📝 Description
Used product. The BENDER IRDH275B-49335, article number B91065123, is an A-ISOMETER® device for continuous monitoring of insulation resistance in ungrounded IT systems, suitable for AC, 3(N)AC, AC/DC, and DC networks. The IRDH275B variant also features an RS-485/BMS interface, event memory with date and time, and an analog output for measuring insulation resistance.
⚙️ Technical Specifications
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Brand: BENDER
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Type: A-ISOMETER® IRDH275B-49335
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Article Number: B91065123
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Software Indicated: D159 V1.51
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System Nominal Voltage Un: 3AC/AC 0…793 V / DC 0…650 V
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System Frequency: 0.1…460 Hz
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Alarm 1 Response Range: 1 kΩ…10 MΩ
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Alarm 2 Response Range: 1 kΩ…10 MΩ
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Supply Voltage Us: AC 88…264 V / DC 77…286 V
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Consumption Indicated on Nameplate: 8.0 VA
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Relay Contacts: AC 250 V / 5 A
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Display: 2-line × 16-character LCD
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Analog Output: 0(4)…20 mA, galvanically isolated, proportional to the insulation value
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Communication: RS-485 with BMS protocol, galvanically isolated
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BMS Addressing: 1…30
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Mounting: DIN rail IEC 60715
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Terminals: screw terminals
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Protection: IP30 for internal components, IP20 for terminals
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Operating Temperature: −10…+55 °C
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Storage Temperature: −40…+70 °C
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Weight: approx. 510 g
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Climatic Class: 3K5
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Housing Material: X112, halogen-free
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Flammability Class: UL94 V-0
⚡ Function in the Electrical System
The IRDH275B continuously monitors the insulation resistance between the IT system and the protective conductor PE. The device applies a measuring signal to the system and determines the insulation resistance value; when the value falls below the thresholds set for Alarm 1 or Alarm 2, the corresponding relays and device indications are activated.
It is particularly suitable for electrical panels, industrial systems, converters, rectifiers, drives, and AC/DC systems where early detection of insulation degradation toward ground is required.
🔌 Inputs, Outputs and Connections
The terminals A1/+, A2/−, L1, L2, AK, and KE are clearly identifiable on the upper section of the front.
The lower section features connections T1, T2, R1, R2, F1, F2, M+, M−, A, B, 11, 12, 14, 21, 22, 24.
The B version provides RS-485/BMS on terminals A/B, with a connection length of up to approximately 1200 m and a 120 Ω termination resistor according to the network configuration. Terminals M+/M− are used for the analog output corresponding to the insulation value.
There are also two alarm relays with changeover contacts, associated with Alarm 1 and Alarm 2/device fault, configurable with normally open or normally closed logic.
🖥️ Control Functions
The device features:
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TEST manual and automatic self-test;
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RESET alarm reset;
- independent configuration of the two insulation thresholds;
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event memory with date and time;
- monitoring of the correct connection of the measuring circuits;
- automatic adaptation to the system's leakage capacitance;
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BMS interface for supervision and communication with other BENDER devices.
🏭 Applications
Suitable for industrial systems, automation panels, IT systems, converters and inverters, AC/DC power supplies, rectifiers, and systems where service continuity and insulation monitoring toward ground are important.
The IRDH275B-49335 is a specific variant for systems up to 793 V AC / 650 V DC; dedicated BENDER coupling devices are provided for higher voltages, so it must not be used beyond the limits indicated on the nameplate.
🛡️ Safety and Product Condition
The component is used, with normal signs of use and handling visible in the photographs, but no obvious breaks in the housing or terminals are visible.
Operation must not be considered verified unless a specific electrical test has been performed. For sale as a tested component, it is advisable to verify at least power supply, display, TEST/RESET, insulation resistance measurement, and switching of the two alarm relays.
Installation and commissioning must be carried out by qualified personnel, respecting the voltage limits and BENDER instructions. The manufacturer also requires a functional check before commissioning.
📦 Package Contents
- 1 × BENDER IRDH275B-49335
- Art.-Nr. B91065123
- Software indicated on the component: D159 V1.51
- The product is supplied exactly in the configuration shown in the photographs, without additional accessories unless expressly indicated.
🚀 Final Description
The BENDER IRDH275B-49335 is a professional component for permanent insulation monitoring in AC/DC IT systems, with dual alarm threshold, LCD display, self-test, two alarm relays, 0/4…20 mA output, and RS-485/BMS communication. The B91065123 configuration is directly identifiable from the nameplate and is specified for 3AC/AC 0…793 V and DC 0…650 V.
