Guide to Heating, Heat Pump, or Air Conditioning Thermostats - how to find, use, adjust, repair thermostats
InspectAPedia^® -

Guide to Thermostats for Heating and Air Conditioning Systems - how to Find, Adjust, or Repair Thermostats - Troubleshooting & Repair Guide
Traditional wall thermostats and how they work
Detailed Guide to Round Honeywell Room Thermostats, including digital thermostats and traditional mercury-bulb thermostats
How to Set the Honeywell Room Thermostat To the Desired Temperature
How the Honeywell Room Thermostat Senses & Responds to Temperature Changes
How & Why to Adjust the Heat Anticipator on a Room Thermostat
How to Use a Mini Ammeter to Check Heat Anticipators and Thermostats for Proper Adjustment
What are the Other Little Switches For on a Room Thermostat: Heat, Air Conditioning, Off, & Fan ON OFF MAN positions
How Do I Install & Wire Up a Room Thermostat like the Honeywell Round Wall Thermostat?
Questions & Answers About Room Thermostats for Air Conditioners & Heating Systems or heat pumps: thermostat operation, wiring, adjustment & repair procedures

This article series explains selection, installation, use, setting, and adjustment of heating or cooling system room thermostats or "wall thermostats". Here we provide A Guide to Finding, Using, and Adjusting Thermostats for Heating & Air Conditioning Systems. 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.

© 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.

Types of Thermostats Used to Control Air Conditioning & Heating Systems

Because some controls are used in common on hot water heat, hot air heat, and steam boilers, readers should see these other articles: see BOILER CONTROLS & SWITCHES, and also see BOILER COMPONENTS & PARTS for a detailed list of heating boiler controls, other heating system components, parts such as circulator pumps & draft regulators. If your building uses warm air heat, see FURNACE CONTROLS & SWITCHES. If your building uses steam heat see STEAM HEATING SYSTEMS. Also see Heat Won't Turn Off - Stop Unwanted Heat. Water heater thermostats are discussed separately at AQUASTAT CONTROL Functions and at Electric Water Heater Thermostats.

Readers needing to find and fix un-wanted air leaks, heat losses, or other energy wasters should see HEAT LOSS DETECTION TOOLS. Readers should see ENERGY SAVINGS RETROFIT CASE STUDY and also see HEAT LOSS DETECTION TOOLS and INSULATION INSPECTION & IMPROVEMENT for energy saving retrofit detailed guides. Also see GAS PIPING, VALVES, CONTROLS for more details on how to inspect and test LP and natural gas piping, controls, valves, and tanks.

Traditional Round Wall Thermostats & How They are Set

Photograph of an oil fired heater stack relay

Heating & Air Conditioning Thermostats where are thermostats usually located, what types of thermostatic controls are used on various heating and cooling systems, how do we find all of the thermostats, how do we set, adjust, and use thermostats

The round Honeywell (R) wall thermostat shown in this photo has been locked in a plastic enclosure to prevent people from changing its set temperature. Set temperature and how the thermostat works are described in excruciating detail below.

Room thermostats for air conditioning work and are set the same as when these devices are used for controlling heating systems. We provide lots of detail about how these devices work - see Detailed Guide to Room Thermostats below.

Traditional Rectangular Wall Thermostats and how they are set

On this wall thermostat the red pointer shows the current room temperature.

The black pointer at the center of the scale at the bottom of the little window shows the temperature that the thermostat has been "set" to.

The "Set Temperature" is the temperature that the room occupant is requesting.

Moving the thermostat adjustment lever (located at the top, side, or bottom of the thermostat depending on the model) will change the set temperature up or down, causing the heating or air conditioning system to turn on or off as needed.

See Detailed Guide to Room Thermostats below.

Programmable, Digital Room Thermostats

Digital room thermostats are illustrated in our two photographs shown here. A modern digital thermostat uses an LCD type display to show the current room temperature along with other information.

Typically the display changes in response to pushing the thermostat control buttons.

Most digital room thermostats are "programmable" - you can set the thermostat to set back the room temperature at night (in heating mode, for example) and many models allow different time and temperature settings both throughout the day and for individual days of the week as well.

Our digital thermostat shown at left indicates the time (5:43 PM) in the left side of the display and the current temperature (53 degF) in the right side of the display. With the thermostat's plastic cover "shut" it's operation is very simple, just showing up and down arrows that temporarily call for a higher or lower room "set" or "desired" temperature.

We opened the plastic thermostat cover to show additional detailed controls and instructions.

Honeywell digital room thermostat (C) Daniel Friedman

A simpler programmable Honeywell® digital room thermostat is show in our photo at left.

The thermostat is showing the current time (12:15 PM) and current room temperature (67 degF).

This unit does not provide additional buttons under a cover. But by pressing the center "Set" button the display changes to allow the user to set a desired time and temperature setting for day and night time temperatures.

We describe the operation of a typical digital room thermostat for heating or air conditioning later in this article at Questions & Answers About Room Thermostats for Air Conditioners & Heating Systems

Radiator Thermostats & Baseboard Thermostats, Automatic - TRVs

Several manufacturers provide thermostatically-controlled radiator valves (Armstrong, Danfoss, Hoffman Specialty, Jacobus (Maid'O'Mist) and others).

Automatic radiator/baseboard valves provide thermostatic controls that can be installed on individual hot water radiators, steam radiators, or heating baseboards. The automatic radiator or baseboard valve will automagically open or close to attempt to control room temperature to the desired level.

Shown at left is an adjustable individual thermostatic control installed on a hot water radiator in Molde, Norway.

For details see RADIATOR VALVES & HEAT CONTROLS This article describes these automatic or thermostatically controlled radiator valves (such as the Armstrong RV-4) that will allow you to set the desired room temperature.

Also see RADIATOR STEAM VENTS, AUTOMATIC for a description of automatic steam vents used to control the rate at which steam heat radiators will get hot. Automatic steam vents can help balance the delivery of otherwise uneven steam heat throughout a building.

Remote Control Room Thermostats for Heating and Air Conditioning

Remote control thermostats such as the unit shown at left are usually used with air conditioning or heating split systems using an outside compressor/condenser unit and one or more indoor wall-mounted cooling or heating units..

