how old the house is?
Most of the time, the older blower fan in the heating system would make certain level of noise. one of the reason is, the blower fan is out of balance due to too many dirt/dust build up on the blade, 2nd if the blower fan bearing is too dry, it also will make noise. as well, the air duct that connected too the blower fan will acting like a "sound box" "共鸣箱效果"it will amplifies the noise that generated by the out of balanced blower fan.
if house is old. clean the fan blade and lub the bearing,By the way, older then 5 years is old....
Most of the time, the older blower fan in the heating system would make certain level of noise. one of the reason is, the blower fan is out of balance due to too many dirt/dust build up on the blade, 2nd if the blower fan bearing is too dry, it also will make noise. as well, the air duct that connected too the blower fan will acting like a "sound box" "共鸣箱效果"it will amplifies the noise that generated by the out of balanced blower fan.
if house is old. clean the fan blade and lub the bearing,By the way, older then 5 years is old....