Guide to Air Conditioning & Heating Blower Fan AUTO ON & COOL OFF HEAT Switches on Thermostats
HeatAPedia ©
- What are the Other Little Switches For on a Room Thermostat: Heat, Air Conditioning like COOL OFF HEAT and FAN ON AUTO ?
- What to do if the air conditioner blower fan runs continuously and won't turn off
- How & why to force an air conditioning or heating fan to run continuously
Our site offers impartial, unbiased advice without conflicts of interest.
We will block advertisements which we discover or readers inform us are associated with bad business practices,
false-advertising, or junk science. Our contact info is at inspect-ny.com/appointment.htm.
This article explains the use, setting, and adjustment of the FAN On-Off and MAN-AUTO switches on room thermostats. We provide A Guide to Finding, Using, and Adjusting Thermostats for Heating & Air Conditioning Furnaces & Boilers, Heat Pumps or Electric Furnaces or Boilers.
This website answers most questions about central heating system troubleshooting, inspection, diagnosis, and repairs. We describe how to inspect
residential heating systems to inform home owners, buyers, and home inspectors of common heating system defects.
The articles at this website describe the basic components of a home heating system,
how to find the rated heating capacity of an heating system by examining various data tags and components, how to recognize common heating system operating or safety defects, and how to save money on home heating costs.
We include product safety recall and other heating system hazards.
Also see GAS PIPING, VALVES, CONTROLS for more details on how to inspect and test LP and natural gas piping, controls, valves, and tanks.
Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.
© Copyright 2008 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.
What are the Other Little Switches For on a Room Thermostat: Heat, Air Conditioning, Off, & Fan ON OFF MAN positions
Guide to Air Conditioning or Heating System Blower FAN ON AUTO Settings on Wall Thermostats
 The air conditioning or heating wall-mounted thermostat may have a fan or blower control switch with (usually) two set positions "ON" and "AUTO" or sometimes "MAN" or "AUTO"
On these switches located usually on the top, side, or bottom of air conditioning or heating thermostats, the "ON" position is not what you might think. But it's simple, as you'll see.
"ON" on the fan switch will cause the heating or air conditioning fan or blower to run continuously. "MAN" or "manual" is the same as "ON" in this situation. There are advantages of running an air conditioning or heating blower fan continuously - which we discuss below.
"AUTO" on the fan switch on your thermostat is the normal switch position for the fan control. Setting the fan control to "AUTO" will allow the fan to turn on when the air conditioning system (or heating system) are ready to blow cool (or warm) air into the building, and to turn off automatically when cooling or heating are not needed.
Guide to COOL OFF HEAT Settings on Room Thermostats
 The thing that confuses some building owners is that a thermostat that is used to control air conditioning as well as heating may have a "mode" switch that allows the occupant to change the thermostat between "Cooling" or "Air" or "Air Conditioning" mode and "Heat" or "Heating" mode.
There may be a third position labeled "Off" which instructs the heating or air conditioning system not to run at all.
"COOL" thermostat switch setting position: During the cooling season when you need air conditioning, set this switch to the "COOL" position. This tells the thermostat what to do as temperature rises above the thermostat's setting (turn on the air conditioning system) or when room temperature falls below the thermostat's set temperature (turn off the air conditioner).
It's a good idea not to turn your air conditioning system on in cooling mode when it has been cold outside in the last 24hours. Unless your system is a heat pump designed to switch back and forth in all seasons, or unless a special heater has been installed on your air conditioning compressor, suddenly turning the air conditioning system (and the compressor component of it) on when it has been cold can damage the compressor.
"HEAT" thermostat switch setting position: During the heating season, when you will need warmth, set this switch to the "HEAT" position. This tells the thermostat what to do when temperatures fall (turn on the heating system) or when temperatures rise to the thermostat setting (turn off the heating system).
"OFF" switch on the thermostat or on the fan switch, if there is one, will tell the thermostat to keep the equipment it is controlling turned off regardless of whether we're in heating or cooling season.
Why Run an Air Conditioner or Heating Blower Fan Continuously?
There are reasons to leave the fan in the ON position on a heating or cooling system, but we do not recommend that you do this without first asking for advice from your heating and service technician.
If your air conditioner or heating system fan blower unit was designed to permit the fan to run all of the time that's great and you can consider the benefits of continuous fan operation which are described in detail in the articles we list just below. But if your fan motor was not intended for continuous duty and you run the fan that way, you may find the motor fails prematurely.
Air Filtration Suggestions
See these articles about how to use air filters, where to buy them, and how to turn on and off HVAC blower fans
What to do if the Air Conditioning or Heating System Blower Fan Runs Continuously and Won't Shut Off?
Some readers have written to say that their air conditioning blower was running continuously and they didn't know why.
If the blower or fan switch is set to MAN or ON, It could be that the FAN switch had simply been set to force the fan to run all of the time. Change the setting to AUTO and see what happens.
Other causes for an air conditioning blower fan that does not turn off could be a problem with the control circuit board for the air conditioning system, or there could be other operating system problems that are preventing the system from cooling air to the desired temperature.
If the blower or FAN switch is set to AUTO and the fan never turns off, call your air conditioning or heating repair company for diagnostic help.
Technical Reviewers & References
Particular thanks are due to experts and also consumers who read these articles and suggest corrections, changes, and additions to
the material. Content suggestions, technical corrections and content critique are invited for any of the content at our website.
Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.
THERMOSTATS
Types of Building & Room Thermostats
How Thermostats Work
Detailed Guide to Room Thermostats
How to Set the Thermostat
How the Room Thermostat Responds to Temperature
How Adjust the Heat Anticipator
Mini Ammeter to Check Heat Anticipators
Other Switches on a Room Thermostat
How To Install & Wire Thermostats
More expert information on this topic
|
Building & Environmental Inspection, Testing, Diagnosis, Repair, & Problem Prevention Advice 
Directory of Professionals to Inspect or Test a Building 
Mobile View
InspectAPedia® Home & Site Map
