Furnace stops working when below freezing outside


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Old 01-01-08, 09:50 AM
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Exclamation Furnace stops working when below freezing outside

Hi all! I have a Conquest 80 furnace that works perfectly fine when the temperature outside is above freezing but when the outside temperature is below freezing the furnace will stop working all together unless I reset the thermstat. Even then I'll have to reset the thermostat numerous times until finally it gets to the temperature that it is supposed to be. By reset I mean turn off then on again. For instance I woke up at 11:30am this morning to 69 degrees and now at 12:40pm it's only up to 71 degrees after resetting the thermostat twice. The temperature outside right now is 27 degrees. I'm not sure how old the furnace is, it was here when we bought the place in Nov. 2005. The filter is clean, the blower is free of dust and debri. Someone suggested that we may have ice on the gas lines outside, is this possible? The furnace itself sits in a backroom that is not heated and it gets pretty cold in there, could this be a problem as well? Help were freezing here in Ohio. Thanks in advance for any and all suggestions.

...The thermostat was purchased new in February 2007. Digital Hunter Model 44260
 

Last edited by 5acres2005; 01-01-08 at 10:15 AM. Reason: Forgot to mention...
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Old 01-01-08, 10:24 AM
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Something as simple as an anticipator adjustment may be what's needed...of course if the thermostat is old; not this if you have a digital type.

Please let us know the maker and M/N of that thermostat.
Is it electromechanical? digital?
 
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Old 01-01-08, 10:11 PM
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Is this natural gas or propane? It's always possible with either that the meter or regulator is getting frozen up and is failing to allow normal gas flow to the furnace.


Do you have other gas appliances? If so, watching the burners on a gas range or water heater might help determine whether that's a problem ---- you'd notice flames being sharply reduced in size on the water heater or gas range when the furnace switches on.
 
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Old 01-02-08, 11:50 AM
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The furnace is a natural gas furnace. The only other gas appliance I have is the water heater. It's really cold here today...9 degrees this morning...brr! Thanks y'all for the replies.
 
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Old 01-02-08, 12:02 PM
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Do you know if the furnace has a LED light on the board that flashes an Error Code?

A full model # may help us look it up for more info.
 
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Old 01-02-08, 12:17 PM
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Conquest 80 model # is GMUA100-E3N
Serial # is EB5D302F329608614

There is'nt anywhere in or on the furnace, that I can see, with a board that has flashing LED lights to check codes.
 
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Old 01-02-08, 01:49 PM
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I was not able to pull much info on this furnace. Down in the blower area, there is a board. Also look on the back door of the blower to see if there is any fault code info on there.
 
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Old 01-02-08, 04:22 PM
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What type of ignition does your furnace have? That is a good place to start as we need to have you tel us not only what kind: Is it a hot surface ignitor type that glows, to directly ignite the burner?; or is it a direct spark to the burner type that is often used on the type of burner that comes out more like a jet engine (no burner tube with holes or slots in them)?; or is it a spark type ignition that then in turn lights a pilot flame?

A furnace I recently had with your exact symptoms, that also required resetting and it would go sometimes, and sometimes not, and then all seemed well for hours or for a whole day, only to have the tenants wake up with the house 10 degrees below set temp, was caused by the inability, in the burner compartment, of the sparkign to properly make it's way to ground due to rusty ignition parts in the burner. And also due to the rust, it could not sense the flame well. I had to pull the ignitor and burner assembly out of the furnace and get rid of the rust and tarnish, and now this furnace is fixed. Did not cost 1 cent to fix, except my labor.

Can't say this is YOUR prtoblem, but this goes to show the importance of how the ignition has to have a good path to ground. Everything about the igniton and flame sensing has to be good.

Could you open up the big furnace panel for us and turn up your heat and then tell us step by step what the furnace does or does not do?

First of all we need to know for sure that this is the newer type furnace that has a draft inducer motor. Usually these furnaces have a PVC exhaust pipe (rather than a metal flue pipe) and some furnaces also have a 2nd PVC pipe to let in fresh air to the burner. If you have this newer type furnace (from the last 20-some years or newer), the sequecnce of these is as follows, so you know what to look adn listen for :

When you turn up the thermostat:

After a little delay of a number of seconds, the draft inducer motor will come on.

Then after a number more seconds the igniton process will occur (either glow, spark or spark/pilot flame.)

Then after a number more seconds, the main gas valve should come on with often a subtle discernable click that can be heard and felt by touching the gas valve.

The blower fan then will come on.

...................

Tell us then, according to my listed sequence, what is happening and what is not happening. We should be able to help you.
 
