Gardner DELCOS 3100 Controller Field Troubleshooting and Maintenance Guide

Gardner DELCOS 3100 Controller Field Troubleshooting and Maintenance Guide

In industrial compressed air systems, the stability of the controller is directly related to the continuous operation of the production line. Gardner Denver's DELCOS 3100 controller is designed specifically for EnviroAire oil-free compressors and comes in three configuration levels: fixed speed (FS), variable speed (RS), and SR drive (SR). Its built-in intelligent control logic, basic load sequence (BLS) function, water circuit management, and rich fault diagnosis capabilities provide powerful monitoring tools for on-site engineers. However, facing complex alarm codes, parameter settings, and hardware failures, quickly identifying the root cause of the problem remains a major challenge.

This article is based on the DELCOS 3100 user manual and combines practical maintenance experience to systematically review the controller's operation panel, menu structure, common fault codes, and troubleshooting methods. It also provides practical guidelines for basic load sequence configuration, water circuit maintenance, and SR drive fault handling, helping engineers shorten downtime and ensure reliable equipment operation.

Overview of DELCOS 3100 Controller

DELCOS 3100 is divided into three versions based on different types of compressors:

FS version: Used for fixed speed compressors, controlled by pressure switches for loading/unloading.

RS version: Used for speed regulating compressors, it adjusts the motor speed through a frequency converter to achieve continuous flow regulation.

SR version: Used for SR specific drive (switched reluctance motor), communicating with the drive unit through CAN interface.

The controller has functions such as multilingual display (17 languages), real-time clock, fault memory, remote control, RS485 communication (Modbus or DELCOS protocol), etc. Its core parameters are set and viewed through the menu system.

Operation panel and status indication

2.1 Buttons and LEDs

Keys: directional keys (up, down, left, right), confirm key（ ⏺）、 Code key（ 🔒）、 Start/stop keys, etc.

LED indicator light:

LED A (flashing green): In standby mode, the motor may automatically start at any time.

LED A (always on): The motor is running.

LED B: In menu operation mode.

LED C: Automatic restart activation.

LED D: Remote control activation (flashing: remote off; constantly on: remote on).

LED e: Timer control (flashing: timed off; constant on: timed on).

LED f: Maintenance interval expires.

LED g: Warning.

LED h: Group malfunction.

Safety reminder: The motor may start automatically in standby mode. Before modifying or maintaining parameters, be sure to disconnect the main power supply. After cutting off the power supply, the SR version needs to wait for 12 minutes for the capacitor to discharge completely.

2.2 Display Area

The first row of the main display area usually displays: exhaust temperature (sensor R2), final compression pressure (sensor B2), and pipe network pressure (sensor B1). When the sensor malfunctions, it displays "[---]" and "FAULT SENSOR..." messages.

The second line displays the current status of the machine, such as "READY TO START", "OFF-LOAD", "ON-LOAD", "SOFT STOP TIME XXs", etc. When a warning or maintenance prompt appears, the status information will alternately display relevant text.

Menu Structure and Common Settings

Before entering the menu, press the "±" key, use the left and right arrows to switch menu branches, and use the up and down arrows to select parameters. Modifying parameters may require entering code 3031 to unlock (factory limit values cannot be changed). The menu will automatically exit after 2 minutes of inactivity.

3.1 [AINTENANCE SCHED.] Menu

View or set maintenance intervals:

TOTAL RUNNING: Total running hours

Loaded HOURS: hours of loading

Air Filter IN: Air Filter Remaining Hours

Water Filter IN: The remaining hours of the water filter

MOTOR GREASING: Motor lubrication remaining hours

When the remaining hours are 0, LED f lights up and displays "MAINTENANCE ELAPSED". If the maintenance shutdown function is activated, it will trigger the "FAULT MAINT PER" shutdown when it reaches -100 hours.

3.2 [Control Menu]

Core control parameters:

CUT-OUT POINT/CUT-IN POINT (FS version): upper/lower limit of pressure switch.

TARGET PRESSURE (RS/SR version): Set the pressure, and the PI controller maintains this pressure.

AUTOMATIC OPERATION / CONTINUOUS OPERATION： Automatic mode (on-demand shutdown standby) or continuous mode (no-load operation without shutdown).

SPEED REGULATION ON/OFF (RS version): Enable/disable speed regulation.

VOL.MAX./VOL.MIN.: Maximum/minimum traffic, used to calculate the current traffic.

Display UNITS: Flow unit (m ³/min, cfm, m ³/h).

Remote Control ON/OFF: Enable remote start stop.

TIMER Control ON/OFF: Enable timer control.

AUTO REST: Automatically restarts after power failure.

POWER LOSS TIME: Allow power outage time (2-999 seconds).

RS485 ROTOCOL/BAURDATE: Modbus or DELCOS protocol, baud rate 4800/9600/19200.

