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
“Jonathan Henrich was very professional and provided expertise background information to my questions when replacing my sump pump and battery backup system. He was obviously knowledgeable about what he was doing and took pride in doing a great job. While the price was more than I expected, the work was…”–
“My experience with ABC was wonderful. The electrician, Bryan, who we worked with was fantastic. I would recommend this company to everyone! Very dependable, professional and friendly.”–
“I recently bought a home. For the first 6 months here I have been experiencing some electric issues. So, just two day ago - I had another shortage. Ryan came out and explained the issues. Im in sales, and he did not try to pressure me into doing the right…”–
“Anthony was my HVAC technician and I could not have had a better experience. He was professional and knowledgeable. He explained everything. I cannot tell you how nice it is to have someone like that to count on for my heating and air conditioning. Great Job Anthony”–
“Your fast, professional handling of the issue was remarkable in today’s business environment. No hassle and solid craftsmanship along with a knowledgeable technician, forces me to call you the next time I require plumbing assistance and makes ABC an easy referral to friends and neighbors. Thank you for your integrity.…”–
“I had a very positive experience with ABC…They even brought over space heaters for us and discounted the price the cost of a replacement part I had purchased two weeks prior. Great customer service.”–