Honeywell XNX-AMAV-RNNNN: Ordering Code Explained and Three-Relay Output Configuration Guide

Honeywell XNX-AMAV-RNNNN is a configurable model within the XNX Universal Transmitter product family. Engineers frequently encounter questions about its ordering code, relay functionality, and sensor compatibility.

The most important distinction concerns the letter R and the four trailing N characters. These characters represent separate configuration fields rather than a relay channel count.

The R identifies the optional relay interface. The following N identifies the local HART configuration, while the final NNN identifies the MPD sensor and range selection.

Therefore, XNX-AMAV-RNNNN specifies a relay-equipped transmitter without factory-installed local HART or an included MPD sensor configuration. The relay option provides three independent Form C contacts for alarm and fault indication.

This distinction matters during equipment selection, replacement, commissioning, and integration with PLC or DCS control systems. An incorrect interpretation can result in missing alarm contacts, incompatible communication options, or an unsuitable sensor configuration.

This technical guide examines the complete ordering code, relay board architecture, electrical specifications, communication interfaces, installation requirements, and practical maintenance considerations. It also explains how engineers should verify the configuration before purchasing or commissioning an XNX transmitter.

1. Core Value: Why the XNX-AMAV-RNNNN Configuration Matters

The Honeywell XNX Universal Transmitter provides a flexible platform for industrial gas detection applications. It supports different sensor technologies, enclosure arrangements, communication options, and output configurations.

The XNX-AMAV-RNNNN configuration combines an aluminum enclosure, an mV sensor personality, and an optional three-relay interface. It also supports the standard analog measurement architecture used for industrial control integration.

Its main advantage lies in combining continuous gas concentration monitoring with independent hardwired alarm and fault signals. This arrangement allows engineers to connect the transmitter to PLC input modules, DCS systems, alarm panels, and external control equipment.

For example, a gas detection system may use the 4–20 mA signal to communicate measured concentration. Meanwhile, the relay contacts can provide separate alarm and fault indications.

This separation helps control engineers design different responses for warning conditions, high gas concentrations, and detector faults. However, the actual alarm assignments depend on the transmitter configuration and commissioning settings.

In our view, the most important purchasing consideration involves the complete interface configuration. Engineers should evaluate sensor compatibility, relay requirements, communication options, and hazardous-area approvals together.

Ordering a transmitter based only on its enclosure or sensor personality can create problems during installation. A correct ordering code should match the electrical design and the intended gas detection application.

2. Complete Honeywell XNX-AMAV-RNNNN Ordering Code Breakdown

Honeywell uses a structured identification system to describe the XNX transmitter configuration. Each character represents a specific hardware, certification, sensor, or interface selection.

The model XNX-AMAV-RNNNN contains the following configuration fields:

• XNX: Honeywell XNX Universal Transmitter product family.
• AM: ATEX/IEC approval configuration with M25 cable entries.
• A: Aluminum enclosure construction.
• V: Millivolt sensor personality.
• R: Optional relay interface.
• N: No factory-installed local HART option.
• NNN: No factory-configured MPD sensor and range selection.

The complete suffix therefore represents several independent selections. It does not describe four relays or four separate output channels.

Honeywell’s XNX Technical Manual, Revision 15, explains this structure in its Product Identification section. The manual also distinguishes the interface option, local HART option, and MPD sensor selection.

3. Understanding the AM Enclosure and Certification Code

The first two characters after XNX identify the enclosure approval and cable-entry arrangement. In this model, AM represents an ATEX/IEC configuration with M25 cable entries.

This selection matters because industrial gas detectors often operate in classified hazardous areas. The transmitter must satisfy the installation area’s applicable equipment protection requirements.

The M25 designation identifies the relevant cable-entry thread arrangement. It does not independently confirm that every installed cable gland, stopping plug, or sensor accessory meets the required certification.

During procurement, engineers should verify the complete equipment certification and the approved accessories. The installation must also follow the manufacturer’s instructions for cable entries, grounding, and enclosure assembly.

