Description
Allen-Bradley 1797-PS2N2 | FLEX Ex Power Supply
Product Overview
The Allen-Bradley 1797-PS2N2 is a FLEX Ex power supply designed for hazardous-area control installations where ordinary 24 VDC distribution cannot be connected directly to intrinsically safe field circuits. It accepts a nominal 24 VDC input and provides four intrinsically safe DC output channels for FLEX Ex modules. Rockwell describes the unit as a 24 VDC-in, quad-Ex DC-out power supply housed in an explosion-proof enclosure, with 1-inch NPT conduit connections.
The engineering distinction is important: 1797-PS2N2 is not a conventional PLC power supply. Its purpose is to control the voltage and available energy delivered to intrinsically safe circuits. Each of its four outputs is rated at 8.5 W, while the documented entity parameters include output voltage UO below 9.5 V and output current IO below 1 A. The four output channels share a common +V line, and Rockwell specifically warns that the channels must not be interconnected because of intrinsic-safety requirements.
For a legacy Allen-Bradley FLEX Ex installation, the 1797-PS2N2 can be a critical infrastructure component because loss of its output can remove power from multiple hazardous-area modules simultaneously. Rockwell lists the product as discontinued effective December 31, 2017, with an engineering replacement category rather than a simple direct replacement designation. That makes exact application verification particularly important when maintaining an existing system.
Product Introduction
Hazardous-area power distribution is where a superficially similar 24 VDC supply can become the wrong component. The 1797-PS2N2 incorporates intrinsic-safety energy limitation rather than functioning as a general-purpose DC supply.
With four 8.5 W outputs and a documented 19–32 VDC input range, it was designed specifically around the FLEX Ex architecture. Its IP66 / NEMA 7B enclosure and hazardous-location certifications are part of the application, not optional packaging details.
Key Technical Specifications
| Parameter | Specification |
|---|---|
| Product Model | 1797-PS2N2 |
| Manufacturer / Brand | Allen-Bradley / Rockwell Automation |
| Product Type | FLEX Ex Power Supply |
| Series | FLEX Ex |
| Input Voltage | 19–32 VDC |
| Nominal Input | 24 VDC |
| Current Consumption | 3.1 A |
| Number of IS Outputs | 4 |
| Output Power | 8.5 W per output |
| Total Nominal Output Capacity | 34 W, based on 4 × 8.5 W outputs |
| Output Voltage UO | < 9.5 V |
| Output Current IO | < 1 A |
| Output Terminals | 10–17 |
| Input Terminals | 1, 2, 4, 5 |
| Input Connection | 1-inch NPT |
| Enclosure / Protection | IP66 / NEMA 7B |
| Operating Temperature | -20 to 70°C (-4 to 158°F) |
| Dimensions | Approximately 174 × 174 × 140 mm |
| Approx. Weight | 6.1 kg with packaging |
| Hazardous Location | Class I Division 1, Groups A–D; Class II Division 1, Groups E–G; Class III under UL/cUL; Class I Division 1 Groups B–D T4 under FM |
| Certification | UL/cUL and FM documentation applies; verify marking on the actual unit |
| Lifecycle | Discontinued December 31, 2017 |
The four outputs are individually rated at 8.5 W. Rockwell’s certification documentation also specifies entity parameters for intrinsically safe field-device connections, so the connected load and cable characteristics must be checked against the applicable installation certification.
1797-PS2N2
Major Features and Advantages
1. Designed for Intrinsically Safe Power Distribution
The central purpose of the 1797- is energy-limited power distribution for the FLEX Ex system. Rockwell states that the supply isolates the incoming power from the control system and limits available energy to intrinsically safe levels. That is fundamentally different from simply reducing 24 VDC to a lower voltage.
2. Four Independent 8.5 W Outputs
Each output can supply up to 8.5 W, giving the system four separately assigned power channels. FLEX Ex planning documentation uses this 8.5 W figure when determining how many modules can be connected to an individual output.
The practical limitation is straightforward: calculate the actual connected module load rather than assuming that all four outputs can be combined. Rockwell specifically states that the channels share a common +V line and must not be interconnected.
3. Hazardous-Area Enclosure
The 1797- uses an enclosure rated IP66 / NEMA 7B in the FLEX Ex selection documentation. Its hazardous-location application includes Class I Division 1 and Class II Division 1 environments under the applicable certification schemes.