The thermostat controls in the hand-held remote control communicates with a wall-mounted air conditioner or heater using infra red signals. The open finned area at the bottom of this Sanyo control permit ambient air to enter the control for purpose of sensing the air temperature.

A control such as this Sanyo (TM) unit can be quite sophisticated and include automatic set back temperatures, timers, etc.

Heat Pump Outdoor Thermostats are used to control the turning on and off of backup heat.

Our photo (left, courtesy of Neal Renn shows the thermostatic control unit in the outdoor compressor/condenser unit of a residential heat pump.

See Heat Pump Thermostats - Outdoors and BACKUP HEAT for HEAT PUMPS and also see Detailed Case of a Heat Pump that Put out Heat when Cooling was Required

Types of Room Thermostat Temperature Sensors

Bimetallic Element thermostats

Bimetallic spring thermostat (C) Daniel Friedman

Bimetallic Element thermostats use a bimetallic spring consisting of strips of two different metals fused together, typically into a coil shape. Our photo (left) shows a coiled spring inside a mercury tube based room thermostat made by Honeywell®.

As the fused metal strip/coil is exposed to different room air temperatures, because the two metals expand or contract at different rates but are fused together, the spring "coils" or "un-coils", causing the spring end to move in response to temperature.

This movement can be used to open or close contacts to turn heating or cooling on or off in a building.

See TEMPERATURE RESPONSE of Room Thermostats for a detailed description of how bimetallic springs used in room thermosats work.

Bellows Element thermostats

Bellows Element thermostats are filled with a volatile liquid that vaporizes at temperatures typically found indoors. As the liquid vaporizes pressure inside the bellows expands, translating temperature change into the movement of a contact to turn heating or cooling on or off in response to building temperature.

Photographs of a bellows-operated line-voltage room thermostat produced by Honeywell, Inc., are found at Honeywell or in Burkhardt.

Mercury-tube Element thermostats

Mercury bulb thermostat (C) Daniel Friedman

Mercury-tube element thermostats use a glass tube containing mercury and a pair of metal contacts at one end of the tube to turn heating or cooling on or off in a building.

The mercury tube is connected to a bimetallic spring that tips the mercury tube in response to changing room air temperature.

When the tube tips in a direction that causes the mercury to move to the end of the tube containing two metal contact wires, the mercury acts as a conductor to close an electrical connection to turn heating or cooling on.

When the tube tips in the opposite direction the mercury moves off of the contacts and the switch is opened or heating /cooling are turned off.

See TEMPERATURE RESPONSE of Room Thermostats for a detailed description of how mercury tube thermosats work.

Thermostat Heaters, heat accelerators, heat anticipators

Heat anticipator control in thermostats (C) D Friedman

Some thermostats models use a source of artificial heat (a very tiny resistor or resistance heating element inside the thermostat) to force the heating system to turn off earlier than it would have if the thermostat only responded to an increase in room temperature.

In other words, the heating system itself will be turned off before the room temperature has reached the thermostat set point.

This feature is added to prevent the heating system from "overshooting" or making the room too warm - a condition that might occur due to additional heat that will be radiated into the room from radiators or heating baseboards that will continue to be warm even after the steam boiler or the hydronic boiler circulator has shut off.

To accommodate variations in heating source and distribution design, heat accelerators or heat anticipators are usually adjustable. Details are at HEAT ANTICIPATOR Adjustment.

A Guide to Using Wall-Mounted Room Thermostats - How to Set the Thermostat

Here is our photo of a traditional round Honeywell (R) round room thermostat. Detailed photos of the major components of this thermostat and a description of how they work are provided below.

Remote Control Thermostats & Remote Heat, Cooling, or Building Temperature Monitoring

A variety of remote control thermostats are offered by HVAC control manufacturers, permitting an owner to monitor, or even change building temperature control settings remotely by telephone or by web-enabled internet connection.

Also see FREEZE-PROOF A BUILDING or WINTERIZE A BUILDING.

Proliphix provides a range of energy control thermostats that offer remote temperature control via web-enabled communication between an individual and the building's HVAC controls. Also see Honeywell Controls, and White Rodgers thermostat controls.

How to Set a Room Thermostat To the Desired Temperature

Heating thermostats: Here we use a traditional, and very simple dial-type round wall-mounted thermostat as an example. Notice that the thermostat face has two temperature scales and two pointers.

The top scale on the thermostat and the red arrow shows the "set" temperature that the thermostat is asking for.

The bottom scale shows the actual room temperature.

Rotating the thermostat dial to the right (clockwise) will increase the "set" temperature. Rotating the dial to the left will decrease the "set" temperature.

Heating thermostats are a simple switch to turn on a heating furnace, boiler, or other heat source. As we explain again below about cooling, for a heating thermostat to actually cause the heating system to turn on, the ambient temperature at the thermostat must be below the set point or temperature to which the thermostat has been set.

Make sure that your thermostat has been set to the proper position for the season: cooling or heating. The air conditioner will not run with the switch set to "heating" and conversely the heating system won't run if the thermostat has been set to "cooling."

An air conditioning system thermostat is a switch to turn on or off the A/C equipment as indoor air temperature varies around the thermostat's set point. Air conditioning thermostats are typically wall mounted in the living area. The thermostat, if it's a combination unit, may have both a temperature setting switch and a switch that can be moved from "cool" to "off", or "heat" positions.

For the thermostat to call for cooling it must be in the "cool" position and the temperature set to a level below the ambient air temperature at the thermostat location. Thermostats contain an internal temperature sensor which compares the air temperature at the thermostat to the temperature called-for by the user, turning the cooling (or heating) equipment on or off as appropriate.

How to Save Heating Cost & Air Conditioning Costs by Thermostat Adjustments

Substantial heating or air conditioning cost savings can be achieved by manually setting back your thermostat when the building is unoccupied or when occupants are asleep. The thermostat is set several degrees (or more) cooler during heating season or warmer during cooling season.

The settings of thermostat "mode" switches into "heating" or "cooling" and the use of other thermostat switches to control an air conditioning blower fan or heating system blower fan are discussed in detail at Other Switches on a Room Thermostat.