Do not assume that an ATEX/IEC marking automatically establishes suitability for every hazardous location. Confirm the protection concept, gas group, temperature class, ambient limits, and installation requirements against the equipment nameplate.

4. Understanding the Aluminum Enclosure and mV Sensor Personality

The third character, A, identifies the aluminum enclosure option. Honeywell uses this configuration for installations requiring its specified aluminum housing arrangement.

The fourth character, V, identifies the millivolt sensor personality. This interface supports compatible millivolt-based sensor arrangements, including applicable MPD sensor configurations.

The sensor personality determines the transmitter’s measurement interface. It should not be confused with the actual sensor element or the target gas measurement range.

For example, an mV personality does not mean that every catalytic or infrared detector can connect directly. Engineers must verify the sensor’s electrical interface, supported model, calibration requirements, and certification.

The distinction becomes especially important when replacing older gas detection equipment. A transmitter with the correct enclosure may still have an incompatible sensor personality.

Before purchasing, identify the existing sensor type and compare it with Honeywell’s approved configuration information. This prevents incorrect assumptions based on product-family compatibility alone.

5. What Does R Mean in XNX-AMAV-RNNNN?

The letter R identifies the optional XNX relay interface. This option provides three Form C, single-pole double-throw contacts for alarm and fault signaling.

Each relay provides three electrical connection points. These include Common, Normally Open, and Normally Closed terminals.

The three contacts allow engineers to select the appropriate switching arrangement for the connected control circuit. A PLC digital input, alarm panel, or external relay interface can monitor the selected contact state.

The relay option supports the following general functions:

• Relay 1: Alarm Level 1 indication.
• Relay 2: Alarm Level 2 indication.
• Relay 3: Fault and special operating-state indication.

These assignments provide a practical structure for separating gas alarm conditions from equipment faults. However, engineers must verify the actual configuration and alarm settings during commissioning.

The R designation confirms the ordered relay option. For second-hand equipment or repaired units, procurement teams should still inspect the actual hardware and terminal arrangement.

A model label alone cannot prove that the relay board remains installed and operational. Physical inspection and functional testing provide stronger evidence.

6. What Does NNNN Mean? Understanding the Four Trailing Characters

The four N characters following R represent two separate ordering fields. Engineers should divide them according to the manufacturer’s ordering structure.

The first N represents the local HART option. The final three characters represent the MPD sensor and range configuration.

First N: Local HART Configuration

N indicates that the transmitter does not include the factory-installed local HART option. The local HART interface provides a separate maintenance and configuration access arrangement.

However, this does not automatically remove HART communication from the standard 4–20 mA output. Engineers must distinguish the local HART interface from HART communication over the analog current loop.

Final NNN: MPD Sensor and Range Configuration

NNN indicates that the ordering code does not specify a factory-configured MPD sensor and its associated range. Therefore, buyers should not assume that a complete sensing element accompanies this transmitter configuration.

Where a project requires a particular MPD sensor, engineers must select the correct sensor configuration separately or specify the appropriate complete ordering code.

The following table summarizes the model structure.

This breakdown helps purchasing teams distinguish transmitter options from sensor accessories. It also provides a consistent reference for engineering documentation and spare-parts identification.

7. Three SPDT Relay Outputs: Electrical Structure and Applications

The XNX relay option provides three independent Form C contacts. Each contact operates as a single-pole double-throw switching arrangement.

Form C contacts provide both normally open and normally closed connection choices. Engineers can select the required contact according to the external control circuit design.

The relay terminal arrangement uses TB3. The remote reset connection uses TB4.

Each relay provides the following terminals:

• COM: Common connection.
• NO: Normally Open contact.
• NC: Normally Closed contact.

The three relays support different alarm and diagnostic functions. Their allocation helps separate gas concentration events from detector operating faults.

For example, a gas detection system in a compressor building may use Relay 1 for an early warning. Relay 2 may report a higher concentration alarm, while Relay 3 monitors detector faults.

The actual control actions depend on the site’s cause-and-effect matrix. Engineers must not assume that a particular relay automatically performs an emergency shutdown function.

