Flames Jumping Out

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  #1  
Old 10-16-02, 11:33 AM
Lon Winters
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Flames Jumping Out

Gas furnance, electronic ignite - it starts, main burner comes on , but the flames are shooting back out, not into the main chamber area.

I have stopped messing with it at this point and called in a pro!

But, I just want to be sure he will do the correct thing - is it just a matter of cleaning the burners? There is some junk in there, like at the least a spider nest. Also, there are little discs nearly which I think are supposed to detect this backdraft and shutdown - but that didn't happen. I want to be sure the technician checks or replaces those if needed.

Any ideas? Thanks!
 
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  #2  
Old 10-16-02, 03:32 PM
lynn comstock
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Delayed ignition will cause flames to backflash out at the start of the burn cycle making an explosive noise. A mispositioned or undersized pilot flame (too far from the burner) usually causes this. A dirty of rusty burner can cause this also (if the burner gas is restricted near the pilot. Then the flame has to spread from the front to the back of the burner and from burner to burner without delays or it will backflash. After the backflash, the flames stay inside where they belong and burn with a normal blue color (NOT YELLOW).

Restricted flue or flue passages may cause a flame rollout (no noise) and the flames will continue to roll out of the heat exchanger after ignition. The flames will usually be yellow and lazy, more like a candle flame.

It is possible to have both conditions at once.

Also if the flame stays inside until the fan starts and THEN the flames shoot out, the heat exchanger is cracked or rusted out. This is best fixed with a new furnace.
 
  #3  
Old 10-17-02, 05:58 AM
Lon Winters
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Thank you for the reply - it sounds like the second condition the way you describe it. However, I was wondering if it may just be due to clogged burner also - in other words, could some of the gas be bouncing backwords because of an obsturction in the burner?
 
  #4  
Old 10-22-02, 03:56 PM
lynn comstock
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Explaining the delayed ignition scenario.

Delayed ignition occurs whenever the gas and air mixture doesn't ignite right away. The accumulating gas finally pushes out to wherever a flame is...and it flashes or BOOMS depending on how much of the explosive gas and air mixture there is backed up inside of the combustion chamber. This explosion will push flames out in a most impressive way.
 
  #5  
Old 10-23-02, 05:09 AM
Lon Winters
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Thank you again - I did have the unit serviced - the condition was termed "flame rollout" by the technician, and was caused by an obstruction - I also made sure the safety shutoff sensors worked should it happen again.
 
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