This is a significant procurement point. Certification markings and entity parameters should be checked on the actual replacement unit before it enters a classified installation.
4. Defined Intrinsic-Safety Entity Parameters
For the output circuits, Rockwell documentation identifies parameters including UO < 9.5 V and IO < 1 A, along with allowable capacitance and inductance values that depend on the applicable gas/dust group. These parameters are part of the installation calculation and should not be replaced with generic “24 VDC output” descriptions.
5. Legacy FLEX Ex Maintenance Use
Rockwell officially lists the 1797- as discontinued, with a discontinuation date of December 31, 2017. This makes it a legacy maintenance item rather than a current-generation FLEX Ex procurement item.
For an operating plant, that changes the procurement approach. Part-number matching, certification status, enclosure condition, terminal integrity, and documented testing deserve more attention than they would for a current-production module.
Related Products
- 1797-PS1N — FLEX Ex 24 VDC input / quad-Ex DC output power supply with a different physical and system configuration.
- 1797-PS1E — FLEX Ex increased-safety power supply variant; not a direct substitute merely because the catalog numbers are similar.
- 1797-PS2E2 — FLEX Ex increased-safety version of the PS2 family; certification and protection concept differ from .
- 1797-IE8 — FLEX Ex analog input module used for hazardous-area signal acquisition.
- 1797-IR8 — FLEX Ex resistance/temperature input module for applicable field measurement applications.
- 1797-OB4D — FLEX Ex digital output module for hazardous-area applications.
- 1797-IBN8 — FLEX Ex digital input module for hazardous-area signal interfaces.
- 1794-FLEX I/O — Related Allen-Bradley FLEX I/O family; standard FLEX I/O and FLEX Ex components should not be treated as interchangeable without checking hazardous-area requirements.
FAQ
What is the Allen-Bradley 1797- used for?
It supplies intrinsically safe DC power to FLEX Ex modules in hazardous-area applications. It is specifically designed for the FLEX Ex architecture rather than serving as a general PLC power supply.
Is the 1797- a 24 VDC output power supply?
Not in the normal sense. Its input is 19–32 VDC, nominally 24 VDC, but its four intrinsically safe outputs have a documented UO of less than 9.5 V. The output is energy-limited for intrinsically safe circuits.
How much power can each output provide?
Each of the four outputs is rated at 8.5 W. The connected FLEX Ex modules must be evaluated against that individual output limit.
Can I connect the four outputs together to obtain more power?
No. Rockwell specifically warns that the output channels are electrically connected through a common +V line and that the lines must not be interconnected because of intrinsic-safety requirements.
Can I hot-swap the 1797-?
Do not assume hot swapping is permitted. This is a hazardous-area power supply with specific enclosure, intrinsic-safety, and de-energization requirements. Rockwell’s documentation also instructs personnel to wait 15 minutes after disconnecting power before opening the enclosure. Follow the site’s approved hazardous-area maintenance procedure.
Can I replace an older 1797-PS2N with a 1797-?
This requires engineering verification. Rockwell explicitly warns that entity parameters changed when replacing a 1797-PS2N with a 1797-, so the intrinsic-safety entity calculations must be re-verified rather than treating the change as a simple drop-in replacement.
Does the 1797- still have an active manufacturer lifecycle?
No. Rockwell Automation lists the 1797- as Discontinued, with a discontinuation date of December 31, 2017, and identifies the replacement category as “Engineering Replacement.”
How should I verify a New Surplus 1797-?
Confirm the complete catalog number, certification markings, enclosure condition, NPT connections, terminal condition, nameplate information, and any available functional-test documentation. For hazardous-area equipment, a visually clean unit is not enough. The certification and entity-parameter information must correspond to the intended installation. Supplier warranty terms should also be confirmed before purchase.
Procurement Note
The 1797- should be purchased as a hazardous-area certified power component, not simply as a 24 VDC supply. Rockwell’s documentation gives specific intrinsic-safety entity parameters and explicitly warns that the parameters changed from the earlier 1797-PS2N version. Verify the installed FLEX Ex architecture, field-device entity calculations, certification marking, and output loading before approving a replacement.
