When Does ASH Eat Holes in Outdoor Boilers?
But, when ash levels get deep, the ash absorbs moisture. "What Moisture!!??" you might ask. Well, wood fuel contains lots of water - even the most seasoned hardwood contains about 20% moisture (unless kiln dried and stored in a climate controlled environment, nobody does this!).
When the wood burns, the moisture leaves the wood in the form of steam. We want that steam to leave the boiler and not get absorbed by the ash.
Because... Moist ash is like CAUSTIC PASTE! It will eat holes in steel. If the ash layer in your outdoor boiler is more than 2-3 inches, the ash will absorb the moisture in the steam, and form CAUSTIC paste that eats holes in steel.
Most often, we see holes form in fireboxes in the bottom rear, and against the rear wall below the ash level. You MUST rake this ash forward and remove it frequently - we recommend removing at least a few shovels full EVERY DAY!
Solution? Simple! Keep your ash levels low - about 1-2 inches in the bottom of your outdoor boiler. Also, remember to remove ALL the ash every two weeks, and scrape out the inside of your firebox to remove all ash. Pay close attention to the rear bottom seam weld area - again this is the most common location where deep layers of ash eat holes in steel.
Deep layers of ash not only destroy steel, but also kill your efficiency! Heat from your wood burning needs to transfer through the steel of your firebox to get into your home. If a large portion of your firebox steel is buried in ash, much of the heat from your wood will not transfer into your water jacket, and that heat ends up going out the stack - wasted!
Remember, maintain your outdoor boiler so it can continue to save you money for decades!