Lots of websites offer calculators that will tell you how much you'll probably save in energy costs for every degree you set back your heating or cooling thermostat. Just don't set the thermostat down so low that you suffer costly damage from freezing pipes in winter or mold from high humidity in summer.

Also see Heat Won't Turn Off - Stop Unwanted Heat explanation of why heat may continue to come out of radiators or baseboards even though you have turned down the thermostat. Stop wasted heat by making sure you are not delivering heat when it is not needed or not wanted.

Backup Batteries & Default Programs for Digital Room Thermostats

Some programmable digital room thermostats include an internal battery that will allow the device to remember the program that you have set even if there has been a power outage.

All programmable digital room thermostats are designed to return to a "safe" or "standard" temperature program to be sure that heat or air conditioning will continue to work in some reasonable range in case a power outage or dead internal battery causes the thermostat to forget how it was programmed by the user.

Frequently Asked Questions (FAQs) about heating & cooling room thermostats

Question: Why Does the Thermostat Display Jump Back to 83 After I set It to 68 Degrees?

My daughter had a thermostat replaced about 2 months ago [Trane unit] replaced with Honeywell digital thermo worked well.

Today she called me and said that the thermostat is saying 83 degrees and when she sets it to 72 degrees it jumps back to 83 degrees/she says the thermo is set on the cool side.

Do you know what the problem may be. Please advise - Thank you John

Reply: How a Single-Display Digital Room Thermostat Works

A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem with air conditioning systems and controls, possibly including something you were not considering. That said, there may not be any thermostat problem in the case you describe. At least not with the thermostat itself.

Our first photograph (above left) shows a basic Honeywell digital room thermostat. This one happens to be set in Heating mode but the principle of how the display works is the same in both heating and cooling modes. You'll see that the display shows the time (12:15 pm) and the current room temperature (67 degF - the house was already cool).

In normal operating mode a digital thermostat whose indicator window shows only a single temperature number displays the current room temperature that it is sensing.

When you press the temperature "set" buttons to call for a decrease in room temperature, (say for air conditioning) or an increase in room temperature (say when in heating mode), the thermostat temperature display temporarily changes to show the "set" temperature - the temperature you are calling for.

When you stop pressing the temperature "set" buttons the thermostat display returns to showing the current room temperature.

Our second digital room thermostat photo (left) shows me pressing the "set down" button until the display shows 54 degF.

This is the new "set" temperature or the temperature I am calling for at the thermostat.

Our third Honeywell digital room thermostat photo (left) shows that a moment after I removed my thumb from the "set" button the thermostat display returned to showing the current actual room temperature (67 degF).

So if the current room temperature for your daughter was actually 83 degF (or in my case 67 degF), that is the number that will show both before and after pressing the "set" buttons.

Only while the set buttons are being pressed will the display show a different temperature (the temperature you are calling for).

As the A/C turns on and begins to lower the room temperature you should see the displayed room temp number gradually drop until it reaches the set temp.

It's possible that your daughter's thermostat is therefore working normally but she simply didn't previously notice how it's display behaves. Often when we notice something for the first time we think there has been a change even if that is not the case.

Two exceptions to this description of how the display on a digital thermostat works

First: if the A/C or heating system is not working properly then even after changing the "set" temperature on the thermostat nothing will happen, or the system may run but never reach the set temperature.

Second: some digital thermostat models show not just one, but two temperatures in the display. One of these is the "set" temperature and the second is the "current" or "actual" temperature. If your daughter's display is one of this type, then it may not be working properly. But from your description it sounds as if she's got a single-display model.

Watch out: if your heating system electrical power has been shut off, when power is restored the thermostat might have "forgotten" the program that you had set into it and you'll need to re-program the device by setting the correct time and then the desired room temperature set back time, and temperature.

Question: Translate the error codes on digital thermostats

My Trane digistat has a red button lit and has error code 90? what does that mean? - Tony 7/7/2011

Reply:

Tony error codes are thermostat or heating/cooling device and model dependent. The meaning of HVAC unit error codes are usually printed on a sticker inside the unit cover or control or device cover. If yours has lost that information look for the installation and service manual for the equipment.

If that fails you'll need to call the manufacturer with your model number, serial number, and ask for the manual. That's because there is not a universal standard for digital thermostast error codes - the codes displayed and just what they mean vary among different heating & cooling devices. Some example thermostat and digistat error codes are listed below:

Trane XL19i A/C Digistat error code 89 or 90 or 91 - check for a loose wire or broken connection in the thermostat wiring;
Trane 900AC43UA error code 126 - condenser unit lost power in mid-cooling cycle. Turn off all power and wiat at least 5 minutes, we recommend 15 minutes, then turn power back on. This may enable the refrigerant pressures in the system to equalize and allow the compressor motor an easier start-up.
Trane 900AC43UA error code 53 - check for blocked air filter or dirty condensing coil
Trane Furnace LED Flashing Error Indicators:
- Slow regular falshing: normal condition, the thermostat is not calling for heat (modern units)
- Fast regular flashing: normal condition, the thermostat is calling for heat (modern units)
- Flashing (older units): System has locked out on safety - unable to start and run safely
- On solid: bad control board
- Off solid: no power to the unit
- 2 flashes then pause: System has locked out on safety - unable to start and run safely
- 3 flashes, then pause: vent pressure switch senses an error
- 4 flashes: the high temperature limit device is not working or high temperature has been reached - safety off
- 5 flashes: burner flame sensed when it should be off
- 6 flashes: reversed hot / neutral electrical power wiring or defective electrical ground connection
- 7 flashes: gas solenoid valve error or circuit error
- 8 flashes: burner flame too low
- 9 flashes: igniter circuit failure & wire marked from terminal "N" to 24VAC voltage is low - check for bad ground
Digistat 3 water heater Error Code 90 - the unit is not heating the water or the fan is finding airflow resistance that causes it to over-correct. Check for insufficient makeup air, an improperly installed or bglocked heater exhaust vent (dangerous), a blocked fan motor or vent, or insufficient BTUs or fuel supply.
Drayton Digistat+2 Code E1 or E2 - sensor fault, system remains off, call for service [UK Product]

Our image above shows a Trane ComfortLink™ II digital thermostat that uses downloadable software that can be transferred into the device using an SD card or similar memory device. This is one of at least ten models offered by the company. Contact Trane Corporation at PO Box 9010, Tyler TX 75711, or via their website, www.trane.com or by calling Trane's Thermostat Customer Assistance Helpline at 1-877-880-3381 - don't expect to find detailed thermostat installation guides or error codes for Trane equipment online - the company does not provide that information.

