ABB CP-A-RU Redundancy Unit for Reliable 24 VDC Power Supply Back-up

The ABB CP-A-RU is a compact redundancy unit designed to decouple two 24 VDC power supplies and keep your PLCs, I/O, motion axes, and safety circuits powered even if one supply fails. From my experience, this is one of those small rail-mounted modules that quietly prevents big downtime—no configuration, no firmware, just robust diode-based OR-ing that seems to work in most cabinets with minimal fuss.

Company’s Order Placement Process and Guarantees

• Warranty: 365 days
• Delivery time: 1 week for in-stock; no more than one month at the latest
• Payment terms: 50% advance payment, full payment for delivery
• Express options: FedEx, UPS, DHL

Key Features

• Redundant 24 VDC decoupling – Uses diode OR-ing to isolate two supplies so a single failure doesn’t pull down the load.
• Backfeed prevention – Prevents one PSU from feeding into the other, protecting both devices and wiring.
• Seamless switchover – The load stays powered when one source drops; typically no PLC brownouts when wired correctly.
• DIN-rail friendly – Quick installation on TH35 rails; fits neatly alongside ABB CP family power supplies.
• No auxiliary power needed – Passive design; it simply works with your existing 24 VDC rails.
• Broad compatibility – Works with ABB CP series (e.g., CP-E, CP-S) and most third-party 24 VDC industrial power supplies.

Technical Specifications

Brand / Model	ABB CP-A-RU
Product Type	Redundancy unit for 24 VDC power supplies (2 inputs to 1 output)
HS Code	8504.40 (Static converters and related power-supply equipment)
Power Requirements	Designed for nominal 24 VDC systems; passive device (no separate supply)
Signal I/O	2 x DC inputs, 1 x DC output for load; no control or signal interfaces
Communication Interfaces	None
Installation Method	DIN rail TH35 (IEC 60715)
Enclosure / Protection	IP20, finger-safe terminals

Application Fields

You’ll typically see the CP-A-RU in control cabinets where 24 VDC uptime matters. Examples that keep coming up with our customers:

• PLC/RTU and remote I/O power rails in factory automation
• Robotics cells, conveyors, and packaging machinery safety circuits
• Process skids for water/wastewater, chemicals, and food lines
• Building automation panels (BMS) and access/alarms
• Material handling and intralogistics with heavy sensor loads

Advantages & Value

• Reliability first – Decoupling means one PSU fault won’t cascade through your 24 V bus.
• Compatibility – Pairs well with ABB CP-E and CP-S power supplies, and in many cases other brands too.
• Lower risk, sensible cost – Redundancy without overengineering; often cheaper than a single oversized PSU.
• Serviceability – If one supply fails, you can typically swap it without killing the load.
• Simple design-in – No programming or communication integration required.

Installation & Maintenance

From my experience, the best results come from treating the redundancy unit like the “neutral arbiter” of your 24 V rail:

• Panel environment – Mount on TH35 DIN rail with adequate ventilation; avoid heat sources directly underneath.
• Wiring – Use identical cable lengths and gauges from each PSU to the CP-A-RU to keep voltage drops similar. Fuse each PSU output individually before the RU.
• Protection – Follow the PSU manufacturer’s recommended output fusing; maintain correct polarity to all terminals.
• Load distribution – Remember diode OR-ing does not actively balance current. You might notice one PSU carrying slightly more load; this is normal in many cases.
• Checks – Periodically re-torque terminals, blow out dust, and inspect for discoloration from heat. No calibration or firmware updates are required.

Quality & Certifications

ABB’s control products are typically compliant with CE and RoHS, and commonly listed by cULus for industrial control equipment. The CP-A-RU follows the same philosophy of robust, standards-aligned design. If you need a specific file (DoC, CB report, EAC/UKCA), we can share the exact document set for your audit package.

• Manufacturer: ABB
• Compliance: CE, RoHS (typical for ABB industrial power components); cULus listing may apply
• Warranty: 365 days (supplier warranty)

Helpful Pairings (Common in the Field)

For a straightforward redundant rail, many teams pair the CP-A-RU with two identical 24 VDC ABB supplies such as:

• ABB CP-E 24/5 (24 VDC, 5 A)
• ABB CP-E 24/10 (24 VDC, 10 A)
• ABB CP-S.1 24/10 (24 VDC, 10 A) – higher performance line

One thing I appreciate is the predictable behavior when both PSUs are set to the same output voltage; you typically get smooth handover and less nuisance tripping. A maintenance supervisor told us they cut unplanned stops on a packaging line to near zero after moving to twin CP-E supplies plus the CP-A-RU—simple, but it worked.