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Traditional wall thermostat Thermostat Switch Setting FAQs-2
Recent Q&A on Room Thermostat Switches

  • POST a QUESTION or COMMENT about switch settings on room wall thermostats, continuous fan operation, & low voltage transformer diagnosis & repair

Recent FAQs about how to set the room thermostat switches:

This article series explains the use, setting, and adjustment of the FAN On-Off and MAN-AUTO switches on room thermostats.

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FAQs #2 - Using the Switches on Room Thermostats

Thermostat COOL OFF HEAT settings explained

Recently-posted questions & answers about the settings of external switches on a room thermostat, posted originally at THERMOSTAT SWITCHES, EXTERNAL - we recommend a look through the switch information given there.

On 2018-10-16 by (mod) - fan wont' turn on

Let's begin with the diagnostics at FAN WON'T START

On 2018-10-15 by Dave

My furnace blower wont come on.. worked great until I turned off the main breaker switch to find our cat that when down the room floor 4x12 vent. I also turned off the a/c breaker.. after finding the cat and removing.. it doesn't work.. no fan, no electronic igniter signal, no motor fan noise to suck any gas fumes out of the chem that usually happens when its working.

On 2018-10-09 16:13:17.674734 by (mod) -

Let's start with identifying the brand and model of your touch screen thermostat - then we can together check the manual to see what's up.

On 2018-10-08 20:24:07.852186 by Linda

Touch screen thermostat won't change from heat to cool when I try, it just stays on heat

On 2018-10-04 22:27:33.825049 by (mod) -

Cherie

If I understand the question you are

- turning the HEAT or COOL switch to OFF

then

- turning the FAN switch on the thermostat to ON

Yes that will cause the fan to run; people do that to improve indoor air circulation, comfort, or filtration even when heating or cooling are not needed.

On 2018-10-03 01:12:23.040527 by Cherie

I meant if you turn the unit to off and run fan not Auto will the fan be working or is the unit off

On 2018-10-03 01:10:21.073728 by Cherie

Aren't air conditioning unit has to setting the first setting is on cold or heat or on Reno heat whatever the second side asked if you want Auto on or fan if you turn on the fan and turn the unit is the fan still working even though

On 2018-08-31 02:36:24.612383 by (mod) -

Scott please see the diagnostic suggestions in these
artickes recommended at the morw reading links just above

THERMOSTAT WON'T TURN OFF.
https://inspectapedia.com/heat/Thermostat_Stuck_On.php
FAN WONT STOP - THERMOSTAT SWITCH inspectapedia.com/heat/Thermostat_Switch_Settings.php#FanStuckOn

FAN ON-AUTO or FAN ON-MAN FAN ON-
https://inspectapedia.com/heat/Thermostat_Switch_Settings.php#FanOnAuto

As I have no information in the tale from you but most likely the case you asked about is one of those three situations

On 2018-08-30 23:42:06.939556 by Scott7707

Why doesnt my unit work on auto it stays running constanly

On 2018-08-30 23:22:15.644650 by (mod) -

Dustin,

I suspect that "Circ" refers to a switch to force the hot water circulator pump to run, independent of the temperature setting. But I am only guessing since I don't know what thermostat brand and model you're asking about.

I've never seen such a thermostat. Please attach a sharp photo of the thermostat and its switches to a comment.

On 2018-08-29 15:13:14.148545 by Dustin

Circ button. What is it for?

On 2018-03-06 17:38:48.264211 by (mod) -

Look for shorted thermostat wires or a failed fan relay

On 2018-03-06 17:34:17.464302 by William

Wall unit has thermostat fan runs constantly thermostat or unit controls don't stop it




On 2018-01-30 17:39:29.362985 by (mod) -

Thank you for an excellent question, Beverly.

Setting the furnace fan from AUTO to MAN or ON, thus causing the fan to run full time will not "get more heat" out of the furnace than leaving the fan on AUTO.

