1756-A17 — 1756 Seventeen-Slot Logix Chassis

The 1756-A17 is the largest standard chassis in the 1756 Logix family, providing a processor slot plus sixteen additional module positions on a single backplane. It's the appropriate choice for large-scale control systems — process units with extensive analog and digital I/O, multiple communication networks, and motion control modules — where even a 13-slot chassis would run out of room before the full module list is accommodated.

Specifications

Parameter	Value
Part Number	1756-A17
Total Slots	17
User Module Slots	16 (Slot 0 = processor; Slots 1–16 = I/O/comm)
Power Supply Slot	Dedicated, left end (separate from the 17-slot count)
Module Compatibility	All standard 1756-series modules
Operating Temperature	0°C to 60°C

Planning a Large-Scale Build

At 17 slots, the chassis comfortably holds a processor, two or three communication modules covering different networks, a dozen or more I/O modules spanning digital and analog types, and a motion or safety module if the system calls for it. The planning discipline that matters most at this scale is backplane power budgeting — communication and motion modules draw disproportionately more 5V current than simple digital I/O, and a fully populated 17-slot chassis can approach the limits of even a high-capacity power supply if the module mix is heavy on those types. Tally the actual planned module list's current draw against the chosen power supply's rating before finalizing the build, rather than assuming any 1756 supply will handle a fully loaded chassis.

For systems anticipating further growth beyond 16 user modules, splitting into multiple chassis connected via EtherNet/IP remote I/O is the appropriate path — there's no larger single 1756 chassis beyond this size.

FAQ

Q: What's the largest power supply needed for a fully populated 1756-A17?

Sizing depends entirely on the specific module mix installed — sum each module's 5V and 24V backplane current draw and compare against available 1756 power supply ratings, selecting the highest-capacity unit that covers the total with reasonable margin.

Q: Can the 1756-A17 be split into a local and remote I/O configuration?

The chassis itself is a single physical unit — it can't be split. For distributing I/O across multiple physical locations, additional chassis connected via EtherNet/IP remote I/O communication modules is the standard approach.

Q: Is the 1756-A17 compatible with redundant controller configurations?

Yes, provided the installed modules and power supply are redundancy-qualified and the system follows the platform's redundancy design requirements — chassis size itself doesn't preclude redundancy, but module and firmware compatibility must be verified.

Q: Does a larger chassis introduce additional backplane communication latency?

No meaningful latency difference exists between chassis sizes in the 1756 family — backplane communication characteristics are consistent regardless of slot count; performance is governed by the modules and processor installed, not the chassis dimensions.

1756-A17 New Sealed 1756A17 17 Slots PLC Chassis Module