GS-X2
GS-X2 Programmable PID Controller
GS-X2 is a 1/8 DIN panel-mounted programmable single-loop PID controller with one universal process input, an optional second input, configurable I/O, isolated 24 Vdc transmitter power and standard EIA-485 communications for thermal and other process control.
GS-X2 programmable PID controller
The Spirax Sarco GS-X2 is a 1/8 DIN panel-mounted programmable PID controller for single-loop thermal and process control. It is intended for applications that need a compact operator interface, accurate measurement and enough configurable I/O to connect the control loop to sensors, alarms, actuators and a wider plant system. The GS-X2 combines a universal process input with a practical set of standard and optional interfaces, allowing the ordered instrument to be matched to the signal types and control strategy of the installation.
GS-X2 is a controller for a complete engineered loop, rather than a stand-alone safety device. The sensor, process, output element, alarm response and loss-of-signal behaviour must be assessed together. When the output is used to position a modulating valve, review the control valve range alongside the controller output type, actuator requirements and fail position. The controller can provide the control algorithm and local visibility, but it does not replace independent protection where the process risk assessment requires it.
Control functions for changing process conditions
The control engine supports PID control with enhanced autotuning and cutback. Cutback is intended to help reduce overshoot and oscillation when the loop approaches its setpoint, while autotuning helps the commissioning engineer establish suitable control parameters for the actual load. The same platform also documents on/off control and valve positioning without a slidewire, so a loop can be configured for the final control element and feedback arrangement that the application requires. The available control functions depend on the hardware and software configuration selected for the instrument.
Two PID sets are documented as standard, with an optional extension to eight sets. Each PID set can provide separate proportional behaviour for heating and cooling. Gain scheduling can select an appropriate PID set as operating conditions change, including conditions related to deviation from setpoint or output level. Feedforward functions can use the measured process variable, setpoint or monitored AC supply voltage where the ordered configuration supports that function. These features are useful when the process load is not constant, but they still require an application-specific tuning and verification procedure.
Setpoint programming is available as an option. The technical information describes arrangements including up to 20 profiles of 8 steps, as well as other profile capacities. Ramp, dwell, holdback, time-to-target and event behaviour can represent a repeatable thermal sequence or another controlled process routine. Confirm the required profile capacity and event I/O when specifying the order code; a function listed for the platform is not evidence that every GS-X2 configuration contains it.
Function-block wiring extends the controller beyond a fixed loop. The documented toolkit includes mathematics, logic and multiplexing, timers, counters, totalisation, recipes, linearisation, zirconia functions and input monitoring. These blocks can hold signal conditioning, selection logic and interlocks close to the loop configuration. Every active path, alarm, manual mode and fallback response should be tested during commissioning before a configured instrument is connected to a live process.
Universal measurement and optional second input
A GS-X2 has one universal primary process input, and a second universal input can be ordered for applications that need an additional measurement. The input family includes thermocouples, Pt100 and Pt1000 resistance thermometers, 4-20 mA and 0-20 mA current signals, 10 V, 2 V, 0.8 V, 80 mV and 40 mV voltage ranges, zirconia oxygen probes and pyrometers. The technical sheet specifies an input accuracy of +/-0.1% of reading. The process path has a 50 ms sample time, with 62.5 ms for thermocouple measurements and 100 ms for RTD measurements.
Input filtering can be set from off to a 60 second time constant. Thermocouple support includes K, J, N, R, S, B, L and T as standard, with two downloadable custom curves also documented. Cold-junction calibration and external cold-junction choices are part of the configured measurement arrangement. Before ordering, record the sensor type, signal range, engineering unit, calibration method and sensor-break response. A universal terminal does not mean that every signal can be connected without the correct wiring, burden resistor or compensation cable.
The optional secondary input can be used for a second process value or for configured dual-input functions such as switchover, redundancy, average, minimum, maximum or zirconia-related control. The exact use is determined by the configuration and the application. Do not treat the presence of the second input as a promise of a particular control mode; confirm the required function in the current order code and commissioning record.
For the Spirax Sarco GS-X2, this distinction matters during selection: record the secondary-input option and its intended function together rather than inferring the control mode from the family name.
I/O for actuators, alarms and plant integration
The standard output arrangement includes one Form C changeover relay. The GS-X2 format also documents two contact-closure logic inputs and a current-transformer input for load monitoring functions. Up to three optional I/O modules can be selected from Form A relay, logic I/O, isolated DC analogue output and TRIAC types. Depending on the selected module, these interfaces can support time-proportioned heat or cool control, proportional valve or SCR drive, retransmission, alarms, event outputs, interlocks and contact inputs.
