Heating, Air Conditioning, Fridge, HVAC/Furnace flame comes on and off


QUESTION: This is the problem i had in 2009 oct.  Bill helped me with.  I have a Model CGK100N06 Ser# L9030 35956 MFG # KUGK100DH06, Installed in 1990 in a new house.  Has always done this.  Starts up and runs fine but after about 10 minutes of running the flame kicks off for a couple of minutes than kicks back on.  Was never really satisfied with the amount of heat out of it.  Looked on the net a year a go and found out this wasn't normal, that the flame should run all the time, after reading many sites I found that a lot of homes are ducted properly and causes a over heating problem which sounds like what I have.  I removed the lower cover on the furnace and installed a second filter, it made a large difference in air flow in the house and it takes a longer period of time before the flame kicks off but it still does, recommend temp. rise is 45 to 75 degrees, manual said to check temp as close to furnaces as possible, intake duct temp about 62 degrees,  hood on furnace 78 degrees,  Limit switch heats to about 210 degrees before flame kicks out and can't tell where cam stat is at.  I finally found a furnace guy that will come in the next 2 weeks but I always like to know what is going on.  Any ideas? I want to by pass each switch one at a time to see which is kicking it out but was a little afraid to do that?  Thanks bob   To solve we open up the furnace to intake and gave it more air.  Worked fine till Friday.  Now doing the same thing.  Acts like it is over heating.

Model and serial numbers as well as manufactures' names mean absolutely nothing to me especially on a 22 year old furnace?
I'm not sure what you mean by "open up the furnace to intake and gave it more air".
Description that works is something like "Gas forced air up-flow furnace in basement", when you say air intake are you talking a return air grill or a blower compartment door/cover?
I'm thinking there is nothing wrong with your furnace and it's working as it is suppose to? I think the return air system is not proper and your furnace over heats and shuts off.
What is the BTU capacity? what size is the smallest size in area of your intake air from grill to blower? what size is your air filter? what size is your return air grill/grills? where is your air filter installed?
Your furnace burners should shut off at about 210, by passing a limit switch isn't going to help.
Get me answers to questions and I'll tell you what you need to solve the problem.

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QUESTION: Furnace specs,100000 max 92000, High eff. temp rise 45 to 75 max temp 170  It is in basement, original house plan it was in the middle but we moved it to sidewall, 1700 sq' house, lots of windows built in 1990,  Air intake to fan compartment 18" x 8" original,  2 years ago i added a 10"x12" and attached the air exchange outlet pipe.  The contractor never finished the job.  Heat out is 20"x20".  Furnace ran for 18 years with the flame kicking off and on till a guy doing a hot water install told me the flame should stay on constant till house comes to temp.  contacted tempstar and they confirmed.  With out having someone coming and looking the complete house over we have assumed that the air intake ducting in the house is too small.  I guess the original problem is the flame would kick on and off as the exchanger box would heat up but after it would shut off the furnace for about 5 minutes the furnace fan would kick back on and run till it would cool down some more...... if the thermostat would try to kick the furnace back on during this period the furnace would just cycle kicking the flame on for 30 seconds then shut down and start over again.  I would have to turn the temp way down so it would not demand more heat then it would work normal.  end of story when i added the extra air inlet and i extend the fan run time it worked perfect...  2 years later same problem.  I think that i need to buy a new furnace possible but have to keep this one going.  One other question what brand of furnace to you like best.

I don't know what your ducting situation is?
What I'm saying is your furnace is doing what it's supposed to do by shutting on and off because of the conditions it's installed under?
I can't tell you how to solve the problem with out you answering the questions I asked.
When the furnace was moved to the "side wall" if you didn't increase the size of the supply duct that would make the furnace over heat, an 8x18 return duct is not big enough for a 100,000 BTU furnace and that would make the furnace over heat,
An extra filter in the return side would make the furnace over heat, It goes on and on Answer my questions so I know what your system is like, I think you you might have some more serious problems. Read my first answer again and answer the questions. Filter size, location, return grill size, return ducts size, supply duct size from the furnace past the 20x20???

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QUESTION: Sorry, Furnace has always been in same place.  We never followed the house plan.  Filter is 20x25x1 mounted on furnace where hole is cut for intake air by fan, only one filter in complete system, Return grills, 10x12, 5x29,5x23,5x13, 5x13, return duct at filter 8x18, hood on furnace 20x20,connected to the hood there are two 8" round going directly to heat vents and one main 8x18 which distributes to the rest of the heat vents in the house.  Do you need to know how many heat vents total?

A  20X20 plenum off of the top of furnace  is 400 square inches of free area, One 8X18 duct connected to the plenum is 144 square inches, 2-8" rounds off of the plenum is 98 square inches 144 + 98=242 inches of free air.
242" of  supply air capacity providing there is that much free area in outlets?
An 8x18 return drop is 144 square inches of free area, Your furnace return air drop should be a minimum of at least 200 square inches, ever time the furnace blower runs it picks up dirt and dust which reduces the area even more and more, which in turn causes your furnace to over heat.
Right now if you run your furnace with the filter out you'll see an improvement in it not shutting off so often or maybe not at all.
Regardless of duct and register size it can only move as much air as it takes in , 144" is not enough.

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Jim Barnhart


Fifty + years conditioning the air.


Answer questions about , residential and commercial. Answer questions about sheet metal fabrication. Fifty years plus experience. No answers for oil equipment, No answers for kitchen appliances, No answers for laundry appliances, I don't specialize in one particular area of the HVAC area, I'm more of a General Practitioner, Limited in refrigeration/

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