3.3 [Fault Memory] menu

Record the last 8 faults/warnings, each containing: serial number (with! Indicating shutdown), fault text, and total operating hours at the time of occurrence. Press the confirm button to view extended information (date and time, compressor status, speed, temperature and pressure, etc.). After eliminating the cause of the malfunction, press the "A" key to confirm.

3.4 [Limit Values] Menu

Display the limit values set by the factory (usually not modifiable by the user):

Design PRESS: Design Pressure

START Protect: Start protection pressure (below which it is allowed to start)

Final Temperature Warning/MAX: Exhaust Temperature Alarm/Shutdown Value

MIN START TEMPLE: Minimum Start Temperature

RUN-ON TIME: Continue running time after uninstallation

SOFT STOP: Soft Shutdown Time

STAR/DELTA TIME (FS/RS): Star Delta Conversion Time

EXT.LIMIT (SR): External speed limit value

3.5 [INTERNATIONAL INPUTS] Menu

Three backup inputs (OPTION 1/2/3) can be configured, with functional options including: FREE (not monitored) BEKOMAT FAULT/WARN、DRYER FAULT/WARNING、EXT FAULT/WARNING、DISCH TEMP、OPERATE_B1、EXT.RPM LIMIT（SR） Wait. After proper allocation, the controller will monitor these external signals and trigger corresponding alarms.

3.6 [WATCH] Menu

Water cooling system parameters:

Change Cycle: Automatic water change cycle (real-time interval)

SUPLY MAX.: Water replenishment timeout

DRAINAGE MAX.: Drainage timeout

The status display is as follows: "22h y8 y9 Y10><": remaining water change hours, status of each solenoid valve (y not triggered/Y triggered), water level (↑ high/≥ normal/↓ low).

3.7 [TIMER CON] Menu

Set real-time clock and timed power on/off (7 timing blocks) as well as pressure switching (another 7 p2 blocks). When the pressure switch is activated, the p2 symbol flashes before the pressure display. Pressure switching can also be achieved through external contacts.

Common fault codes and troubleshooting methods

DELCOS 3100 has a comprehensive fault self diagnosis function. The following table summarizes the most commonly encountered fault phenomena, possible causes, and solutions on site (based on section 1.5.2 of the manual).

Possible causes and solutions for displaying information

Fault Power Loss: Power interruption, cable damage, loose terminals. Check the power supply, cables, all terminals, and plugs

FAULT EM-STOP emergency stop button is pressed or damaged to unlock emergency stop; Check button contacts

Frequent starting, poor cooling, and high power limit the number of starts per hour for the FAULT MOTOR TEMP motor; Improve ventilation; Check the motor

FAULT COMP TEMP Exhaust Temperature Exceeding Limit Check Cooling System, Environmental Temperature, Temperature Sensor R2

Warning High Temperature: Improve ventilation in the computer room due to high intake temperature and insufficient cooling. Close the chassis door

Fault OVER PRESS: High pressure loss in the pipeline network, high pressure switch point, high external pressure request. Check the pipeline, lower the set point, and check the remote pressure signal

FAULT SENSOR B1/B2/R2 sensor malfunction or wiring damage. Check the sensor and cable and replace them if necessary

Fault Direct ROT motor phase sequence error (no pressure difference during startup phase), swap the two-phase incoming lines

FAULT CONVERTER RS version: The frequency converter is not ready; SR version: CAN communication failure check for variable frequency drive incoming line, filter, internal fan; Check the CAN line and terminal resistance

Final compression pressure is too high when starting FAULT HEAVY STARTUP. Check if the intake control valve is not tightly closed

FAULT SPEED LOW: The minimum speed has not been reached (SR version). Check the connection between the emergency stop circuit and the SR drive and notify the service

FAULT COOLING air cooling: fan failure, air duct blockage; Water cooling: If the cooling water is insufficient or the water temperature is high, check the fan and clean the filter screen; Check the waterway, solenoid valve, and exhaust system

Warning Air Filter: High differential pressure in the air filter. Clean or replace the filter element

Warning OIL LEVEL: Add lubricating oil when the oil level is low

FAULT BYPASS RS Version: Bypass Not Ready Check Bypass Contactor and Control Circuit

Fault SR-DRIVE (1)~(55) SR drive internal faults (see table below for details) are checked according to specific numbers

Warning BATTERY: Real time clock battery depleted, replace RTC module

FAULT LEVELSWITCH water circuit has two liquid level switches closed simultaneously (mechanically impossible). Check the liquid level switches and their wiring

The inspection of the drainage solenoid valve and liquid level switch was not completed during the 1/5 water exchange of FAULT DRAINAGE; Increase DRAINAGE MAX time

