A-4000 Gas Controller

Overview

Not every gas detection installation needs to manage eight zones from a single controller. A mid-sized industrial facility, a single process building, a ship’s engine room complex, or a commercial facility with gas monitoring across two to four distinct areas needs a controller that is correctly scaled — powerful enough to handle multi-zone alarm management, MODBUS data integration, and programmable relay logic, but without the physical footprint and cost of a controller designed for twice the zone count.

The A-4000 gas alarm controller from Bosean is a compact, wall-mounted gas detection control panel supporting between one and four monitoring zones within a single enclosure measuring just 28×20×6.5cm and weighing approximately 3350g. Despite its compact form factor, the A-4000 delivers the full feature set expected of a professional-grade gas detection controller: dual RS485 MODBUS data transmission, editable control logic for programmable alarm response sequences, three high-capacity relay outputs (10A/250VAC or 10A/30VDC), dual battery backup, and — critically — universal signal input compatibility that accepts both the analogue 4–20mA current loop signal and the RS485 digital signal from any connected gas transmitter.

Supplied by Alright Engineering Solutions Pte Ltd — Singapore-based authorised distributors of fixed gas detection equipment serving the maritime and industrial sectors across the Asia-Pacific region — the A-4000 stands apart from comparable compact gas detection controllers through one specific differentiator: its input signal universality. Unlike controllers that accept only RS485 digital signals, the A-4000 accepts both 2-wire and 3-wire 4–20mA analogue current loop signals alongside RS485 digital inputs. This means it integrates directly with the vast majority of fixed gas transmitters currently installed in industrial facilities worldwide — including older analogue-output detectors that would require signal conversion hardware to connect to an RS485-only controller. For facilities that are upgrading or extending an existing detection installation rather than starting from scratch, this input universality is a decisive practical advantage.

Key Features

1. Universal Signal Input — 4–20mA (2-Wire and 3-Wire) and RS485

The A-4000 accepts three types of input signal: 2-wire 4–20mA current loop, 3-wire 4–20mA current loop, and RS485 digital signal. The 4–20mA current loop is the dominant analogue signal standard in industrial instrumentation and is used by the large majority of fixed gas transmitters currently in service globally — including virtually all transmitters installed before the widespread adoption of digital field buses. The 2-wire and 3-wire variants cover the two main wiring configurations for 4–20mA loop-powered and separately-powered transmitters respectively. RS485 digital input with MODBUS protocol support is additionally available for newer digital transmitters that output structured digital data rather than an analogue signal. This three-input-type compatibility makes the A-4000 the correct controller for mixed-technology installations where some detectors are legacy analogue units and others are newer digital-output transmitters — a common scenario in facilities that have been incrementally upgrading their gas detection infrastructure over several years.

2. Scalable 1–4 Zone Configuration — Extendible as Required

The A-4000 supports between one and four monitoring zones within a single controller enclosure, with the zone count configurable at installation and extendible as the facility’s monitoring requirements grow. For a new installation starting with a single monitored location, the A-4000 can be commissioned in a one-zone configuration and expanded zone by zone without replacing the controller panel. For facilities requiring up to four zones of coverage from day one, the A-4000 provides full four-zone management in a compact enclosure that fits comfortably in a standard control panel cabinet or on a plant room wall. The four-zone ceiling makes the A-4000 the appropriate choice for small to medium facilities, individual process buildings, or discrete areas within a larger site where four zones covers the complete monitoring requirement without the overhead of a larger eight-zone panel.

3. Editable Control Logic — Site-Specific Alarm Response Programming

The A-4000 supports editable control logic — user-programmable alarm response sequences that define the relationship between alarm events and relay output activations for each monitored zone. In practice, this means the controller can be configured to implement staged alarm responses, cross-zone activations, zone inhibit functions, and other site-specific logic that a formal safety management plan or emergency response procedure may require. For facilities with documented emergency response procedures, formal HSE permit-to-work systems, or ATEX/IECEx zone management plans that specify particular automated responses to gas alarm events, the ability to program those responses directly into the controller hardware ensures the automated safety response matches the human safety plan precisely — not just approximately. This programmability is what distinguishes the A-4000 from basic alarm relay panels that implement only fixed alarm-to-relay logic.

