Room thermostat calibration & accuracy questions & answers:

Q&A on the accuracy of room thermostats and on how to calibrate or adjust thermostat accuracy.

This article series explains why a room thermostat may not be responding correctly to the actual room temperature.

We describe the factors that affect the room thermostat's behavior include is location in the building, for some models how level the thermostat was installed, the thermostat's heat anticipator adjustment, even dust and debris in or on the thermostat.

Guide to Room Thermostat Accuracy, Calibration & Adjustment

Recently-posted question & answers about room thermostat accuracy and calibration. These questions and answers were posted originally at THERMOSTAT CALIBRATION - be sure to review the diagnosis and repair advice given there.

On 2020-02-09 - by (mod) -

Try rotating the thermostat so that when you set the tt to 50 deg you're about 5 clockwise.degrees

On 2020-02-09 - Tilting Thermostat

Hi, I am still playing with it. Thanks for the information. It hasn’t been cold enough in the garage this winter so that I can get a good accurate reading. So, not sure if I am heating higher or lower than the set point with the clockwise tilt!

On 2020-02-03 - by (mod) -

Thanks for the question, Holz.
I'll take a stab, but the caveat is that depending on the specific Honeywell round T87 type wall thermostat the mercury bulb doesn't always tilt in the same direction;

I pull the cover, turn the heat up or down, see which way the bulb tilts, then rotate the thermostat so that turning the heat down to say "50", the lowest on the thermostat, I've rotated the thermostat further so that "50" is really about "40" F.

You're right that that's almost clockwise to "fool" the thermostat into thinking it's warmer in the room than it really is, but pull the cover and look at your TT directly to see how the bulb is moving when you move the dial.

On 2020-02-01 by Holz

I have an older honeywell mercury thermostat in the garage, and I would like it to heat lower than the 50F lower dial limit. You indicate in your Thermostat Accuracy and Calibration article that you did this by adjusting the level by tilting the thermostat backing plate “in the proper direction”. I am thinking this proper direction to let it get a bit colder would be to tilt or rotate it to the right (clockwise) slightly, but I just wanted to double check. Can you confirm? Thank you.

On 2019-11-11 by Jesus King

Hi,
I have a propane gas heater and last night I noticed that I set the temperature to 80 but the heater didnt turn on until it reached 68 degrees. By then, it took about two hours to get back to 80 again. Today, I tried to set it to 78. The room temperature was 75 at the moment.

The heater went on and heated up the room to 78 and then went off. I noticed that about 20 minutes later, the temperature, (still set to 78) was 76 inside the house but the heater wasnt going on.

You think the thermostat need to be replaced or is there any recommendation on what to do? Thanks in advance.
Image Lost, please re-post.

On 2019-08-07 by (mod) -

Ara Lowel said:

I found this blog to be very resourceful and well written.

On 2019-08-01 - by (mod) -

If the set temperature on your thermostat is below the actual indoor temperature then the heat should not run. If it is running I suspect thermostat wires are shorted together somewhere or there's a bad relay or control board in the heater.

On 2019-07-31 by Anonymous

Sorry .. asking wby did it turn tbe heat on in tbe house ... it is Summer

On 2019-07-31 by Deb

My thermastat is heating my home ... why did ot turn on the ... it is Summer

On 2019-02-07 - by (mod) - How to set inside thermastat for heat to auto come on according to inside temp.

Reatha

see the instructions at

THERMOSTAT SETTING INSTRUCTIONS

On 2019-02-07 by Reatha

How to set inside thermastat for heat to auto come on according to inside temp.

On 2018-10-13 - by (mod) -

If an inspection shows no external cause for the inaccuracy such as bad location, bad connections, I'd replace the control.

On 2018-10-13 by Scott

The outdoor temperature on my thermostat reads 20 degrees lower than what it really is outside, which will not allow my heatpump come on and uses the propane instead. Can I calibrate this or is something up in the wiring. It has been off by 4 or 5 degrees in the past but when I looked to turn on the heat for the first time this year, it has increased the differance.