Question: Control Voltage for Thermostats

I've read several pages of these troubleshooting tips and none of them refer to "control voltage" .I have found this to be the problem in more than one HVAC unit that I had to work on . FYI folks . - Charlie G 7/7/11

Reply:

Charlie G:

It would be great if you'd expand your comment and explanation about control voltage - it would surely help other readers. Working together and exchanging information makes us better informed than any individual can be working alone.

InspectAPedia is an independent publisher of building, environmental, and forensic inspection, diagnosis, and repair information for the public - we have no business nor financial connection with any manufacturer or service provider discussed at our website.

We are dedicated to making our information as accurate, complete, useful, and unbiased as possible: we very much welcome critique, questions, or content suggestions for our web articles.

Question: We changed our A/C unit and Theremostat - now it Stopped Working

Hello, Mr. Friedman. I seem to be having a strange problem. We just had our A/C unit and thermostat changed in February, and it was working wonderfully up until today. We just got back from vacation yesterday and had left the thermostat at 80 degrees. We came home, and I switched it from 80 to 75 and then from 75 to 70. And it was working fine up until about three hours ago (it is now 7:15 pm).

The thermostat registers the inside temperature, but there is no side number indicating what temperature I wish to have it at. (Ex.: It's 85 degrees, and I would set it so that it would be 75 degrees, but that number isnt showing up). The fan will run if I switch it to "on", but not on auto. I have switched the batteries, called Honeywell, flipped all the switches I can find. I'm assuming that this would be the cause of the thermostat, as opposed to the actual unit itself?

We have been having problems for a while now, with strange things. (Last month, the carpet directly across from the unit was sopping wet, and took a week to get up! But there was no leakage directly at the AC unit.) It's been kind of a Murphy's Law joke. I'm not sure what I hope to hear, but any kind of advice would be glady received.
Thank you.
Jillian 7/9/11

Reply:

I'm not sure about your model but many thermostats show the current room temperature and do not show the set temperature except while you are pressing the set buttons to change the temp up or down. If you have set the temperature well below the current room temp and the A/C won't start, then you will want to take a look at the air conditioning diagnosis suggestions found in the article linked to at page left and titled LOST COOLING CAPACITY

About that wet carpeting, if your air conditioning condensate drain system is clogged or leaking that could be the problem; watch out for hidden mold or even insect damage or rot if such a leak is left unrepaired.

Question: We changed our thermostat settings and now the A/C unit won't come back on

We had our thermostat set at 79 and it read 79. My wife had some friends over and they were hot so we turned it down to 75. The reading never changed from 79. I decided to turn it off and then on again to see if it would help. When I turned the switch back on to "cool" it would not turn back on. We usually hear a click and then it starts going. Nothing now. What do you suggest? - Mike 7/11/11

Reply:

Mike on at least some air conditioning systems if you switch the compressor component off and then back on again quickly the compressor can have trouble re-starting against the head pressure in the system. Usually if you leave the system switched off for 30 minutes or longer you'll get past that problem, but it might be worth looking out for a hard-starting compressor.

Question: My new digital thermostat worked for just 6 hours then stopped

I replaced my thermostat with a digital one and it worked great for like six hours and then before it reached the desired temperature it just shut down. Now the ac nor the fan will come on. The fan will not even come on in manual mode. I flipped the breaker and nothing has worked. What is up with this A/C? Maybe I wired wrong but the unit was working perfectly for a hours. - Mike in Lubbock

Reply:

Check for a wiring error, broken or loose connection, lost power.

Question: Our digital thermostat is blank

When we came home from the store the digital thermostat was blank. We tried to take off the face of the thermostat to look for a battery as we were doing that the thermostat kicked on. Problem was it statrted to blow hot air. We went back to the thermostat and when we fiddled with it it went off but then came back on this time it blew cold air. Everything fine right?

Not so fast. In the middle of the night I woke up drenched with sweat. For some reason the AC started blowing hot air. I simply touched the thermostat and it went blank. I haven't touched it since.

Help..its hot and we have three kids. - Pearl in Annapolis

Reply:

Pearl:

When the display on a digital thermostat goes blank that means that power has been lost to the unit. Power for a digital TT comes from one or at most two sources:

1. the low-voltage transformer mounted somewhere, often near the electrical panel or near the heating or cooling equipment supplies normal power to the thermostat; if one of those wires is disconnected, the transformer burned up, or power to the equipment where the transformer is mounted is turned off, the thermostat will go blank

2. Some thermostats also use a backup battery to remember settings when someone has turned off power or there has been a power outage. If the batteries are dead that'd be a second reason for a blank display. This is a less serious concern, as thermostats have a fall-back default program that will get things running after a power outage - which takes us back to reason #1 - power is off to the thermostat.

Question: A/C system cools for just an hour, suspect thermostat or control board trouble

ok joe this is what i got. Ac system set to 75 get home flipped it on started to cool 1 hour later no more air. Flipped fan switch to on instead of auto on thermo, nothing. pulled the cover off fan unit and saw contactors go on to start fan motor than flipped off. Decided it must be a bad start /run capacitor, put a new one in and the same thing. I then pulled out the magnetic coil /contactor /control board and jumped the contactor thatwas for the fan motor. The motor started right up and ran fine. Either the thermostat went bad and is not sending the proper signal to the control board or the control board is bad. Got any good tests to figure what is bad? - Ray 7/19/11

Reply:

Hey Ray, try this:

If you suspect a bad thermostat you can just temporarily eliminate it from the circuit: a thermostat is basically an on-off low-voltage switch. If you connect the TT wires to the cooling circuit it's the same as the thermostat calling for cooling.