8. Relay Contact Ratings and Electrical Design Considerations

Honeywell specifies the following relay contact ratings for the XNX relay option:

• AC rating: 250 VAC, 5 A.
• DC rating: 24 VDC, 5 A.
• Contact arrangement: Three independent Form C contacts.

These ratings define the specified contact limits, not a universal recommendation for every connected load. Engineers must also consider load characteristics, switching frequency, inrush current, and applicable electrical requirements.

Inductive loads such as contactor coils can produce voltage transients during switching. Suitable suppression components may therefore be necessary within the external circuit design.

For PLC integration, engineers commonly use the relay contacts as dry-contact signals. The PLC input circuit supplies its own sensing voltage, while the transmitter relay changes the contact state.

However, the external circuit must remain within the specified contact ratings. Verify the voltage, current, load type, and isolation requirements before connecting field wiring.

Never apply an external supply to a terminal without checking the official wiring diagram. Incorrect wiring can damage equipment or create hazardous conditions.

9. Fault Relay Operation and Fail-Safe Monitoring

The fault relay deserves special attention because it provides information about the detector’s operating condition. Honeywell recommends using the fault relay in installations to support reliable fault monitoring.

Under normal operating conditions, the fault relay remains energized. When the transmitter experiences a fault or loses power, the relay de-energizes.

In this condition, the documented C-NO connection opens. This behavior allows the external control system to detect certain failures through a change in contact state.

Engineers should incorporate this behavior into the PLC or DCS alarm design. The external logic must distinguish a healthy energized condition from a de-energized fault condition.

For example, a control system can monitor the normally closed or normally open contact according to the documented wiring arrangement. The selected logic should provide an unambiguous fault indication.

During commissioning, verify the actual contact state under normal operation and approved simulated fault conditions. Do not rely on assumed contact behavior from a generic relay symbol.

Also review how the PLC input behaves during a broken field cable or loss of external input power. A reliable fault-monitoring design should consider the complete circuit rather than only the transmitter relay.

10. Relay Refresh Time and Remote Reset Function

Honeywell documentation identifies a relay-state refresh interval of approximately two seconds. Engineers should consider this behavior when designing control sequences that require relay status monitoring.

This timing does not represent a universal guarantee for every external PLC response. The total system response also depends on transmitter processing, contact operation, wiring, and controller input filtering.

The XNX relay option also provides a remote reset connection through TB4. This input allows an external momentary contact to initiate the supported remote reset function.

Typical applications include resetting a latched alarm after personnel investigate the event. However, the reset command does not replace the underlying safety response or confirm that the hazardous condition has disappeared.

Before using remote reset, engineers should verify the control philosophy and applicable alarm management requirements. The external reset circuit should not create an unsafe automatic restart or suppress an active hazard indication.

Separate relay signal wiring from remote reset wiring as instructed by the manufacturer. Correct cable routing helps reduce electrical interference and improves installation quality.

11. Understanding 4–20 mA and HART Communication

The XNX transmitter uses an analog current output for gas concentration monitoring and integration with industrial control systems. A PLC or DCS analog input can receive the current signal and scale it according to the configured measurement range.

The 4–20 mA signal and relay contacts serve different purposes. The analog output communicates measurement information, while the relays provide discrete alarm and fault states.

This arrangement offers useful flexibility in gas detection system design.

• 4 mA: Represents the configured lower measurement reference under normal measurement conditions.
• 20 mA: Represents the configured upper measurement reference under normal measurement conditions.
• Intermediate current: Represents measurement values across the configured range.
• HART: Provides supported digital communication over the analog current loop.
• Relay outputs: Provide separate hardwired alarm and fault indications.

The exact output mapping and fault-current behavior depend on the transmitter configuration. Engineers should verify these settings against the applicable manual and commissioning records.

An important purchasing distinction concerns the N code after R. It indicates the absence of the local HART option, not necessarily the absence of HART communication over the 4–20 mA loop.

This distinction matters when maintenance teams plan configuration access. They should confirm the available communication method and required tools before installation.

12. Sensor Personality V and MPD Sensor Compatibility

The V personality identifies the millivolt sensor interface. It supports applicable MPD sensor configurations within the XNX product architecture.

