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 Mobile ViewHEATING SYSTEMS AFUE DEFINITION, RATINGS AGE of CHIMNEYS & FIREPLACES AGE of AIR CONDITIONERS & HEAT PUMPS AGE of FOUNDATION MATERIALS AGE of FRAMING MATERIALS AGE of FLOORING MATERIALS AGE of ELECTRICAL WIRING AGE of HEATERS, BOILERS, FURNACES AIR CONDITIONING & HEAT PUMP SYSTEMS AIR FILTERS for HVAC SYSTEMS AIR HANDLER / BLOWER UNITS AIRBOUND HEAT SYSTEM REPAIRS ANODES & DIP TUBES on WATER HEATERS ANTI SCALD VALVES ANIMAL ALLERGENS / PET DANDER ANIMAL ENTRY POINTS in buildings ANIMAL ODORS IN buildings ANODES & DIP TUBES on WATER HEATERS APPLIANCE EFFICIENCY RATINGS ASBESTOS IDENTIFICATION IN buildings BACKDRAFTING HEATING EQUIPMENT BACKFLOW PREVENTER VALVE, HEATING SYS BACKFLOW PREVENTER, HEATER WATER FEEDER BACKUP HEAT for HEAT PUMPS BANGING HEATING PIPES RADIATORS BAROMETRIC DAMPERS BIOGAS PRODUCTION & USE BLEVE EXPLOSIONS BLOWER DOORS & AIR INFILTRATION BLOWER FAN CONTINUOUS OPERATION BLOWER FAN OPERATION & TESTING BLUE vs YELLOW COMBUSTION FLAMES BLUERAY Recall BOILERS, HEATING BACKDRAFTING HEATING EQUIPMENT BACKFLOW PREVENTER VALVE, HEATING SYS BANGING HEATING PIPES RADIATORS BOILER COMPONENTS & PARTS BOILER CONTROLS & SWITCHES CARBON MONOXIDE - CO CHIMNEY INSPECTION DIAGNOSIS REPAIR CHIMNEYS & Flues - Asbestos Transite Pipe DUCT SYSTEM & DUCT DEFECTS DUST CONTAMINATION FROM HVAC? ELECTRIC HEAT, DIAGNOSIS, REPAIR ELECTRIC MOTOR DIAGNOSTIC GUIDE ELECTRIC MOTOR OVERLOAD RESET SWITCH ELECTRICAL POWER SWITCH FOR HEAT EVAPORATIVE COOLING SYSTEMS FAN, AIR HANDLER BLOWER UNIT FAN AUTO ON Thermostat Switch FAN, COMPRESSOR/CONDENSER UNIT FAN CONVECTOR HEATERS - HYDRONIC COILS FAN LIMIT SWITCH FAN NOISES FILTERS, AIR for HVAC SYSTEMS FILTERS, OIL on HEATING EQUIPMENT FIRE SAFETY CONTROLS FIREPLACES & HEARTHS FLAME COLOR, BLUE vs YELLOW COMBUSTION FLOODED HEATING EQUIPMENT REPAIR FLOODED WATER HEATER REPAIR FLUE VENT CONNECTORS FREEZE-PROOF A BUILDING FUEL OIL TYPES & CHARACTERISTICS FUEL UNIT, HEATING OIL PUMPS FURNACES, HEATING FURNACE CONTROLS & SWITCHES FURNACE OPERATION DETAILS FURNACE OPERATING TEMPERATURES HEAT EXCHANGER LEAKS GALVANIC SCALE & METAL CORROSION GAS BURNER Flame & Noise Defects GAS FIRED WATER HEATERS GAS PIPING, VALVES, CONTROLS HEAT LOSS INDICATORS HEAT LOSS PREVENTION PRIORITIES HEATING COST FUEL & BTU Cost Table HEATING COST SAVINGS HEATING LOSS DIAGNOSIS-BOILERS HEATING LOSS DIAGNOSIS-FURNACES HEATING OIL CLOUD WAX GEL POINT HEATING OIL EXPOSURE HAZARDS, LIMITS HEATING OIL - OLD, USEABLE? HEATING OIL PIPING TROUBLES HEATING OIL SHELF LIFE HEATING OIL SLUDGE HEATING OIL USAGE RATE HEATING SYSTEM INSPECT DIAGNOSE REPAIR HOT WATER HEATERS HOT WATER IMPROVEMENT INSULATION INSPECTION & IMPROVEMENT LP & Natural Gas Safety Hazards MANUALS & PARTS GUIDES - HVAC NO HEAT - BOILER NO HEAT - FURNACE NOISE / SOUND DIAGNOSIS & CURE NOISE AIR CONDITIONER / HEAT PUMP NOISE, DUCT VIBRATION DAMPENERS NOISE, HEATING SYSTEMS NOISE, PLUMBING NOISE, WATER HEATER ODORS GASES SMELLS, DIAGNOSIS & CURE ODORS FROM HEATING SYSTEMS OIL BURNERS OIL BURNER FUEL UNIT OIL BURNER INSPECTION & REPAIR OIL BURNER NOISE SMOKE ODORS OIL BURNER NOZZLE & ELECTRODES OIL BURNERS, RETENTION HEAD OIL BURNER SOOT & PUFFBACKS