Description
Allen-Bradley 1797-PS2E2
Product Introduction
In a hazardous-area FLEX Ex installation, the power supply is part of the protection concept—not simply a source of 24 VDC. The Allen-Bradley 1797-PS2E2 is a FLEX Ex power supply designed to accept 24 VDC input and provide four independent intrinsically safe power outputs for compatible FLEX Ex I/O equipment. Each output is rated at 8.5 W, giving the installer four separately distributed power paths rather than one common field supply.
The 1797-PS2E2 accepts 18–32 VDC and has an input power rating of approximately 55 W. Its documented intrinsic-safety parameters include U₀ below 9.5 V and I₀ below 1 A, with specified capacitance and inductance limits for the IIC application group. This is legacy equipment—Rockwell lists the product as discontinued—so replacement work should include the exact hazardous-area certification, output loading, wiring arrangement, and enclosure requirements rather than treating it as an ordinary FLEX power supply.
Key Technical Specifications
| Parameter | Specification |
|---|---|
| Product Model | 1797-PS2E2 |
| Manufacturer | Allen-Bradley / Rockwell Automation |
| Product Family | FLEX Ex / Bulletin 1797 |
| Product Type | Intrinsically safe FLEX Ex power supply |
| Nominal Input | 24 VDC |
| Input Voltage Range | 18–32 VDC |
| Input Terminals | 1, 2, 4, 5 |
| Current Consumption | Approximately 3.1–1.6 A |
| Input Ripple | 5% AC |
| Input Power | 55 W |
| Number of Outputs | 4 |
| Output Terminals | 10–17 |
| Output Power | 4 × 8.5 W |
| Intrinsic-Safe Output Voltage U₀ | <9.5 V |
| Intrinsic-Safe Output Current I₀ | <1 A |
| C₀, IIC | <500 nF |
| L₀, IIC | <8 µH |
| Maximum Output Cable Resistance | <0.1 Ω, both directions |
| Power Dissipation | 21 W |
| Thermal Dissipation | Approximately 71.67 BTU/hr |
| Operating Temperature | -20 to +70°C |
| Dimensions | Approximately 140 × 174 × 280 mm |
| Weight | Approximately 7.7 kg |
| Protection | IP65 / NEMA 7B in the installation documentation |
| Hazardous-Area Application | Zone 1 / Zone 22 |
| Certification Reference | DMT 02 ATEX E253 X |
| Lifecycle | Discontinued |
Rockwell’s installation documentation gives the detailed electrical values above. Some older FLEX Ex selection literature presents slightly different enclosure dimensions/weight figures depending on the publication and configuration context, so the current installation manual should take precedence for a replacement installation.
1797-PS2E2
Application Scenarios & Pain Points
A common mistake during FLEX Ex maintenance is to size the power supply by total module count. That is not how the 1797-PS2E2 should be evaluated. Each of its four outputs has an 8.5 W limit, and modules connected to an individual output must remain within that allocation.
- Hazardous-area FLEX Ex I/O: Provides intrinsically safe power distribution for compatible Bulletin 1797 FLEX Ex modules.
- Zone 1 installations: The unit is designed for hazardous-area applications where the power interface must satisfy the applicable Ex protection concept.
- Distributed process instrumentation: Four separate outputs allow FLEX Ex I/O loads to be distributed closer to the controlled equipment.
- Legacy DCS/PLC remote I/O: Useful when maintaining an existing Allen-Bradley FLEX Ex architecture without replacing the complete remote-I/O installation.
Field note: Before replacing one of these supplies, map every connected module to its specific output. A replacement may have the correct catalog number and still be unsuitable if one output is carrying more than its permitted 8.5 W load.
Related Products
- 1797-PS2N2 — Related FLEX Ex power supply using a different hazardous-area installation arrangement; it should not be substituted solely on the basis of output capacity.
