Fault Finding Glow-worm 30ci, 30si and 35ci Boilers
This fault finding guide covers the following models:
- Glow-worm 30ci – G.C. No. 47-047-20
- Glow-worm 30si – G.C. No. 41-047-70
- Glow-worm 35ci – G.C. No. 47-047-28
Fault Finding and Diagnostics
This page provides a comprehensive fault-finding guide for the Glow-worm Betacom2 boiler range, including the 30ci model. The procedures cover common issues related to central heating, domestic hot water (DHW), and ignition failures. All gas boiler repair and servicing work must be performed by a qualified gas engineer.
Preliminary Checks
Before commencing any fault-finding procedures, ensure the following basic checks have been completed.
- Confirm all gas supply cocks are fully open and that the gas supply line has been properly purged of air.
- The heating system water pressure must be at a minimum of 1 bar.
- Verify a permanent 230V mains electrical supply is present at the boiler and that the polarity is correct.
Electrical Safety Warning
WARNING: Always isolate the Glow-worm Betacom2 boiler from the mains electrical supply before performing any work on electrical components like the PCB, fan, or gas valve. After completing any fault-finding task that involved altering electrical connections, it is crucial to repeat continuity, polarity, short circuit, and resistance-to-earth checks using a suitable multi-meter. Always check for gas soundness after completing any service or repair work on gas-carrying components.
Overheat Thermostat Reset
The overheat thermostat is a safety device. If it has tripped, the boiler will lock out. The device is fitted with a manual reset button. To reset the system, depress the small reset button located on the overheat thermostat assembly.
General Fault Symptoms
If the boiler exhibits general faults such as no display or a failure in both heating and hot water modes, consult the following checks.
| TYPE OF FAULT | CHECK |
|---|---|
| No display on control panel | • 230V supply • PCB fuse • Connection between PCBs |
| No domestic hot water (30ci Only) No central heating (Red flashing warning light and flashing fault code in display) |
• Loose connections on control board (PCB) • Connections on air pressure switch (electrical or tubes) disconnected • Faulty control or interface board (PCBs) • Water pressure, flashing pressure • Shortage of air or gas • Faulty temperature sensor • Overheating |
Fault: No Central Heating
To diagnose a lack of central heating, follow this logical sequence. First, check if the external heating controls (e.g., room thermostat, programmer) are calling for heat. If not, rectify the fault on the external controls.
If the external controls are calling for heat, check if the mains electrical polarity is correct. If it is not, rectify the polarity and check the 230V controls board.
If the polarity is correct, connect terminals 1 and 2 on connector J10. If the boiler successfully fires for central heating, the 230V controls board is faulty and requires replacement. If the boiler does not fire, the main PCB is faulty.
Fault: No Domestic Hot Water (DHW) / Heating Working (30ci Only)
For the Glow-worm Betacom2 30ci model, if the central heating works but there is no domestic hot water, begin by checking the system water pressure is greater than 0.5 bar. If it is not, the appliance will not operate. The cause for the low pressure must be investigated and rectified.
If the pressure is correct, check if the domestic hot water flow rate is greater than the threshold of 1.7 litres per minute. If the flow rate is too low, check the cold water inlet filter for debris, ensure the cold water tap is fully open, and inspect the plate heat exchanger for scaling.
If the flow rate is sufficient, check if the flow detector is operating correctly. If it is not, it should be cleaned or changed.
If the flow detector is operating, the final step is to check the electrical connectors on the flow sensor and the control board (PCB). If the fault persists after these checks, the control board (PCB) is likely faulty and should be replaced.
F1 Fault: Burner Does Not Light (Ignition Spark Present)
When an F1 fault is displayed and the burner does not light despite a spark being present, first confirm that the gas taps are open. If they are closed, open them.
If gas taps are open, check for 24Vdc at the gas control valve during the ignition sequence. If there is no voltage, check the wiring back to the control board (PCB). If the wiring is sound, the PCB is likely faulty and requires replacement.
If 24Vdc is present at the gas valve, test the gas control valve itself. Check the resistance of the safety valve coil. A faulty gas valve will need to be replaced.
F1 Fault: Burner Lights Then Goes Out (No Flame Detected)
This fault occurs when the flame does not spread across the entire burner to reach the sensing electrode. First, check if the gas pressure is correct. If not, ensure all gas taps are fully open and check the incoming gas pressure. If the gas pressure is correct, clean the gas filter and the main burner assembly.
F1 or F4 Fault: Burner Lights Then Goes Out (Flame Detected)
This fault indicates the flame is established across the burner but is not being detected by the boiler’s control system. With the power off, check the continuity of the flame sense electrode and its lead back to terminal H2.4 on the control board (PCB). Also, check the connector on the end of the wire. Ensure the spark electrode is correctly positioned and pointing towards the flame. If necessary, check and replace the spark electrode. If the problem persists after these checks, the flame detection module on the control board (PCB) is faulty, and the PCB should be replaced.
Fault: Fan Does Not Start
If the fan fails to start on demand, check for a 230V AC supply at the fan’s electrical connection. If 230V is present, the fan is faulty and must be replaced. If there is no 230V supply, check the continuity of the fan wiring harness. If the fan harness has continuity, the fault lies with the main PCB, which will need to be replaced.
Fault: Fan Runs But No Ignition Spark
If the fan runs but the boiler does not produce an ignition spark, the issue is with the ignition circuit. Check the continuity of the spark electrode and its lead. Also, check the power supply from the main PCB to the ignition unit.
