Get now the 1794-TBNF, the fused version of the NEMA-style terminal base for the Allen-Bradley FLEX I/O system. This unit provides critical circuit protection at the point of termination, ensuring that field-side faults do not damage your expensive I/O modules or halt your entire automation process.
What Is the 1794-TBNF?
The 1794-TBNF is a specialized terminal base unit that incorporates 8 fuse holders directly into the NEMA-style barrier terminal strip. It is designed for applications where per-point or per-group fusing is required to protect the I/O module from overcurrent or short-circuit conditions in the field. This is particularly vital when using high-voltage AC output modules (like the 1794-OA8 or 1794-OM16) to drive solenoids or motors. By placing the fuse on the terminal base, Allen-Bradley allows for easy maintenance; if a field fault occurs, only the fuse on the 1794-TBNF blows, protecting the internal electronics of the I/O module. The base maintains full support for «Removal and Insertion Under Power» (RIUP), facilitating rapid hardware swaps.
Key Technical Specifications
- Terminal Type: NEMA-style with 8 integrated fuse holders
- Fuse Type: 5 x 20 mm (user-supplied, typically 1.6A or 2A)
- Number of Terminals: 10
- Voltage Rating: 250V AC/DC
- Current Capacity: 10A maximum total
- FlexBus Current: 640mA
- Wire Size: 0.34…2.5 mm² (22…12 AWG)
Circuit Protection and Architecture
The architecture of the 1794-TBNF is focused on system availability. In a standard I/O rack, a single short circuit can often take out an entire module or trigger a power supply shutdown. With the 1794-TBNF, the fault is isolated to the specific fused circuit. This is an essential design choice for «fail-safe» architectures in process industries. The base snaps onto a standard DIN rail and connects to adjacent bases via the FlexBus, maintaining a consistent communication path across the entire distributed I/O station.
Expert Tips
When selecting fuses for the 1794-TBNF, always match the fuse rating to the maximum current of the I/O module channel, not the maximum capacity of the wire. For example, if your output module is rated for 0.5A per channel, use a 0.5A or 0.63A fast-acting fuse. Using a fuse that is too large (e.g., 5A) will render the protection useless, as the module’s internal circuitry will likely fail before the fuse blows.
Frequently Asked Questions
Q: Does the 1794-TBNF come with fuses included?
A: No, fuses must be purchased separately. This allows you to select the specific amperage and blow-characteristic (fast-acting vs. slow-blow) required for your specific load.
Q: How do I know if a fuse has blown on the base?
A: While the base itself doesn’t have an LED, the field device will lose power. Many technicians use indicate-type fuses that show a visual change when blown, or check the diagnostic bits on the I/O module if supported.
Do you need more references from this brand? Explore our full catalog of Allen-Bradley here: https://atlantechdrives.com/manufacturers/allen-bradley/