4. Dual RS485 Data Transmission — Two Simultaneous MODBUS Connections

Like the S-8000, the A-4000 provides two independent RS485 ports, both supporting two-way MODBUS protocol communication. Dual RS485 ports allow simultaneous connection to two separate upstream systems — for example, a local SCADA workstation and a remote building management or enterprise HSE reporting platform — without RS485 signal splitters or repeaters. For facilities where gas monitoring data must feed multiple data consumers simultaneously, the dual RS485 output provides this capability directly from the controller without additional hardware. Two-way MODBUS communication also allows remote configuration — alarm setpoints, zone parameters, and logic settings can be adjusted from the connected supervisory system without requiring physical access to the controller panel, which is particularly valuable for controllers installed in locations that are inconvenient or time-consuming to access physically.

5. Three High-Capacity Relay Outputs — 10A / 250V AC or 10A / 30V DC

The A-4000 provides three sets of relay contact outputs rated at 10A/250VAC and 10A/30VDC — the same high-capacity relay rating as the larger S-8000. This 10A rating allows the A-4000 to drive industrial-rated external devices directly: ventilation fan motor starters, high-intensity alarm sirens, solenoid valves, emergency lighting circuits, and process control actuators — without intermediate relay amplifier hardware. The three relay channels support a fully staged safety response: one relay for local alarm activation, one for automatic ventilation control, and one for process shutdown or emergency system triggering. Free-contact (volt-free) relay outputs are compatible with both AC and DC external circuits across the full 10A capacity, giving installation engineers maximum flexibility in wiring the controller to existing site safety infrastructure.

6. AC 220V Supply with Dual Battery Backup

The A-4000 operates from a standard AC 220V 50/60Hz mains supply and incorporates dual battery backup using two sections of DC 12V/1.3AH sealed lead acid batteries — identical to the S-8000’s backup configuration. For a gas detection controller, battery backup is not a convenience feature; it is a safety requirement. If the mains supply fails during an incident — a fire-related electrical fault, a power cut during a storm, a tripped circuit breaker — the gas detection system must continue operating precisely when it is most needed. The dual battery configuration provides redundancy within the backup supply, ensuring that degradation or failure of one battery section does not leave the system without backup power. The DC 24V output from the controller can power connected gas transmitters directly from the controller supply — simplifying wiring by combining power delivery and signal return in a single cable run to each detector location.

7. Dual Power Supply Protection

The A-4000 incorporates dual protection on its power supply circuitry — hardware-level overvoltage, overcurrent, and fault protection that maintains controller operation reliability in the variable power supply conditions of industrial electrical environments. Switching surges from large motor loads, voltage transients from nearby electrical equipment, and supply quality fluctuations from industrial generators or UPS systems can all cause false alarm outputs or controller resets in under-protected panels. The A-4000’s dual supply protection is designed to maintain stable, reliable operation across the power quality range encountered in real industrial installations.

8. Compact Enclosure — 28×20×6.5cm for Space-Constrained Installations

At 28×20×6.5cm and approximately 3350g, the A-4000 is meaningfully more compact than the eight-zone S-8000 (34×27×10cm, ~7000g) — making it appropriate for installations where panel space is constrained. It fits within a standard 300mm-wide control panel cabinet, on a narrow plant room wall, or in a ship’s accommodation or control space where larger panels cannot be physically accommodated. Despite its reduced dimensions, the A-4000’s LCD display and status indicators, keypad interface, and all input/output terminals are front-panel accessible, maintaining full operational functionality without requiring the enclosure to be opened for routine use.

Technical Specifications

Model: A-4000 Gas Controller (Bosean — Supplied by Alright Engineering Solutions Pte Ltd)

Display: LCD display + status indicator LEDs

Zone Capacity: 1–4 zones (optional, extendible)

Input Signal: 2-wire 4–20mA current loop; 3-wire 4–20mA current loop; RS485 digital signal

Output Signal: Three sets of relay contact outputs — 10A/250VAC or 10A/30VDC (free contact)

Digital Upload Protocol: Two-way RS485; MODBUS protocol — dual RS485 ports

Output Voltage: DC 24V (for powering connected gas detectors)

Controller Power: AC 220V 50/60Hz mains supply

Battery Backup: Two sections DC 12V/1.3AH sealed lead acid battery (dual redundant backup)

