Ash Removal - Don't Make This FATAL Mistake! Step 8 of 10 - 2019 Summer Shutdown Checklist

By:Warren Walborn

 
The level of ash in the furnace should never be deeper than THREE INCHES.

A deep layer of ash causes two main problems:
1. Deep ash reduces efficiency
2. Ash can be highly corrosive and it can eat holes in your firebox steel.

During the summer months, ALL ash should be removed, and the firebox should be completely scraped clean.

EFFICIENCY: The heat from your burning wood transfers into the furnace water through the furnace walls. If the level of ash is too thick in the firebox, it does not allow for efficient heat transfer to the water in the water jacket of the furnace.

It is sometimes funny for us to see poorly maintained furnaces with more than 18 inches of deep ash! You could put your hand into the deep ash and feel cool ash because it is so deep (do NOT do this!). And a significant portion of the firebox steel is buried in ash so that a large portion of the steel surface area is covered and unavailable to transfer heat. 

CAUSTIC PASTE: If the ash becomes wet it is corrosive to the metal of the furnace.  All wood contains moisture. That moisture should leave the furnace in the form of steam.

However, deep layers of ash can absorb that moisture and form a CAUSTIC paste that can eat holes in your furnace firebox. It is NEVER good to have deep ash, no matter what you have been told in the past. But if you keep the ash layer less than three inches, the ash remains dry and powder-like. Ash is harmless in its powdery state.
 

Coming Soon - Part 9! "Filter Kit - Why Needed for ALL Outdoor Boilers"