While there are some reasons to run the fan full time in some situations (such as to improve IAQ by filtering dust from the air), generally you should leave your fan control set to AUTO.

During the heating season, running the fan full time means that the fan will be blowing even when there is no call for heat (the thermostat is satisfied). An effect of doing that is that at some points the room occupants might be made uncomfortable when the fan blows cool air out of the supply registers.

Furnace controls (particularly the fan limit switch) are designed (in AUTO mode) to avoid turning on the fan until the furnace supply air plenum has warmed-up, specifically to avoid blowing cold air on occupants.

Take a look at
https://inspectapedia.com/heat/Furnace_Guide.php FURNACES, HEATING - home, to review the basics of warm air heating systems.

Then be sure to read AIR FLOW TOO WEAK https://inspectapedia.com/aircond/Weak_Air_Flow.php since that article WILL help you get the most heat from your existing furnace system.

On 2018-01-30 02:53:45.405262 by Beverly Dunham

To get the most heat, should it be set at Auto or Fan?

On 2018-01-08 22:48:48.382674 by (mod) -

That may be a control board or relay or outdoor temperature sensor failure in your heat pump system. It should be possible to simply turn off the heat pump and switch on your oil furnace. In emergency one may be able to simply move thermostat wires to the furnace control.

On 2018-01-08 22:35:40.206090 by Mil

I have a dual system, oil furnace and heat pump. Furnace is not switching on when the outside temperature foles under -16 c.

On 2018-01-07 17:06:44.128205 by (mod) -

Set thermostat mode to HEAT
Set fan to AUTO

If the fan never stops, even after the furnace has turned off and the thermostat is satisfied, search InspectApedia.com for FAN WON'T STOP RUNNING to see how to diganose and fix the trouble

On 2018-01-07 15:55:19.085486 by patrick k

had a new installed a while back now that the heat is being used the fan is running all the time .should the thermostat be set to the heat yes .Should the other switch be on auto or fan on position .I know that it has been cold out but this is not the first time that it has been cold .is it possible that the installer may have crossed a wire.

On 2018-01-06 23:48:34.049502 by (mod) -

Warren

Let's start diagnosing at FURNACE BLOWS COLD AIR https://inspectapedia.com/heat/Furnace_Fan_Blows_Cold.php

On 2018-01-06 19:28:08.293691 by Warren Anthony

We have a columbia gas furnace baseboard heat.
When heat comes on fan for ac kicks in and blows air out of ac vents making for drafty house...colder outside air is comming out of vents.

On 2018-01-05 18:37:32.491115 by (mod) -

Diane,

Use the search box just above to find our article on BLIWER FAN WON'T TURN ON

To see suggested steps to diagnose a nd fix the air handler blower fan

Let me know how that goes.

On 2018-01-05 13:15:02.110225 by Diane MCCOY

The blower on the central system is not working

On 2017-11-29 22:50:48.682104 by (mod) -

Let me add that if you have a thermostat that uses mercury bulbs, as I'm looking for those old thermostats for technical study, you can contact me by email and I will send you a free Honeywell thermostat that you can try in replacement of the old unit. If interested use the page bottom CONTACT link.

On 2017-11-29 22:49:42.272212 by (mod) -

Melanie, let's start with some simple diagnostics beginning at NO HEAT - HEAT PUMP https://inspectapedia.com/aircond/Air_Conditioner_Wont_Start.php

since when a heat pump won't turn on at all it's almost the same as if an air conditioner won't start.

On 2017-11-29 19:54:28.160778 by Melanie

My thermostat has two bulbs of Mercury in it. Thanks

On 2017-11-29 19:52:03.199352 by Melanie

My heat does not come on at all. I have a carrier heat pump thermostat. It is not working at all. It will not turn on at all. It was working yesterday morning when I left for work. When I came on yesterday evening it was not working.


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Or see THERMOSTAT SWITCH FAQs-3 - more-recent questions and answers about the switch settings on a room thermostat.

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