Description
Product Introduction & Engineering Value
The 05701-A-0327 does two jobs in a System 57 channel. It provides the field wiring interface between the detector and its control card, and it adds voltage-free relay contacts for the A1 alarm, A2 alarm, and fault states. That makes it the appropriate interface where external shutdown, annunciation, or alarm circuits need discrete relay contacts rather than only an electronic status signal.
The card should not be confused with the 05701-A-0326 Field Interface Card. The 0326 provides the sensor/control-card interface without relays, whereas the 0327 adds the three relay functions. Honeywell’s parts documentation places both cards within the System 57 5701 field-interface architecture.
Technical Specifications
- Part Number: 05701-A-0327
- System: Honeywell System 57 / 5701
- Card Type: Double SPCO Relay Card
- Relay Outputs: A1, A2, Fault
- Contact Configuration: SPCO — Single Pole Changeover
- Contact Rating: 5 A at 250 VAC / 32 VDC, non-inductive
- Relay Operation: Selectable latching or non-latching
- Energization: Selectable normally energized or de-energized
- Terminal Capacity: Up to 2.5 mm² / 14 AWG cable
- Typical Power Consumption: 0.8 W
- Operating Temperature: −5°C to +55°C
- Storage Temperature: −25°C to +55°C
- Operating Humidity: 20–99% RH, non-condensing
- Environmental Compliance: EN 50270 listed by distributor documentation
- Approximate Card Weight: 155 g
The key electrical distinction is the voltage-free contact output. The relay card does not merely reproduce the detector’s 4–20 mA signal; it provides discrete alarm/fault switching that can be wired into external plant equipment. Honeywell’s operating documentation describes the 0327 as providing relay outputs for the A1, A2, and fault conditions.
Field Application & the “Trench” Experience
A practical failure scenario is a System 57 gas-detection channel that still displays a valid detector reading, while the plant’s external alarm circuit no longer responds correctly to an A2 alarm. The control card may be processing the detector signal normally, but the relay interface can still be the point of failure.
In that situation, replacing the 05701-A-0327 addresses the physical relay interface without unnecessarily replacing the detector or single-channel control card. Before doing so, however, the technician should verify the relay wiring and determine whether the installed configuration uses energized or de-energized fault logic.
Specific application scenarios
- Gas detector A1/A2 alarm annunciation — relay contacts connected to local alarm panels or remote indication systems.
- Process shutdown interlocking — A2 alarm relay used as an input to an external shutdown or permissive circuit.
- Fault monitoring — the dedicated fault relay used to report channel or detection-system problems.
- Legacy System 57 fire-and-gas cabinets — maintaining relay-based plant interfaces without replacing the complete rack.
Honeywell’s System 57 documentation explicitly lists the 0327 as the Double SPCO Relay Card and distinguishes its A1/A2/Fault configuration from the 0328 and 0329 relay cards.
05701-A-0327
05701-A-0327
Transparency SOP: QA & Testing
For New Surplus 05701-A-0327 inventory, the meaningful inspection is a combination of visual, mechanical, and relay-function testing.
- Part-number inspection — verify the PCB and identification label against 05701-A-0327.
- Physical inspection — examine relay bodies, terminal blocks, PCB traces, connectors, and solder joints for corrosion or overheating.
- Contact testing — verify the A1, A2, and Fault relay contacts with the card isolated from the customer’s control system.
- Mode verification — check the configured relay behavior, including energized/de-energized and latching/non-latching arrangements.
- System simulation — where the appropriate System 57 test equipment is available, simulate the relevant alarm/fault states and verify the external relay outputs.
- Documentation — record the part number, revision, condition, and test results before shipment.
Current aftermarket documentation identifies the 05701-A-0327 as discontinued, while other distributors continue to list individual new or surplus examples.
The Veteran’s Tech Trap Guide
⚠️ Trap #1 — Confusing 0327 with 0326.
The 05701-A-0326 is the Field Interface Card and does not provide the same A1/A2/Fault relay functionality. If the existing installation depends on hardwired relay outputs, substituting the 0326 changes the system interface.
⚠️ Trap #2 — Forgetting relay philosophy.
The relay operation can be configured for latching/non-latching and normally energized/de-energized operation. A replacement that is electrically functional can still produce the wrong plant response if the relay configuration does not match the original installation.
PRO TIP: Photograph the existing relay-card wiring and record which terminals are used before removing the card. On an older System 57 installation, the cabinet wiring often contains application-specific interlocks that are not obvious from the part number alone.
⚠️ Trap #3 — Assuming the three relay outputs are equivalent.
They represent different system conditions: A1, A2, and Fault. Do not reconnect them solely by terminal position without checking the System 57 wiring documentation and the actual cabinet drawings.
Dynamic FAQ
What is Honeywell 05701-A-0327?
It is the Double SPCO Relay Card used in the Honeywell System 57 / 5701 gas-detection system. It provides voltage-free relay contacts for A1 alarm, A2 alarm, and Fault conditions.
What does SPCO mean?
SPCO means Single Pole Changeover. Each relay provides a common contact and changeover contacts, allowing the external circuit to be configured according to the required alarm or control philosophy.
What is the relay contact rating?
The published specification is 5 A at 250 VAC or 32 VDC for non-inductive loads. Actual system wiring should still be checked against the load type and applicable electrical requirements.
Is 05701-A-0327 interchangeable with 05701-A-0328?
No, they should not be treated as interchangeable. The 0327 provides A1, A2, and Fault, while the 0328 adds A3 and Inhibit through its triple-SPCO configuration.
Is 05701-A-0327 obsolete?
It is listed as discontinued by current aftermarket documentation. Honeywell’s published System 57 spare-parts documentation nevertheless identifies it as the original 5701 Double SPCO Relay Card.
Can I buy a New Surplus 05701-A-0327 with warranty?
Availability and warranty depend on the supplier. Some current listings advertise new units with a stated warranty, while other listings identify the part as discontinued. For a critical gas-detection application, confirm whether the unit is unused original surplus or refurbished, and request relay-function test results and the applicable warranty terms before purchase.
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