On 2018-10-13 by (mod) - what if we can't find a problem with an inaccurate thermostat

If an inspection of all of the thermostat error causes outlined at THERMOSTAT CALIBRATION shows no external cause for the inaccuracy such as bad location, bad connections, I'd replace the control.

On 2018-10-13 by Scott

The outdoor temperature on my thermostat reads 20 degrees lower than what it really is outside, which will not allow my heatpump come on and uses the propane instead.

Can I calibrate this or is something up in the wiring. It has been off by 4 or 5 degrees in the past but when I looked to turn on the heat for the first time this year, it has increased the differance.

On 2018-06-28 7 by (mod) - one or two degree error is not significant

It's possible that's entirely within the range of accuracy that your thermostat claims to provide.

Keep in mind that what temperature the thermostat senses is the air temperature it its own location - you will almost always find different air temperatures at other room locations.

Maybe you could show me a photo of the thermostat and we could see or you could tell us its brand and model.

On 2018-06-27 by Dave

My thermostat is set for 73 on cold setting. It turns on when it is on the brink of hitting 75, then it cools the house to 72, then shuts off. Is this normal?

On 2017-10-26 by (mod) -

It may be a bad thermostat, but before replacing it I have a couple of questions for you.

When the heat has come on but takes a long time to go off is that because the room is not reaching the temperature set on to the thermostat? if so it's possible that you have a problem with warm air delivery such as a blocked furnace filter or disconnected ductwork.

Those problems wouldn't explain why the heat doesn't come on but they might explain why it takes a long time to go off.

before replacing the thermostat I would also check for a loose connection or loose wire at the thermostat or at the other end with a thermostat wires connect to the heating equipment.

If you don't find a problem with the wiring I would replace the thermostat

On 2017-10-26 by Judy

Heat won't come on. If we turn up past 80 it will come but takes a long time to go off. Forced air gas heat. 1990 Thermostat and furnace.

On 2017-10-04 by James I

Forgive my spelling mistakes, my phone is having problems. The room temperature climbs to over 100 degrees meaning my heat is never triggered to turn on. Taking the batteries out and replacing them starts the thermostat back at 72 degrees, but it rises from there.

Hello. To anyone that could help me, my thermostats room temperature just continues to climb and climb, well over 100 degrees. This means my best never comes on because the thermostat is telling the boiler the house is already very hot. Replacing the batteries start a the temperature back at 72 degrees again, but it ride a right back up. Are there any fixes for this? Thank you for any help.

On 2017-09-18 by Anonymous

Thank you for ALL of that information. I really appreciate the quick response. The blue wire was tucked within the wall, and not hooked up to anything on the blower end. I used it as a common on both ends.

When i tried to run just the red wire to R or RC, the blower kicked on, but i was not getting the tstat to display. That's when i learned the tstat required a common hookup. This setup is a forced air. No heat pump, hot water or steam. My original tstat was only using 4 wires. my new one required 5.

My apologies for my lack of knowledge. I am not experienced in any way HVAC. My forced air system is gas. I will look more in depth at the setup options. When i initially looked, it didn't look like there were a lot of config options. I may have overlooked it. Thank you again.

On 2017-09-18 by (mod) -

Marc

Also see wiring details, guides, manuals for your thermostat at https://inspectapedia.com/heat/Honeywell_Thermostat_Wiring_Guide.php

On 2017-09-18 by (mod) - what's the red or blue wire for? Instructions for Sourc 1 Thermostat Wiring

Marc,

First, did you confirm what the blue wire is doing in your wiring harness?

In the Honeywell TH9320 installation manual, as I read the wiring instructions they expect the blue wire to be operating a reversing valve - for heat pumps. And in setup you are to "In Setup, set changeover valve to O or B."

Red wire: Usually the R (red) wire or Rc wire is the power source to the thermostat and carries 24VAC.

In the thermostat Custom Setup did you make sure that your thermostat is set for the proper type of heating system:

Your system type Select Forced Air (default), Heat Pump, or Hot Water or Steam.