Logic I/O choices must be matched to the connected circuit. The open-collector option uses an external 15 to 35 Vdc supply and can sink up to 40 mA; it is documented for alarm, event and interlock functions and cannot be used as a control output. The current-transformer input is supplied as standard and uses an internal burden resistor. A load-monitoring function can help identify partial-load, open-circuit or short-circuit conditions, but it does not remove the need for correctly rated protection and a defined response to a detected fault.
A built-in isolated 24 Vdc transmitter supply is available for this format and is documented with a maximum 28 mA load. This can simplify a two-wire transmitter arrangement, but the actual loop current, sensor wiring, isolation boundary and configured input must be checked before connection. The controller also provides standard EIA-485 digital communications. An Ethernet option uses a shielded grounded RJ45 connection with 10/100BASE-T auto-sensing and can use a fixed IP address or DHCP. Modbus TCP, BACnet and EtherNet/IP are listed for the Ethernet option; the exact protocol and role depend on the ordered hardware and software.
Operator visibility and panel fit
The high-visibility backlit LCD presents a 4.5-digit main process value with four decimal places. A 5-character second line, a scrolling text line, units, output and alarm indicators, programmer status, communications activity and a bar graph can provide local context during operation. Two programmable function keys are available on this controller format, in addition to the navigation controls. Passcode-protected operating and configuration levels help separate routine adjustments from engineering changes.
The GS-X2 is a nominal 48 x 96 mm instrument. Its panel cut-out is 92 x 45 mm with a -0/+0.8 mm width tolerance and a -0/+0.6 mm height tolerance. The depth behind the panel is approximately 90 mm, and the product weight is approximately 350 g. Front dimensions vary with the bezel: the source drawing gives approximately 48.1 x 96.1 mm for the washdown version and approximately 49.4 x 97.3 mm for the curved version. Check the complete drawing and surrounding clearance before finalising a panel layout.
Environment, installation and selection boundary
GS-X2 is intended for permanent indoor installation in an electrical panel or cabinet. The technical information specifies operation from 0 to 55 deg C, storage from -20 to +70 deg C and 5% to 90% RH non-condensing. The atmosphere must be non-corrosive and non-explosive. A washdown bezel provides EN 60529 IP66 and UL50E Type 4X-equivalent front protection for indoor use, while the rear is rated IP10. The enclosure must still control access, condensation, conductive contamination and the hazards of connected circuits.
When planning the installation, allow the documented rear depth and at least 10 mm between adjacent controllers. The manual permits a panel up to 15 mm thick and recommends a minimum 2 mm mild-steel panel with a non-textured mounting surface for effective sealing. Keep low-level sensor and communication wiring away from power wiring, use the specified cable types and observe the isolation diagram. The primary sensor input, CT input and digital inputs or outputs are not isolated from one another, so a sensor at a hazardous potential can place associated terminals at that potential.
For a migration or replacement assessment, the existing process variable, I/O allocation, control action, alarm strategy, configured logic and commissioning records should be compared with the proposed GS-X2 order code. The SX80 process controller page is available as a related process-controller reference, but its existence does not establish interchangeability with GS-X2. The final specification must be based on the process and the current configuration requirements.
GS-X2 ordering checklist
Specifying a Spirax Sarco GS-X2 is therefore an application and order-code exercise. Confirm the required signals, control functions, interfaces and installation conditions before selecting the final instrument configuration.
- Define the primary process variable, sensor type, range, engineering units, calibration method and sensor-break response.
- Decide whether the optional secondary universal input is required and document its intended measurement or dual-input function.
- Choose the control action, heating or cooling strategy, PID sets, autotune approach, alarms and any ramp/soak or function-block options.
- Confirm the Form C relay, optional I/O modules, contact inputs, current-transformer circuit and any open-collector channels against the load and interlock design.
- Confirm the 24 Vdc transmitter load, EIA-485 or Ethernet communication option, protocol role, bezel style and supply voltage from the current order code.
- Check the cut-out, rear clearance, environmental conditions, enclosure rating and isolation boundaries before installation.
Installation, wiring, commissioning and maintenance must be carried out by qualified personnel. Isolate power and connected I/O as required by the instructions, and verify normal and fault behaviour before the controller is returned to service.
Product function
GS-X2 is a panel-mounted programmable single-loop PID controller in a 1/8 DIN format. The documented functions include PID control with enhanced autotuning and cutback, on/off control, valve positioning without a slidewire, gain scheduling, feedforward, alarms, recipes and optional setpoint programming. The functions available on an installed instrument depend on the ordered hardware and software configuration.