Or just replace the thermostat - they're not costly.

If the TT is not the problem then from what you described there could be a bad contactor relay or control board itself - that is, if the relay is not damaged then it could be the ocntrol board circuit not calling for cooling.

Reader follow-up:

Well I got to your e mail a few hours too late . I replaced the contactor/relasy to no avail, after scratching my head for about 20 minutes I decided to find your advice. I found an old thermo and viola!! the system came right on and cooled the house quickly. Hey i just wanted to say thank you for taking the time to help all of us save hundreds if not thousands of dollars with your expert advice. There are millions of people out there that are willing to tackle problems with a little guidance keep up the good work we all appreciate it even if you don't hear back from us. Ray D

Reply:

Ray D - so glad you got things working, and that our website was helpful. We are dedicated to making our information as accurate, complete, useful, and unbiased as possible: we very much welcome critique, questions, or content suggestions for our web articles. And working together always gives us better information than struggling on alone.

Often a good general approach to trying DIY repairs is to try the easy inexpensive tests and fixes first. Replacing a questionable thermostat is a good example of that approach.

Question: A/C blower making loud sound - doesn't respond to the thermostat properly

My ac blower was making a loud sound so it went bad i replace it with a new one and know the thermostat is not working properly the setting on the thermostat it works wrong when i set it on the auto and cool it does not turn on the blower when i set it on fan and cool it works but it does not shut off i change the thermostat and it does the same thing. Do you know what it could be? - Angelo 8/5/11

Reply:

Angelo I'm not sure but most likely there was a wiring change needed, or perhaps someone shorted a control board or relay

Question: A/C freezes up after blower was shut off - compressor doesn't stop

Resently my A/C began to freeze up after the blower was shut off by thermostat at right temp, I noticed that the thermostat would shut off the blower but not the outside unit causing it to keep running and freeze up the inside coils, but when I turn thermostat to "ON" and just let it blow, it keep running and getting too cold. How do I find out what is making the themostat only control the inside unit. - Kewl Jungles 8/8/11

Reply:

KewlJ
It sounds to me like a control problem - it's odd for the comprssor/condenser to keep running after your thermostat says the indoor temp is satisfied. I'd ask for an HVAC service call to check the thermostatic expansion valve and the A/C control board circuits. Let us know what you're told - it'll help other readers.

Question: How do I Calibrate my Thermostat

How to calibrate the thermostat?My temp reads 4degrees lower than my set temp,inAC mode. - NC

Reply:

NC

Calibrating wall thermostats: most modern wall thermostats do not provide an adjustment that will calibrate the TT to the actual room temperature (and most of them are quite accurate). OLDER round Honeywell and other TTs that use a mercury bulb sensor can be tipped slightly on the wall - changing the TT out of level will change its calibration, since on those models a blob of mercury in a moving bulb rolls to connect or disconnect the two TT wires.

But take a look at other factors that might make your thermostat inaccurate, including

- its location:
is air from the A/C blowing right on to the TT,
is the TT on an exterior wall,
is the thermostat exposed to direct sunlight

and also check that the thermostat openings are not blocked by dust or debris

Finally, some thermostats include an adjustable heat anticipator that could be improperly set - see
HEAT ANTICIPATOR Adjustment

Question: Inadequate cooling, tech says just keep running the system

We just had evap coils replaced on both a/c systems. One system has been cooling fine ever since. The other only seems to cool at night. The thermostat seems to be working OK and the air coming out of the vents is cool although perhaps not quite as cool as that coming out of the vents driven by the other system. The system that not working correctly gets to be six degrees warmer than the set temperature on the thermostat. The company that installed the new coils came back and just checked pressures at the condenser and said everything seems to be working OK and that it may take some time for the everything to cycle through the new equipment. Any suggestions of problems that may result from new coil installation or what else could be causing the problem? Mike

Reply:

A/C equipment does not normally need a "break-in" period to begin working properly. There are a number of explanations for inadequate cooling, including in a new installation (where we figure we don't have blocked air filters etc) improper refrigerant charge, or a refrigerant metering device not working properly. Call the service company and ask for help from a more experienced technian.

Mike:

A cooling system that works only at night suggests that it is not producing enough temperature drop across the cooling coil, or it's working so hard during the day that a control is failing or the coil is icing up.

The line about needing time for everything to cycle thorough the equipment is not a diagnostic I understand.

When coils are replaced on an A/C system it's easy for contaminants to enter the refrigeration piping system, compressor, and controls. Debris can clog a thermostatic expansion valve or cap tube, resulting in improper system operation. The installer usually pulls a vacuum for some time on the system to remove as much debris and moisture as possible, then installs one or two filter/dryers on the refrigeration piping.

Question: A/C fan turns on but A/C won't turn off? Is it the thermostat

my fan will turn on and off when i set mode on thermistat, but ac will not turn off. Is it safe to say I need a new stat? - Roll 8/22/11

Reply:

Roll, the thermostat is a simple "on-off" switch as far as your A/C equipment is concerned. I suspect the problem is elsewhere, in a relay or switch in the equipment itself.

Reader follow-up:

fixed. cleaned contactor, now it does not lock on or off, workes as desined. case closed.

Reply:

Glad a simple cleaning step at the contactor fixed the thermostatic control. Just watch out: cleaning of electrical contact points needs to be as gentle and smooth as possible. I used to literally file off burned contactor points, but I learned that the contact point surfaces are plated and that once I too-aggressively filed them down they pitted and burned rather quickly. If the problem recurs, replace the entire thermostat or the contactor relay itself.

Reader follow-up:

Dan: thanks for the advice. I used a small flat head with caution and then used a compressed can of dustoff for a final cleaning. This is a 1991 Fedders that purrs like a kitten. I clean every year myself. It feeds to a 1991 Goodman Janitrol that has new fan motor and ignitor. Runs great. Key is cleaning annually including electric board. I replace filters regulary.

Reply:

Roll that sounds like a perfect wall thermostat clean-out job, and good advice for others whose thermostats seem to be acting strangely. Indeed on older thermostats I've found amazing clots of dust inside.