Each option offers different choices on the following screens.

Your forced air heating system type Select how your forced air system is powered: Gas/Oil (default) or Electric.

Efficiency of your heating system Select Standard Efficiency Forced Air (default) or High Efficiency Forced Air.

Your heating system type If you selected Hot Water or Steam on “Your system type,” select the specific heating system here.

Note: Touch the orange Help button on any screen for more information.

46 Changing system setup System Setup Options (concluded) Screen Title Settings and Options Number of cooling stages

Select 1 Stage (default) or 2 Stages.

If you are unsure, note which wires are connected: ‘Y’ wire only (1 stage) or ‘Y’ and ‘Y2.’

Number of heating stages Select 1 Stage (default) or 2 Stages.

If you are unsure, note which wires are connected: W’ wire only (1 stage) or ‘W’ and W2.’

Your fan control Select whether your thermostat (default) or heating system controls the fan.

Type of changeover valve

If you selected Heat Pump on “Your system type,“ select whether it uses a cooling changeover valve (default) or heating changeover valve.

If you are unsure, note which wires you have connected.

Number of heat pump compressor stages

elect 1 Stage (default) or 2 Stages.

If you are unsure, note which wires are connected: ‘Y’ wire only (1 stage) or ‘Y’ and ‘Y2.’

Your backup heat No or Yes (default) you can determine whether you have backup heat.

On 2017-09-18 0 by Marc

I previously had a Source1 tstat. Battery powered. No issues. I decided to upgrade to a programmable tstat. I went with the honewell TH9320.

The wiring was the same W to white, Y-yellow, and G- green. I hooked up the Red to R (previously it was hooked to the RC-RH loop). There was an additional blue wire that was not used, but i needed now for the 24volt power. I hooked it up on the control board.

Now, as soon as i connect the tstat, the blower kicks on. I have it set to auto. Even if i turn it off, it still runs. Only way to turn off the blower is to disconnect the tstat or unplug the blower. I turned the temp up to 80 in my house. the tstat read 73, and stayed running. (this is the AC).

Do these units take time to sync, or anything? Should i let it run longer? Or is my tstat defective? I hooked my old source1 back up and it is fine. turns on and off when temp is reached.

On 2017-08-10 by Brad

My thermostat screen is stuck on calibrate 0%

On 2017-08-01 by Deborah Garland

My thermostat is set to come-on in cool at 75ﾟ however temperature gauge is showing that it is 67ﾟ in the house and it still blowing cold air and not shutting off . What Would-be the problem

On 2017-06-23 by Sonny

My a.c. display on the thermostat reads 15 room temp, and is set to 70 degrees. It's blowing cool air. WHAT'S WRONG?

On 2017-04-17 by (mod) - replaced an old mercury thermostat with a new Honeywell RHT 2300

I'm surprised at so much difference. The thermistors used in modern thermostats including the Honeywell RTH 2300 series that we've installed are highly accurate - to less than a degree.

See THERMISTORS at https://inspectapedia.com/electric/Thermistors.php for details.

Is it possible that your new RTH is affected by the wall temperature or air currents in the wall cavity that don't affect our mercury thermometer?

E.g. a large wiring opening in drywall can blow warm or cool wall cavity air into the thermostat by natural convection.

Don't forget to be sure you're reading the actual temperature on the thermostat, not the set temperature. You probably have the manual but if not it's at

https://customer.honeywell.com/resources/techlit/TechLitDocuments/33-00000s/33-00100EF.pdf

There are not any adjustments that would re-calibrate the temperature sensing response/temperature-display of your Honeywell TT.

Or you could ask Honeywell what they think but I'll bet they'll say you've got an air bubble in your Certified Lab Quality Mercury-in-Glass thermometer.

Honeywell Customer Care is at 1-800-468-1502.