- 1797-PS1E — FLEX Ex power-supply family member with a different input-voltage arrangement.
- 1797-PS1N — Related FLEX Ex power supply for the North American-certified installation configuration.
- 1797-ACNR15 — FLEX Ex ControlNet adapter used for network communication rather than power distribution.
- 1797-IBN16 — FLEX Ex digital input module; typically powered from the FLEX Ex power-distribution architecture.
- 1797-OBN8 — FLEX Ex digital output module in the same general I/O family.
- 1797-IRT8 — FLEX Ex thermocouple input module.
- 1797-IE8 — FLEX Ex analog input module.
The 1797-PS2E2 should be matched to the specific FLEX Ex hazardous-area architecture. The related PS1/PS2 and E/N variants can differ in input arrangement, enclosure configuration, and certification details.
Engineer’s Guide — Field Pitfalls to Avoid
Pitfall 1: Treating it as a standard 24 VDC power supply
The 1797- is specifically an intrinsically safe FLEX Ex power supply. Its output characteristics and hazardous-area certification are integral to its intended application.
Avoidance: Match the Ex certification and system architecture before considering any substitute.
Pitfall 2: Exceeding the 8.5 W limit on an output
Each of the four outputs is rated at 8.5 W. The total supply rating does not mean 34 W can be arbitrarily concentrated onto one output.
Avoidance: Calculate the load on each output separately and leave practical operating margin.
Pitfall 3: Mixing intrinsically safe wiring
The output terminals are part of the intrinsic-safety interface. Wiring them as ordinary control-power circuits can compromise the intended protection concept.
Avoidance: Follow the approved terminal arrangement and hazardous-area wiring rules for the installed system. Rockwell documentation identifies terminals 10–17 as the four output pairs.
Pitfall 4: Ignoring the long-discontinued lifecycle
Rockwell officially lists the 1797- as discontinued as of December 31, 2017.
Avoidance: When purchasing legacy inventory, record the exact catalog number, series/revision, nameplate information, enclosure condition, certification markings, and test history.
Pitfall 5: Opening the enclosure immediately after shutdown
The certification documentation specifically warns that the unit should remain closed for a specified discharge period after power has been applied; the referenced documentation states 15 minutes after disconnecting before opening the cover.
Avoidance: Follow the manufacturer’s hazardous-area maintenance procedure rather than treating the unit like a standard low-voltage DIN-rail supply.
FAQ
What is the Allen-Bradley 1797-?
It is a FLEX Ex intrinsically safe power supply from the Allen-Bradley Bulletin 1797 family. It converts a 24 VDC input into four independent intrinsically safe power outputs for compatible FLEX Ex I/O equipment.
What input voltage does the 1797- require?
The nominal input is 24 VDC, with a documented operating range of 18–32 VDC. Current consumption is approximately 3.1–1.6 A across the specified input range.
How many outputs does the 1797- provide?
It provides four independent outputs, with each output rated at 8.5 W. The output terminals are 10 through 17, arranged as four +V/-V pairs.
Can I use a standard 24 VDC supply instead?
Not as a direct replacement. The 1797- provides specific intrinsic-safety characteristics, including U₀, I₀, C₀, and L₀ limits. A conventional 24 VDC supply does not automatically provide the same hazardous-area protection characteristics.
Is the 1797- still manufactured?
Rockwell Automation lists the 1797- as discontinued, with a discontinuation date of December 31, 2017.
What should I check when buying a replacement?
Verify the complete catalog number, series/revision, certification markings, enclosure condition, terminal arrangement, output loading, and hazardous-area application. For used or surplus equipment, actual-unit photographs and inspection records are worth requesting.
Is 1797- interchangeable with 1797-PS2N2?
Not automatically. They are related FLEX Ex power supplies, but the E/N designation corresponds to different installation/certification arrangements. The installed hazardous-area requirements should determine the acceptable replacement, not simply the nominal voltage and output count.
