Gas Furnance Problems

[staselwood]

Hello All, First time poster...

I have an old gas furnance in my greenhouse that I just re-lit the pilot light tonight for the first time since last winter. The pilot lights fine and will stay lit as normal. Next I turn the heat up at the thermostat to run it. this works ok as well. The gas flames, it heats up and the blower comes on and runs for about 3-5 min. and then all the flames (both pilot and heating) just cut off. The Blower continues to run like a normal cooling phase...

Dont think that it can be the thermocouple can it, or it wouldnt light. Seems like its some high temperature limit switch or something killing the gas????? dont know where to start. Any help would be great.

[<kjpro]

Phone book, heating contractors.

Why would you want to mess with something which you don&#39;t have the knowledge or tools to do the work properly?

[TH]

Cause he wants to, dick head. If you can&#39;t give advice keep your opinion to yourself. People come here for help &#39;cause they&#39;re not afraid to tackle problems, that most of the time can easily be fixed by yourself and save a lot of money, if you just put a little effort in finding out how things work. I get tired of all the dick head contractors lurking in here trying to convince people that only contractors are qualified to do anything. In my experience, the more you can keep the contractors away and learn to do things yourself, the better off you will be.

[Caesar Romano]

On Sun, 30 Sep 2007 21:57:02 -0700, TH wrote Re Re: Gas Furnance Problems:

Well said.

[You Know Who]

Amen to that, besides, that kjpro dude wouldn&#39;t know how to fix a heater properly if the instructions were pasted on it. I know because I&#39;ve worked with him. He is what we call a hack. Any advice he gives, I would seriously think twice before I followed it, unless of course you want to get something really screwed up.

[hallerb]

i would begin by replacing the thermocouple they are cheap and easy to replace.....

this elminates one failure area and it may well be the cause

[Jesse]

Thermocouple problem for sure. jesse

[jazon48]

This is a common method of running furnaces with thermostats. Many thermostats (e.g. all that I have every owned) have some sort of anticipatory or "pre-act" control which shuts off the furnace before the room has reached the setpoint temperature. The "pre-act" feature reduces temperature overshoot. Temperature overshoot is regarded as undesirable by most folks.

The pre-act in simple thermostats is activated by a little electric heater close to the temperature sensor in the thermostat.

Your thermostat might have a pre-act control which you could adjust. However, if the thermostat ultimately allows the furnace to heat your greenhouse to whatever temperature you selected, you really don&#39;t have to fool around with anything.

My old fashioned mechanical thermostats all had adjustable pre-acts. My current, fancy electronic model does not but really needs it.

-J

[staselwood via HomeKB.com]

I will do that, BTW, it is a new one from last year. Would they go bad in a season? And if the thermocouple is bad would it not allow the pilot light to start right? Not second guessing your idea, just trying to make sure I state the facts and understand the componets correctly... J

[e-mail] wrote:

[staselwood via HomeKB.com]

Thanks Jason, Would this "pre-act" feature turn off the pilot light as well? I understand the concept you are stating about overshoot, but this is killing all the gas. Not just the burners. So after this I have to relight the pilotlight.

Maybe I should note that i did replace the thermocouple and gas valve last year.

J

[e-mail] wrote:

[staselwood via HomeKB.com]

I would also like to note... I looked in the archives (as suggested) for other issues like this before posting and came across several other posts just like the KJPRO one, and all the subsequint posts. I thought, should i even bother. I do need a fix, and I always like to know something about what i am either working on or asking someone to work on. So I dont get taken for a ride by unscrupulous contractors that pray on the un-knowing consumer. If I blow my self up, shame on me... I should know that gas is flamable and will ignite if exposed to flame... Thanks to those who posted in my behalf. He should rethink his marketing plan if he thinks he is getting business from here... haha

j

You Know Who wrote:

[Meat Plow]

Makes sure the thermocouple is in a good portion of the flame. Take a wrench and give the nut at the end of the thermocouple line to the gas vale a little bump towards more tight.

[Stormin Mormon]

How&#39;s the air flow? If the filter is clogged, or if the vents are closed, it may very well be shutting off, with the high temp safety.

[Stormin Mormon]

The term he&#39;s seeking is "heat anticipator". No, that should not shut off the pilot. Makes me wonder if you have some air in the line, or some other problem with the gas supply?

[hallerb]

I had a 6 month old thrmocouple fail once. as others pointed out make sure its in the flame.

[jim]

Not meaning to piss people off but somethings diy wern&#39;t meant to do as I a plumber have found to many times. They mean well but they get the Bob Vila syndrome and think they know it all. Just give them a hammer and nail and it will be fixxed. Not to say that there arn&#39;t bad contractors butt there are more good 1 check thermocoupler as stated for flame contact , 2 Check to see how long the burn goe&#39;s for before going out. 3 If you have never played with a gas heater call a pro gas tech not a generel contractor and have it done right. 4 Sounds like a temp sensor to me and you can replace 3 to get it right or one if you know your unit. Do you not have warranty! To the th who dissed contractors you are the type I come to fixx the most I can tell. I aggree people can fixx but know you limits and gas is something not to play with as it blows up when you do it wrong.

[staselwood via HomeKB.com]

this is one a well. An oil well that we get the gas from. The pressure gage on the well seems to be normal. It could be. But it relights normal and will stay lit for long time. but when the burner is kicked on it only runs for a short time and ALL is cut off. I will blow off the gas lines to make sure there is not mositure or air.

thanks j

Storm>The term he&#39;s seeking is "heat anticipator". No, that should not shut off

[staselwood via HomeKB.com]

flow is good. filter was off when i was working on it, so there shouldnt have been a restriction there. All the vents were open on the run. Last season, I had a furnance guy come in and look at it, thats where the new thermocouple and gas valve came from... He did mess with the temperature settings for the blower. wonder if that had something to do with it. (it was really cold when he was working on it... Its still int he 50&#39;s night and

80&#39;s >How&#39;s the air flow? If the filter is clogged, or if the vents are closed, it

[<kjpro]

I gave him good advice, you&#39;re just too stupid to understand that.

Most homeowners don&#39;t have manometers to set/check gas pressures... do you? Now STFU.

[<kjpro]

You&#39;re such a liar. You must be related to Clark.