Quick investigation of common internal faults in SR drive

Handling of Fault Number Meaning

15 motor overcurrent inspection motor wiring and insulation; Check the current sensor

19. Overvoltage check of intermediate DC circuit power supply voltage (not exceeding 506V between phases)

28/29 Phase loss or undervoltage check incoming fuse, phase sequence, voltage detection circuit

31/32/33 Motor, check the cable and winding of a certain phase for an open circuit

34-39 IGBT faults require maintenance by service personnel

46 motor temperature sensor fault inspection control board J11 plug and sensor

52 CAN Communication Error Check: Control Board to DELCOS CAN Line and Terminal Resistance

54 motor stalling manual turning, check if the compressor is stuck

General screening principles:

Confirm that the power supply voltage is within the allowable range and the control transformer gear is correct.

Check if all plugs and wiring terminals are securely fastened.

The temperature of the control cabinet shall not exceed 55 ℃.

The length of the remote control circuit should not exceed 20 meters, otherwise intermediate relays need to be used.

Be sure to tighten all connecting screws after each repair.

Basic Load Sequence (BLS) Function and Settings

BLS is an optional feature (FS and SR versions) of DELCOS 3100, used for master-slave control. The main compressor (K1) controls the loading/unloading of up to 4 slave machines (K2~K5) through the relay module (A06), and automatically rotates the basic load machines according to the operating hours.

5.1 BLS Menu Key Parameters

Suggestion for parameter meaning setting

Operation ON/OFF/TIMER enables BLS or timed activation

CUT-OUT POINT/TARGET PRESSURE Pressure band upper limit/set point pressure band width should not be less than 0.3 bar

CHANGEOVER TIME rotation interval (1-999h or 300s test) is set based on the balanced operation of each compressor

Number of slave machines participating in rotation for QUANT.SLAVES: 1-4

Quantity of spare machines (not participating in rotation) 0~(4- number of slave machines)

VOL.COMP2... 5 (RS/SR) rated flow rate (m ³/min) of each slave input according to the nameplate

SWITCH OFF DELAY peak machine cut-off delay recommended 30 seconds

Load NET IN: Charge the network within a limited time to avoid multiple machines starting simultaneously on Monday mornings

The accurate value of the total volume (m ³) of the NET VOLUME (RS/SR) pipeline network affects control stability

5.2 BLS Status Display

Example: The meaning of "123h K1 K3 k4 r2 r5" is:

123h: Remaining hours until next rotation

K1 (uppercase K): Current base load machine

K3, k4 (lowercase k): Medium load, peak load machine

R2, r5 (lowercase r): Backup machine

The faulty machine displays as' k1 'and moves to the end, alternating every second.

5.3 Common BLS Malfunctions

Warning MS-BUS: A06: Relay module failure, slave cannot load. Check the module power supply and fuses.

BLS not working: main station power outage, pressure sensor B1 malfunction, module A06 failure. After confirmation, BLS can be forcibly enabled through external contacts (input E07.4).

Inaccurate flow calculation: Check if VOL.COMP2... 5 is entered correctly and confirm that the slave returns a 'run' signal (otherwise BLS will incorrectly calculate the total flow).

Maintenance and troubleshooting of water circuit

The automatic water level adjustment and regular water replacement of the pressure tank of the water-cooled compressor are managed by the controller.

6.1 Principle of automatic water level regulation

High water level: Delay opening the drainage solenoid valve (y9) until the water level is normal. If the timeout is not completed, report FAILT DRAINAGE 5.

Low water level: Only open the water replenishment solenoid valve (y8) during loading and operation. If the timeout is not compensated to normal, report Warning Supply 5.

When the motor stops, the drain stop valve (Y10) is closed to prevent water from flowing back into the compressor.

6.2 Water exchange process

After the Change Cycle is reached, the following sequence should be executed:

Open the drain valve to the lower limit.

Open the water replenishment valve to the upper limit position.

Drain again to the normal water level and reset the cycle timer.

If the machine is unloaded or stopped during the water change period, the process will pause and continue after loading.

6.3 Troubleshooting of Water Circuit Malfunctions

Possible causes and measures of the malfunction

The simultaneous closure of two liquid level switches and inspection of the switches and wiring may be due to mechanical jamming

Warning Supply 2/Fault Supply 2 Water replenishment timeout check for inlet pressure, water treatment unit tank, water replenishment solenoid valve, and control transformer

Check if the drain solenoid valve and pipeline are blocked during the drainage timeout of FAULT DRAINAGE 1/4, and increase the DRAINAGE MAX value appropriately

Frequent water changes fail due to insufficient water supply in the water treatment unit, resulting in an increase in the water change cycle (such as 48 hours or longer)

Operation mode and remote control

7.1 Automatic mode vs. continuous mode

Automatic Operation: The most economical mode, with on-demand shutdown and standby.

