Modern boiler control cabinets are equipped with a variety of alarm functions, which will promptly issue alarm prompts when the boiler operation is abnormal or potentially dangerous. These alarms are both protective measures and reminders for operators to take prompt action. However, for engineers and end users, facing frequent alarm failures, it is necessary to understand the reasons behind them and master basic troubleshooting methods. Below, we introduce several common alarm types, cause analysis and corresponding troubleshooting suggestions in boiler control cabinets from the professional perspective of Henan Rentai.
Abnormal Water Level Alarm
Low or high water level alarms are one of the most common faults in boiler operation. Once the water level deviates from the normal range, the control system will alarm or even shut down the boiler to prevent dry burning or full water accidents. If the boiler often has low water level alarms (or even wrong shutdowns), common reasons include insufficient water supply in the water supply system, poor grounding, water level sensor failure, or controller's incorrect judgment of the water level. For example, when the water level electrode is scaled or the sensor line is loose, the controller may misjudge the water level as too low, thereby issuing a false alarm. For water level alarm, the troubleshooting sequence should start from the actual water level and water supply system: first check whether the water supply pump, water tank, etc. are supplying water normally, and whether the water level gauge display truly reflects the boiler water level; ensure that the water source is sufficient and the water supply pipeline is unobstructed. Then check the water level sensor and its wiring, clean the probe electrode, and tighten the line terminal. If the sensor is found to be damaged or aged, it should be replaced in time. After completing the above inspections and treatments, re-operate the boiler to observe whether the water level alarm is lifted. Regular maintenance of the water level monitoring system (such as cleaning the electrode and calibrating the water level controller) is an effective measure to avoid false alarms.
Combustion Flameout Alarm
Combustion flameout alarms usually refer to boiler ignition failure or accidental flame extinguishment during operation. This type of alarm will trigger an emergency shutdown because continuing to supply fuel after flameout may cause danger. The causes of ignition failure/flameout are more complicated, including electrical and combustion system aspects. Electrically, if the controller does not issue an ignition command, the high-voltage ignition wire is loose, the ignition transformer is faulty, and the ignition electrode gap is incorrect, it will cause ignition failure. In terms of the combustion system, poor fuel supply (such as low gas pressure, clogged fuel nozzle) or insufficient air supply (improper damper opening, blower failure) may also cause the flame to go out. In case of flameout alarm, the fuel supply should be quickly shut off to prevent the accumulation of unburned fuel. Then carry out the inspection: confirm that the fuel valve is open and the gas pressure/oil pressure is normal, and the burner nozzle or gas nozzle is not blocked; check whether the blower is operating normally and the damper opening is appropriate to ensure sufficient combustion air. Next, check whether the ignition system is working: observe the flame monitor or fire detection electric eye to determine whether there are sparks and flames during the ignition process; if the ignition component is suspected, the spare parts (ignition needle, high-voltage package, etc.) can be replaced and the electrode spacing can be adjusted to the manufacturer's specified value. After completing the above operations, restart the boiler for trial ignition. If ignition difficulties still occur repeatedly, it may involve the control program parameters, and professional technicians need to check and optimize the combustion control logic and proportional adjustment parameters.
Overpressure or Overtemperature Alarm
The boiler overpressure or overtemperature alarm is another type of fault that needs to be paid attention to. The boiler must keep the pressure and temperature within the safe range during operation. Once the set upper limit is exceeded, the control cabinet will immediately alarm and take protective actions such as limiting combustion and stopping the boiler. The cause of overpressure/overtemperature may be that the actual pressure or water temperature is too high due to changes in operating conditions or improper control: for example, the evaporation of a steam boiler suddenly decreases, causing the pressure to rise, and the load of a hot water boiler suddenly decreases but the combustion rate is not reduced in time. At this time, the load of the boiler and the output of the controller should be checked, and the combustion load should be manually reduced or the pressure relief device (such as a safety valve) should be opened to reduce the pressure to the normal range. On the other hand, some overpressure and overtemperature alarms are "false alarms", that is, the failure of the sensor or measuring device causes the controller to misjudge. For example, the zero drift of the pressure sensor will make the control system mistakenly believe that the boiler pressure has increased, and the failure of the high-temperature sensor may trigger an unnecessary overtemperature alarm. Therefore, when troubleshooting, it is necessary to identify the alarm information: verify the actual working condition of the boiler through the local pressure gauge and thermometer. If the on-site reading is normal but the control cabinet alarms, the corresponding pressure/temperature sensor and transmitter should be checked to see if they are accurate and reliable. You can try to recalibrate the sensor or replace the suspicious sensor to see if the alarm is lifted. If the false alarm is caused by sensor misalignment, the instrument should be regularly calibrated and maintained after the problem is solved to prevent similar situations from happening again.