Alarm: Two-level sound and light alarm; 65dB–100dB at 1 metre (adjustable)

Control Logic: Editable — user-programmable alarm response sequences

Power Supply Protection: Dual power supply protection

Working Temperature: 0°C to +40°C

Working Humidity: ≥95% RH (no condensation)

Dimensions: 28×20×6.5cm

Weight: Approximately 3350g

Installation: Wall-mounted

IP Rating: Indoor enclosure — confirm specific IP classification for application requirements

Wireless Connectivity: None (dual RS485 hardwired MODBUS digital communication)

Data Logging: Via connected SCADA or supervisory computer through RS485 MODBUS interface

Compatible Detector Inputs: Any fixed gas transmitter with 2-wire or 3-wire 4–20mA output, or RS485 MODBUS output — covering CO, H2S, O2, LEL, SO2, NH3, NO2, CO2, Cl2, H2, and other gas types

Benefits

The A-4000’s most operationally significant benefit for many facilities is its ability to accept 4–20mA signals directly from existing analogue gas transmitters — without requiring signal converters, transmitter replacement, or additional interface hardware. In a facility that already has fixed gas detectors installed and outputting 4–20mA signals, adding the A-4000 as a central controller connects those detectors directly, giving the facility centralised alarm management, MODBUS data integration, and programmable relay logic without touching the existing detector infrastructure. For facilities managing a gas detection upgrade programme on a limited budget, the ability to retain existing detectors while upgrading the control and data management layer is a significant cost saving.

The compact form factor — less than half the volume of the eight-zone S-8000 — makes the A-4000 the practical choice for installations where panel space is a genuine constraint. In marine applications, ship’s control rooms, small plant rooms, and equipment cabinets where a larger panel simply will not fit, the A-4000 delivers four-zone control capability in a package that accommodates the physical realities of the installation environment. This is not a compromise on capability — the A-4000’s relay ratings, MODBUS connectivity, editable logic, and battery backup are identical to the S-8000’s; only the zone count and physical size differ.

The dual RS485 MODBUS output means gas monitoring data reaches both operational and management platforms simultaneously. For HSE managers required to demonstrate continuous gas monitoring records for regulatory compliance — under Singapore’s WSH Act, Australia’s WHS Regulations, or equivalent frameworks — the MODBUS connection to a central data logging system provides the automatic, timestamped exposure record needed without additional manual data handling. Remote alarm setpoint management via two-way MODBUS means configuration changes can be made from the control room without dispatching a technician to the panel location — reducing the administrative effort of managing alarm threshold updates across a multi-zone installation.

The 10A relay outputs, matching the larger S-8000’s relay capacity in a significantly smaller enclosure, allow the A-4000 to drive industrial-rated external safety devices — ventilation contactors, solenoid valves, high-current alarm devices — directly, without relay amplifier panels. For a four-zone installation, having three 10A relay channels is typically sufficient to cover the complete staged alarm response requirement — local alarm, ventilation activation, and process or isolation shutdown — from a single compact controller.

Who It’s For

Electrical and Instrumentation Engineers Upgrading Existing Analogue Gas Detection Systems: If you are adding centralised control, MODBUS data integration, and programmable alarm logic to a facility that already has 4–20mA fixed gas transmitters installed, the A-4000 connects directly to those transmitters without requiring signal conversion hardware or transmitter replacement. The dual RS485 MODBUS output connects the upgraded controller into your SCADA or building management system, and the editable relay logic allows the controller’s automated response to match your site’s emergency response plan — all without touching the existing detector infrastructure.

HSE Officers and Safety Managers in Medium-Sized Industrial Facilities: For a single process building, a refrigeration plant room, a paint spray facility, or a marine vessel engine room complex where two to four gas monitoring zones covers the complete requirement, the A-4000 provides professionally specified gas detection control at a scale that matches the installation. You get dual battery backup for continuity through power interruptions, editable alarm logic that implements your emergency response procedures automatically, and MODBUS data integration for your compliance reporting platform — in a panel that fits the available wall space without requiring a dedicated electrical panel room.

