The ABCs of Heating – The Fan Limit Control Switch
The blower on a forced-air gas furnace is controlled by the fan limit switch. This switch has three settings: FAN ON, FAN OFF and LIMIT.
The FAN ON setting ensures the blower won’t turn on until there’s warm air in the supply air plenum, preventing the blower from sending cold air into your home.
The FAN OFF setting keeps the blower operating even after the burner has turned off. The blower will run until the heat exchanger has cooled down and there’s no more warm air to send to your rooms.
The LIMIT setting, a safety control, turns the burner off if the air in the warm air plenum reaches an unsafe temperature. This rarely occurs, but may happen due to blocked ducts or improperly operating system controls.
Neighbors Are Saying About ABC
“Tom was awesome! He is very personable and explains the whole process well. He did a great job and ensured that he used 5-star service throughout the process. I will definitely use ABC and Tom again in the future for electrical work.”–
“Bill showed up on time to repair our broken air conditioner. ABC kept in touch throughout the day to let me know time he would be arriving too. Bill was professional, friendly, helpful, and knowledgeable. We wound up signing up for monthly care package because Bill and ABC really made…”–
“We were very pleased with the service performed by Brett Pack in performing the annual maintenance of our air conditioning unit. He noted it was low on refrigerant, which he then added after consulting with us. He also made sure we took advantage of all available discounts.”–
“Tom did a super job fixing our electrical problem. He is one of the best electricians I have ever had in my home for repair work. I would highly recommend Tom and ABC Company if you need any type of electrical work. He took his time and explained everything and…”–
“I am so impressed with Chris and ABC Plumbing, Sewer, Heating, Cooling and Electric. His friendliness honest approach to his Job is remarkable. Thanks Chris for making my day and believing that they are still great honorable people out there.”–
“Our AC was not working in the 90-degree summer heat. Josh identified that power was not going to the furnace blower. He identified that power was not going to the furnace breaker. His keen eye spotted that the wire leading into the breaker had frayed. He cut out the frayed…”–