Gas Furnace Thermostat

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  #1  
Old 10-25-08, 11:00 AM
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Gas Furnace Thermostat

Hi,

I recently started up my Carrier brand Gas Furnace for the first time. After it warmed up the house I noticed that it would not stop at the pre-programmed temperature I have set (71 degrees) on the thermostat in my living room. I noticed the temperature climb to 75 degrees so, I shut-off the power switch and the gas to the furnace since I had tried to turn-off the thermostat with the switch on the thermostat istself which did not seem to make it turn off.

I then waited for 10 minutes and re-lit the pilot lite in the furnace and turned it on to see if that would correct the problem, which it seemed to do because the furnace turned on/off correctly according to the pre-programmed temperature (71 degrees) which I had set.

So, I thought the problem wa solved, but, this morning the same problem occured. while the furnace worked fine forabout the last 18 hours since yesterday, this morning the temperature that registered on the thermostat said 75 degrees , so I have the same situation as yesterday.

My question is that since I switched out the batteries and looked at the wire connection on the thermostat itself which seemed fine (no loose or missing connections) do you think it is just the thermostat that might be the problem?.
 
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  #2  
Old 10-25-08, 01:48 PM
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Sounds like it may be the thermostat if it didn't do it again until today.

What is the make and model of the old stat?
 
  #3  
Old 10-25-08, 09:24 PM
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thermostat help

If you checked the connections and did not see any of the iwres getting together it is probably your stat. the only other possibility is the wires getting together in the furnace.
 
  #4  
Old 10-27-08, 08:50 AM
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Jay11J & mike n,


Thanks for the very quick help. I understand if my problem might not seem much compared to some of the others I have read about on this forum. But for folks like me that have basically no knowledge of how these furnaces & thermostats work it can be a a scary thought that you might have to call a repairman and possibly be socked with a huge repair estimate that basically you have to believe (since you do not know any better) is the cause of your problem. To be honest, it is hard to trust a repairman nowadays because in this troubled economic evironment it is harder for most everyone to make money and that can cause you to think twice about his findings on your problem when an estimate for repair is done.

Forums like this are phenominaly helpful becuase they tend to very much alleviate some of the anxiety in dealing with these repair issues as there is no vested interest on the part of the moderators or others that help with their answers to peoples questions on here. The insight all of those that post help on here give us that we wouln't know unless we are in the business or truly understand how these things work is extremly comforting.

BTW, Jay11J, the make of my old thermostat is HUNTER, the model I am not sure since I have not taken it off to replace yet, although, this morning I went to HOME DEPOT and bought a [B]rite temp[B] brand, model:[B]6022[B] digital programmable thermostat for around $32 & change (with tax) that I will install today to see if my problem gets alleviated.
 
  #5  
Old 10-27-08, 01:47 PM
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Hey Guys,


I installed a new "rite-temp" brand thermostat.The model is; 6025. My Furnace is a "Carrier". The model number on it is; 58GP100-2. The series is; 211.

Now here is another problem which actually also occured the first time but I failed to mention it. The first problem is still occuring which the rep at the rite-temp said to check by disconnecting the red wire to the thermostat. he said by doing this you will know if the furnace is staying on because of a faulty thermostat (which in my case the odds are very low since I just bought it this morning). If the furnace does not shutt-off with this red wire diconnected, then he said it could be a faulty relay switch in the furnace itself.

Now the other problem which I failed to mention in my original post is that when I slide the switch on the thermostat that controls the Heat / Cool to the "off" position and wait several minutes the Furnace did not shutt-off. Why do you guys think this happened? Is it related to the first problem I had with the furnace staying on and going past the temperature I pre-set on it???

Help please!!! before I got to make the expensive call to the HVAC guy to come fix my problem.
 
  #6  
Old 10-27-08, 07:31 PM
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So does it stop when you undo the R wire at the t-stat?

If it keeps on going, then undo the R wire at the furnace.. If it stops, then you may have a short in the wire between the t-stat and the furnace..

If it keeps going, then it's pointing towards the control board on the furnace.

Make sure there is no wire crossing each other on the thermostat hook up at the furnace.
 
  #7  
Old 10-28-08, 11:10 PM
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Latest news below as of 4 P.M. (Chicago time)
***********************************
Jay11J,


This thing is now making me go nuts. After reading your last response and question here is the latest that happened.

The unit did stay on after I disconnected the red wire to the thermostat. I have not done what you said to do. But I turned up the setting on the thermostat to 73 (as a setting). When I did this the heat kicked in as I felt the warm air from the living room vent (register). Then, when the thermostat temperature reached 73.5 the heat shut-off but the fan kept blowing air, again...

