Combustion chamber lining Q's

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Old 11-19-08, 04:55 AM
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Combustion chamber lining Q's

I'm using an old American Standard boiler (35 years old) with a modern Beckett AFG burner. The combustion chamber on this beast has a ceremic-like concave target wall opposite the burner and also has what appears to be the same stuff on the bottom of the chamber. The forward wall has about 3 in of firebrick-like stuff. The sides of the (more/less) rectangular chamber are bare cast iron. I have no idea what it looked like in there when new but am wondering if the heat load is too high for the bare cast iron. The flame cone spreads out and almost licks the surface. I also noticed some small areas with white deposits in there. Any idea what causes this?
 
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Old 11-19-08, 05:48 PM
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Chamber

Don't worry about the bare cast iron. Below that cast is water. The white deposits are products of combustion often caused by condensation.
 
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Old 11-19-08, 06:01 PM
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If you have a target wall on the back side of the chamber and it is black, you have what is called flame impingement. If this is happening you may need to make air or nozzle adjustments so you have a nice orange glow when you shut the burner off and no black spots on the target wall. On a wet base boiler (water all around the chamber area) most boilers only require a target wall, bottom blanket and burner protection. All steel boilers, dry base (water stops above combustion chamber ares) have full combustion chambers to accept the high heat because there is no water jacket surrounding the chamber.


If the return piping for the boiler returns down at the floor, or bottom of the boiler, you have a wet base boiler.

If the return piping for the boiler returns about 1/2 way down the boiler and the burner is lower than the return piping, you have a dry base boiler.
 
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Old 11-19-08, 07:09 PM
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Thanks PG, it is definitely a wet base boiler. The target does glow brightly for a few seconds after shut down. The (visual) flame does not appear to come close to the target (flame tips look to be at least 4 - 5 inches away. And it's underfired too.
 
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