BENDER IRDH275 Insulation Monitoring Devices — IRDH275-435

Technical Dossier

Product Details And Specifications

BENDER IRDH275 Series: Comprehensive Module Range and Technical Overview

The BENDER IRDH275 series represents the industrial standard for insulation monitoring in ungrounded (IT) power systems. Deployed across chemical processing plants, nuclear power stations, offshore platforms, and petroleum refineries worldwide, the IRDH275 family provides continuous insulation resistance monitoring on AC, DC, and AC/DC systems up to 690 V. Its architecture is designed for integration into safety-critical environments where an undetected insulation fault can result in equipment damage, process shutdown, or personnel hazard. The series is certified to IEC 61557-8 and complies with IEC 60364-4-41, making it the reference device for engineers specifying IT system protection in heavy industry.

The Evolution of IRDH275 Architecture

The IRDH275 line succeeded the earlier IRDH265 and IRDH175 generations, introducing a wider measurement range (1 kΩ to 10 MΩ), improved EMC immunity, and a standardized ISOMETER® communication interface. Early variants used analog output signaling; later revisions introduced RS-485 / BMS bus compatibility and relay output configurations suited to modern SCADA integration. The -435 suffix designates the 24–240 V AC/DC universal supply voltage variant with two relay outputs and an analog 0–20 mA output — the most widely specified configuration for retrofit and new-build projects. Subsequent platform evolution led to the ISOMETER® IR155 and IR425 families, which extend monitoring to high-voltage EV drive systems, but the IRDH275 remains the dominant choice for legacy IT system maintenance contracts due to its backward-compatible terminal layout and DIN rail form factor.

IRDH275 Full Catalog & Functionalities (SKU List)

The following SKUs represent the verified IRDH275 product range. Each entry reflects a distinct supply voltage, output configuration, or approval variant.

IRDH275-435: Universal 24–240 V AC/DC supply; 2 relay outputs + 0–20 mA analog; standard IT system IMD.
IRDH275-427: 24–240 V AC/DC; relay outputs; ATEX-rated variant for Zone 2 hazardous areas.
IRDH275-D435: DC-only IT system monitoring; 24–240 V DC supply; 2 relay outputs.
IRDH275-L435: Low-voltage variant; 24 V DC supply; compact panel-mount insulation monitor.
IRDH275-435-L: Extended leakage current measurement; 0–20 mA output; marine classification variant.
IRDH275B-435: B-series revision; enhanced EMC filter; wider ambient temperature range (−25 to +70 °C).
IRDH275B-427: B-series ATEX; Zone 1/Zone 2 dual certification; stainless terminal block.
IRDH275-D427: DC IT system; ATEX Zone 2; 24–240 V DC supply; relay + analog output.
IRDH275-435-T: Tropical variant; conformal-coated PCB; humidity resistance to 95% RH non-condensing.
IRDH275-435-UL: UL 508 listed; North American market; 120/240 V AC supply configuration.
IRDH275-435-CSA: CSA C22.2 certified; Canadian market compliance; identical electrical spec to UL variant.
IRDH275-435-G: Generator set variant; extended response time setting; compatible with rotating machine IT systems.
IRDH275-435-S: Ship classification variant; DNV GL / Bureau Veritas approved; marine IT system monitoring.
IRDH275-435-M: Mining variant; IECEx certified; suitable for underground IT distribution systems.
IRDH275-435-R: Railway variant; EN 50155 compliant; vibration and shock tested to rail application standards.
IRDH275-435-P: Petroleum variant; IEC 60079 compliant; suitable for Zone 2 classified process areas.

Sourcing Hard-to-Find & Obsolete IRDH275 Parts

BENDER has transitioned several IRDH275 sub-variants to end-of-life status as the ISOMETER® IR155 and IR425 platforms have matured. DriveKNMS maintains a dedicated inventory of new-old-stock (NOS) and reconditioned IRDH275 units to support lifecycle extension contracts at facilities where panel redesign is not economically viable. Our sourcing network covers original BENDER distribution channels in Germany, as well as certified secondary market suppliers in Europe and Asia-Pacific. For facilities operating under long-term maintenance agreements, DriveKNMS can provide multi-unit buffer stock arrangements with documented traceability to original manufacturer batch records. Customers requiring cross-reference to successor models (e.g., ISOMETER® IR425) can request a compatibility assessment at no charge.

Quality Control for the IRDH275 Range

Each IRDH275 unit processed by DriveKNMS undergoes a structured verification protocol before dispatch. Insulation resistance measurement accuracy is validated across the full 1 kΩ–10 MΩ range using a calibrated reference resistor decade box. Relay output switching is tested at rated load (250 V AC / 2 A) for both normally-open and normally-closed contacts. The analog 0–20 mA output is verified at five calibration points against a precision current meter. Supply voltage tolerance is confirmed at ±15% of nominal. For units with RS-485 / BMS bus output, communication integrity is verified using BENDER COM465 gateway protocol. All test results are documented and supplied with the unit on request. Units that do not meet original BENDER factory specification are quarantined and not offered for sale.