Not enough heat coming through!

Old 10-20-04, 07:17 PM
TDot Dave
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Not enough heat coming through!

Hi there - hope you can advise

I have a Coleman model # G8T08012UHA11A, input 80K, output 64K mid-efficiency furnace. I'm frustrated because I can't tell whether my furnace is not working, or whether its too small for our house, or whether I've got insulation problems.

When I turn the thermostat up, the intake fan kicks in for about 10 secs. Then the pilot light ignites and gas burns for about 1 minute. Finally, the fan starts blowing, but the flames look (from the slits in the top of the furnace) like they go out. The fan blows what feels like luke-warm air for about 2 minutes and then shut off. Also when this fan is blowing, there is cool air blowing out the intake duct.

I'm frustrated because no matter what temperature I set the T-stat to, the temperature in the house never rises about 20 degrees celcius. The T-stat is located in the same room as the air-intake, not sure whether this has anything to do with it.

I also noticed that there is a gassy smell after the fan shuts off around the furnace, and that the vent for the furnace is a lot hotter than the actual ducts going to the rest of the house.

Can anyone tell me whether all of this is normal, or whether I should be calling an expert in?

Thanks soooo much!
Old 10-21-04, 10:52 AM
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Hello Dave. Welcome to the Heating Furnaces forum topic & the Do-It-Yourself Web Site.

Certainly not normal for premature burner shut down. Many causes that can effect that type of condition described. Many of them already covered in other questions already posted within this forum topic.

Every possible cause from a dirty flame sensor, restricted return air system, dirty air filter, venting problems or conditions, power vent fan, fan blower, etc.

Most likely cause is a defective or dirty flame sensor. Flame sensor is an element rod like part that burner flames heat when burners are on. Located in burner area where burner flames can heat it once flames are present. Locations vary but always in the front of burners and usually close to the glowing hot surface igntior.

First turn off all electrical power to the heater and turn the thermostat to the off position or lower the temp to it's lowest possible temp.

Cleaning the element is a simple matter of using a fine grit piece of sanding paper or steel wool. The part may have to be removed to accomplish this task. The connection points of this device should also be checked to insure a good clean connection.

If cleaning this part does not resolve the problem, replacing it should. However, it may not. Which indicates there could be any number of other problem possibilities.

If the element has to be removed to perform this task, make note of how it is currently installed and how it is attached to the electronic module, etc prior to removal.

Reinstall it exactly as it currently is. At this time also check the flame sensors electrical connection. Both of these 2 steps, cleaning and checking the connections should or could correct the problem. If not, it's possible the sensor element is defective and needs replacing, providing this part is in fact the cause of the problem.

Check back on your question several more times. Heating professionals and other members posting replies in this forum topic may offer you additional advice, ideas and or repair methods.

Use the reply button to add additional information or questions. Using this method moves the topic back up to the top of the list of current questions automatically.

Be sure the electrical power to the appliance is turned off, the thermostat is turned down and the gas control valve is in the off postion before attempting any repairs.

Regards & Good Luck. Sharp Advice.
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