Question: hand held A/C remote control does not seem to be working

Have a hand held remote for TCL air-conditioner (split model TAC-30CHS/G). when we set temperature, conditioner blinks what you want it to be, then it goes to inside temperature (suppose to do this) but then it quickly jumps to 34 degrees & switches off. Guessing it is thermostat? Anne Webber 9/2/11

Reply:

Anne, sounds odd to me too. Try

- putting a new battery in the hand held remote and reinitializing it
- turn off all system power when you're not already in the middle of a cooling cycle and leave it off for a minute - or if you were in cooling cycle, wait an hour, then turn power back on - resetting everything.
- be sure you've got clear line of sight between the remote A/C controller and the receiving unit
- be sure that the wall mounted thermostat (if there is a separate one) is properly located where it can see or communicate with the indoor wall mounted blower assembly.

If those steps don't fix the problem and you don't see more help in the installation and use manual, it's time to ask for an HVACR service call as there could be a bad controller, thermostat, or control board.

Question: My inside air handler blower fan won't stop running no matter what

My inside fan will not shut off even when the thermostat is in the off position and continually blows hot air. The outside unit is not coming on in either on or off positions. I've had to turn the breaker off on both sides. Would this be a problem with the thermostat, the inside fan circuit or the outside unit? - RG 9/6/11

Reply:

RG

- check that no one has pulled the "fan on" switch on the fan limit switch - this only applies if your blower fan is on a combination heating furnace and air conditioning system.

- if that's not your case and the thermostat is not in FAN ON position, and if you are not calling for heating or cooling, I'd try disconnecting the thermostat entirely - it's basically an on-off switch; if it's removed the wires will not be connected; if the fan still runs there's a short in the wiring or a bad control board in the air handler. Most likely; or something else we haven't thought of.

Question: electric wall heater turned itself on when the thermostat was not calling for heat

My electric wall heater turned itself on last night. The thermostat was off or not set to a temp. During spring and summer I have my couch in front of it bc I don't use it. During the winter I arrange my apt accordingly to have proper clearance. But tonight I heard it running and I thought that was weird. I pulled my couch away and saw that the screen was literally red instead of white. I'm guessing it was too hot especially with my couch right up against it. So I turned it off from the breaker since at the poiint I couldn't turn the dial off anymore than it was. To turn it on I have to turn it above 50 degress. Under 50 means its off. And it has been off since the end of winter. My place stays warmer than byd itslf so it should never cut on. Not sure why this happened. Just looking for any help. Bc had I not checked on it it could have caught fire.

Reply:

If your electric wall heater came on while the thermostat was in the OFF position then your unit probably has either a bad internal switch, thermostat, or short circuit in the thermostat or control wiring. As you suggest, the unit is unsafe and should not be used before it is repaired or replaced. And indeed, a couch, curtains, or other combustibles should never be placed in front of an electric heater exactly because of the overheating and fire risk that you observed. Thank goodness you detected the condition and turned off power to the heater. Had no one been at home, or had people been asleep the result could have been a fatal fire.

Can you tell me the brand and model of the heater?
And if you can send photos of the heater and any labeling on the unit, please do so using the CONTACT link found at top, left, or bottom of our web pages.

Question: My A/C blows warm air for a while before cool air comes out

when I turn the air conditioner onto heat it blows out warm out for a few minutes and then cool air, would this be the thermostat or would it need gassing, it is just over five years old. - Marylin 3/14/12

Reply:

Marylin, if the air produced by your system is adequately cool after the initial warm air delivery I suspect your building may have poorly insulated ductwork running through a hot attic of some length. The hot duct is warming the initial airflow.

Reader follow-up:

Hi Dan, if it was the ductwork wouldn't it have played up by now i have had the unit for just over five years, when I go downstairs to the main unit and touch the pipe it is hot,but we just cant seem to get enough heat upstairs..

Reply:

Yes Marylin I agree - that's part of the difficulty of guessing at a question with not much information. However depending on duct type, routing, condition, insulation can fall off, be torn off by animals, or open and leak - it's worth a careful inspection in any case.

You describe initial warm air followed by cool air from your cooling system supply ducts. Is it always the case at every "on" cycle? Or only when the system has been off for some time? We're trying to sort out whether the air handler or piping or other components are just warming up and warming the initial air, or whether there is a delay in startup of the cooling compressor. Working with an accomplice turn down the thermostat and see how quickly the outside cooling compressor starts up and whether it's starting normally or with buzzing, humming, a delay.

Question: My thermostat only works on a call for heat; on call for cooling a fuse blows

when I call for heat the thermostat works, when I call for ac t blows the fuse what is going on - George 4/21/12

Reply:

George,
Calling for cooling turns on the outdoor compressor-condenser unit that is not user during heat calls (presuming it's not a heat pump system). I am guessing your compressor is not starting and is tipping the breaker or blowing the fuse.

Question: How do we balance air temperatures in a triangular shaped room?

hi, i am at work in a triangular room, the shape is /_\, so at the bottom we have the regular wall, and the other 2 sides are formed of long big windows. at the top of the triangle it is always colder than at the bottom... the people in one side are always colder than the others.

We have 5 thermostats; the air vents are on the margins of the 2 glass walls; in the middle of the room we have another air vent; now we were told to keep all of them on Heat or Cold, and at the same temp.

Nevertheless the difference between temp in the room is quite big; for ex we set the temp at 73, and on heat, but the top of the triangle has temp 62 and the bottom 79.... Quite huge difference. could you help in advising what could be done or if it is ok nonetheless to set 2 thermostats on cold in the hotter part of the room and the other ones on heat in the cooler part?
or do we need to do other changes in the room? - Maria

Reply:

Maria balancing temperature in a large but irregularly-shaped open space can be difficult, but the solution usually lies in not only where the conditioned air supply registers are located but also the location of the air returns. Also whenever anyone changes "just their local area" - like moving a suspended ceiling tile or changing their supply register outlet, they upset the balance of the system. You need an experienced HVAC designer/installer to take a look at the problems you describe.

