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  • New item   Modular photo relay | twilight switch with external sensor | 25 A | 230 V AC | 2–100 lx | 1CO | DIN | Promfactor | FRS21
    New item   Modular photo relay | twilight switch with external sensor | 25 A | 230 V AC | 2–100 lx | 1CO | DIN | Promfactor | FRS21 1
    New item   Modular photo relay | twilight switch with external sensor | 25 A | 230 V AC | 2–100 lx | 1CO | DIN | Promfactor | FRS21 2

    Modular photo relay | twilight switch with external sensor | 25 A | 230 V AC | 2–100 lx | 1CO | DIN | Promfactor | FRS21

    Code: PF-FRS21
    Barcode: 4772151003105
    Inquire about this item
    Price 16.94 € VAT incl.
    ( 14.00 € VAT excl. )
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    DIN rail twilight switch with external sensor: 2–100 lx, 1CO 25 A, 230 V AC, 2 modules, LED indication.

  • Product description

    Modular photo relay with external sensor | 25 A | 2–100 lx | Promfactor FRS21

    Promfactor FRS21 is a twilight switch that turns lighting on at dusk and off at dawn. The relay is mounted in the panel on a DIN rail (2 modules), while light is measured by an external sensor installed where it sees daylight. The 2–100 lx range suits street, yard, facade and shop window lighting.

    Key point:
    The main difference of FRS21 is its 25 A changeover contact. A small lighting group can be controlled without an additional device, and the 1CO contact lets you choose whether the circuit switches on at dusk or during daylight.
    Sensitivity
    2–100 lx
    Output
    1CO, 25 A
    Supply
    230 V AC, 50/60 Hz
    Mounting
    2 modules, DIN rail
    Sensor
    external, wired to the relay

    Operating principle

    The external sensor continuously measures ambient illuminance. When light falls below the set threshold, the relay switches the output contact and turns the lighting on; when light rises again, the contact returns to its initial position.

    The threshold is set with a front-panel knob within 2–100 lx. Switch-on is delayed by about 2–5 s and switch-off by about 10–15 s, so a short flash of light (car headlights, lightning) does not turn the lighting off.

    LEDs indicate supply and relay status – you can see in the panel at once whether the output is on.

    Why 2–100 lx?
    Street and yard lighting is usually switched on at 5–20 lx, shop windows and signage earlier, at 30–80 lx. The 2–100 lx range covers both cases. Control by bright daylight requires a relay with a wider range.

    Technical specifications

    Product type Modular twilight switch (photo relay) with external sensor
    Manufacturer / model Promfactor FRS21
    Supply voltage 230 V AC, 50/60 Hz
    Output 1 changeover contact (1CO)
    Rated current 25 A
    Light sensitivity range 2–100 lx, adjustable by knob
    Switching delay on approx. 2–5 s, off approx. 10–15 s
    Sensor external (remote), wired to the relay
    Indication LED – supply and relay status
    Mechanical life 100,000 cycles
    Protection rating IP20 (relay housing)
    Dimensions 90 × 36 × 65 mm, 2 modules
    Mounting 35 mm DIN rail
    Operating temperature −5…+40 °C

    Main functions

    • Automatic switch-on at dusk – lighting is on only when it is dark.
    • 1CO changeover contact – the circuit can be switched on at dusk or during daylight.
    • 25 A output – more current headroom than typical 16 A photo relays.
    • Protection against false triggering – on and off delays ignore short light changes.
    • LED indication – supply and relay status are visible.

    How does it differ from similar models?

    • VEXEN TWR1 – 1–100 lx, 1NO 16 A, 1 module, wide 110–240 V AC supply and AUTO / ON / OFF modes; IP65 sensor.
    • VEXEN TWR923 – Two ranges 1–1000 lx and 10–10,000 lx – when the threshold may be in daylight; 16 A, 1 module.
    • F&F AZ 112 – 2–1000 lx, 1NO 16 A, 1 module, hermetic IP65 sensor with cable up to 10 m; LED load up to 250 W stated by the manufacturer.
    • GTV CZ-1 – The same 2–100 lx range, IP65 sensor – when a 25 A contact is not needed.