So, same thing, I tried to switch the furnace off by sliding the switch on the thermostat from "heat" to "off" to no avail, as the fan stayed on, although the burners must have stopped properly because the air from the vents was not warm, just regular room temperature air was blowing from them.

Since I have had it with this unit with the cold now approaching here in Chicago, I called a service technician to come take a look (for $89). Upon inspecting the furnace he said that the unit was very old (1982-1984 I think he said). He said that there was a lot of soot in/near the outer walls above where the burners rest ("heat exchanger walls"). Most of the soot was black but, on the first burner (nearest the pilot light) some of the 'soot' on that wall area was white.

His deduction from this short diagnostic (25 minutes of looking here and there) is that I have two options as listed below.

Option #1 - The computer board can be replaced since he said it looked like there might be some water damage. Then he say's the 'supposed' water damage to the computer board might be from a leak in my AC unit which has worked fine this past summer and shows no signs of water on the inside of the floor of the furnace when you open the access panel. I am not saying he is fibbing to me but why isn't there a drop of water on the furnace floor near the fan & motor or in the sides of the floor. This option is "around" $700 he said with not a solid guarantee it wuld solve my problem long term since the furnace is so old he said.


Option #2 - Get a new furnace since he mentioned the soot-build up which indicates something -or-other he said. Of course the scariest part he saved for last as he mentioned the "killer" carbon-monoxide build-up inside the house from a very old furnace like mine. Death,he mentioned, is a remote possibility with these things and of course the more minor things like CO pisoning, respitory illness and such. So, this option for installing a new TRANE furnace, model # TR80 for $2,875.

After drinking a glass of cold water and also splashing my face with as much as I drank (to help me overcome and wake-up from my sticker shock induced hazy state of consciousness), I called a co. called "Four seasons Heating & Air conditioning" for another Furnace install estimate. They are quite big as I found out with over 250 employees in the Chicago and suburban area. I then confirmed an estimate with the customer rep woman and after hanging-up I thought that I might be in for more of a sticker shock as this outfit is literally 10x as big as the first one I called. Well, the gentleman they sent was very nice and courteous and gave me two estimates.

One was for a Lennox' Merit single-stage, model# G40-UH36B-090 for $2,070.
The second option is for The Lennox' Elite two-stage, model# G60-UH36B-090 for $2,660.

The only option to add would be for a $375 additional humidifier that is a Healthy Climate (brand), model# HCWB12.
This second guy said since my old humidifier is "so old" it "probably does not work".



If I go with this second guy's first option, I would like to know if it is easy enough to install the humidifier myself because I found the same model on the internet from a HVAC dealer for around $109. By my calculations it would save me around $250-$260 on the install of the humidifier from the second company I called above.



***************************************
Latest news below as of 11:45 P.M. (Chicago time)
***************************************

I must either be going crazy -or- my furnace has a mind of its own (besides te computer board) because now for the last several hours since the last HVAC guy came to give me an estimate on a new furnace, THE DAMN THING WORKS FINE!!!

It is turning on and off when it should according to the temperature setting on the thermostat (72 degrees) I made.

Now, I honestly don't know what I should do...

The first guy who did the diagnostic inspection (that I paid for) has me worried with all the talk about soot being bad and possible carbon monoxide leaks -or- high levels -or- poisoning type of things which are the stuff I am most worried about. But, again I used the furnace last year without getting a yearly inspection done and, I am still breathing so the carbon monoxide isn't that bad is it?

Should I wait a few days -or-weeks to get a new furnace or should I get it done ASAP -or- whatever else do you suggest (according to this long post above)???...
 

Last edited by Wineman25; 10-28-08 at 11:20 PM. Reason: grammar
  #8  
Old 10-29-08, 06:58 AM
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I wouldn't leave the furnace like this very long, get it replaced or cleaned.

The soot can be from a poor or dirty burner, and that and the heat exchanger can be cleaned. They also should inspect the heat exchanger for any cracks.

How big is your home, and age? I would suggest the 90% furnace since gas price isn't going down, and two stage furnace with a two stage thermostat will give you the best comfort.

The biggest thing of CO is you can not smell it. I would get a CO detector in your home soon.
 
  #9  
Old 10-29-08, 11:26 AM
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Jay 11J,


This morning (since 6 A.M. Chicago time) the furnace heats up the house fine but, the fan just keeps blowing and won't stop.