Fan and Water Pump Fault Alarm
When boiler auxiliary equipment such as induced draft fan, blower, feed water pump, circulating pump, etc. fails, an alarm will also be given on the control cabinet. This type of alarm usually comes from the action of motor overload protection or abnormal speed/flow detection. For example, the "fan fault" alarm may mean that the thermal relay of the fan motor has tripped or the fan has not reached the required speed; the "water pump fault" alarm is mostly caused by the water pump motor overload shutdown or the water outlet flow switch cannot detect the flow. When troubleshooting this type of fault, first confirm the equipment status on site: check whether the corresponding motor is running (can be judged by sound and vibration). If it is not running, check the power supply circuit and protection device of the motor. The focus includes whether the fuse is blown, whether the contactor is attracted, whether the thermal relay is tripped, etc. If the protection action is caused by overload, the mechanical cause should be further identified (such as fan jamming, bearing damage, water pump blocking, pipeline valve not opened, etc.), and the protection should be reset and the equipment restarted after eliminating the mechanical fault. It should be noted that sometimes the output circuit failure of the controller itself will also cause the auxiliary machine to fail to start. For example, if the output relay of the PLC controller burns out, the corresponding fan or pump will not receive the start signal; or the related I/O module is damaged, and the feedback signal cannot be transmitted to the controller. Therefore, when the electrical and mechanical parts are checked to be normal and the alarm still exists, the problem of the control unit inside the control cabinet should be considered. At this time, the indicator light status of the PLC or relay module can be observed. If there is a fault indication, replace the module or have it repaired and replaced by a professional. Through the above steps, the root cause of the auxiliary machine failure alarm can usually be found.
Sensor Failure and False Alarm
The alarm of the boiler control cabinet depends largely on the data accuracy of various sensors. When the sensor itself fails or the signal is distorted, the control system often generates false alarms or even malfunctions and stops. Such situations are not uncommon, such as the water level electrode feedbacks false low water level signals due to scale accumulation, the pressure transmitter aging drifts and causes false overpressure alarms, and the temperature probe is damaged, causing the system to mistakenly think that the temperature is too high. For false alarms caused by sensors, the processing ideas are: on the one hand, verify the authenticity of the alarm by comparing independent instruments or manual measurements, and on the other hand, check the status of related sensors and their circuits. Specific measures include regular calibration of pressure gauges and temperature controllers, inspection or replacement of sensors that exceed the accuracy range or calibration cycle; regular cleaning of water level electrodes and water level sensor probes to ensure that the measuring end is clean and free of dirt; and checking the sensor terminals to ensure that there is no looseness or poor contact. For intelligent controllers with self-diagnosis functions, it is also necessary to pay attention to whether they directly report "sensor failure" alarms, which usually means that the sensor circuit is open, short-circuited or the signal is over-limit, and the corresponding sensor needs to be replaced or the circuit repaired. By strengthening the daily maintenance and care of sensors, the occurrence of the above false alarms can be greatly reduced. Henan Rentai recommends that users choose industrial sensors with reliable quality and follow the manufacturer's recommendations for regular calibration, which will effectively improve the stability of the boiler control system.
Summary
Faced with various alarms issued by the boiler control cabinet, operators should remain calm and check in sequence according to the alarm category and prompt information. Start from the actual working conditions to determine whether the problem comes from the equipment itself (such as the water level is really low, the water pump is indeed stopped), or due to abnormal detection or control links (such as sensor inaccuracy, controller failure). Only by finding the cause in a timely and accurate manner and taking targeted measures can we eliminate false alarms and ensure that the real hidden faults are dealt with in a timely manner. Henan Rentai has a complete alarm interlocking strategy and rich experience in fault diagnosis. We can provide users with remote guidance and on-site services to help quickly eliminate various fault alarms of boiler control systems and ensure the safe and stable operation of the heating system. For more information, please contact Henan Rentai Electric immediately: Tel: 17638563962 / 0371-56520104 and Email: info@hnrentai.com.