However, the personality code does not identify one specific sensor type. Engineers must also verify the sensor model, target gas, measuring range, mechanical connection, and certification.

Honeywell’s ordering information identifies several MPD sensor selections:

These codes describe defined configurations rather than universally interchangeable sensor elements. The exact range and approval depend on the selected sensor and product documentation.

For example, a catalytic bead sensor and an infrared methane sensor use different measurement principles. Their calibration procedures, environmental limitations, and application suitability also differ.

Engineers should identify the target gas and required measurement range before selecting the sensor. They should also verify the sensor’s approval status for the installation area.

13. Relay, Modbus, and FOUNDATION Fieldbus Compatibility

The XNX transmitter offers several optional interface configurations. These include the relay option, Modbus interface, and FOUNDATION Fieldbus interface.

However, Honeywell identifies the relay option as incompatible with the Modbus and FOUNDATION Fieldbus options. These selections are mutually exclusive within the specified interface configuration.

This limitation directly affects purchasing and system architecture. A project requiring three hardwired relay outputs cannot simply assume that it can also install the optional Modbus or FOUNDATION Fieldbus interface.

Compare the available configurations before finalizing the order.

Engineers should select the interface according to the control-system architecture. If the PLC or DCS requires three physical relay signals, the R configuration may suit the application.

If the project requires Modbus or FOUNDATION Fieldbus, select the corresponding interface configuration instead. Do not assume that the transmitter can accommodate mutually exclusive options simultaneously.

14. Installation Guide: Inspecting the Relay Option Board

Correct installation begins with confirmation of the ordered configuration. The transmitter label, installed option board, and terminal arrangement should match the project documentation.

For repaired or previously installed equipment, verify the actual board rather than relying only on the external model label.

Follow this general inspection sequence:

1. Confirm the complete XNX model and serial identification.
2. Review the approved wiring diagram and relay configuration.
3. Isolate external electrical supplies according to site procedures.
4. Open the enclosure using the manufacturer’s approved procedure.
5. Verify the relay board and associated terminal arrangement.
6. Inspect wiring, terminals, cable entries, and visible component condition.
7. Check that the installation follows the specified enclosure and grounding requirements.
8. Close the enclosure correctly before restoring the equipment to service.

Honeywell identifies TB3 as the relay wiring terminal block. TB4 provides the remote reset connection.

Relay wiring enters through an available cable or conduit port. Select the port according to the transmitter’s cable-entry requirements and approved installation arrangement.

Do not use the same cable or conduit port for relay reset and relay signal wiring where the manual prohibits this arrangement. Follow the manufacturer’s routing guidance to reduce electrical noise.

All installation work in hazardous areas requires appropriate authorization and safety precautions. Disconnect external supplies before servicing the relay terminals.

15. Commissioning Procedure: Testing All Three Relay Outputs

Relay testing should form part of the commissioning process. It verifies the complete path from transmitter logic to the external control-system input.

Honeywell provides Test Menu functions for relay forcing and alarm or fault simulation. Engineers can use these functions to test connected warning devices and control-system inputs.

Before testing, establish an approved commissioning plan. Identify affected alarms, bypass requirements, external loads, and personnel responsible for restoring normal operation.

Step 1: Verify the initial relay state.

Confirm that the transmitter operates normally and record the current contact conditions. Compare the actual states with the documented wiring diagram.

Step 2: Test Alarm Level 1.

Use the appropriate approved test function to activate the first alarm relay. Confirm that the corresponding PLC or DCS input changes correctly.

Step 3: Test Alarm Level 2.

Repeat the procedure for the second relay. Verify that the external alarm logic identifies the correct alarm level.

Step 4: Test the Fault Relay.

Use an approved fault simulation to confirm the expected fault indication. Check the relay contact state and the corresponding controller input.

Step 5: Verify remote reset.

Test the TB4 remote reset input according to the manufacturer’s instructions. Confirm that the intended reset behavior occurs without suppressing an active hazard condition.

Step 6: Restore normal operation.