Question: After installing a new thermostat the A/C worked fine, then started making noise

2 days ago I replaced my old honeywell digital thermostat with a new honeywell digital thermostat beause the old one just stopped working - there would be nothing at all on the display and nothing would appear when I pressed any of the buttons. It was not a battery backed up type. After replacing the thermostat - the AC seemed to be working quite well and I was so pleased with myself. I left to run some errands and when I returned home I could hear the outside unit clicking loudly as if it were trying to come on but then shorting out and then trying again repeatedly. It kept doing this until I got inside and turned the thermostat to "off".

Several hours later I tried again by turning thermostat to "cool" and the ac came on and blew cold air fabulously for about 10 minutes then the outside unit started making that noise again (It's a terrible noise - you know something's wrong). The AC keeps blowing cold, even when the outside unit is making that noise until I turn it to the off position again. I didn't have the problem with the old thermostat and this only started happening when I replaced the thermostat. Did I buy the wrong Thermostat? What could be causing this?

Reply:

I don't have enough information to make a good guess onthis one, but it sounds as if you need a service tech to take a look at the compressor and outdoor fan. Clicking noises could be a bad relay, or even a loose fan blade or a stick that fell into the fan unit.

Question: our heat won't stay on

Thermostat has 2 readings, actual temp inside the home and the temp we set that we want inside the home, the heat comes on for 1 to 2 minutes then turns off, and will not warm up the home,we have to turn it completely off then on again for it to start again for another few minutes, whats wrong with the thermostat or is it that? - Sam

Reply:

Sam, take a look at the room temperature and compare it to the "set" temperature of the thermostat. If the room temp is different from the set temperature then the thermostat is calling for heat (in your case). If the heater wont' keep running and the thermostat keeps calling for heat, the problem is most likely not the thermostat but a start or operating problem at the heater. It may be going off on safety, then automatically resetting - not a cycle that you should continue as it could be unsafe.

Questions & Answers regarding this article

Questions & Answers About Room Thermostats for Air Conditioners & Heating Systems or heat pumps: thermostat operation, wiring, adjustment & repair procedures.

Ask a Question or Search InspectAPedia

HTML Comment Box is loading comments...

Recommend / Share this Article

...

Technical Reviewers & References

InspectAPedia.com^® - Daniel Friedman - Publisher & Editor.
InspectAPedia Bookstore lists recommended books, organized by topic & available for purchase. Most of our articles also include a list of recommended books for the specific article topic as well as other references, and information sources.
Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
Additional technical contributors & reference sources for this article are listed below.

Use links just below or 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, 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

Proliphix Corporate Headquarters, 3 LAN Drive Suite #100 Westford, MA 01886 Phone: +1.978.692.3375 Toll Free (U.S.): 866-IP-LIVING (866.475.4846) Fax: +1.978.692.3378 - Sales: sales@proliphix.com Marketing: marketing@proliphix.com Customer support: support@proliphix.com http://www.proliphix.com/ - quoting from the company's website:
All Proliphix Network Thermostats come with our free Uniphy Remote Management Service. This unique offering lets you monitor and control your HVAC systems by simply pointing your Browser to our secure Proliphix Web Site. Enjoy the convenience of programming a thermostat from any location, using a simple graphical interface. No computer equipment or software is required. And since Proliphix takes care of the network configuration for you, you’ll be up and running in no time. We’ll even proactively monitor your thermostats and send you an immediate email or SMS message when an HVAC problem is detected.
Honeywell Controls, the company wants you to use their contact form at this web page: http://www51.honeywell.com/honeywell/contact-support/contact-us.html
Honeywell Consumer Products, 39 Old Ridgebury Road Danbury, CT 06810-5110 - (203) 830-7800
World Headquarters, Honeywell International Inc., 101 Columbia Road, Morristown, NJ 07962, Phone: (973) 455-2000, Fax: (973) 455-4807 1-800-328-5111
White Rodgers Thermostats and HVAC controls,
Homeowner information: http://www.emersonclimate.com/en-US/brands/white_rodgers/Pages/wr-homeowner-info.aspx
Contractor information: http://www.emersonclimate.com/en-US/brands/white_rodgers/wr_contractor_info/Pages/white-rodgers-contractor-info.aspx
White Rodgers Product Catalog (don't misspell the company's name as White Rogers Thermostats) -
http://www.emersonclimate.com/Documents/thermostats.pdf - Thermostat Catalog
Domestic Central Heating Wiring Systems and Controls, 2d Ed., Raymond Ward, Newnes, ISBN-10: 0750664363, ISBN-13: 978-0750664363, Quoting from Amazon.com:
This unique A-Z guide to central heating wiring systems provides a comprehensive reference manual for hundreds of items of heating and control equipment, making it an indispensable handbook for electricians and installers across the country. The book provides comprehensive coverage of wiring and technical specifications, and now includes increased coverage of combination boilers, recently developed control features and SEDBUK (Seasonal Efficiency of Domestic Boilers in the UK) boilers ratings, where known.
In addition to providing concise details of nearly 500 different boilers fuelled by electric, gas, oil and solid fuel, and over 400 programmers and time switches, this invaluable resource also features numerous easy-to-understand wiring diagrams with notes on all definitive systems. Brief component descriptions are provided, along with updated contact and website details for most major manufacturers.
"Automatic Oil Burner Controls - Thermostats", Domestic and Commercial Oil Burners, 3rd Ed., Charles H. Burkhardt, McGraw Hill, 1969 (and later editions), ASIN B0000EG4Y8

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.

The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop. The Home Reference Book is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. InspectAPedia.com ^® author/editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.