Marine Vessel and Offshore Installation Safety Officers: For shipboard gas detection installations where physical space is at a premium and the controller must fit within an existing control console or equipment cabinet, the A-4000’s compact 28×20×6.5cm enclosure is a practical solution that the larger eight-zone panel cannot offer. The dual battery backup maintains monitoring operation through vessel power management events, the 4–20mA input accepts signals from the wide range of fixed marine gas transmitters currently in service, and the MODBUS output connects into the vessel’s integrated alarm and monitoring system — meeting the SOLAS and class society requirements for enclosed space gas detection control.

Possible Applications

Single-Building Process Facilities — Compact Four-Zone Control: Centralised gas alarm management for a single process building with up to four distinct monitored areas — compressor room, chemical storage, pump room, and corridor — in a wall-mounted controller that fits within the building’s existing electrical panel space.

Marine Vessel Gas Detection — Engine Room and Cargo Spaces: Four-zone gas detection control for commercial vessels monitoring engine room combustibles, cargo pump room H2S and LEL, battery room hydrogen, and deck gas detection points — with 4–20mA input compatibility for existing marine gas transmitters and MODBUS output to the vessel’s integrated alarm management system.

Refrigeration Plant Rooms — Ammonia and Hydrocarbon Refrigerant Monitoring: Compact four-zone controller for refrigeration machinery rooms with multiple monitored areas — compressor hall, condenser deck, evaporator space, and refrigerant storage — activating emergency ventilation and refrigerant isolation valve relays through the 10A relay outputs on alarm.

Commercial Car Parks — CO Monitoring and Ventilation Control: Wall-mounted four-zone gas alarm controller for multi-level car parks, with 4–20mA CO detector inputs from each monitored level and relay outputs activating zone-specific ventilation fan systems automatically when CO concentrations exceed alarm thresholds — meeting local building code requirements for car park ventilation control.

Wastewater Treatment — Small-to-Medium Site Multi-Zone Monitoring: Central controller for a smaller wastewater treatment facility with up to four monitored locations — pump station, digester building, chemical dosing area, and operations room — managing H2S, methane, CO, and O2 monitoring from a single compact panel with SCADA integration for regulatory data logging.

Paint Spray Booths and Surface Treatment Facilities: Four-zone LEL and solvent vapour monitoring controller for multi-booth spray painting facilities, with relay outputs activating booth-specific ventilation systems and triggering emergency shutdown of spray equipment when solvent vapour concentrations reach alarm thresholds.

Hospital and Healthcare Plant Rooms — Medical Gas Monitoring: Compact wall-mounted controller for hospital plant rooms monitoring medical oxygen enrichment, nitrous oxide, and combustible gas concentrations across up to four zones — activating local alarms and ventilation controls with MODBUS integration into the building management system for centralised facility monitoring.

Small Offshore Platforms and Unmanned Installations: Gas detection controller for smaller offshore installations with limited panel space — subsea production control rooms, unmanned wellhead platforms, and small process skids — where the A-4000’s compact enclosure and dual battery backup provide reliable four-zone gas monitoring in a form factor suited to constrained control room environments.

Trust and Certifications

4–20mA Signal Compatibility — Universal Analogue Standard: The 4–20mA current loop signal is the universal standard for analogue process instrumentation, used by fixed gas transmitters from every major gas detection manufacturer globally. By accepting both 2-wire and 3-wire 4–20mA configurations, the A-4000 covers the full range of analogue transmitter wiring types in use across industrial installations — including the large installed base of legacy analogue detectors that would require signal conversion hardware to connect to RS485-only controllers.

MODBUS RTU over RS485 — Industry-Standard Open Protocol: MODBUS RTU over RS485 is the most widely adopted open communication protocol in industrial instrumentation, compatible with SCADA systems, DCS platforms, and building management systems from all major automation vendors. Two-way dual RS485 MODBUS in a compact four-zone controller is a specification that most controllers at this price point do not offer — particularly the dual-port configuration that allows simultaneous connection to two separate upstream systems.

Relay Output Ratings — 10A/250VAC and 10A/30VDC: The 10A relay contact rating — identical to the larger S-8000 panel — confirms the A-4000’s relay outputs are suitable for direct connection to industrial-rated electrical circuits without intermediate relay amplification. For a compact controller in its zone class, 10A relay capacity is a specification that significantly exceeds the 2A–3A relay ratings common in smaller gas detection panels.

