Heating furnace

The reasons are as follows: First, the opening of the flue damper is insufficient, causing obstruction at the outlet of the heating circuit. II. The air intake volume is too high; the opening degree of the inlet damper is too large. III. If there is a convection section, the pipes in that section may accumulate too much ash on their exterior, requiring soot blowing. If your heating furnace is automatically controlled, it’s also possible that the furnace’s heat load is insufficient or that the furnace tubes are coked, resulting in an insufficient outlet temperature and thus an excessive increase in fuel consumption.

There are many reasons: 1. Poor exhaust from the chimney, with blocked flues. 2. The exhaust fan is faulty, resulting in insufficient suction force. 3. Furnace air leakage, loose viewing ports, burner air leakage, etc. 4. To increase the outlet temperature of the furnace, an excessive amount of gas leads to incomplete combustion. 5. The opening degree of the blower inlet butterfly valve is too large.

Furnace chamber pressure is one of the important parameters that need to be monitored at all times. Negative pressure may occur due to insufficient opening of the flue dampers, which results in poor exhaust flow, or because too much combustion air enters the furnace.

One more thing: The blower is working properly, but the exhaust fan failed during operation and did not trigger the shutdown of the blower, resulting in a positive pressure in the furnace

There are many reasons for a positive pressure to occur in the furnace chamber of a heating furnace, as mentioned by everyone above. For a heating furnace that is operating normally, the most likely causes of positive pressure are poor exhaust flow, blocked flue ducts, or severe air leaks in the flue ducts between the exhaust fan and the hot air furnace. For safety reasons, hot air furnaces operate under negative pressure; therefore, sufficient capacity is built into the design of the blowers, exhaust fans, and flue ducts/collars. In other words, the exhaust capacity in the hot air furnace system must be significantly greater than the blower capacity. As long as the exhaust system functions properly, even if the butterfly valve at the blower’s inlet is opened to its maximum, if the viewing ports are not sealed properly, or if there are leaks in the burners, positive pressure will not occur. This applies to heating furnaces that are operating normally; it’s a different situation if positive pressure occurs during the first trial run of a newly designed furnace.

Those upstairs have said everything they needed to; I can only back them up, haha

Thanks, that really helped me. Thank you