Exit the test functions and confirm that all relay states return to their configured operating conditions. Remove approved bypasses and document the final results.

Honeywell warns that relay conditions forced through the Test Menu return to normal operating settings after exiting the menu. Therefore, technicians must verify the final operating state.

Never treat a successful simulated test as proof of complete gas detection performance. Sensor calibration, response testing, alarm settings, and the full cause-and-effect sequence require separate verification.

16. PLC and DCS Integration: Designing Reliable Gas Alarm Signals

The XNX-AMAV-RNNNN can support different control-system integration strategies. Engineers may use the analog output for continuous measurement and the relay contacts for independent discrete indications.

A typical PLC or DCS arrangement includes one analog input and several digital input channels. The analog channel monitors gas concentration, while the digital channels monitor alarm and fault conditions.

For example, a compressor station may use the following arrangement:

• Analog input: Monitors the configured gas concentration signal.
• Digital input 1: Receives Alarm Level 1 status.
• Digital input 2: Receives Alarm Level 2 status.
• Digital input 3: Receives detector fault status.

The control system can then display measurement trends and separate alarm messages. Operators can distinguish an increasing gas concentration from a detector malfunction.

However, the final control philosophy must come from the site’s approved cause-and-effect documentation. Engineers should define alarm priorities, latching behavior, reset conditions, and any required shutdown actions.

Do not assume that a gas detector relay alone provides a complete safety instrumented function. Where a safety instrumented system requires a certified safety function, the entire loop must satisfy the relevant design and verification requirements.

17. Practical Application Scenario: Gas Detection in a Natural Gas Compressor Building

Consider a natural gas compressor building that requires continuous combustible gas monitoring. The engineering team selects an XNX transmitter with a compatible MPD sensor and three relay outputs.

The transmitter sends its analog measurement signal to the DCS. The control system uses this information for concentration display, historical trending, and configured alarm processing.

The relay contacts provide additional hardwired signals. Relay 1 indicates the first alarm level, while Relay 2 indicates the second alarm level.

Relay 3 reports detector faults and relevant special operating states. The DCS uses this signal to distinguish a measurement-system problem from an actual gas concentration alarm.

During commissioning, engineers verify the sensor response, analog scaling, relay contact states, and remote reset function. They also check the external alarm circuits against the approved cause-and-effect matrix.

If the detector reports a fault, the control system generates a separate maintenance alarm. This helps operators identify unavailable detection coverage and initiate the required response.

This example illustrates a possible system architecture rather than a guaranteed factory configuration. Actual alarm thresholds, relay assignments, and shutdown actions depend on project engineering.

18. Hazardous-Area Certification and International Standards

Gas detection equipment frequently operates in hazardous areas where flammable gases or vapors may create an ignition risk. Equipment selection must therefore consider the complete installation environment.

The AM configuration identifies an ATEX/IEC arrangement with M25 entries. However, this code alone does not establish the suitability of every sensor, gland, stopping plug, or accessory.

Engineers should verify the applicable certification documents and installation requirements. These include the protection method, gas group, temperature classification, ambient operating range, and equipment marking.

The IEC 60079 series addresses different aspects of equipment and installations in explosive atmospheres. Relevant parts include equipment selection, installation, inspection, and maintenance.

For example, IEC 60079-14 addresses electrical installations design, selection, and erection in explosive atmospheres. IEC 60079-17 addresses inspection and maintenance of electrical installations in explosive atmospheres.

These standards support engineering assessment, but the applicable edition and local regulatory requirements must also be checked. The manufacturer’s certification documentation remains essential for the specific XNX configuration.

For systems with safety-related gas detection functions, engineers should also review the relevant functional safety requirements. IEC 61508 and IEC 61511 may apply depending on the system architecture and safety function.

Do not assume that a transmitter with an approved enclosure automatically establishes the safety integrity of the complete gas detection loop. Sensor, transmitter, logic solver, final element, and testing requirements must be assessed together.

19. Industry Perspective: Why Gas Detection Reliability Matters

Oil and gas facilities require effective leak detection, alarm management, and equipment maintenance. Gas detection systems support personnel protection and help operators identify abnormal conditions before they escalate.

