
    7.5 A
    Speeds
    2 × 5 steps, sinusoidal voltage
    Control
    Knobs + external timer (CL) + TK
    Protection
    IP54, surface mounting

    Operating principle

    The controller is wall-mounted in the room. The 230 VAC supply (L, N, PE) and the motor (regulated output M/U and N) are connected, and the unregulated 230 VAC output L1 can supply a damper actuator or another device that must operate together with the fan. The TK terminals are connected to the motor thermal contacts, CC / OC – to the remote switch-on contact, AL – to the alarm system.

    The heart of the controller is an autotransformer with several taps (steps). Each step supplies the motor with a different fixed voltage, while the output voltage remains SINUSOIDAL, as in the mains. As a result, the motor runs quietly even at low speed – the transformer speed controller is also suitable for motors that hum or heat up with an electronic (semiconductor) controller.

    Each speed has a separate 5-step knob with an OFF position. High speed (left knob): 0–120–150–170–190–230 VAC; low speed (right knob): 0–80–100–120–150–170 VAC. Which speed is active is determined by an external timer or thermostat connected to the CL terminals (normally closed contact).

    Control is in steps, not stepless: the speed changes in jumps between fixed voltages. Engineer's note: the speed at each step depends on the motor and fan characteristics, so after commissioning it is worth checking that the motor reliably starts at the lowest step used. The TK terminals are intended for connecting the motor thermal contacts, and the alarm output AL (230 VAC / 1 A) sends the fault signal to an alarm system or BMS.

    Benefits SC2A1-75L25?
    Two-speed control, motor TK protection, remote switch-on and alarm in one IP54 enclosure – quiet sinusoidal voltage control with automation for day / night mode.

    Technical specifications

    Product type Two-speed fan transformer speed controller with TK protection
    Manufacturer / code Sentera Controls / SC2A1-75L25
    Series SC2A1 (1.5 / 2.5 / 3.5 / 5 / 7.5 / 10 / 13 A)
    Supply voltage 230 VAC, 50–60 Hz
    Max. motor current 7.5 A
    High speed steps 0 – 120 – 150 – 170 – 190 – 230 VAC
    Low speed steps 0 – 80 – 100 – 120 – 150 – 170 VAC
    Output voltage waveform Sinusoidal (autotransformer)
    Unregulated output L1 230 VAC
    Speed switching External timer / thermostat, CL terminals (NC contact)
    Motor thermal protection TK terminals
    Remote on / off CC (NC contact), OC (NO contact)
    Alarm output AL, 230 VAC / 1 A
    After a power failure Automatic restart
    Indication Blue LED – device switched on
    Fuse 5×20 mm, T-12.5 A-H
    Housing plastic, R-ABS, UL94-V0, grey RAL 7035
    Protection class IP54 (EN 60529), for indoor use only
    Operating environment -20…+35 °C, 5–95 % rH non-condensing
    Mounting dimensions A 200 × B 305 × C 155 mm (mounting D 183 / E 235 mm)
    Packaging dimensions 320×210×160 mm
    Weight 8.20 kg net / 8.60 kg gross
    Compliance LVD 2014/35/EU, EMC 2014/30/EU (EN 61326), RoHS 2011/65/EU, WEEE 2012/19/EU

    Manufacturer documentation

    ✔ Recommended by Elektrotechnikos sprendimai

    Original manufacturer documentation – technical data, wiring diagrams and installation instructions.

    Main functions

    • Two speeds with separate knobs – high and low speed are set with 5 steps each; each knob has an off position.
    • Switching by a timer or thermostat – CL terminals for an external contact – day / night mode without programming.
    • Sinusoidal output voltage – quiet motor operation even at low speed.
    • Unregulated 230 VAC output L1 – for a damper actuator or other device operating together with the fan.
    • TK protection and alarm – connection of motor thermal contacts, AL output (230 VAC / 1 A) for the fault signal.
    • Remote switch-on – CC (normally closed) or OC (normally open) contact – switch, BMS or fire alarm.
    • Automatic restart – when power is lost and restored, the controller resumes operation by itself.

    Where is it used?

    • Ventilation of offices, schools, retail premises with day/night mode
    • Production and warehouse premises with working and non-working hours mode
    • Extract ventilation for restaurants and kitchens
    • Duct, roof and axial fans with single-phase AC motors
    • Sites where quiet fan operation is important

    On-demand operation

    For the electrician.
    Clear terminals, PE, CL input for an external timer, TK and AL terminals.
    For the ventilation installer.
    Both speeds are set on site with knobs, no programming required; the step voltages can be changed if needed.
    For the building owner.
    Lower energy consumption outside working hours and quiet fan operation.