On 2017-04-17 by Jim McGovern

I just replaced an old mercury thermostat with a new Honeywell RHT 2300. So of course the new thermostat is dust free and has new batteries. The thermostat is installed in an ideal location away from any drafts, direct sun, direct ventilation air flow etc. Our house has single stage gas heat and central air. Currently we are in the AC Mode time of year.

I have a Certified Lab Quality Mercury-In-Glass ( MIG ) thermometer hanging very close and just above the new Honeywell. After many hours of time to allow both to normalize

The Honeywell reads 69F and the MIG reads 74F.

As the thermostat changes to a new preset temp this 5F differential follows.

Is there an adjustment to the Honeywell that I can do to bring the thermostat into calibration with the accurate MIG.

Yes or No ???

If no? . . . it would not take much of a design change to make calibration possible. Not good to make a product designed to measure and control something . . . without any sense of accuracy ???

On 2017-04-04 by (mod) - What is the temperature uncertainty of ordinary commercial home thermostat ?

Nice question, Henry.
As my smart home inspector educator Mark Cramer (Tampa FL) says, "... well, it depends"

That is to say it depends on the thermostat technology.
Older mercury bulb type round Honeywell wall thermostats were in my experience accurate to about 2 degrees or more of precision, and most "thermostat accuracy" complaints we found to be due to the thermostat installation location such as in sun, draft, or on a hot or cold wall.

Newer home thermostats usually use a thermistor that is very accurate, to a tenth of a degree 0.1 C ( 0.18F) or +/- 0.2C (0.36F) for some versions, but temperature sensing accuracy of thermistors too can be subverted by

- dust and debris covering the thermistor sensor

- location in sun, draft, or on a warm or cool wall or other surface, as I cited above.

By thermostat accuracy or thermistor accuracy as I discuss here, I mean the accuracy with which the temperature sensor measures the room air temperature where the thermostat or thermistor is located.

Naturally the temperature sensed at a wall-mounted thermostat will rarely be identical to the air temperature or surface temperatures measured elsewhere in that room much less in that building.

See THERMISTORS at https://inspectapedia.com/electric/Thermistors.php for more details about accuracy ranges of thermostats using these and similar devices.

On 2017-04-04 by Henry

What is the temperature uncertainty of ordinary commercial home thermostats used for controlling a hot-water circulating system?

On 2017-04-04 by (mod) re: temperature uncertainty of ordinary commercial home thermostats

Generally new thermistor-based room thermostats are accurate to +/- 0.1C or +/- 0.18F or in some models +/- 0.2C or +/- 0.36F

Please see THERMISTORS for details about accuracy ranges of room thermostats and thermistors using these and similar devices.

See also TEMPERATURE RESPONSE of ROOM THERMOSTATS for an explanation of things that "throw off" the accuracy of a room thermostat.

On 2017-04-04 by Henry

What is the temperature uncertainty of ordinary commercial home thermostats used for controlling a hot-water circulating system?

On 2017-01-09 by (mod) re: difference between the temperature sensed by a room thermostat and other room temperature measurements

Let's separate a couple of things.

It is very common for thermostat to read a temperature that's different than thermometers that you might Place elsewhere in the same room. In fact even a thermometer held close to the thermostat may give a different temperature because the thermostat may be affected by the temperature of the wall on which it is mounted.

Separate, we have the problem that the air coming out of your Forest warm air supply registers is not warm enough.

That's tough to diagnose without knowing a lot more about your system. For example is it an electric furnace. If so I suspect that some of the sequencers or heatig elements are not working. But there are other problems that can cause cool air out of warm air heat Supply registers.

For example a fan velocity that is too high, or an undersized furnace, or air leaks or other damage to the ductwork itself.

For example if you have air ducts that are poorly insulated and running through a cold area the air will be chilled before it comes to the supply register and we might hear the complaint that you have stated. So I think you need to look through the duct system and you need to look at the furnace itself to see whether the air leaving the furnace is hot or warm.

On 2017-01-09 by Kat A.

Thank you for your response, but I don't think I explained myself well. Please let me try again.

