Purchase now: Allen-Bradley 1756-A4 ControlLogix Chassis
Purchase now: Atlantechdrives provides you the 1756-A4, an ultra-compact, industrial-grade 4-slot chassis engineered by Rockwell Automation for the highly advanced ControlLogix 1756 programmable automation controller (PAC) platform. Despite its remarkably small physical footprint, the 1756-A4 houses the exact same high-speed, multi-layer backplane printed circuit board as its massive 17-slot siblings. This enables ultra-fast data transfer and precise power distribution in deeply space-constrained environments. The 4-slot chassis is the absolute premier choice for specialized «edge» applications across industrial facilities. It is heavily deployed as a highly intelligent Remote I/O (RIO) drop panel, a dedicated communication routing gateway (e.g., bridging EtherNet/IP down to a legacy DH+ or ControlNet network), or as the main controller rack for localized, small-footprint OEM skid machinery (like a standalone industrial chiller, a specialized pumping station, or a robotic welding cell). Constructed from rugged extruded aluminum, it delivers phenomenal structural rigidity and superior EMI shielding in a miniature package.
Technical Specifications of the 1756-A4
The 1756-A4 features exactly 4 usable module slots, numbered from 0 to 3. The system power supply mounts on an independent extended rail on the far-left side of the chassis, meaning the power supply does not consume any of your 4 valuable expansion slots.
- Part Number: 1756-A4
- Platform: ControlLogix 1756 System
- Number of Available Slots: 4
- Mounting Type: Back-panel surface mount (horizontal orientation only)
- Backplane Current Capacity (1.2V DC): 1.5 A
- Backplane Current Capacity (3.3V DC): 4 A
- Backplane Current Capacity (5.1V DC): 15 A
- Backplane Current Capacity (24V DC): 2.8 A
Expert Tips: The Ultimate Network Gateway Architecture
While often used for small I/O drops, the true superpower of the 1756-A4 lies in communication architecture. Expert Tip: Large automotive and packaging plants often struggle with integrating disparate, legacy networks into their modern plant-wide EtherNet/IP infrastructure. The 1756-A4 is the perfect physical chassis to build a «Gateway Rack.» By populating this 4-slot rack with a 1756-EN2T (EtherNet/IP), a 1756-CN2 (ControlNet), a 1756-DHRIO (Data Highway Plus), and a 1756-DNB (DeviceNet) module, you create a localized, ultra-fast routing hub. The ControlLogix backplane acts as the universal translator between these modules without even requiring a main CPU (processor) in the rack. This incredibly efficient architecture allows older PLCs and drives to seamlessly pass data up to the modern SCADA system while occupying an incredibly small footprint inside a tight NEMA 12 or NEMA 4X wall-mounted enclosure.
Installation Advice: Orientation and Thermal Convection
Because the 1756-A4 is so physically small, automation engineers often mistakenly believe they can mount it vertically to save DIN-rail space inside a Motor Control Center (MCC) bucket or a tight machine guard panel. This is a fatal engineering error. Rockwell Automation strictly dictates that the 1756-A4 chassis must be mounted horizontally. The ControlLogix architecture relies entirely on passive thermal convection—heat naturally rising—to cool the microprocessors inside the modules. Vertical mounting forces the heat from the lower modules to wash directly over the upper modules, destroying the electronics. Furthermore, even in this small rack, if you only use 3 slots, you must install a 1756-N2 blank slot filler module in the empty slot to ensure proper cooling airflow and protect the gold backplane pins.
Frequently Asked Questions (FAQs)
Q: Can I install a full ControlLogix processor (like an L7 or L8) in this small 4-slot chassis?
A: Yes, absolutely. You can install a top-tier processor (like a 1756-L81E), a communication module, and two high-density I/O modules, creating a massively powerful, fully functional PAC system in a tiny physical space.
Q: Does the 1756-A4 require a special, smaller power supply?
A: No. The 1756-A4 utilizes the exact same standard ControlLogix power supplies (such as the 1756-PA72 or 1756-PB72) as the larger chassis. The power supply snaps securely onto the dedicated left-hand extension of the rack.
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This compact 4-slot chassis is ideal for localized control nodes requiring a 1756-CN2 ControlNet bridge.