    Application guide: how it is used in practice

    Typical SC2A1-75L25 applications:

    Site What is connected Result Installer's note
    Office, school Fan → M/U, N; timer → CL High speed during working hours, low at night Use a potential-free contact for the timer
    Restaurant kitchen Extract fan → M/U, N; switch → CL High speed during production, low at other times Select the low speed step according to the minimum required extraction
    Fan with damper Damper actuator → L1, N The damper is powered together with the fan L1 – unregulated 230 VAC phase
    Motor with thermal contacts Motor TK → TK terminals; signalling → AL The motor is protected, and the fault signal is passed on AL output – 230 VAC / 1 A
    Control from a BMS or fire safety system NC contact → CC or NO contact → OC The fan is started / stopped remotely Select the input according to the contact type

    How to select the controller current

    Rated current of the motor(s) Recommended model
    up to 1.5 A SC2A1-15L25 (1.5 A)
    1.5–2.5 A SC2A1-25L25 (2.5 A)
    2.5–3.5 A SC2A1-35L25 (3.5 A)
    3.5–5 A SC2A1-50L25 (5 A)
    5–7.5 A SC2A1-75L25 (7.5 A) ← this model
    7.5–10 A SC2A1100L25 (10 A)
    10–13 A SC2A1130L25 (13 A)
    Rule: controller max. current ≥ rated current of the motor (or the sum of several motors) from the motor nameplate. For a transformer controller the motor starting current is already taken into account by the manufacturer, so no additional margin is needed. Connect several fans only with AC motors of the same type that are voltage-controllable.
    When to choose another solution: no need for TK and alarm – the simpler SC2-1 series; a built-in weekly timer with LCD needed – ST2R1 series; stepless control by a 0-10 VDC signal or Modbus – electronic EVS-1 series; temperature-based speed – GTT-1 series.

    Pros

    • Sinusoidal output voltage – quiet motor operation
    • Two speeds, each with a 5-step knob
    • Switching by an external timer or thermostat (CL)
    • TK motor thermal protection and alarm output
    • Remote switch-on via NC / NO contact
    • Automatic restart after a power failure
    • Unregulated 230 VAC output L1
    • IP54 enclosure

    Cons / limitations

    • Step, not stepless control
    • Heavy weight (8.20 kg) and large dimensions compared with electronic controllers
    • No 0-10 VDC input and no Modbus
    • Single-phase voltage-controllable AC motors only; not suitable for EC fans
    • Indoor use only, operating temperature up to +35 °C
    • No built-in timer – an external one is needed

    Safety and installation notes

    • Installation and connection must be carried out by a qualified electrician with the power disconnected.
    • Always connect the protective earth (PE).
    • The total rated current of the connected motors must not exceed 7.5 A.
    • Replace the fuse only with one of the same type and rated current as specified in the datasheet.
    • The controller is intended for indoor use only (-20…+35 °C).
    • Connect only potential-free contacts to the CL, CC, OC terminals according to the manufacturer's diagram.
    • The terminal layout of the 10 and 13 A models is different – wire according to the diagram of the specific model.

    Quick selection guide

    7.5 A
    230 VAC
    2 speeds
    TK + alarm
    IP54
    Suitable when you need:
    • two-speed fan control up to 7.5 A;
    • quiet sinusoidal voltage control;
    • day / night mode with an external timer or thermostat;
    • protection of a motor with TK contacts and an alarm signal.
    Check before use:
    • the motor rated current and whether it is voltage-controllable;
    • which voltages are needed for high and low speed;
    • whether you have an external timer / thermostat with a potential-free contact;
    • the ambient temperature (up to +35 °C) and space for the enclosure.
    Important reminder: SC2A1-75L25 does not control EC fans or three-phase motors; the timer is connected to the controller separately.

    FAQ

    How are the speeds switched?
    With an external timer, thermostat or switch whose normally closed contact is connected to the CL terminals.
    What voltages are possible?
    High speed: 120, 150, 170, 190, 230 VAC; low speed: 80, 100, 120, 150, 170 VAC.
    Why transformer rather than electronic?
    The output voltage is sinusoidal, so the motor does not hum even at low speed.
    Can several fans be connected?
    Yes, provided the sum of their rated currents does not exceed 7.5 A and the motors are voltage-controllable.
    How do I connect the motor thermal protection?
    The motor TK contacts are connected to the TK terminals; the fault signal is transmitted via the AL output (230 VAC / 1 A).
    Will the controller restart after a power outage?
    Yes, the datasheet specifies automatic restart after power failure.

    Two-speed fan transformer speed controller day/night | TK | 7.5A | 230VAC | surface-mounted | IP54 | Sentera Controls | SC2A1-75L25

    Sentera SC2A1-75L25 – two-speed day / night transformer fan controller, up to 7.5 A, 230 VAC, sinusoidal output voltage, TK protection, alarm output, remote on, IP54, fuse T-12.5 A-H.

    Illustrative image may have been created using AI. The appearance of the product may differ slightly from the image shown. Please refer to the technical specification.

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