The IR425-D4-2 is an insulation monitoring device from Bender, designed for unearthed systems (IT systems). It continuously monitors the insulation resistance of AC or DC control circuits and triggers an alarm when the insulation resistance falls below a preset threshold. The device complies with IEC 61557‑8 and uses the AMP measuring principle, providing accurate measurement results even in systems with DC components and high leakage capacitance.
The IR425-D4-2 is particularly suitable for control cabinets where compact installation is required, with its 36 mm width saving installation space.
Technical Specifications
· Rated system voltage (Uₙ): AC/DC 0…300 V, 15…460 Hz
· Supply voltage (Uₛ): AC/DC 70…300 V, 15…460 Hz
· Response value range (Rₐₙ): 1 kΩ … 200 kΩ, two independently adjustable thresholds
· Maximum permissible system leakage capacitance: ≤ 20 μF
· Measuring voltage: ±12 V
· Power consumption: ≤ 4 VA
· Alarm relays: Two independent changeover contacts (Alarm 1 and Alarm 2), AC 250 V / 5 A
· Display: Multi‑function LC display
· Connection type: Push‑wire terminals (each connection point with dual terminals)
· Mounting: DIN rail mounting
· Width: 36 mm (2 standard modules)
· Dimensions (W × H × D): 36 × 71 × 90 mm
· Weight: Approx. 150 g
· Operating temperature: –25 °C … +55 °C
· Protection class: Internal components IP30, terminals IP20
· Housing material: Polycarbonate
· Standards compliance: IEC 61557‑8, DIN EN 61557‑8
Key Features
· AMP Measuring Principle – Uses the Bender AMP measuring principle. The device superimposes a pulsating measuring voltage onto the monitored IT system, detects ohmic insulation faults through a closed measuring circuit, and displays the current insulation resistance value on the screen. This method ensures accurate measurement even in systems with high leakage capacitance or DC components.
· Two Independently Adjustable Response Values – Equipped with two independently adjustable alarm relays (Alarm 1 and Alarm 2), with a response value range of 1 kΩ to 200 kΩ. Two‑stage alarm levels (pre‑warning and critical alarm) can be configured.
· Preset Function – When the device is first powered on, the preset function automatically measures the rated system voltage and sets basic parameters. When Uₙ ≤ 72 V, the response values are preset to 20 kΩ and 10 kΩ; when Uₙ > 72 V, they are preset to 46 kΩ and 23 kΩ.
· Multi‑Function LC Display – Equipped with a multi‑function LC display showing real‑time insulation resistance values, alarm information, and device parameters.
· LED Status Indicators – Front panel includes LED indicators: Power On, Alarm 1, Alarm 2.
· Connection Monitoring – Continuously monitors the connection status of measuring leads and earth, ensuring measuring circuit integrity.
· Built‑In Self‑Test – Features an automatic self‑test function that continuously verifies internal measuring circuits and system control components. A fault triggers an automatic alarm.
· External Test and Reset – Self‑test and reset can be triggered via front‑panel keys, or by connecting external test and reset push‑buttons.
· Selectable Fault Memory – The fault memory function can be activated as needed. When activated, alarm relays remain in the alarm condition until manually reset, helping to identify intermittent faults.
· Adjustable Response Delay – Response delay time can be configured to prevent nuisance alarms caused by system transients.
· Password Protection – Integrated password protection prevents unauthorised changes to critical alarm threshold parameters.
· De‑Energised System Monitoring – Powered by an independent external supply, the device can monitor the system even when the main circuit is de‑energised.
· Push‑Wire Terminals – Push‑wire terminals provide gas‑tight, vibration‑resistant connections that require no regular screw tightening, with dual terminals at each connection point.
Typical Applications
· Industrial control circuits – Monitoring auxiliary and control circuits in machine electrical equipment according to IEC 60204‑1
· Power plant automation – Ensuring insulation integrity of unearthed control systems in power generation facilities
· Elevator systems – Monitoring insulation of DC control panels and safety chains in elevators
· Marine and offshore applications – For unearthed electrical systems on ships
· Railway technology – Protecting signal and control infrastructure that relies on IT systems for operational continuity
· Small AC/DC IT systems – Such as lighting systems
· AC/DC auxiliary circuits – Complying with DIN VDE 0100‑725
· Automation systems – Control circuit insulation monitoring in mechanical engineering and automation equipment
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