OIL FILTERS on HEATING EQUIPMENT OIL FILTER MISSING OIL FUEL TYPES & CHARACTERISTICS OIL & GAS PIPING OIL LINE CLOGGING FIX OIL LINE QUICK STOP VALVES OIL LINE SAFETY VALVES OIL ODORS, LEAKY OIL TANK PIPING OIL PUMP FUEL UNIT OIL SPILL CLEANUP / PREVENTION OIL TANKS OIL TANK SAFETY OIL TANK SLUDGE OIL TANK TESTING OIL TANKS, BURIED OIL TANK WATER REMOVAL PLASTIC HEATER VENT PULSE COMBUSTION HEATERS PASCAL CALCULATIONS RADIANT BARRIERS RADIANT HEAT RADIANT HEAT Floor Mistakes to Avoid RADIANT HEAT TEMPERATURES RADIANT SLAB FLOORING CHOICES RADIANT SLAB TUBING & FLUID CHOICES RADIATORS RELIEF VALVES - TP Valves on Boilers RELIEF VALVES - STEAM TP VALVES RELIEF VALVES - Water Heaters RELIEF VALVES - TP Valves on Boilers RELIEF VALVES - STEAM TP VALVES RELIEF VALVES - Water Heaters RELIEF VALVES - Water Tanks Reset Switch - Heater Primary Control Reset Switch Broken - Quick Repair Reset Switch - Electric Motors Reset Switch - Stack Relays SAFETY HAZARDS & INSPECTIONS SAFETY HAZARDS GUIDE SAFETY, HEATING INSPECTION SAFETY,HOME HEATING TIPS Safety Recalls, Chimneys, Vents, Heaters BLUE vs YELLOW COMBUSTION FLAMES BLUERAY Recall CHIMNEYS & Flues - Asbestos Transite Goodman HTPV RECALL Heat Recovery Ventilator RECALL Lennox Furnace Manuals Lennox SAFETY WARNING PLASTIC Plexvent / Ultravent RECALL Weil McLain RECALL SAFETY, HEATING INSPECTION SAFETY,HOME HEATING TIPS STEAM HEATING SYSTEMS TANKLESS COILS THERMAL TRACKING & HEAT LOSS THERMOSTATS, HEATING / COOLING Types of Building & Room Thermostats How Thermostats Work Detailed Guide to Room Thermostats How to Set the Thermostat COOL OFF HEAT, Thermostat Switch FAN ON AUTO Thermostat Switch HEAT ANTICIPATOR Adjustment HEAT ANTICIPATOR Mini Ammeter to Check HEAT PUMP Thermostats - Outdoors INSTALL & WIRE Thermostats TEMPERATURE RESPONSE of Room Thermostats SWITCH FUNCTIONS on a Room Thermostat THERMOSTATS, WATER HEATER AQUASTAT CONTROL Functions Electric Water Heater Thermostats THERMOSTATIC EXPANSION VALVES Transite Pipe Chimneys & Flues More Information |
This article explains the use, setting, and adjustment of the FAN ON- AUTO button or switch or the FAN ON-MAN switch on room thermostats. This website answers most questions about central heating system troubleshooting, inspection, diagnosis, and repairs. InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers nor with topics or services discussed at this website.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. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution. © Copyright 2012 InspectAPedia.com, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website. Guide to Air Conditioning or Heating System Blower FAN ON-AUTO and FAN MAN-AUTO Settings on Wall ThermostatsHow does the FAN switch work on a digital heating or cooling thermostat and how should I use the FAN switch? Details are just below. FAN Button AUTO and ON functions on Digital Thermostats
FAN switch set to: "AUTO" run let the fan be turned on or off automatically under control of the heater or air conditioner itself - when the thermostat asks for heat and the furnace warms up the fan will turn on. At the end of a heating cycle when the therostat is satisfied, the fan will automatically turn off.