1. Set thermostat for heat with fan set on auto to 72 degrees.

2. Observe manually that air from supply vents is barely warm, almost cold. (I have not measured the temperature split yet, although I've been thinking that should be my next step).

3. Heat runs. When air stops blowing thermostat reads 72 degrees.

4. However, indoor digital thermometers located in all 4 rooms of the apartment read from 64-66 degrees.

5. Experiment: I increased the thermostat setting from 72 to 80 degrees. The air blew for one hour and When the air stopped blowing the thermostat read 75 degrees. The temperature range in the apartment, based on the 4 indoor digital thermometers had only gone up to 66-68 degrees.

On 2017-01-07 by (mod) re: importance of room thermostat settings & location on accuracy

Kat

Once your electric furnace has turned OFF then air should stop blowing out of the supply air vents. If it doesn't then I suspect either a blower control switch problem or a thermostat that has a manually-set FAN-ON switch in the ON position.

I agree that the thermostat location can throw off its calibration if it's getting hot or cold air from another source, but that wouldn't explain cold air coming out of the vents.

On 2017-01-07 by Kat A.

My electronic thermostat is set on 72 degrees for my electric heat. The thermostat will reach 72 degrees and turn the unit off, as expected. The main rooms in my apartment are ranging from 60-66 degrees (I'm using separate temperature gauges and nowhere in the apartment ever reaches 70-72 degrees).

Using just my hand, I've noted the the air coming from every vent is not even warm. I'm considering purchasing a gauge to get an accurate reading on the air temp coming from the vents.

The outside temperature has been in the 20s and 30s. NOTE: Based upon what I've read on your page I've noted that the thermostat is located immediately below the heating and cooling air supply register.

Please advise me if you have any suggestions regarding how to resolve this problem. Thank you.

On 2016-12-16 by GarY

GreeTinGs I would like to know how to ADJUSTING GENERAL ELECTRIC MODEL 3AHT10B1A2 THERMOSTAT ? It is from 1963-4 and has no mercury bubble but two metal bars in it

. If I turn the temperature knob all the way down the heater kicks on in upper 40s . I would like to adjust it so it kicks on in upper 30s There is a small slider inside of thermostat , slides up and down is this how I do it and do I slide it up or down ? I need to save money from heating bill but do not want pipes to freeze even if I am . Ha-Haa .ThanK YoU for your time

On 2016-12-02 by Ramona

My forced air furnace will not turn on until the temp in the house drops well below the set temp. I have thermostat set at 75°and it will register 67°or lower before it turns on. I replaced my electric thermostat with a new Honeywell thermostat but I still have the same issue.

On 2016-11-28 by cory huffman

o all electronic thermostats have batteries. I removed the thermostat cover and I did not see batteries. My heat pump does not come on. With the blower in the ON status on the thermostat the blower blows air.

However the fan on the outside compressor/condenser unit does not turn and I get no heating. Could this still be a thermostat problem? It has three wires, how do I check if it is working? What else could it be?

On 2016-10-22 by (mod) re: measuring room temperature

For both Suzanne and James,

Measuring temperature say near the center of a room will usually give a different reading than the temperature reported by the wall-mounted thermostat. In the article above we list typical reasons for that. For example a thermostat mounted on a wall near a heat source or in sunlight or well away from drafty windows or doors will think that the room is warmer than you-do.

A simple solution is to set the thermostat up to a higher temperature until you're comfortable in the room.

To reduce heating costs you'd look for and fix the main points of heat loss such as drafty windows.

On 2016-10-22 by James

My thermostat on the wall is levelled. The temperature of the room that is shown on the thermostat is must lower on my thermometer.

I got a floor heater in the meantime because I was cold. If the super of the building do not come to fix it I will contact the owners of this building because it's starting to be cold out and I pay a high rent for this apt so it should be looked after asap.