The International Energy Agency’s Global Methane Tracker 2025 estimated that fossil fuel operations released more than 120 million tonnes of methane annually. The report also identified significant opportunities to reduce emissions through existing technologies and operational improvements.

The IEA’s findings demonstrate the importance of monitoring and managing methane emissions across the energy sector. However, these emission statistics do not represent gas detector failure rates or prove the effectiveness of any individual transmitter.

From an engineering perspective, reliable gas detection requires more than selecting a transmitter with the correct sensor interface. The complete installation needs suitable detector placement, correct calibration, verified alarm settings, reliable power, and tested output circuits.

As industrial facilities adopt more integrated monitoring systems, hardwired relay outputs and digital communication serve different operational purposes. Engineers should select the architecture according to availability, diagnostic requirements, and the site’s safety philosophy.

20. Troubleshooting Common Relay and Communication Problems

Even correctly selected equipment can experience installation or configuration problems. A systematic approach helps technicians separate hardware faults from wiring and application issues.

Problem 1: Relay output does not change during an alarm.

Check the configured alarm threshold, relay assignment, operating state, and test procedure. Then inspect the TB3 wiring and confirm that the external circuit uses the intended COM, NO, and NC terminals.

Problem 2: PLC input remains unchanged.

Verify the PLC input supply, field wiring, input configuration, and relay contact state. Check whether the selected contact changes under the approved test condition.

Problem 3: Fault relay reports an abnormal condition.

Inspect the transmitter’s diagnostic information and operating status. Verify power supply conditions and confirm that the external circuit interprets the de-energized fault state correctly.

Problem 4: HART communication cannot connect.

Distinguish local HART access from HART communication over the 4–20 mA loop. Check the available interface, communication tool, wiring, and applicable loop requirements.

Problem 5: The selected transmitter cannot communicate through Modbus.

Review the ordering code and installed interface board. The R relay option cannot be treated as interchangeable with the optional Modbus interface.

Problem 6: A replacement transmitter does not match the original system.

Compare the complete ordering codes, sensor personality, relay configuration, cable-entry type, and certification. Confirm the terminal wiring and application settings before returning the equipment to service.

These checks should follow the manufacturer’s service procedures. Do not open or modify hazardous-area equipment without appropriate isolation and authorization.

21. Purchasing Guide: How to Verify an XNX-AMAV-RNNNN Before Ordering

Industrial procurement teams should verify the complete transmitter configuration before placing an order. Similar model references can represent different sensor, enclosure, or interface arrangements.

Use the following checklist when requesting quotations or evaluating replacement equipment.

• Full model: Confirm XNX-AMAV-RNNNN or the exact required alternative.
• Enclosure approval: Verify the ATEX/IEC configuration and M25 cable entries.
• Housing material: Confirm the aluminum enclosure requirement.
• Sensor personality: Verify that the mV personality matches the installed sensor technology.
• Relay option: Confirm the three-relay interface and actual board availability.
• Local HART: Determine whether local HART access is required.
• Sensor package: Confirm whether an MPD sensor and measuring range must accompany the transmitter.
• Communication: Check whether the project requires relays, Modbus, or FOUNDATION Fieldbus.
• Certification: Verify the complete assembly and accessory approvals.
• Documentation: Request applicable manuals, wiring information, and product identification details.

For replacement applications, compare the old and proposed model codes character by character. Do not assume that two transmitters with the same enclosure and personality provide identical output functionality.

Where the existing installation uses three hardwired relay signals, replacing an R configuration with an N configuration may remove those interfaces. The control system could then require additional interface hardware or a revised engineering design.

Correct ordering information reduces the risk of commissioning delays and unnecessary modification work.

22. Author’s Engineering Perspective: Choose the Complete Interface Architecture

Gas detector selection should begin with the required measurement function and system architecture. Engineers should identify the target gas, sensor technology, measuring range, and environmental conditions first.

Next, define how the detector communicates with the control system. A 4–20 mA loop supports continuous measurement, while relay contacts provide independent discrete signals.