On a digital room thermostat when you press the "FAN" button, look closely at the thermostat's digital display - you should see the word AUTO (photo above left) or MAN (Photo above right) appear somewhere in the display to let you know which setting you have selected. Typically in the AUTO mode in a heating cycle the fan won't actually turn on until the furnace has warmed-up and the fan will turn off shortly after the furnace turns off at the end of a heating cycle. Running the fan "ON" all the time, which we like to do in lots of cases, distributes air and temperatures more evenly all the time in the home and produces less of a surge of heat or cool air when the heater or air conditioner actually turns on. 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 some room thermostats the FAN switch may show positions labeled MAN and AUTO instead of ON and AUTO. On these thermostats "MAN" or "manual" is the same as "ON" in this situation. There are advantages of running an air conditioning or heating blower fan continuously, and "AUTO" is the same as "AUTO which we discussed just above. Don't mix up the digital thermostat's display of the word AUTO regarding fan control with the display's use of the same word AUTO elsewhere in the thermostat's display window to describe the overall thermostat MODE setting which we discuss at SWITCH FUNCTIONS on a Room Thermostat. How Should I Set the FAN ON-AUTO or FAN MAN-AUTO Switch on My Thermostat?"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. "ON" or "MAN" on the fan switch: 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. SWITCH FUNCTIONS on a Room Thermostat - and also FAN ON AUTO Thermostat Switch discuss how to set the HVAC blower fan to continuous operation, and what to do if the blower fan won't turn on or won't turn off Also see the Fan Limit Switch Control for another method to cause a blower fan to run continually. 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. You might not want to keep the fan in "ON" mode if Your furnace or air conditioner air handler is not designed for continuous fan duty - it might wear out the fan motor or bearings a bit early (ask your system's manufacturer or your HVAC tech about your system's capability) Your building's heating system and return air duct design results in blowing uncomfortably cool air out of heating supply ducts when the furnace is not actually in heating mode. See at CONTINUOUS BLOWER FAN OPERATION for details of continuous blower fan operation. What to do if the 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. Questions & Answers regarding this articleQuestions & answers about using and wiring the thermostat FAN AUTO, ON, OFF switch control for heating, heat pump, and air conditioning systems Question: Where does the white wire go?on a york roof mount heat and air system thermostat wire white go to the com terminel or the white terminal - Gary Reply: Not sure for your system which wire goes to which terminal - take a look at the wiring instructions on the appliance or in the installation manual to be sure. Also see INSTALL & WIRE Thermostats where we give common and standard thermostat wire color coding and hookups. Question: the A/C blower is not working properly in response to the thermostatA friend's a/c unit has the blower fan that will only work in auto, it will not work on manual. On the other hand, even when you turn the unit from cool to off, the blower still remains on. The only way the blower will turn off, is to turn the fan to manual. He changed the thermostat, and the unit will cool to the desired temp and kick off, but you can't tuen the fan off on your own unless you turn it to manual. Anyone ran into this before? - John Reply: check thermostat wiring connections against the schematic for your unit and see these standard wire color codesThe wiring to the unit depends on if you have a heat pump, or straight a/c unit. It also depends on how the installer has wired the thermostat. With the heat pump, the red is power, the yellow is for cooling, the white is for heat, the green is for the fan, the orange is for the reversing valve, and the blue is usually always common. Again, you will have to check to see how the installer has ran the wires from the thermostat. If you have a a/c only unit outside, you will only have a red wire, and a white wire coming form the inside unit, to the outside unit. These will go on the contactor to send 24 volts to the coil to pull the contactor in. These are the traditional wiring scematics, again, check the thermostat to see if this is the case with yours. - Bryan Also see INSTALL & WIRE Thermostats where we provide lists and tables of color codes and wire connections for thermostats in various uses. Ask a Question or Search InspectAPediaHTML Comment Box is loading comments...
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