On 2016-10-22 by Suzanne

I noticed that my wall thermostat which is at least 5 degrees higher than my digital thermometer which is next to it. I was told to buy a digital thermometer to make sure that it is the right reading since I had another thermometer but is not digital. What is the cause of this. The room temperature shows 77 on my thermostat and my digital shows 72....I know the temp in the room is not 77 but I'm cold. What to do

On 2016-09-25 by Luke

I believe these old Honeywells could be calibrated by twisting the inner adjustment nut, thereby rotating the heat element, very similar to the thermostat or autochokes on old cars. In other words, the tilt of the thermostat should remain level and the metal element's anchor point should be rotated to calibrate to the specified temp.

A very thin wrench was provided by the manufacturer for this purpose and can be acquired at good old-school hardware stores.

On 2016-07-23 by (mod) re: problem with thermostat generating its own heat

I was confused: you said that when the A/C system runs "the thermostat air reading goes up" - which I took to be an increase in temperature - which would not be cooling.

Thermostats, some models anyway, include a very tiny heater (a heat anticipator) that works in *heating* mode (not cooling) to prevent the room from overheating at the end of a heat-on cycle - by turning the heat off a tiny bit early.

A defective thermostat or one that's mis-wired might be itself overheating.

Or if your thermostat is a line-voltage unit (120V) - which would be unusual in a residential set-up - there could be a more dangerous wiring error.

I'd check the thermostat wiring for improper connections, loose connections, short circuits and if that's all OK I'd replace the thermostat.

On 2016-07-23 by Sandra

The AC is definitely cooling the area. We have a separate thermometer and it shows the temperature going down, even below the thermostat setting.

The problem is that the thermostat itself seems to be generating heat when the AC is running and the thermostat temperature reading goes up when in reality the air temperature is going down.

On 2016-07-23 by (mod)

Sandra
It sounds as if your air conditioner is not cooling - perhaps the compressor is not operating or the cooling coil is blocked by ice or debris;
Or if your system is a heat pump it may be in HEAT mode rather than COOL mode.

If a review of just how you've set the thermostat doesn't correct the trouble I would leave the system off and ask for repair from an HVAC service technician.

On 2016-07-23 by Sandra

Thermostat set on cool. When it goes on, it will run and run and the thermostat air reading goes up rather than down. We turn the thermostat Off and the temperature reading gradually goes down to the correct air temperature.

On 2016-06-24 by (mod) re: A/c does not cut off when reaching desired temp

Try disconnecting the thermostat wires at the thermostat end - if the unit keeps running next disconnect them at the control end - that'll eliminate the problem of shorted wires. as well as a bad thermostat or thermostat location.

Search InspectApedia for AIR CONDITIONER WON'T TURN OFF to see detailed suggestions

On 2016-06-24 by Dan

A/c does not cut off when reaching desired temp. Keeps running and running. It seems the thermostat itself is generating heat which makes it keep running.

On 2016-02-04 by Len

Manually put red & white wires on thermostat. Temperature display increased temperature but no heat came out of vents

On 2016-01-07 by Jaffthau@yahoo.com

Thanks, 'll swap out the TT and hope for the best. Great service you guys offer, especially helpful to novices like me. Happ New Year!

On 2016-01-06 by (mod)

If you can rule out a loose connection, dirt or debris blocking air flow to the thermosat, or having located the thermostat where it is being fooled by sunlight or another warmth source, I suspect the thermostat is defective.

At a time when the heat is set to 68 and the room temp is below say 65, take a look at what room temperature the thermostat thinks it is sensing. If the thermostat's read of actual room temp is well below the set temp and if at that point it's not turning on the heat, if the other problems I cite are not present (such as a loose wire) the unit is probably bad.

On 2016-01-06 by Jaffthau@yahoo.com

i installed a Honeywell non-programmable electronic thermostat to replace a mechanical TT.

No problems for the first 30 days, but now when TT heat temp is set (e.g. 68), it does not send signal to engage furnace until room temp display reaches 64 (and sometimes 61, and then sometimes at the expected 67 degrees...very sporadic and non consistent). Any suggestions as to problem source? Thanx

On 2015-10-15 by (mod)

Watch the fan limit control at the furnace - it may be overheating and shutting off at high limit. Check for a dirty air filter or blower.