Digital fieldbus options may simplify some integration arrangements. However, they do not automatically replace the need for independent hardwired alarms or other project-specific interfaces.

The XNX ordering structure makes these choices explicit. The R option provides relay functionality, while M and F identify different communication interfaces.

Our recommendation is to finalize the control philosophy before selecting the transmitter option. This avoids purchasing an interface combination that cannot satisfy the approved system design.

Maintenance teams should also preserve the original configuration records. These records simplify future replacements and help prevent incompatible spare-parts selection.

23. Oiltech Controls Limited: Industrial Gas Detection and Automation Components

Reliable gas detection depends on correct product selection, compatible components, and accurate configuration information. Industrial maintenance teams need to consider the complete detector assembly rather than the transmitter reference alone.

Oiltech Controls Limited provides an online resource for industrial automation components and spare-parts inquiries. Our website supports purchasing teams and maintenance engineers researching equipment for industrial control applications.

If you are sourcing a Honeywell XNX-AMAV-RNNNN, provide the complete model reference and required interface configuration. Include the sensor type, measuring range, enclosure requirements, and existing wiring details where available.

These details help clarify the required equipment configuration and identify potential compatibility questions. They also reduce confusion between relay-equipped transmitters and models with alternative communication options.

Visit Oiltech Controls Limited to explore industrial automation components and submit an inquiry about your gas detection equipment requirements.

Frequently Asked Questions

FAQ 1: Can I install a relay option board in an existing XNX transmitter that originally had no relay option?

Do not assume that every XNX transmitter supports a straightforward field retrofit. Honeywell provides specific configuration and retrofit guidance for relay installations.

Before planning an upgrade, verify the original model, installed interface options, internal hardware compatibility, and required certification conditions. Also check whether the existing transmitter already uses Modbus or FOUNDATION Fieldbus.

These communication options conflict with the relay option in the documented configuration. An authorized service provider should confirm whether the proposed retrofit is technically and commercially supported.

FAQ 2: Why does the fault relay change state when the transmitter loses power?

The XNX fault relay normally remains energized during healthy operation. A power failure or relevant fault causes the relay to de-energize, opening the documented C-NO connection.

This arrangement helps external control systems recognize certain detector failures. During commissioning, verify the actual contact state and confirm the PLC or DCS alarm logic.

Also consider cable breaks and loss of external input power. A complete monitoring circuit should identify these conditions according to the site’s fault-handling philosophy.

FAQ 3: What should engineers verify when replacing an XNX transmitter in an existing gas detection system?

Start by comparing the full ordering code and the existing nameplate information. Check the sensor personality, target gas, measuring range, cable-entry configuration, and hazardous-area certification.

Next, compare the relay board, analog output settings, communication interface, and terminal wiring. Confirm that the replacement supports the existing control-system architecture.

After installation, verify the sensor response, analog scaling, alarm thresholds, relay functions, fault indication, and remote reset behavior. Complete the required commissioning tests before restoring the system to normal service.

Conclusion: Correctly Interpret RNNNN Before Selecting the XNX Transmitter

Honeywell XNX-AMAV-RNNNN represents a specific combination of enclosure, sensor personality, and interface options. The R identifies the optional three-relay interface, not four relay channels.

The following N indicates that the transmitter does not include the factory-installed local HART option. The final NNN identifies the absence of a factory-configured MPD sensor and range selection.

The relay board provides three Form C contacts for Alarm Level 1, Alarm Level 2, and fault or special-state indication. Each relay has COM, NO, and NC connections, with documented ratings of 250 VAC at 5 A and 24 VDC at 5 A.

Engineers should also remember that the relay option conflicts with the optional Modbus and FOUNDATION Fieldbus interfaces. The standard analog measurement and HART communication arrangement must remain distinct from the local HART option.

For procurement, installation, and maintenance, always verify the complete ordering code and actual hardware configuration. Check sensor compatibility, terminal wiring, relay behavior, and hazardous-area approvals before commissioning.

A correctly selected transmitter supports reliable gas monitoring and effective PLC or DCS integration. For industrial automation component inquiries, visit Oiltech Controls Limited.