Outdoor Wood Furnace Ash Removal - Don't Make This FATAL Mistake!

Outdoor Wood Furnace Ash Removal - Don't Make This FATAL Mistake!

How Fast Will Ash Eat Holes in Steel?

Step 8 of 10 - 2023 Summer Shutdown Checklist

We know that you are very happy with your outdoor wood furnace!  It keeps you warm in the winters, and you couldn't be any more satisfied. However, you are stuck as to what to do with the ashes on the woodstove. You don't know if it would be safe to just leave it there if it would not cause any harm to your furnace. Or do you have to remove it?

Ash is a result of the combustion of wood. Basically, its existence is unavoidable. However, we must avoid other problems that may arise if the ash is not cleared. You need to consider the level of ash in your outdoor wood stove. Remember 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.

What will happen if you will not remove the ash?

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 outdoor furnaces with more than 18 inches of deep ash! You could put your hand into the deep ash and feel the cool ash because it is so deep (do NOT do this!).

If a significant portion of the firebox steel is buried in ash and a large portion of the steel surface area is covered it would be unavailable to transfer heat. That heat from your wood ends up going out the stack - wasted!

CAUSTIC PASTE: Ash is harmless in its powdery state. But 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, if ash stays in your furnace, 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.

The first step to taking care of your outdoor wood boiler, ensuring your safety, and taking care of your family is to take the necessary precautions. 


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