Description
⚙️ Product Overview
The BENDER A-ISOMETER IRDH375B-425 is an insulation monitoring device for unearthed AC, AC/DC, and DC power systems. It continuously monitors insulation resistance in IT systems and provides early warning when insulation deterioration or an insulation fault occurs.
The IRDH375B series uses Bender’s AMPPlus measuring method and is designed for modern electrical systems that may contain rectifiers, converters, variable-speed drives, thyristor-controlled DC drives, and relatively high system leakage capacitance.
The IRDH375B-425 variant uses a low-voltage DC supply configuration and includes the additional functions of the IRDH375B series, including an electrically isolated RS-485/BMS interface, alarm-history memory with real-time clock, and a 0(4)…20 mA output related to the measured insulation value.
🔧 Key Features
- ✅ Bender A-ISOMETER insulation monitoring device
- ✅ Model: IRDH375B-425
- ✅ Monitors unearthed IT systems
- ✅ Suitable for AC, AC/DC, and DC systems
- ✅ AMPPlus insulation measurement technology
- ✅ Nominal monitored voltage up to AC 0–793 V / DC 0–650 V
- ✅ Two independently adjustable insulation-resistance response values
- ✅ Alarm response range: 1 kΩ to 10 MΩ
- ✅ Electrically isolated RS-485 interface with BMS protocol
- ✅ Real-time alarm history memory
- ✅ 0(4)…20 mA insulation-value output
- ✅ Backlit two-line LC display
- ✅ Automatic adaptation to system leakage capacitance
📊 Product Datasheet
| Parameter | Specification |
|---|---|
| Brand | Bender |
| Model | IRDH375B-425 |
| Series | ISOMETER IRDH375B |
| Product Name | Insulation Monitoring Device |
| Product Type | IT-System Insulation Monitor |
| Monitored System | Unearthed AC / AC-DC / DC systems |
| Nominal System Voltage | AC 0–793 V / DC 0–650 V |
| Response Value Range | 1 kΩ–10 MΩ |
| Communication Interface | Electrically isolated RS-485 / BMS |
| Analog Output | 0(4)…20 mA |
| Power Supply | DC 10.2–36 V |
| Power Consumption | ≤14 VA |
| Weight | Approx. 0.65 kg; verify actual revision |
| Condition / Status | Used; insignificant signs of use, no dents, reported fully operational |
| Country of Origin | Germany |
🏭 Typical Applications
The IRDH375B-425 is intended for electrical systems where maintaining insulation integrity is important and an insulation fault should be detected before it develops into a more serious system problem.
Typical applications include:
- ⚡ Industrial power distribution
- 🏭 Process-control plants
- 🚢 Marine and shipboard electrical systems
- 🛢️ Oil and gas installations
- 🚆 Transportation electrical systems
- 🔋 DC power systems
- ⚙️ Variable-frequency-drive installations
- 🏥 Specialized electrical installations
- 🔧 Control and automation power networks
It can also be used in systems containing power electronics and converter equipment where conventional insulation monitoring can be affected by leakage capacitance.
🔌 Monitoring & Technical Functions
Insulation Resistance Monitoring
The IRDH375 continuously measures the insulation resistance between the unearthed system and protective earth. Two independently adjustable response values can be used to establish different warning and alarm levels.
AMPPlus Measurement
Bender’s AMPPlus measuring method is designed for modern AC/DC systems containing rectifiers, converters, and other power-electronic loads. The device automatically adapts to the existing system leakage capacitance.
Alarm & History Functions
The IRDH375B provides alarm-history storage with a real-time clock. This allows insulation-related events to be retained for troubleshooting and maintenance analysis.
BMS Communication
The IRDH375B version provides an electrically isolated RS-485 interface using the Bender Measuring Device Interface (BMS) protocol. This allows the device to exchange status and measurement information with compatible Bender monitoring and control equipment.
Analog Output
The 0(4)…20 mA output can be used to transmit the measured insulation value to an external monitoring, PLC, DCS, or instrumentation system, subject to the specific system configuration.
🛠️ Installation & Maintenance
Before installation:
- Confirm the complete part number IRDH375B-425.
- Verify that the monitored system is an appropriate unearthed IT system.
- Confirm the DC supply voltage before energizing the device.
- Check the L1/L2 measuring connections and PE/KE connections.
- Verify that another insulation monitoring device is not already connected to the same conductively connected system.
- Inspect terminals and wiring for contamination, looseness, or insulation damage.
Commissioning checklist:
- Confirm correct auxiliary supply voltage.
- Verify the displayed system insulation value.
- Set Alarm 1 and Alarm 2 according to the electrical-system requirements.
- Test the alarm relay and indication functions.
- Check the RS-485/BMS connection if communication is used.
- Verify the 0(4)…20 mA output where an external monitoring system is connected.
- Record the initial insulation value as a maintenance reference.
Important maintenance note:
When carrying out insulation or high-voltage tests on the monitored electrical system, the ISOMETER should be isolated from the system for the test period as specified by the installation instructions. Incorrect connection or simultaneous use of multiple insulation monitoring devices on the same conductively connected system can cause malfunction or equipment damage.
❓ Common Questions & Answers
Q1: What is the BENDER IRDH375B-425?
A: It is an A-ISOMETER insulation monitoring device for continuously monitoring insulation resistance in unearthed AC, AC/DC, and DC IT systems.
Q2: What is the difference between IRDH375 and IRDH375B?
A: The IRDH375B adds functions including BMS communication, real-time alarm-history memory, and additional system-control capabilities.
Q3: What is the supply voltage of the IRDH375B-425?
A: The -425 variant uses a DC supply of approximately 10.2–36 V, according to the IRDH375 ordering information.
Q4: What system voltage can it monitor?
A: The IRDH375 series is specified for nominal system voltages up to AC 0–793 V or DC 0–650 V without an additional coupling device.
Q5: Can it communicate with a control system?
A: Yes. The IRDH375B provides an electrically isolated RS-485 interface using the Bender BMS protocol.
Q6: What should be checked before replacement?
A: Verify the complete IRDH375B-425 designation, supply voltage, monitored system voltage, terminal configuration, alarm settings, and communication arrangement.
⭐ Recommended Bender Models
- IRDH375B-425 – ISOMETER Insulation Monitoring Device
- IRDH375-425 – ISOMETER Insulation Monitor
- IRDH375B-427 – ISOMETER Insulation Monitoring Device
- IRDH375B-435 – ISOMETER Insulation Monitoring Device
- IRDH375-435 – ISOMETER Insulation Monitoring Device
- IRDH375W-425 – ISOMETER Marine / High-Vibration Version
- IRDH375BW-425 – ISOMETER BMS Marine Version
- IRDH375BW-427 – ISOMETER Insulation Monitor
- IRDH375BW-435 – ISOMETER Insulation Monitor
- AGH204S-4 – ISOMETER Coupling Device
📦 Spare-Parts Recommendation
For critical IT power systems, the BENDER IRDH375B-425 should be managed as a configuration-specific spare. When preparing a maintenance package, also verify compatible Bender coupling devices, remote indication equipment, BMS communication components, alarm relays, and auxiliary power arrangements.
For replacement work, match the complete IRDH375B-425 designation rather than selecting an IRDH375 device only by its front-panel appearance. The supply-voltage suffix and BMS functionality are important parts of system compatibility.