Fault: Inadequate Room Temperature or Luke-Warm Radiators
If the heating performance is poor, first ensure the room thermostat and any thermostatic radiator valves (TRVs) are set high enough and are calling for heat. If not, turn up the settings.
Next, check that the central heating temperature on the boiler itself is set high enough.
If settings are correct, verify that the heating power output is adequate by checking set point P3 (refer to commissioning instructions). Also, check the adjustment of any internal or external bypasses. For the 30ci/35ci models, you must also check that the 3-way diverter valve is not stuck partially open, allowing heat to pass into the domestic hot water heat exchanger during a heating demand.
Fault: Luke-Warm Domestic Hot Water (DHW) (30ci Only)
If the hot water from the taps is only luke-warm on the 30ci model, first test if the water temperature increases when you reduce the flow rate at the tap.
If the temperature does increase with a reduced flow rate, it indicates the boiler is struggling to heat the water quickly enough. Check that the flow restrictor on the cold water inlet is correctly fitted. Check the overall rate of flow, and verify that the burner gas pressure is correct.
If reducing the flow rate does not increase the temperature, check that the 3-way diverter valve is not passing hot water into the central heating circuit. The radiators should remain cold when the boiler is in its summer (hot water only) setting.
Fault Codes and Display Messages
The Glow-worm Betacom2 boiler uses a system of fault codes displayed on the user interface to aid in diagnostics. A fault is typically indicated by a code number, a flashing ‘F’, and a flashing red LED.
| DISPLAY | FAULT |
|---|---|
| ’01’ and ‘F’ and ‘flashing red LED’ | Ignition fault (lockout) caused by no gas, no detection |
| ’02’ and ‘F’ and ‘flashing red led’ | Air fault, pressure switch, no power to fan |
| ’05’ and ‘F’ and ‘flashing red LED’ | Overheat fault |
| ’06’ and ‘F’ and ‘flashing red LED’ | Central heating flow NTC fault |
| ’09’ and ‘F’ and ‘flashing red LED’ | Water pressure sensor fault |
| ’11’ and ‘F’ and ‘flashing red LED’ | No reception by the main board (MMI Lead) |
| ’12’ and ‘F’ and ‘flashing red LED’ | User interface or distant control panel fault |
| ’13’ and ‘F’ and ‘flashing red LED’ | Main board fault |
| ’14’ and ‘flashing red LED’ | Over temperature on primary water circuit |
| ’15’ and ‘F’ and ‘flashing red LED’ | Stepper motor fault (gas valve) |
| ’16’ and ‘F’ and ‘flashing red LED’ | Gas safety value failure |
| ’17’ and ‘F’ and ‘flashing red LED’ | Power supply \<170V |
| ’18’ and ‘F’ and ‘flashing red LED’ | Local user interface fault |
| ’19’ and ‘F’ and ‘flashing red LED’ | Central heating NTC not connected to pipe |
| ’20’ and ‘F’ and ‘flashing red LED’ | User interface not compatible with boiler |
| ‘0.5bar’ flashing and ‘F’ and ‘flashing red LED’ | Lack of water fault (\<0.5b) |
| ‘2.7bar’ flashing and ‘F’ and ‘flashing red LED’ | Upper water pressure (>2.7b) |
Component Testing and Data
This section provides normal operating values and checks for key components within the Glow-worm Betacom2 boiler.
Gas Control Valve Test
To test the gas control valve, check the voltage at its electrical connection during an ignition demand. You should measure 24V DC for the first 1-2 seconds, which then drops to a constant 12V DC. If you measure 0 Volts, the gas control valve is not the source of the fault. If the correct voltages are present but no gas is being delivered to the burner, check if the gas valve is mechanically stuck. If not, check the adjustment valve. The resistance of coil 1162 should be checked.
Adjustment Valve (Stepper Motor) Test
To test the stepper motor, first close the gas inlet. Dismantle the stepper motor (note: the screw is not sealed). Initiate a demand for heat or hot water and check that the valve physically opens during the ignition sequence. If the valve does not move, check the electrical connections at both the motor and the control board (PCB). If connections are good, change the motor. If the fault persists, replace the control board (PCB).
Three-Way Valve Test (30ci Only)
The three-way valve motor can be tested electrically. Normal resistance values are 9.6kΩ between terminals 1 and 2, and 9.6kΩ between terminals 1 and 3.
During a central heating demand, you should measure 230V AC between terminals 1 and 2, and approximately 25V to 35V AC between terminals 2 and 3.
During a domestic hot water demand, you should measure 230V AC between terminals 2 and 3, and approximately 25V to 35V AC between terminals 1 and 2.
If the measured voltages are incorrect, check the connections, the three-way valve lead, and the main control board (PCB).
Three-Way Valve Motor Thrust Action Test
A physical test of the motor’s action can be performed. Unfasten the retaining clip to pull out the motor, leaving it electrically connected. During a hot water demand, the motor’s spindle should pull in. During a heating demand, the spindle should push out. If the electrical supply is correct but the motor axle does not move, replace the motor. If the problem continues, replace the control board (PCB).
Domestic Water Flow Detector Test (30ci Only)
To test the domestic water flow detector, connect a new detector electrically in place of the suspect one. Simulate a demand for hot water by blowing through the new detector and observe if the boiler responds correctly.
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