Key Technical Specifications
- Product Model: IRDH575B1W-435
- Manufacturer: Bender
- Product Series: ISOMETER IRDH575
- System Type: IT AC, IT DC, IT AC/DC (isolated power)
- Voltage Range: AC 0-793V / DC 0-650V
- Response Values: Two adjustable thresholds, 1 kΩ to 10 MΩ
- Communication: RS-485 interface (BMS protocol)
- Signal Output: 0(4)…20 mA analog output
- Display: Four-line LC display with backlight
- Special Option: “W” = Improved shock & vibration resistance
- Mounting: Panel mount, 133 x 144 x 96 mm
Product Introduction
Ground faults in ungrounded IT systems don’t always trip a breaker. They just sit there, waiting for a second fault to create a dead short. The Bender IRDH575B1W-435 exists to catch that first fault before it becomes a fire or a catastrophic shutdown. It’s an ISOMETER device built for AC, DC, and mixed systems up to 793V, and the “W” suffix means it’s been validated for high-vibration environments like ships, rolling stock, and seismic zones.I’ve installed these in marine engine rooms and mining substations where standard monitors would have shaken themselves to death in six months. The IRDH575B1W-435 gives you two independent alarm relays, a 4-20mA output for trending insulation degradation over time, and an RS-485 port to tie into your BMS. One thing to watch: this unit runs a self-test on power-up that takes 15-20 seconds. Don’t panic if the display shows a bar graph during startup. That’s normal. If it says “!Error!” after that, you’ve got a real problem.
Quality SOP & Tech Pitfalls
The Lab Report (SOP)
Every IRDH575B1W-435 gets bench-tested before it ships. We start with a visual inspection for shipping damage and verify the “W” option marking. Then it goes on a test bench with a variable AC/DC source. We inject known insulation resistances across the full 1 kΩ to 10 MΩ range and verify the 4-20mA output tracks correctly. We check both alarm relay trips at their setpoints. Finally, we log the firmware version and seal it in anti-static packaging with the original manual.The Engineer’s Warning (Pitfalls)
Here’s the mistake that costs people days of downtime: forgetting to set the system leakage capacitance compensation. The IRDH575B1W-435 has auto-adaptation, but on long cable runs or systems with big VFDs, the capacitance can fool it into nuisance alarms. I had a client call me at 2 AM because their new monitor kept tripping Alarm 1 on a healthy system. Turned out they had 800 meters of shielded VFD cable and never ran the capacitance measurement routine. Another common one: wiring the RS-485 backwards. It won’t fry the port, but you’ll get garbage data and waste three hours blaming the BMS. Double-check your A and B leads.
Installation & Configuration Guide
- Pre-Installation: ⚠️ De-energize the IT system completely. Verify zero voltage with a calibrated meter. Take photos of all existing wiring and DIP switch positions.
- Removal: Label every wire at the terminal block. Release the DIN rail or panel mounting hardware carefully. Do not yank wires.
- Installation: Copy all DIP switch and menu settings from the old unit to the IRDH575B1W-435 before applying power. This includes alarm thresholds, BMS address, and self-test interval. Seat the module firmly and secure the mounting screws to spec.
- Power-On & Testing: Restore power. Watch the self-test bar graph complete (15-20 seconds). Verify “Test ok” appears. Check that the current insulation value displays correctly. Force a test fault with a known resistor to confirm both alarm relays operate and the BMS receives the message.
Compatible Replacement Models
| Model | Compatibility Tier | Notes |
|---|---|---|
| IRDH575B1-435 | ✅ Drop-in Replacement | Identical specs, non-“W” version. Use if vibration is not a concern. Slightly lower cost. |
| IRDH575B2-435 | ⚠️ Software Compatible | Same hardware platform, different firmware feature set. Requires ~1 hour to reconfigure BMS parameters. |
| IRDH375B-435 | ❌ Hardware Mod Required | Smaller form factor, fewer channels. Requires panel cutout modification and wiring changes. Not recommended as direct swap. |
Frequently Asked Questions (FAQ)
What does the “W” option actually mean?
It’s not just marketing. The “W” designation means the internal PCBs are conformally coated and mechanically reinforced to withstand higher shock and vibration levels. If this is going on a ship, train, or anything with a diesel engine within 10 feet, you need the W version. Standard units will develop cracked solder joints.Can I use this on a grounded TN-S system?
No. The IRDH575B1W-435 is designed exclusively for IT (ungrounded or high-impedance grounded) systems. For TN-S or TT systems, you need a Bender RCM residual current monitor instead. Wrong tool for the job.How long does the self-test take?
Fifteen to twenty seconds after power-up. The display shows a progress bar. If you see “!Error!” after it completes, check the manual for the specific error code. Common causes: earth connection missing, system voltage out of range, or internal memory fault.Do I need the FTC470XET for remote configuration?
Only if you want to adjust parameters over Ethernet or the internet. For local setup via the front panel buttons, no. The FTC470XET is an add-on gateway. Most field installations don’t need it unless the panel is in a hazardous area or physically inaccessible.Will this work with my existing Bender EDS fault locator?
Yes, if your EDS supports the BMS protocol over RS-485. The IRDH575B1W-435 can send test currents to the EDS for automatic fault location across up to 1068 circuits. Verify your EDS model’s compatibility in the Bender system planning guide before ordering.Is hot-swapping safe on this unit?
No. Always de-energize the IT system before removing or installing the IRDH575B1W-435. The measurement circuit is connected directly to the live conductors. Pulling it hot can arc the terminals and damage the internal measurement bridge. Plan for a scheduled shutdown.
