Gas and Oil Home Heating Furnaces - Pilot is on, Burners aren't

I have a boiler that is approximately 10 years old The pilot is on the circulating pump turns on when i turn the thermostat on. I've replaced the thermocouple and gas valve thing before the burners everything seems to be working but it just doesn't light the main burners i've looked for loose or broken wires, i've tried everything i can think of i've run out of ideas. please help it's getting real cold inside my house

It sounds like the thermostat is calling for heat because the circulator is on. The high limit control may be interrupting the circuit. Check it out and make sure it is allowing power to the gas valve.

Ken

Did you make sure the thermocouple you replaced is currently in the pilot flame?

What kind of unit is this? Is there an ignition control board?Do you see any blinking indicator light or hear any clicking by a gas valve or anything?

the flames aren't escaping out the flue properly a sensor that is by the flames got tripped and that is what didn't let the gas go threw to the burners. why won't the flames stay inside the furnace?

You need to find out what is wrong with the venting system before you try to relight the furnace. Carbon monoxide gives no warning. Get a low level CO detector now and keep it handy even after you fix the furnace.

Ken

Flame roll out switch tripped. (If this switch is out in front of the burners) When you reset it does it trip out again or work now?

You could have had a delayed ignition that made the ignition poof like an explosion and made it go out, due to dirty burners. Or you have some severe low pressure condition in your basement where the fire is choosing to come toward the room rather than up- draft (But this would seem like a stretch with a ventor, drafting) Does your boiler have a pressure switch? (A diaphram device with one or two 1/4 inch sized vacuum tubes atached)? First of all, are they attached? If so, I would presume your venting is good. If your exchanger were bad, being a boiler, you'd think it be leaking water. But if not, you could have rust scale blocking passages. But if THAT were the case, then the pressure switch should be tripping out rather than just a rollout switch. Hmmm.

That's why I'm curious if it now trips out the switch again, or if it was a one-time anomoly. I've personally had them trip out and reset them and have had no further issue.

IF you indeed do have a venting problem, could be from blockage in the boiler or poor exhausting from a weak motor or pipe blockage or something with the condensate even blocking.

Does your unit have pvc exhaust through the wall where you can go outside and feel the exhaust when the unit first comes on? And if you have pvc, do you have 1 for exhaust, or do you have 2 (one for intake and 1 for exhaust)?

I jumped the sensor. that's how i know the flames roll out i don't think it can be reset i think i need a new one. I'm in the process of taking the flue apart to see if there is any blockage. it's just one flue a tin one. there is something that looks like a diaphram atop the unit in the flue seems to control a butterfly valve for the exhaust fumes. that works fine. when the pump kicks on it opens. i by passed the switch again with the flue off just for a second to see if it's the block is in the chimney on in the boiler. the flames rolled out again the blockage seem to be in the boiler

If the flames are still rolling out with the flue pipe disconnected, you'll need to access the heat exchanger passages. You'll probably find they are sooted up.

they are sooted up i'm in the process of cleaning them up. i does kind of make sense that this would be the problem