Continuation Operation: To prevent frequent start stop situations, do not shut down after unloading and only run without load.

7.2 Speed Control (RS Version)

SPEED REGULATION ON: Normal speed regulation, PI control maintains target pressure.

SPEED REGULATION OFF: Fixed maximum speed, used for testing or bypassing.

Bypass operation: If the frequency converter fails, it can be switched to the star delta bypass (option). Shutdown is required first, switch the menu to BYPASS Operation, confirm that the bypass is ready, and restart.

7.3 Remote start stop and pressure switching

Remote start stop: Set [REMOTE Control ON], LED d lights up, controlled through dry contacts on terminals X3.25/X3.26 (closed=remote open, open=remote close).

Pressure switching: The second pressure band can be activated through a timer or external contacts (SR version terminals X4.6/X4.14), and the p2 symbol flashes.

Remote loading/unloading (FS version): External contacts (X3.23/X3.24) are connected in parallel with internal pressure switches for forced loading. Pay attention to the overpressure protection logic (external loading will be temporarily disabled after exceeding the set pressure of 0.5 bar).

7.4 Automatic restart and power outage recovery

Standard automatic restart: only valid when the power outage time is ≤ POWER LOSS TIME (2-999 seconds). There is a START-UP DELAY to stagger before restarting.

Unlimited automatic restart: You need to apply for a code from the Gardner Denver service, and it can automatically restart at any time after a long power outage. Before use, safety regulations must be evaluated, warning signs must be installed, and the computer room must be locked.

Analog output and communication

8.1 Analog output (RS version)

Channel 2: 4-20 mA, corresponding to 0-maximum flow rate. When BLS is activated, the output is the total flow rate of all controlled compressors.

Attention: An isolation amplifier needs to be installed at the output end to prevent interference.

8.2 Analog Output (SR Version, Options)

Channel 1: 4-20 mA, corresponding to 0 to maximum speed.

Channel 2: 4-20 mA, corresponding to 0-maximum flow rate (total flow rate when BLS is activated).

8.3 RS485 Communication

Supports Modbus RTU or DELCOS protocols, baud rates of 4800/9600/19200, and can set station addresses. Combined with Gardner Denver Profibus module or Modbus master, DELCOS 3100 can be connected to higher-level control systems.

Regular maintenance and calibration recommendations

To prevent unexpected shutdowns, it is recommended to perform maintenance according to the following cycles:

Monthly: Clean the ventilation filter of the control cabinet; Check if all wiring terminals are loose; Check the warning records in the fault memory; Observe the status of the water circuit (water level, solenoid valve action).

Quarterly: Calibrate pressure sensors (B1, B2) and temperature sensors (R2); Check the pressure difference of the air filter and replace it if necessary; Check the condition of the motor grease.

Every six months: Backup controller parameters (record all menu settings); Test the emergency stop circuit; Check the discharge time of the SR drive capacitor (measured after power failure).

Every year: replace the real-time clock battery (when Warning BATTERY occurs); Check the solenoid valve and liquid level switch of the water circuit; Verify the safety valve.

Operation after replacing the electronic board:

If the DELCOS 3100 electronic board is replaced, it will require the input of three setup codes after startup. These codes are located on the labels inside the electrical control cabinet. After input, all parameters will be restored to their factory default values. It is necessary to reconfigure: optional input allocation, BLS parameters, water circuit parameters, pressure set points, communication parameters, etc.

Fault case sharing

Case 1: The RS version compressor frequently reports "FAULT CONVERTER", but the frequency converter panel has no faults

Phenomenon: Sudden shutdown during operation, displaying FAULT CONVERTER. Check that the frequency converter has no alarms, and the multimeter measures that there is no 24V signal at the "ready" output terminal of the frequency converter.

Reason: The auxiliary contacts of the frequency converter are aging and have poor contact. Sometimes there is no measurement.

Solution: Replace the auxiliary relay of the frequency converter; Simultaneously check the 24V power supply and wiring terminals inside the frequency converter.

Case 2: SR version displays "FAULT SR-DRIVE (52)" and "FAULT SR-LOCKOUT (3)"

Phenomenon: Immediately display CAN communication error after power on, unable to start.

Troubleshooting: Check if the flat cable connection between the measurement control board and the gate drive board is secure; Check the CAN bus terminal resistance (120 Ω). The plug J19 (emergency stop connection) was found to be loose, and the fault disappeared after re plugging it.

Case 3: Frequent occurrence of Warning Supply 2 in the water circuit

Phenomenon: Water replenishment exceeds the time limit, and the actual pressure tank water level remains low.

Inspection: The inlet solenoid valve is not functioning. The resistance of the multimeter coil is infinite, and it is normal after replacing the solenoid valve. At the same time, check if the water supply pump of the water treatment unit has sufficient pressure.