Carbon Monoxide Gas Toxicity, exposure limits, poisoning symptoms, and inspecting buildings for CO hazards
DUST CONTAMINATION FROM HVAC? An Investigation of Indoor Dust Debris Blamed on a Heating/Cooling System Reveals Carpet Dust
Fuel Oil & Oil Heating Magazine, 3621 Hill Rd., Parsippany, NJ 07054, 973-331-9545
Goodman Furnace High Temperature Plastic Vent HTPV safety recall US CPSC notice
Home Heating System Should Be Checked [for proper venting and for CO Carbon Monoxide Hazards - DJF]
Inspection Procedures for Oil-Fired Heating Systems Detailed step by step approaches for inspecting complex systems]
Lennox Pulse Furnace Safety Inspection/Warranty Program: Carbon Monoxide Warning
Oil Tanks - The Oil Storage Tank Information Website: Buried or Above Ground Oil Tank Inspection, Testing, Cleanup, Abandonment of Oil Tanks
Oil Tanks Above Ground, UL Standards, guidance for home owners, buyers, and inspectors
Plastic Heating Vent Pipe & Other Heating Safety Recall Notices
Weil McLain Model GV Gas Boiler/gas valve CPSC recall/repair
Domestic and Commercial Oil Burners, Charles H. Burkhardt, McGraw Hill Book Company, New York 3rd Ed 1969.
National Fuel Gas Code (Z223.1) $16.00 and National Fuel Gas Code Handbook (Z223.2) $47.00 American Gas Association (A.G.A.), 1515 Wilson Boulevard, Arlington, VA 22209 also available from National Fire Protection Association, Batterymarch Park, Quincy, MA 02269. Fundamentals of Gas Appliance Venting and Ventilation, 1985, American Gas Association Laboratories, Engineering Services Department. American Gas Association, 1515 Wilson Boulevard, Arlington, VA 22209. Catalog #XHO585. Reprinted 1989.
The Steam Book, 1984, Training and Education Department, Fluid Handling Division, ITT [probably out of print, possibly available from several home inspection supply companies] Fuel Oil and Oil Heat Magazine, October 1990, offers an update,
Principles of Steam Heating, $13.25 includes postage. Fuel oil & Oil Heat Magazine, 389 Passaic Ave., Fairfield, NJ 07004.
The Lost Art of Steam Heating, Dan Holohan, 516-579-3046 FAX
Principles of Steam Heating, Dan Holohan, technical editor of Fuel Oil and Oil Heat magazine, 389 Passaic Ave., Fairfield, NJ 07004 ($12.+1.25 postage/handling).
"Residential Steam Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
"Residential Hydronic (circulating hot water) Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
"Warm Air Heating Systems". Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
Heating, Ventilating, and Air Conditioning Volume I, Heating Fundamentals,
Boilers, Boiler Conversions, James E. Brumbaugh, ISBN 0-672-23389-4 (v. 1) Volume II, Oil, Gas, and Coal Burners, Controls, Ducts, Piping, Valves, James E. Brumbaugh, ISBN 0-672-23390-7 (v. 2) Volume III, Radiant Heating, Water Heaters, Ventilation, Air Conditioning, Heat Pumps, Air Cleaners, James E. Brumbaugh, ISBN 0-672-23383-5 (v. 3) or ISBN 0-672-23380-0 (set) Special Sales Director, Macmillan Publishing Co., 866 Third Ave., New York, NY 10022. Macmillan Publishing Co., NY
Installation Guide for Residential Hydronic Heating Systems
Installation Guide #200, The Hydronics Institute, 35 Russo Place, Berkeley Heights, NJ 07922
The ABC's of Retention Head Oil Burners, National Association of Oil Heat Service Managers, TM 115, National Old Timers' Association of the Energy Industry, PO Box 168, Mineola, NY 11501. (Excellent tips on spotting problems on oil-fired heating equipment. Booklet.)
Links to our list of additional information on heating system inspection, repair, maintenance
...

Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair

Ask a Question or Search InspectAPedia

Types of Thermostats Used to Control Air Conditioning & Heating Systems

Traditional Round Wall Thermostats & How They are Set

Traditional Rectangular Wall Thermostats and how they are set

Programmable, Digital Room Thermostats

Radiator Thermostats & Baseboard Thermostats, Automatic - TRVs

Remote Control Room Thermostats for Heating and Air Conditioning

Types of Room Thermostat Temperature Sensors

Bimetallic Element thermostats

Bellows Element thermostats

Mercury-tube Element thermostats

Thermostat Heaters, heat accelerators, heat anticipators

A Guide to Using Wall-Mounted Room Thermostats - How to Set the Thermostat

Remote Control Thermostats & Remote Heat, Cooling, or Building Temperature Monitoring

How to Set a Room Thermostat To the Desired Temperature

How to Save Heating Cost & Air Conditioning Costs by Thermostat Adjustments

Backup Batteries & Default Programs for Digital Room Thermostats

Frequently Asked Questions (FAQs) about heating & cooling room thermostats

Question: Why Does the Thermostat Display Jump Back to 83 After I set It to 68 Degrees?

Reply: How a Single-Display Digital Room Thermostat Works

Two exceptions to this description of how the display on a digital thermostat works

Question: Translate the error codes on digital thermostats

Reply:

Question: Control Voltage for Thermostats

Reply:

Question: We changed our A/C unit and Theremostat - now it Stopped Working

Reply:

Question: We changed our thermostat settings and now the A/C unit won't come back on

Reply:

Question: My new digital thermostat worked for just 6 hours then stopped

Reply:

Question: Our digital thermostat is blank

Reply:

Question: A/C system cools for just an hour, suspect thermostat or control board trouble

Reply:

Question: A/C blower making loud sound - doesn't respond to the thermostat properly

Reply:

Question: A/C freezes up after blower was shut off - compressor doesn't stop

Reply:

Question: How do I Calibrate my Thermostat

Reply:

Question: Inadequate cooling, tech says just keep running the system

Reply:

Question: A/C fan turns on but A/C won't turn off? Is it the thermostat

Reply:

Question: hand held A/C remote control does not seem to be working

Reply:

Question: My inside air handler blower fan won't stop running no matter what

Reply:

Question: electric wall heater turned itself on when the thermostat was not calling for heat

Reply:

Question: My A/C blows warm air for a while before cool air comes out

Reply:

Question: My thermostat only works on a call for heat; on call for cooling a fuse blows

Reply:

Question: How do we balance air temperatures in a triangular shaped room?

Reply:

Question: After installing a new thermostat the A/C worked fine, then started making noise

Reply:

Question: our heat won't stay on

Reply:

Questions & Answers regarding this article

Ask a Question or Search InspectAPedia

Technical Reviewers & References

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair