Centrifugal blower fans require impeller cleaning every two years to remove accumulated dust. Sometimes, bearing replacement or even the entire fan needs to be done. Low voltage can cause the centrifugal blower fan to reduce its size, leading to air pressure switch malfunction.
The centrifugal blower fan in a wall-hung boiler is responsible for venting waste gas outdoors. Wall-hung boilers must be balanced-type, meaning waste gas is vented outdoors. Centrifugal blower fans are located behind the combustion chamber (negative pressure combustion mode), and this is the most common type in wall-hung boilers. The centrifugal blower fan draws out combustion waste gas, while the negative pressure in the sealed combustion chamber draws in air. Centrifugal fans and blowers located in front of the combustion chamber are in a forced-air (positive pressure combustion) mode.
Centrifugal fans and blowers are crucial components in wall-hung boilers, and their selection is quite sophisticated. As mentioned a few days ago, the flue gas analyzer calculates the thermal efficiency by measuring the CO and O2 temperatures of the waste gas from the centrifugal fans and blowers. The selection of CO, O2, and centrifugal blowers is inextricably linked.
Efficiency is frequently discussed nowadays. The efficiency of a wall-hung boiler is essentially the combustion efficiency minus the flue gas heat loss, and airflow (the choice of blower size) is crucial. Under normal circumstances, the airflow of a wall-hung boiler blower is very small; this is to achieve the certified efficiency. It needs to operate at over 93% full load and over 90% at 30% load. A series of improvements are needed to the combustion chamber, air intake, centrifugal blowers, and air pressure switch.
Previously, a 24kW wall-hung boiler had a flue gas volume of over 70 m³/h; now, even a 36kW boiler has less than 70 m³/h, and a 24kW boiler only 34 m³/h. The flue gas volume has been reduced by half, meaning the excess air coefficient at full load has decreased. Currently, the flue gas temperature of a typical wall-hung boiler is around 120°C; this is how the efficiency of ordinary wall-hung boilers has increased.