    Where is it used?

    • Street and driveway lighting
    • Yard, path and car park luminaires
    • Facade, shop window and sign lighting
    • Floodlights at warehouses, farms and industrial sites
    • Outdoor entrance and driveway lighting in apartment buildings
    • Replacing timers and manual switches in existing panels

    Use by need

    For the electrician.
    A 25 A changeover contact – one device for both lighting and a control circuit; 2 modules in the panel.
    For the home or farmstead owner.
    The yard lighting switches on at dusk without adjusting a timer and is never left on during the day.
    For the company or farm manager.
    Site lighting follows real light – lower costs and less manual work.

    Practical use

    If several floodlights and driveway luminaires must be controlled on a farm, mount FRS21 in the panel and the sensor on the north wall where the floodlights themselves do not light it. Threshold – about 10 lx. A small group of incandescent or halogen luminaires can be connected directly through the 25 A contact, while an LED floodlight group should be switched by a modular contactor whose coil is controlled by the relay.

    Pros

    • 25 A changeover 1CO contact
    • 2–100 lx range for outdoor lighting
    • Switch-on and switch-off delay
    • LED indication
    • Mechanical life of 100,000 cycles

    Cons / limitations

    • The manufacturer does not state a permissible LED load – for LED drivers and floodlights with high inrush current use a modular contactor
    • Takes 2 modules on the DIN rail – VEXEN TWR1 or F&F AZ 112 fit in 1 module
    • Operating temperature −5…+40 °C – for an unheated outdoor panel VEXEN TWR923 (−35…+75 °C) is better suited
    • No timer for night-time switch-off – a separate timer or VEXEN DTWR972 is needed

    ⚠ Safety and installation notes

    • Mount the sensor where daylight reaches it but the controlled luminaires do not – otherwise the relay will start switching itself off.
    • Do not point the sensor directly at the sun or towards the road where car headlights hit it.
    • The IP20 relay housing is intended for a panel – only the sensor is installed outdoors. The panel must be dry, operating temperature −5…+40 °C.
    • For LED luminaire groups with high inrush current the relay must control a modular contactor coil, not the luminaires directly.
    • Protect the circuit with a circuit breaker selected for the wire cross-section and load.
    • Installation must be carried out by a qualified electrician after disconnecting and verifying the absence of voltage.

    Quick selection guide

    2–100 lx
    1CO 25 A
    230 V AC
    2 DIN modules
    Suitable when you need to:
    • switch outdoor lighting on automatically at dusk;
    • have a changeover contact with more current headroom;
    • mount the relay in a heated or indoor panel.
    Check before use:
    • load type and inrush current (LED – via a contactor);
    • whether there are 2 free modules in the panel;
    • where the sensor will be mounted and how its wire will be routed.
    Important reminder: a photo relay controls lighting by light level, but it does not replace protective devices and does not switch lighting off at midnight – that requires a timer.
    ☝ Elsprendimai.eu recommends:

    FAQ

    What threshold should I set for yard lighting?
    Usually 5–20 lx is enough; for shop windows and signage 30–80 lx.
    Where should the sensor be mounted?
    Outdoors, on the north side of the building, where daylight reaches it but not the controlled luminaires or car headlights.
    Can LED floodlights be connected directly?
    The manufacturer does not state an LED load, so use a modular contactor for LED groups.
    What is the changeover contact for?
    One side of the contact closes at dusk, the other during daylight, so the relay can both switch lighting on and control another circuit during the day.
    Why does the lighting not switch off immediately?
    Switch-off is delayed by about 10–15 s, so the relay ignores short flashes of light.
    Can the relay be installed outdoors?
    No, the relay (IP20) is mounted in a panel on a DIN rail; only the sensor is installed outdoors.

    Modular photo relay with external sensor | 2–100 lx | 25 A | Promfactor FRS21

    Promfactor FRS21 is a modular twilight switch with an external sensor, a 2–100 lx range, a 25 A changeover 1CO contact and LED indication. Designed for controlling outdoor lighting from the panel; connect LED groups via a contactor.

    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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