Description
Product Introduction and Engineering Value
The AS-B814-108 provides eight independent relay outputs for legacy Modicon PLC installations. Each channel can switch an external load through relay contacts, allowing PLC logic to operate contactors, solenoid valves, pilot lamps, and other discrete-control devices. Its relay-based design is useful where electrical separation between the PLC backplane and field circuits is required.
For maintenance and replacement work, verify the contact arrangement, load ratings, terminal connector, and rack compatibility before installation. The module is part of an older I/O platform, so exact hardware identification is essential.
Technical Specifications
| Parameter | Specification |
|---|---|
| Manufacturer | Schneider Electric |
| Model | AS-B814-108 |
| Module family | Modicon 800-Series |
| PLC family | Modicon 984 / 800-Series I/O |
| Output type | Relay, normally open / normally closed |
| Number of outputs | 8 |
| DC operating voltage | 0–30 VDC |
| AC operating voltage | 0–240 VAC, 47–63 Hz |
| Maximum current per point | 5 A at 30 VDC or 120 VAC; 4 A at 240 VAC |
| Maximum switching capacity | 960 VA AC or 150 W DC |
| Typical response time | 6 ms; 15 ms maximum, both switching directions |
| Contact resistance | Less than 300 mΩ, including fuse, wiring, connectors, and contacts |
| Terminal connector | AS-8534-000 |
| Output protection | One 7 A fuse per output |
| Internal power requirements | +5 V at 107 mA; +4.3 V at 800 mA |
Specifications are drawn from the 800-Series I/O reference manual. The maximum current ratings are not interchangeable with the maximum switching-capacity ratings; both must be considered when selecting a load.
Important operating limit: The reference manual also specifies a maximum load of 1 A for 48 VDC operation. Do not extrapolate the 30 VDC rating to higher DC voltages.
AS-B814-108
AS-B814-108
Field Applications and Practical Maintenance
Consider an older packaging line where a Modicon 984 controller operates pneumatic actuators and motor starters. One relay output stops switching reliably, interrupting the machine sequence. During a planned maintenance window, the technician identifies the installed card as an AS-B814-108 and checks the replacement against the existing rack, terminal connector, wiring diagram, and field-load requirements.
After replacement, the technician verifies each affected output under the approved test procedure, confirms that the external devices respond correctly, and checks the PLC’s output status before returning the machine to production.
This is an illustrative maintenance scenario, not a verified historical incident involving this model.
Other suitable application scenarios include:
- Conveyor and material-handling systems: Switching motor-starter coils, diverter solenoids, and machine-sequence indicators.
- Packaging machinery: Operating pneumatic valves, interposing relays, and discrete actuators.
- Legacy process-control cabinets: Maintaining existing relay-output circuits in facilities that continue to use Modicon 800/984-series hardware.
Quality Assurance and Testing
For new-surplus or refurbished AS-B814-108 inventory, request evidence that goes beyond a visual inspection.
- Part identification: Confirm the full model number, manufacturer markings, and any available serial or traceability information.
- Physical inspection: Examine the PCB, relay components, connector, and fuse positions for corrosion, heat damage, cracked joints, or signs of unauthorized repair.
- Electrical checks: Verify relay contact continuity and isolation using a suitable test procedure. Confirm the correct NO/NC behavior for the installed configuration.
- Functional testing: Exercise all eight outputs using appropriate test equipment and representative loads within the manufacturer’s limits. Check both switching directions.
- Final documentation: Obtain the inspection report, test results, declared condition, warranty terms, and any restrictions on use.
A new-surplus module may be unused without having undergone recent functional testing. A refurbished module should be supplied with a clear account of the inspection and repair work performed.
Replacement Pitfalls: What to Check Before Power-Up
1. Treating the current rating as a universal load rating
The per-point current rating does not override the 960 VA AC and 150 W DC switching limits. DC inductive loads, including solenoid coils, can impose demanding interruption conditions. Verify the load characteristics and required suppression before connecting the circuit.
2. Ignoring terminal wiring and NO/NC configuration
Confirm the terminal assignments and relay configuration against the original wiring documentation. A replacement that fits the rack can still produce incorrect field behavior if the contact arrangement or wiring is misunderstood.
3. Assuming the active indicator proves every output works
The reference documentation warns that the module’s active indicator can remain lit even when one or more output channels are malfunctioning. Test the individual channels rather than relying on the indicator alone.
Electrical Engineering
Frequently Asked Questions
Q1. What does the AS-B814-108 do?
It is an eight-point relay output module that allows a compatible Modicon PLC to switch external AC or DC loads through relay contacts.
Q2. Is the AS-B814-108 compatible with Modicon 984 systems?
It belongs to the Modicon 800-Series I/O family and is associated with legacy Modicon 984 installations. Confirm the specific rack, backplane, connector, and controller configuration before ordering.
Q3. Can it switch 240 VAC loads?
The reference manual specifies operation up to 240 VAC at 47–63 Hz, with a maximum current of 4 A per point at 240 VAC. The 960 VA switching-capacity limit and the load’s electrical characteristics must also be respected.
Q4. Is the AS- still available?
The module is listed by industrial spare-parts suppliers in refurbished and other condition categories. Availability and condition vary by supplier. Check the current listing and request confirmation of the actual unit before purchasing.
Q5. How can I verify that a new-surplus unit is genuine?
Check the nameplate, manufacturer markings, part-number consistency, and available traceability records. Request actual-unit photographs and a functional-test report. New-surplus status alone does not establish authenticity or operational condition.
Q6. What warranty should I expect?
Warranty coverage is supplier-specific. Some resellers advertise a two-year warranty, but this is not automatically an original Schneider Electric factory warranty. Confirm the warranty provider, duration, exclusions, and return procedure in writing.
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