Overview
Manuals
Measurement and Alarms
Supply, BMS and Output
Installation and Safety
Features:
- Insulation monitoring for unearthed 3(N)AC, AC/DC and DC IT systems within the documented voltage range.
- The -427 version accepts 19.2–55 V AC or 19.2–72 V DC auxiliary supply; match the printed variant and.
- The B execution adds an isolated BMS RS-485 interface, time-stamped alarm memory and configurable isolated current output.
The Bender ISOMETER IRDH275 monitors insulation resistance between an unearthed IT system and protective earth. The manual describes use in 3(N)AC, AC/DC and DC networks, including AC systems with galvanically connected DC loads such as converters or thyristor-controlled DC drives.
The IRDH275B variant adds a BMS interface, real-time-clock alarm memory and an electrically isolated 0(4)–20 mA output related to the measured insulation value. The -427 suffix identifies the auxiliary supply variant; verify the order number and wiring from the nameplate and approved drawings.
The IRDH275B-427 may still be available for purchase and support from Moore Automated Company beyond End-Of-Life (EOL) by the manufacturer (OEM).
IRDH275B-427 documentation and reference links.
Important Notice: Confirm the complete catalog identity, hardware revision, receiving-system configuration and required document revision before replacement.
Bender gives two separately adjustable insulation-response settings, Alarm 1 and Alarm 2, each within 1 kΩ to 10 MΩ. When the measured insulation value falls below the applicable setpoint, the associated relay and alarm indication respond. The device's measuring voltage is no more than 50 V and maximum measuring current is 280 μA at zero fault resistance; permissible system leakage capacitance is up to 500 μF.
The device performs automatic self-tests and can retain fault indications according to configuration. Review response values, memory behavior, function input, external coupling device and alarm relay wiring against the actual IT system design before work.
The exact -427 supply variant accepts 19.2–55 V AC at 42–460 Hz or 19.2–72 V DC. The monitored nominal network range is 3(N)AC 0–793 V or DC 0–650 V; coupling devices are required where a design extends the stated range. These are separate ratings: do not confuse the auxiliary supply with the system under monitoring.
The B version provides an electrically isolated RS-485 Bender Measuring Device Interface (BMS) bus and an isolated current output configurable as 0(4)–20 mA in relation to the measured insulation value. Confirm bus address/protocol and output mode from the installed configuration before replacement.
Bender specifies DIN-rail mounting to IEC 60715 or screw mounting with the optional trapezoidal support. The manual requires the designated earth terminals to be connected to protective earth and states that only one insulation monitor should be connected to each conductively connected system. Maintain at least 30 mm separation from adjacent devices and follow the terminal diagram for conductor size and tightening torque.
Before installation or connection, qualified personnel must isolate the electrical system and observe site electrical-safety rules. If insulation or voltage tests are performed, isolate the monitor from the system during the test. Verify the actual coupling device, supply, alarm circuit and IT topology before energizing.