The controller has one universal primary process input and an orderable second universal input. The standard output hardware includes one Form C changeover relay. Up to three optional I/O modules can be selected from Form A relay, logic I/O, isolated DC analogue output and TRIAC types. Two contact-closure logic inputs, a current-transformer input and an isolated transmitter power supply are documented for this controller format.
Environmental specifications and protection
| Item | GS-X2 documented value |
|---|---|
| Operating temperature | 0 to 55 deg C (32 to 131 deg F) |
| Storage temperature | -20 to +70 deg C (-4 to 158 deg F) |
| Operating/storage humidity | 5% to 90% RH, non-condensing |
| Atmosphere | Non-corrosive and non-explosive |
| Installation environment | Indoor use only, in an electrical panel or cabinet |
| Front protection | Washdown bezel: EN 60529 IP66 and UL50E Type 4X, equivalent to NEMA 4X for indoor use |
| Rear protection | EN 60529 IP10 |
| Electrical safety | EN 61010-1, installation category II, pollution degree 2 |
| EMC | EN 61326-1 industrial immunity; supply emission class depends on the power-supply version |
Dimensions, cut-out and weight
| Dimension or mass | GS-X2 value |
|---|---|
| Panel cut-out | 92 x 45 mm, -0/+0.8 mm width and -0/+0.6 mm height (3.62 x 1.77 inch, -0/+0.03 and -0/+0.02 inch) |
| Nominal front size | Approximately 48 x 96 mm |
| Bezel-dependent front size | Approximately 48.1 x 96.1 mm for the washdown version or 49.4 x 97.3 mm for the curved version |
| Depth behind panel | Approximately 90 mm |
| Product weight | Approximately 350 g (12.34 oz) |
Universal process inputs
| Characteristic | GS-X2 specification |
|---|---|
| Input arrangement | One universal primary input; one additional universal input available as an option |
| Input types | Thermocouples, Pt100/Pt1000 RTD, 4-20 mA, 0-20 mA, 10 V, 2 V, 0.8 V, 80 mV, 40 mV, zirconia oxygen probe and pyrometers |
| Input accuracy | +/-0.1% of reading |
| Process input sample time | 50 ms (20 Hz) |
| Thermocouple sample time | 62.5 ms (16 Hz) |
| RTD sample time | 100 ms (10 Hz) |
| Input filter | Off to 60 s filter time constant |
| Thermocouple types | K, J, N, R, S, B, L and T as standard, plus two downloadable custom curves |
| Nominal linear ranges | 40 mV, 80 mV, 0.8 V, 2 V, 10 V and current input up to the documented +/-32 mA range; RTD resistance range up to 400 or 4000 ohm as applicable |
| Sensor break | AC sensor-break detection; worst-case detection within 3 s |
| User calibration | Two-point input offset/gradient adjustment and transmitter-output scaling |
Optional input and I/O arrangements
| Interface | Documented GS-X2 arrangement |
|---|---|
| Secondary universal input | Orderable second process input for thermocouple, RTD or linear measurement; the configured application determines its function |
| Standard output | One OP3 Form C changeover relay, isolated 300 Vac CAT II; contact rating 2 A at 230 Vac +15% resistive |
| Optional I/O modules | Up to three freely selectable modules: Form A relay, logic I/O, isolated DC analogue output or TRIAC output |
| Contact-closure inputs | Two digital contact inputs; open above 400 ohm and closed below 100 ohm |
| Current-transformer input | 0-50 mA rms, 48-62 Hz; internal 10 ohm burden resistor; used for partial-load and load-fault functions |
| Open-collector logic I/O | Optional 4 or 8 channels; external 15-35 Vdc supply; maximum current sinking 40 mA; not a control output |
| Transmitter power supply | Isolated 24 Vdc supply; 2-28 mA load in the technical sheet and 28 mA maximum in the installation guide |
Power and communications
| Item | GS-X2 specification |
|---|---|
| High-voltage AC supply | 100-230 Vac +/-15%, 48-62 Hz |
| Low-voltage AC supply | 24 Vac +10%/-15%, 48-62 Hz |
| Low-voltage DC supply | 24 Vdc +20%/-15%, maximum 5% ripple voltage; polarity is not important |
| Power rating | Maximum 9 W |
| Overvoltage category | CAT II |
| Standard communications | EIA-485 (RS-485) digital communications |
| Ethernet option | Shielded grounded RJ45, 10/100BASE-T auto-sensing, fixed IP address or DHCP, with Bonjour auto-discovery |
| Ethernet protocols | Modbus TCP, BACnet and EtherNet/IP, subject to the selected option and software configuration |
| Serial protocol details | Where applicable, serial communication uses the documented EIA-485 arrangement and configured protocol parameters; verify the current order code before wiring |
Display and operator interface
| Item | GS-X2 documented value |
|---|---|
| Display | High-visibility backlit LCD with a washdown membrane bezel or a sculpted bezel with tactile keys |
| Main process variable | 4.5 digits with four decimal places |
| Second line | 5-character 16-segment text or numeric display |
| Scrolling line | 16-segment scrolling text or numeric display |
| Displayed status | Process value, units, setpoint, output status, alarm indication, programmer status, communications activity and configurable bar graph |
| Function keys | Two programmable function keys, subject to configuration |
| Protection | Passcode level protection with configurable lockout period |
Control, approvals and ordering notes
- Enhanced autotuning includes a cutback function intended to reduce overshoot and oscillation.