Do you think this is the computer board problem or something like a fan-limit switch problem?

Why won't the fan shut-off?

When I turn the whole furnace off for about a half hour to let the thermostat temperature reach a degree or so below the pre-set temp that I have set and then restart it the furnace works fine by which I mean that the blower will give heat to the pre-set temp and the fan will work fine and shut-off properly when the desired temp is reached.

But, now the second time the furnace went on the only thing that did not work properly was the fan. It still is running even a hour after the heat shut-off.


BTW, my home is about 1300 sq feet & is built in the 1950-60's (I think).
 

Last edited by Wineman25; 10-29-08 at 11:38 AM. Reason: add more info
  #10  
Old 10-29-08, 12:40 PM
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What is the make and model # of your furnace?

I could be the control board, but hard to say right now with out seeing what you got there.

Being that your home is that small, I don't see why the dealer would quote you a 90k furnace! Unless you have nothing in the wall and attic for insulation, and leaky windows?
 
  #11  
Old 10-30-08, 08:24 AM
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Jay 11J,


The make and model# of my gas furnace is in an early post on this thread.

I also want to say that I finally bit the expensive bullet and decided to get a new furnace due to the following reasons.

I am tired of dealing with this thing and the costs to just repair what is in fact (as I am told) a very old furnace (being 26 years old). The repairs are not exactly guaranteed on something this old as I am told by the service technician. Being a unit this old something else is bound to go wrong with this thing, sooner, than later I am sure.

Calling around to get better pricing on a computer board install will cost me another service call fee ($89 average) since every other HVAC repair tech wants to do his own diagnostic of my problem, which is understandable.

Besides the possibly bad computer board, there is the issue of the soot on the heat exchanger walls, the cracked heat exchanger itself, the CO fumes thing, the leaking gas fumes, the fan issue, etc...

Most importantly, this morning I heard 3 loud bangs eminating from the room in the basement where the furnace is housed. This is of course the leaked gas that must have built up and then ignited from the flame in the furnace. That scraed the crap out of me becuase it sounde like a mini-explosion in my basement which eminated throughout the house. needless to say, I shut the cursed thing off, thankfully it was not cold yesterday in the nightime.

I, in my gut, feel it is time to put the old furnace out-to-HVAC-pasture. I think its time and considering all the running around with the calls to techs for service and/or advice and/or escalating costs with the multitude of variable things that seem to be in need of repair.

So, I am going with the Lennox G40 UH36b-090, option #1 listed in an above post. I got the sales rep to go down on price after a few back and forth negotiating calls. It boils down to him giving me the humidifier, which was an extra option at $375, for only an extra $80 bucks. So the total bill for this Lennox Gas Furnace option #1 is $2150. The original quote was $ 2445 (with the $375 humidifier).

Is this a good deal? I think so and have been told so by my friend who is a commercial HVAC technician.

Finally, I just want to say thanks... Jay 11J ...for the interest and help in my major heating problem. It is nice to know that in this world of greed ther are people that will take the time to give you advice on issues that you have no understanding of or expertise in, yet, matter greatly to the safety and comfort of you and your family and for that I can never thank you enough.
 
  #12  
Old 10-30-08, 09:13 AM
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Originally Posted by Wineman25 View Post

So, I am going with the Lennox G40 UH36b-090,
STOP

I don't know if you saw my post above.

Being that your home is that small, I don't see why the dealer would quote you a 90k furnace! Unless you have nothing in the wall and attic for insulation, and leaky windows?
Did the dealer do a Manual-J on your home!? I would ask for this before anything is done, or you are going to have a oversized furnace! My guts say you'll need a -070 model (70,000 BTU vs 90,000)

On your old furnace, on the coldest cold snap, did it cycle on and off or did it run non stop?

Gas price is not going down, and you are in a cold area, have you looked at 90% save money, and or look at two stage for better comfort?
 
  #13  
Old 10-30-08, 07:50 PM
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I agree with Jay. There is no way a 90,000 BTU furnace should be installed in a 1300 sq. ft. house. You do need to insist on a Manual J and get the new furnace sized correctly. 26 years is an ancient furnace unless it has had regular cleaning and servicing its whole life so I agree that you need a new one. Every year I do maintenance on two furnaces that deny the odds and keep holding up. One is 26 yrs. old and the other is now 24. They are the exception and not the rule and will both be replaced in the next few years. Most are ready for the scrap heap between 15 and 20 yrs. I am kind of interested though on the new models because I think they are actually built better. Good luck.
 
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