Dual Battery Backup — Continuous Operation Through Power Interruption: Dual DC 12V/1.3AH sealed lead acid battery backup maintains controller operation through mains supply failures. For safety-critical gas monitoring applications where uninterrupted operation through a power failure is a regulatory requirement or class society condition, dual battery backup provides a higher level of supply resilience than single-battery designs.

Bosean Electronic Technology Co., Ltd.: Bosean is a specialist gas detection manufacturer operating under the ISO9001 quality management system, producing fixed gas detectors, portable monitors, gas alarm controllers, and environmental monitoring instruments for industrial and commercial safety applications globally. The A-4000 is part of Bosean’s gas alarm controller product line alongside the S-8000 and BH-KZ101, providing a scalable range of controller options for installations of different sizes and signal type requirements.

Alright Engineering Solutions Pte Ltd — Authorised Distributor: Alright Engineering Solutions is a Singapore-based engineering solutions company serving the maritime and industrial sectors across the Asia-Pacific region. As an authorised distributor of fixed gas detection and alarm control equipment, Alright Engineering Solutions provides full product support including supply, system design consultation, installation guidance, MODBUS integration support, and after-sales service. Full product portfolio available through alrightes.com.

Warranty: Available on request through Alright Engineering Solutions. Battery replacement intervals and controller maintenance schedules documented in the product manual supplied with each unit.

Accessories and Variants

Compatible Fixed Gas Transmitters (4–20mA or RS485 Output): The A-4000 accepts signals from any fixed gas transmitter with a 2-wire or 3-wire 4–20mA output, or RS485 MODBUS output — including Bosean’s own fixed detector range (BH-60, K-G60, GTQ-DX401, GT-K90) and third-party detectors monitoring CO, H2S, O2, LEL, SO2, NH3, NO2, CO2, Cl2, H2, and other gases. Alright Engineering Solutions can supply matched detector-controller packages with all zones pre-configured for your specific gas combination requirements.

Replacement Battery Sections (DC 12V/1.3AH Sealed Lead Acid): Replacement sealed lead acid battery sections for the A-4000’s dual battery backup — recommended for scheduled replacement every 3–5 years depending on backup duty cycle and operating temperature. Available through Alright Engineering Solutions.

External Audible/Visual Alarm Beacons: Horn sounders, strobe lights, and combined alarm devices wired to the A-4000’s relay outputs for alarm coverage beyond the panel’s built-in alarm. Available in standard, weatherproof, and explosion-proof variants for different installation environments through Alright Engineering Solutions.

RS485 to Ethernet Gateway: For connection of the A-4000’s RS485 MODBUS output to an Ethernet-networked SCADA or building management system — protocol conversion without replacing the controller or wiring infrastructure.

4-Core Shielded RS485 Signal Cable: Standard instrumentation cable for RS485 wiring between the A-4000 and connected transmitters, supporting cable runs up to 1,000 metres. For 4–20mA wiring, 3-core shielded instrumentation cable. Available locally or through Alright Engineering Solutions.

Controller Range Comparison — Choosing the Right Panel:

BH-KZ101: Single-zone controller — 4-20mA or RS485 input, 3 relay outputs (3A), single RS485 MODBUS port, DC powered, no battery backup — for simple single-zone installations

A-4000 (this model): 1–4 zone controller — 4-20mA (2-wire/3-wire) and RS485 input, 3 relay outputs (10A), dual RS485 MODBUS, AC mains + dual battery backup, editable logic — for small to medium multi-zone installations or analogue-input installations

S-8000: 1–8 zone controller — RS485 input, 3 relay outputs (10A), dual RS485 MODBUS, AC mains + dual battery backup, editable logic — for larger multi-zone installations requiring RS485 digital detector inputs

Ready to Specify the A-4000 for Your Gas Detection System?

Whether you are connecting a new four-zone installation with current-output gas transmitters, upgrading an existing analogue detector network with centralised MODBUS-connected alarm control, or specifying a compact multi-zone controller for a space-constrained marine or commercial facility, the A-4000 delivers the signal universality, relay capacity, and data management connectivity that a professionally managed gas detection installation requires — in a panel sized for real-world installation constraints.

To request a formal quotation, discuss zone configuration and detector matching, or get technical guidance on 4–20mA wiring, MODBUS integration, and relay logic programming for your specific application, contact the Alright Engineering Solutions team directly. We support the full specification and procurement process — from initial system design through to installation, commissioning, and ongoing maintenance support.