- Two PID sets are documented as standard, with an optional extension to eight PID sets.
- Setpoint programmer options include up to 20 profiles of 8 steps; confirm the selected application and option code.
- When the necessary field calibration is completed, the source states that supplied controllers can meet the accuracy requirements described for AMS2750F and CQI-9 applications. This is not a substitute for the applicable quality-system validation.
- Order the controller against the current hardware and software code. Confirm the sensor, second input, output modules, transmitter load, communications, bezel, supply, labels and application before purchase.
- The controller contains no user-serviceable parts. The source lists a USB backup lead, iTools configuration software, snubbers, resistors and current transformers as accessories.
Installation and Maintenance Guide
- Safety information
- Controller introduction
- Panel installation and removal
- Terminal wiring and isolation
- Start-up and configuration
- Operator interface and commissioning
- Cybersecurity, maintenance and disposal
These instructions apply the verified GS-X2 installation, wiring and operating boundaries from IM-P794-03 to the single-model product page.
1. Safety information
Electrical equipment must be installed, operated and maintained by qualified personnel. Before installation, removal, wiring, maintenance or inspection, turn off all power to the controller and to connected I/O circuits such as alarms and control outputs.
Intended use and system responsibility
Use the controller only within the specified technical data, instructions and applicable regulations. Perform a risk assessment for the planned application and implement the required safety measures. The controller is a component of a larger machine or process; the designer and commissioning person remain responsible for the safety of the complete system.
Electrical and fire hazards
Install the unit in an enclosure or cabinet that provides fire containment and restricts access to hazards. Do not exceed the ratings. Wire and fuse power-line and output circuits according to local and national requirements. Use the correct supply version shown on the controller label and use isolating PELV or SELV supplies for low-voltage equipment.
Live sensor boundary
The primary sensor input is not isolated from the current-transformer input or digital inputs and outputs. If the sensor is at a hazardous potential, associated terminals can be at the same potential. Protect service personnel and use cables, connectors and switches rated for the applicable voltage and category.
Control and configuration hazards
Do not use the controller as the sole protection in a critical application where people or equipment rely on the control circuit. Do not configure it while connected to a live process: entering Configuration mode pauses outputs. Use suitable interlocks and test all normal and fault conditions before approval for service.
2. Panel installation
GS-X2 is intended for permanent indoor installation in an electrical panel. Choose a low-vibration location with an ambient operating temperature of 0 to 55 deg C and use the conservative technical-sheet humidity range of 5% to 90% RH non-condensing. The controller can be mounted in a panel up to 15 mm thick. A minimum 2 mm mild-steel panel and a non-textured mounting surface are recommended to maintain effective sealing and the stated front protection.
- Prepare a 92 x 45 mm cut-out with -0/+0.8 mm width and -0/+0.6 mm height tolerances. When multiple controllers are fitted, allow at least 10 mm spacing.
- Switch off all power and carefully remove the panel retaining clips from the sleeve.
- Check that the gasket is behind the front bezel, is not twisted and is suitable for the panel surface.
- Insert the sleeve and controller through the cut-out, then push both retaining clips forward until the instrument is secure and the panel seal is maintained.
- Remove the display protective film after installation. If the sleeve must be removed, first isolate all power and remove any Ethernet cable from the rear of the controller.
Polarising features help prevent an inverted installation, an incompatible power-supply unit being inserted into a sleeve and an instrument being inserted into a sleeve with a non-compatible terminal assignment. Do not rely on the polarising features in place of checking the order code and terminal label.
3. GS-X2 terminal layout and options
The GS-X2 terminal arrangement provides the primary sensor input, optional secondary sensor input, OP3 Form C changeover relay, standard 24 V transmitter supply, current-transformer and digital-input connections, power terminals and option positions. I/O1, I/O2 and I/O4 can be ordered as relay, TRIAC, logic or analogue functions according to the installed modules. Do not connect a module or signal to a terminal solely because the location appears available; verify the supplied hardware and wiring label.
4. Wiring and isolation
Secure cables and wiring harnesses with appropriate strain relief and prevent conductive material from entering the case. Use only the identified terminals and the originally supplied connectors. Keep sensor and low-voltage DC wiring away from high-current power wiring. Where separation is impractical, use suitable shielded cable with the shield grounded as specified by the installation design.
| Wiring item | Installation requirement |
|---|---|
| Terminal wire size | 0.5-1.5 mm2; maximum two wires per terminal, identical in type and cross-sectional size |
| Stripping | Strip at least 6 mm of insulation and do not leave more than 2 mm of exposed conductor |
| Terminal screws | Tighten to the specified torque of 0.5 Nm and verify the conductor is secure |
| Power supply | Match the supply to the rating on the controller label; do not connect a low-voltage version directly to line voltage |
| Transmitter supply | The internal 24 Vdc supply is isolated and limited to the documented 28 mA maximum; verify transmitter wiring and input configuration before connection |
| Current transformer | If fitted or used in the ordered configuration, provide voltage limiting across the CT terminals to reduce hazardous voltage when the controller is unplugged |
| Inductive load | Use the specified snubber/protection arrangement where required; confirm that leakage current will not hold a high-impedance load on |
Isolation diagrams in the source identify 300 Vac double or basic isolation boundaries. The primary sensor, CT, digital-input and digital-output relationships require a specific safety review because these circuits are not isolated from one another. Do not infer isolation from a terminal position or from the use of a low-voltage sensor alone.
5. Start-up and configuration
At power-up the controller performs a display diagnostic and checks the fitted hardware. A hardware mismatch or keyboard-check failure can place the instrument in standby. A new unconfigured controller enters Quick Start mode, where two sets of five characters are used to select the application, sensor type, range and available digital functions. A controller supplied with a hardware and software code can start directly in its configured operator display.
- Confirm the supply, primary and secondary sensor wiring, output wiring, enclosure, interlocks and isolation before energising the controller.
- For a new unconfigured unit, enter the Quick Start selections for the actual application. Do not select a function whose required hardware is not fitted.
- For a configured unit, check the application, input ranges, control action, setpoint limits, alarm thresholds and output behaviour.
- Use Configuration level or the iTools configuration package for functions not exposed by the quick codes. Save a verified configuration backup before making major changes.
- Test sensor-break, alarm, manual, standby, communication-loss, transmitter and output-fault behaviour under controlled commissioning conditions.
Changing configuration or flash-memory settings can place the controller in Configuration mode and stop process control. Configuration changes must therefore be made with the process in a safe state and must be approved before returning the system to service.
6. Operator interface and commissioning
GS-X2 uses Page, Scroll, Lower and Raise navigation controls together with two programmable function keys. Page selects displays or list headers, Scroll selects parameters, and Lower/Raise adjust values within the permitted limits. The function keys can be assigned to configured actions such as Auto/Manual selection. Holding Page for more than three seconds selects the Goto function, and Page plus Scroll returns to the Home display.
Commissioning should confirm the process-variable indication, engineering units, active setpoint, output indication, alarm indication, manual/automatic behaviour, programmed sequences, bar graph and communications status. Check the response after a process disturbance and verify that the selected control output cannot drive an actuator beyond the safe operating boundary. Where the controller drives a valve, confirm that the output action and actuator fail position agree with the process risk assessment.
7. Network and cybersecurity
When a communications option is used, protect the controller as part of the industrial control network. The installation guidance recommends that controllers and associated devices are placed on a firewalled network segment separated from the public Internet, rather than being directly exposed. Disable unused communication features, change default access credentials where applicable, restrict configuration access and document the permitted master devices and network paths.
Validate the complete system after a power cycle, communications interruption or configuration recovery. A network message can continue to influence an output if the output is configured for communications control, so the loss-of-communications response and local fallback must be tested explicitly.
8. Maintenance, cleaning and disposal
The controller contains no user-serviceable parts. Isolate all power and I/O before inspection or removal, observe electrostatic-discharge precautions and do not disassemble, repair or modify the equipment. Contact the supplier for repair or replacement. Use only the specified accessories and genuine replacement items.
A mild soap solution may be used on exterior surfaces; isopropyl alcohol may be used for labels as described by the source instructions. Prevent liquid or conductive material from entering the case. If stored before use, keep the instrument within the specified storage temperature and humidity conditions. Dispose of the equipment in accordance with the applicable WEEE and local electronic-equipment requirements.