On 2015-10-15 by Tom. tpjshel@yahoo.com.com

The temperature in the house reads 68. When I turns the thermostat up to 72 the furnace runs then shuts off and then starts running again. When I turned it down to 70 it runs and shuts off properly but still reads 68 in the house.

On 2015-08-17 by (mod)

Andrew,

Indeed the 5-2 Day Programmable Thermostat - RTH2300B1012 by Honeywell is one I personally like and have installed. I've not had the trouble you describe.

I would check first for improper thermostat wiring and second for a short between the cooling wires in your thermostat circuit.

On 2015-08-17 by Andrew Sistrunk

We have changed our thermostat in this new house we moved to the rth2300. Im hoping since you know about it you can help me.

. I have the settings programed to 72 yet we are getting a continuous ac flow until the thermostat shows 59 yet the compressor (Model: FADC-024JAS) nor the blower (Model: ?) ever shuts off. so I think the thermostat is never telling the system to shut off. I am tasked to figure out why so please help ASAP or mom will kill me when she sees our new bill! Andrewsistrunk@gmail.com

On 2015-03-22 by (mod)

Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies,

Question:

(Feb 4, 2015) Tyler said:
I recently replaced the booster assembly on my furnace. The lowest temperature setting on my thermostat is 45. I use to set it at this when I left the house

. Now I set it at that and come home with the furnace running for about 3 minutes, shutting off for a minute, then back on for a few minutes again. If I set it above 55 degrees, it runs normally. Could this be the new part or the digital thermostat going bad at the same time?

Reply:

I tend, Tyler, to be slow to assume double-faults though of course it's possible.

You're seeing heater short cycling - possibly this article will help

inspectapedia.com/heat/Furnace_Fan_Cycles_During_Heat.php

Question: heating thermostat seems to show wrong temperature

My heater's thermostat is showing wrong temp. At off setting , it shows the room temp at about 80 when it feels like 60 degree in the house. I tried removing and putting batteries again but doesn't solve the problem. Do I need to replace it? - P. 1/2/2013

Reply:

P

You might, but first check the thermostat's room temperature reading (not its SET temperature reading) against the actual room temperature - use a room thermometer;

Then be sure the thermostat is set to HEAT mode and make sure that the SET temperature is above room temperature. Then heat should run until the sensed temperature at the thermostat turns it back off; See the next Q&A for more details.

Question: why do we have to turn our heat up higher than previously just to get warm

Our heating and air unit is roughly 8 or 9 years old. When we first moved here (6 years ago) we kept the air set on 73-74 during the summer months. We were comfortable.

Now, we have to keep it up to 79-80 and we still feel like the house is too cold. We had the unit checked out last year ( because we started having double and triple utility bills) and the guy said it was fine. Could this be thermostat problems? I don't really feel that the unit runs more than it should though. - Rachel 8/22/12

Reply:

Rachel,

First, are we looking at the same outdoor temperatures as previously? If not, if it's colder now than previously, the problem could be with your home's rate of heat loss - bad insulation, leaky windows &c.

If weather conditions are the same, then we have some other questions to ask: you don't say if your heat is from hot water or forced warm air. In either of those systems, even if the equipment is running as before, you could have a simple maintenance problem like a clogged air filter or air bound radiator that's the problem. I'd need to know more.

...

Continue reading at THERMOSTAT CALIBRATION - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• HEAT ANTICIPATOR ADJUSTMENT
• HUMIDITY RESPONSE, NEST THERMOSTATS
• TEMPERATURE RESPONSE of ROOM THERMOSTATS
• THERMISTORS - very accurate temperature sensors in modern room thermostats
• THERMOSTAT CALIBRATION
• THERMOSTAT WIRING OPENING SEAL - how to improve the accuracy and response of a wall themostat by sealing wall leaks

Suggested citation for this web page

THERMOSTAT CALIBRATION FAQs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to HVAC THERMOSTATS

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