AirMASTER FORM Controller — Overview & Navigation – South-Tek Systems

Applies to: STS Series (5–100HP) · STSH Series · STSD · STSP · STSP2 — all South-Tek screw compressor models use the AirMASTER FORM controller (UL certified).

Overview

The AirMASTER FORM is a microprocessor-based compressor controller manufactured by CMC NV. It manages all compressor operating states, provides real-time parameter monitoring, displays faults and maintenance reminders, and supports optional networking and remote monitoring via RS485 Modbus, IoT (Ethernet / TCP-IP), or fieldbus modules.

⚠ Warning — The Controller Is Not a Safety Device The FORM is a machine controller, not a safety component and not a means of isolation. No part of it is under pressure and it does not protect personnel. Always isolate and lock out the electrical supply and relieve stored air pressure before opening the enclosure or servicing the compressor. Configuration and operation are for trained personnel working to local health and safety requirements.

Hardware

Controller Configurations

South-Tek compressors ship with the AirMASTER FORM in one of two front-panel configurations. Both run the same software, show the same menus, and use the same three command buttons. The difference is how you move through the menus.

Configuration	How to identify it	How you navigate
7-key (non-touch)	Four round navigation keys arranged in a diamond beside the display, plus the three command buttons. Seven keys in total.	Physical ENTER, UP, DOWN, and ESCAPE keys. The screen is not touch sensitive.
Touch-screen	No navigation keys on the panel. Only the three command buttons, with the status LEDs above the display.	Touch the on-screen buttons in the navigation toolbar (Select, Select, Exit) and touch a menu item directly to open it.

FIG-01A — 7-key (non-touch) configuration.

FIG-01B — Touch-screen configuration.

ℹ Note Everything in this article applies to both configurations. Where a step says "press ENTER" or "press ▲ / ▼," touch-screen users touch the matching on-screen button instead.

Keypad

The FORM front panel has three command buttons (START, STOP, RESET) and, on 7-key models, four navigation keys (ENTER, UP, DOWN, ESCAPE). The buttons are not labelled with words on the panel, only with symbols. Use the legend below to identify them.

command button and navigation key legend

Command Buttons (all configurations)

Button	Symbol on the panel	Function
START	Green button, single white vertical bar	Start the compressor
STOP	Red button, ring around a solid centre dot	Stop the compressor (normal unloaded stop)
RESET	Dark button, two parallel diagonal slashes	Reset an alarm or fault that has already been resolved. Press it once with the Home screen displayed.

Navigation Keys (7-key models)

Key	Symbol on the panel	Function
ENTER	Green return arrow, right-hand key of the diamond	Open the menu from the Home screen, enter a selected tab or submenu, and confirm a selection or value
UP	White triangle pointing up with a plus, top key	Move to the previous tab or item / increase a value
DOWN	White triangle pointing down with a minus, bottom key	Move to the next tab or item / decrease a value
ESCAPE	Red open arc (a "C" shape), left-hand key of the diamond	Step back one level, exit an edit without saving, and return toward the Home screen

Note — Emergency Stop: The red mushroom-head Emergency Stop is a separate device on the compressor enclosure, not one of the controller buttons. Release the E-stop, then press RESET on the controller to clear the fault.

Status Indicators (LEDs)

Four status LEDs sit next to the display, above it on touch-screen units and beside it on 7-key units. They are marked with symbols rather than words.

Indicator	Symbol	Meaning
Power	Yellow lightning bolt	On = controller powered. Off = controller not powered.
Motor / Run	Green running figure	Off = motor not running. Slow flash = running or in a start sequence. On = running loaded.
Maintenance	Orange wrench	On = maintenance required. Off = none due.
Alarm	Red warning triangle	Slow flash = warning active (A:…). Fast flash = immediate-stop active (E:…).

Graphic Display

The Home screen is the default view after power-up, and the display returns to it after a period of no keypad use (set by the Logout Time). Each preset Home screen shows the compressor's key live values: delivery pressure, outlet temperature, percent load, operating status, and any active-function icons. A status toolbar runs along the top of the screen and a navigation toolbar along the bottom. After about 60 seconds of no use the backlight dims until a key is pressed or the screen is touched.

Active-function icons in the status toolbar flag conditions such as locked or unlocked access, service due, warning, fault, drain valve, remote control, remote pressure control, ISC master active, fan, automatic restart, run schedule, IoT module, and clone key. They are listed in priority order, highest first.

If more than four icons are active and the status text is too long to fit, the icons collapse behind a "<<" symbol. On a touch-screen unit, touch "<<" to expand them and ">>" to collapse them again. On a 7-key unit, press UP and DOWN together to toggle between expanded and collapsed.

ℹ Note — Alarm Indication on Screen When the controller detects an alarm or fault, the status toolbar and navigation toolbar flash between red and blue. This is in addition to the Alarm LED on the panel.

User Account Levels

The FORM supports multiple access levels. The default account needs no PIN code and is what the controller normally sits in. It can view tabs P00 through P09 and cannot edit them. Operators can therefore read all operating data, review the error and event logs, and reset a resolved alarm, but cannot change settings.

Higher access levels are protected by a four digit PIN. Each account can be given its own menu-by-menu rights, so a parameter may be hidden, visible but read-only, or editable depending on which account is active. Service and configuration tabs require an authorized service account. Contact South-Tek if service-level access is needed.

ℹ Note If a menu or parameter described in this article is not visible on your controller, check which account is active before troubleshooting anything else. After a period of no keypad use the controller returns to the default account on its own, so a menu that was visible earlier may simply be hidden again.

Note — Display Units: Pressure and temperature units, along with language, time format, and date format, are stored per user account under the P09 Access tab. If your controller is showing bar or °C instead of PSI and °F, the account settings need to be changed rather than the sensors. Open a ticket and we can walk you through it.

Menu Navigation

After power-up the controller shows the Home screen. From there you reach every parameter through a set of menu tabs. The steps below name the physical keys used on a 7-key controller. On a touch-screen controller, touch the matching button in the navigation toolbar at the bottom of the screen, or touch the menu item directly.

Open the menu. From the Home screen, press ENTER (or the Menu button in the navigation toolbar) to enter the menu tabs.
Move between tabs. The menu tabs are arranged in a continuous loop. Use ▲ and ▼ to move between them. Press ESCAPE to return to the Home screen.
Open a tab. With a tab highlighted, press ENTER to open it. The first item in the tab is highlighted.
Move between items. Items are listed vertically in a continuous loop. Use ▲ and ▼ to move between them, or touch the item directly on a touch-screen unit. Items with a submenu show an enter indicator; press ENTER to open the submenu.
Edit a value. For an editable item, press ENTER to open the edit popup. Use ▲ and ▼ to change the value or selection; press and hold to change faster. Press ENTER to confirm, or ESCAPE to exit without saving.
Back out. Press ESCAPE to step back one level. Pressing ESCAPE from a tab returns you to the Home screen.

Menu Tabs

The FORM groups parameters into numbered menu tabs. The tabs available depend on the model and installed options; service and configuration tabs require an authorized account.

Tab	Contents
P00 — Home	Home and main operating values
P01 — Service Timers	Maintenance countdown timers per component
P02 — Utilisation	Running hours and load / utilisation counters
P03 — Error Log	Active and historical fault / alarm log
P04 — Event Log	Logged operating events
P05 — Service Provider	Service provider contact information
P06 — Controller Data	Serial number, software version and ID, network / IoT data
P07 — Asset Data	Equipment / asset identification data
P08 — Graph	Trend graph for pressure and temperature (up to one month of data)
P09 — Access	User account / access level entry
P10 / P11 / P12 — EQUIP Settings 1, 2, 3	Equipment setup parameters (service access required)
P13 — VSD Settings	Variable-speed drive parameters (VSD models)
P14 — Motor Protection	Motor protection thresholds
P15 — Inhibits	Start / load inhibit conditions
P16 / P17 — Warning & Immediate-Stop Alarms	Warning-alarm and immediate-stop alarm thresholds
P18 / P19 — I/O & Sensor Config	Digital / analog I/O and sensor configuration
P20 — Diagnostics	Live diagnostic values and I/O status
P21 — Run Schedule	Scheduled start / stop programming
P22 / P23 — Modbus Fan Control & Modbus INV Info	Modbus-driven fan control and inverter (VSD) information
P24 / P25 — IO Extension & IO Sensor Config	IO extension module and its sensor configuration
P26 — RS485 Extension	RS485 / Modbus extension settings
P27 — IoT Settings	IoT module settings, MAC address, and IP configuration

ℹ Note Additional advanced tabs may appear depending on installed options: P28 / P29 (I/O XPM and XPM sensor configuration), P40–P44 (user-defined menus), and P80–P82 (ISC system-control menus). The exact tabs and tab numbers shown depend on your compressor model and configuration.

Operating States

Phase	State	What is happening
Stopped	Power-Up Initialisation	Controller is powering up and initialising.
Stopped	Start Inhibit	Controller checks start-inhibit conditions. If an inhibit exists, the start is blocked and an inhibit message is displayed.
Stopped	Ready to Start	Energised, no active faults, awaiting a start command.
Stopped	Fault / Immediate Stop	Stopped by a protective (immediate-stop) alarm, or by the Emergency Stop button. The condition must be resolved and reset before restarting.
Started	Run Inhibit / Vent Time	After a start or a motor stop, a vent time runs and internal pressure must vent before the motor starts. A run inhibit sends the unit to Standby.
Started	Standby	Started but the motor is stopped. The unit automatically starts and loads when pressure falls to the Load setpoint (or when the inhibit clears).
Running	Motor Start	Main motor starting in a star-delta sequence (or VSD ramp).
Running	Load Inhibit Time	Loading is held off for a set time after the motor start to let motor speed stabilise.
Running · Loaded	On Load	Load relay energised; the compressor is producing air. It unloads at the Unload setpoint or on a remote offload command.
Running	Reload Inhibit Time	After unloading, reloading is held off until this timer expires.
Running	Off-Load Run Time	Running unloaded. If it runs unloaded for the Off-Load Run Time, the motor stops to Standby.
Running	Stop Run Time	On a stop command the unit unloads first, then the motor runs for the Stop Run Time before stopping.

The diagram below shows the same sequence as the controller's state diagram, including the timed intermediate states, grouped under the STOPPED, STARTED, RUNNING, and LOADED conditions.

Message and Alarm Codes

Every message the FORM displays is prefixed with a single letter that tells you what class of condition it is. The prefix matters more than the number when you are deciding what to do next, and it is the first thing to report when you open a ticket. Active and historical messages are listed under the P03 Error Log tab.

Prefix	Class	What it means
A:	Warning alarm	The compressor keeps running. Something needs attention before it becomes a shutdown. The Alarm LED flashes slowly.
E:	Immediate stop (shutdown)	The compressor has been stopped by a protective function. The condition must be corrected, then reset. The Alarm LED flashes fast.
S:	Start inhibit	A start command is blocked. Common causes are an enclosure door interlock, an operator inhibit, or a remote start inhibit.
R:	Run inhibit	The start was accepted but the motor is held off, so the unit sits in Standby until the condition clears.
L:	Load inhibit	The motor runs but loading is held off. Cold-start conditions are a common cause, for example a low outlet or ambient temperature.

ℹ Note An inhibit is not a failure. S, R, and L messages are the controller telling you it is deliberately holding off, usually because a condition has not been met yet. A unit that starts and then sits in Standby with an R or L message is behaving as designed. The full code list is in the AirMASTER FORM Configuration Manual.

Control Modes

Start and Stop Sources

The Start Source parameter sets where a start command is allowed to come from. Only one start source is active at a time. The choices are the local keypad START button, an equipment digital input (a wired remote start/stop signal), or communications (Modbus RS485, or the IoT module). Local keypad control is the normal arrangement on a standalone South-Tek compressor.

ℹ Note All available stop functions stay active at all times regardless of the selected start source, so the panel STOP button and the Emergency Stop always work. Note also that if the start source is set to communications and the link is lost, the controller does not fall back to keypad control on its own.

Capacity Control Modes

Separately from where the start comes from, the controller has a capacity control mode that governs how it loads and unloads to hold system pressure. The mode is set at the factory to suit the compressor and the application.

Mode	How it behaves
Load / Off Load	Loads and unloads at the load and unload pressure setpoints. If it runs unloaded longer than the Off Load Run Time it stops to Standby, then restarts and loads when pressure falls to the load setpoint.
Continuous Run	Same as Load / Off Load, except the Off Load Run Time is ignored and the unit runs unloaded indefinitely rather than stopping to Standby.
Pressure Decay / No Load	Same as Load / Off Load, except the off-load run time is extended when load periods are short, so the motor cannot exceed the permitted starts per hour.
Dynamic / No Load	The off-load run time is calculated continuously from how often the unit has been stopping, tightening up as the starts-per-hour limit is approached.
Variable Speed	VSD models. Motor speed is varied by a PID algorithm to hold the load pressure setpoint, and drops to the set off-load speed when unloaded.
Modulation	Loads and unloads on the pressure setpoints, and above the modulation pressure the status changes to On Load Modulation while a valve returns outlet air to the inlet.

▲ Attention Control mode, pressure setpoints, and starts-per-hour limits are service-level parameters. Changing them affects motor life and energy use, and on a system with a dryer, storage, or a nitrogen generator downstream it can change how the whole package behaves. Contact South-Tek Service before changing any of them.

Automatic Restart After a Power Failure

The controller has an automatic restart function governed by a restart inhibit time. When that time is set, the compressor restarts on its own after power is restored, delayed by the set number of seconds. It only does so if the unit was in a started state (Standby, running off load, or loaded) at the moment power was lost. If it was stopped when power was lost, it stays stopped when power returns.

⚠ Warning — Automatic Restart Where automatic restart is configured, the compressor will start without any operator input once power returns. Confirm the setting on your unit before working on the machine, and never rely on the controller alone to keep it stopped. Isolate and lock out the disconnect before any service work. An automatic-restart icon in the status toolbar indicates the function is enabled.

Maintenance Warnings

The AirMASTER FORM displays maintenance reminders when a component reaches its service interval. The compressor continues running while maintenance warnings are active, and the warnings remain on screen until manually reset. The Maintenance LED on the panel lights whenever any service item is due.

The countdown timers themselves are under the P01 Service Timers tab, which any user can view. Depending on how your unit is configured, P01 can show hour-based counters for individual components such as the air filter, oil filter, oil service, and cabinet filter, plus calendar-based counters for weekly, annual, and two-year items and for pressure vessel and safety valve service. Running hours and load and off-load hours are under P02 Utilisation.

Resetting a service timer after the work is done is a service-level function and must be done at the controller itself. If a timer needs to be reset and you do not have service access, open a ticket and we will take care of it.

▲ Attention Do not reset a maintenance warning until the corresponding maintenance has been physically performed. Resetting without completing service is a warranty violation and the manufacturer cannot be held liable for resulting damage.

Optional Modules

Module	Function
RS485 / Modbus RTU	Fieldbus communication (Airbus485 proprietary or Modbus RTU slave/master). Enables integration with building management systems and SCADA.
IoT (Ethernet / TCP-IP)	Web browser monitoring over Ethernet. Provides Health, Performance, Custom, and Events dashboard pages. Supports remote start/stop flagging. Automatically syncs controller timestamp if internet-connected.
IO Extension	Additional analog and digital I/O for expanded sensor inputs (inlet vacuum, oil temperature, delivery temperature, oil pressure, oil filter differential, cooler approach temperatures).
Fieldbus Network Cards	Optional cards for Profibus, DeviceNet, EtherNet/IP, and other industrial protocols.

ℹ Note The complete AirMASTER FORM Configuration Manual (V3) is included as Addition Chapter 1 of your compressor documentation package. It covers the full parameter list, menu map, message codes, symbol definitions, and IoT module setup in detail.

Need help? South-Tek Systems Service — Phone: (910) 415-1880 · Open a support ticket at support@southteksystems911.zendesk.com or through the Help Center.