Description
Honeywell 05701-A-0325 | System 57 DC Input Card | 24VDC Rack Power Interface
Key Technical Specifications
| Parameter | Specification |
|---|---|
| Part Number | 05701-A-0325 |
| Manufacturer | Honeywell Analytics / Sieger |
| System | System 57 |
| Associated Systems | 5701 / 5704 / 5704F |
| Product Type | DC Input Card |
| Primary Function | Rack DC power entry and distribution |
| Nominal Input | 24VDC |
| Input Source | External DC power supply |
| Auxiliary Supply | Standby battery input |
| Input Protection | Fuse protection |
| Reverse Polarity | Yes |
| RFI Filtering | Yes |
| Main Terminal | TB1, two-part removable terminal block |
| Auxiliary Supply Isolation | PSU and AUX isolated by diodes |
| Engineering Interface | TB2 interface to Engineering Card plug-in modules |
| Mounting | System 57 subrack |
| Lifecycle | Legacy / discontinued |
The System 57 operating instructions state that external nominal 24VDC enters the rack through this card, passes through the Engineering Card and subrack backplane, and is protected by a fuse on the DC Input Card. The card also provides reverse-polarity protection and RFI filtering.
Product Introduction
What the Honeywell 05701-A-0325 Does
The Honeywell 05701-A-0325 is the DC power-entry card for the System 57 gas detection control system. It provides the connection point for the external DC supply and routes that power into the System 57 rack architecture rather than functioning as a conventional PLC digital-input module.
The card uses a two-part TB1 terminal block, allowing the card to be removed without individually disconnecting the connected power wiring. A standby battery can also be connected through the auxiliary DC input, with diode isolation between the primary and auxiliary supplies.
05701-A-0325
Application Scenarios & Field Pitfalls — Engineer’s Perspective
Engineering Pain Point
A failed DC Input Card can take an entire System 57 rack offline even when the external 24VDC power supply itself is healthy. Troubleshooting therefore needs to distinguish between the plant DC source, the 05701-A-0325 protection circuitry, the Engineering Card, and the rack backplane.
Typical Applications
- Honeywell System 57 gas detection racks — 5701 and related rack configurations.
- 5704 gas detection systems — provides the DC power entry point for the subrack.
- Legacy fixed gas detection panels — replacement of failed rack power-interface hardware.
- Redundant/standby DC arrangements — installations using the auxiliary battery input.
Technical Pitfalls to Avoid
- Do not confuse this card with a 24-channel digital input module.
Some current online listings incorrectly describe 05701-A-0325 as a high-density 32-channel DC input card. Honeywell’s own documentation identifies it as a DC Input Card for rack power, not a field signal acquisition module. - Check the rack current requirement.
Honeywell documentation warns about current flowing along the rack backplane. Where many 5704 catalytic cards or higher-power sensors are installed, the control cards may need to be powered through their associated relay interface cards, leaving the DC Input Card to supply the Engineering Card. - Do not bypass the card’s protection circuitry during troubleshooting.
The DC Input Card incorporates fuse protection, reverse-polarity protection, and RFI filtering. A direct wiring workaround can remove protection intended by the original System 57 architecture.
Related Products
- Honeywell 05701-A-0361 — System 57 Engineering Card; provides engineering access, backplane communication control, system functions, and interfaces for expansion modules.
- Honeywell 05701-A-0301 — Single Channel Control Card for 4–20mA sensor inputs.
- Honeywell 05701-A-0302 — Single Channel Control Card for catalytic sensor applications.
- Honeywell 05701-A-0351 — System 57 single-channel control card.
- Honeywell 05701-A-0326 — Field Interface Card; provides sensor/control-card field wiring interface rather than rack power entry.
- Honeywell 05701-A-0327 — Double SPCO relay card for alarm/fault relay functions.
- Honeywell 05701-A-0328 — Triple SPCO relay card with additional alarm/fault/inhibit relay functions.
- Honeywell 05701-A-0405 — 16-way System 57 AC-to-DC power supply assembly.
- Honeywell 05701-A-0406 — 8-way System 57 AC-to-DC power supply assembly.
- Honeywell 05701-A-0440 — 50W power-supply module used with the System 57 power-supply assemblies.
Honeywell’s System 57 ordering information places the 05701-A-0325 DC Input Card in both 8-way and 16-way rack configurations, including front-access and rear-access variants.
Procurement Verification
Before purchasing a 05701-A-0325, verify:
- Exact part number: 05701-A-0325
- System generation: 5701, 5704, or 5704F
- 8-way or 16-way rack
- Front-access or rear-access rack
- External DC supply arrangement
- Auxiliary/standby battery wiring
- TB1 and TB2 terminal condition
- Fuse condition and rating
- PCB revision and connector condition
- Whether the card is new surplus, used, or refurbished
Important: The strongest documentation identifies 05701-A-0325 as a System 57 DC Input Card, not a digital signal input card. For procurement, the distinction is critical: this component handles rack power entry and distribution, while field gas-detector signals are handled by the appropriate System 57 control/interface cards.