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Old 01-04-08, 06:32 PM
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Thumbs up All's warm here...finally

Hi all! Thank you so much for the replies and the info, I appreciate you taking the time to help. I paid a furnace man
($92.00) to come in and check it out...he took a piece of steel wool and cleaned the flame sensor...walah! As far as it acting up during below freezing weather...I have about 1483 sq. ft. of living space and running a 100,000 btu furnace...he said I should be running at the very least 140,000 btu for the amount of space I have to heat and the fact that I live in an old farm house. So I guess I'll being investing in a new furnace in the future. Thanx again!!
 
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Old 01-04-08, 07:06 PM
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Before getting excited about installing a larger furnace answer this question:

During the coldest weather does your furnace heat the house to the thermostat setting and cycle on and off?

If the answer is yes then you do not need a larger furnace.

Do not allow anyone to install a new furnace without first doing a "Manual J" heat loss calculation.
 
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Old 01-04-08, 07:20 PM
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I'm with Furd on his reply!!

Before you even think of doing a new furnace, update the windows, attic insulation, and doors!

Do that stuff first, and I would bet you that a smaller furnace is needed.

I have a 1,400 sq ft home, and I had a 120,000BTU, and now I have a 60,000 BTU two stage, and the furnace runs first stage most of the time..
 
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Old 01-04-08, 08:25 PM
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Originally Posted by Jay11J
I have a 1,400 sq ft home, and I had a 120,000BTU, and now I have a 60,000 BTU two stage, and the furnace runs first stage most of the time..
Jay, this is a little off-topic, but since not everyone out there downsizes their furnace to such a degree, I am curious what your heat register temp was with your old 120,000 btu and what it is now with your 60,000 btu. Thanks.
 
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Old 01-05-08, 05:22 AM
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Originally Posted by ecman51`
Jay, this is a little off-topic, but since not everyone out there downsizes their furnace to such a degree, I am curious what your heat register temp was with your old 120,000 btu and what it is now with your 60,000 btu. Thanks.
As for the old one, I never took a reading, it was used 2 weeks after we moved in, then the blower motor bit the dust, so instead of new motor, put in the new one.

The old one did put out TONS of heat, I hated cuz the "cloud of heat" near the ceiling in our family room. If we were sitting on the couch we were cold, the two far back bedroom were ice box since the furnace didn't run long.

With the two stage on a two stage stat, the furnace runs pretty steady when we are in the teens, the vent temps are about 110 - 115˚ on first stage (36,000 BTU output). We no longer have this "Cloud of heat" in our family room, all rooms in the house is with in about =/-1˚ from one another. (This is a '68 split level home with tuck under garage under the bedrooms.)

Gas bill from a $126 a month budget plan down to $66 a month budget.

I know lot of the houses in the neighborhood had the same large furnace as I had, and their new replacements are in the 60k as well.
 
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Old 01-05-08, 02:56 PM
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Thanks Jay.

Originally Posted by Jay11J
Gas bill from a $126 a month budget plan down to $66 a month budget.
And wow. That is substantial. Not chump change.
 
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Old 01-05-08, 03:33 PM
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Originally Posted by ecman51`
Thanks Jay.



And wow. That is substantial. Not chump change.
Yeah.. They cut me a check since I've paid them far more than what I needed! I used that money to upgrade my garage, and new window, and patio door in the kitchen.
 
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Old 06-25-09, 08:57 AM
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Conquest 80 gas furnace, similar issue

Hi, I have a similar issue with my Conquest 80 from heat controller. The glow plug lights up, the 3 jets light when the gas is released then after a few seconds the gas shuts off and the jets die. The blower still runs but no heat. This was installed back in 1993 and does not have the new PVC vent. Its probably only about 80% efficient.

I see 3 little glass looking things that look likt they might be there to detect the flame. I'm not really sure. I've wiped them with a paper towel but not sure if this is where the issue is. I opened the door to the circuit board. There are 2 green lights that come on when I turn the unit on but no flashing lights ever.

Any thoughts?
 
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Old 06-26-09, 04:19 PM
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Common symptom, right on down to the seconds of occurance! -is the flame sensor not acknowledging a flame, even though you have a flame. The cause is - the flame sensor rod gets coated with an oxidation, that you cannot really tell. You simply look for the lone skinny wire electrical wire that enters the combustion chamber, and at the end of it should be a screw mounting it to the furnace. Unscrew that one screw and remove the flame sensor and polish up that rod (about 3 inches long), with a scotch brite pad or fine steel wool. They claim sandpaper leaves grooves in the rod and speeds up oxidation - although I have used fine sandpaper and have not had callbacks.
 
 

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