Continued from Progress on the Thermal Mass
The core consists of two parts: the firebox and a modified riser. The riser is basically an internal chimney of specific length. It's purpose is to complete the burning of the wood (exhaust) gases produced by the fire. The port is a specific opening between the firebox and the riser. It regulates the exit of heat and exhaust from the firebox. It's the combination of the burn chamber, riser, and port that makes for an efficient, clean, smokeless burn of the firewood.
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| Dan poured the base for the core before he started the brickwork. |
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| First layer of firebrick. Refractory mortar is typically used for these. |
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| The firebox (burn chamber) is in front, the modified riser is behind. The opening between the two is called the port. |
There are a number of designs and variations for a core. Our's is called a "double shoe box," chosen because of our space limitations.
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| You might recall this cutaway image from my Masonry Heater Project post. |
It's designed to retain the heat and smoke to facilitate a clean, efficient burn.
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| For the top, Dan used ceramic fiber board. |
The smokeless heat exits the core through the slot in the top.
The heat is held in the thermal mass to radiate heat to the bricks, and in turn to the rest of the house. As it cools, the warm air sinks and exits the chimney at the bottom of the mass.
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| The channel in the bottom is for the secondary air tube, pictured here. |
The firebox door is next.
Masonry Heater: Building the Core © Sep 2024
10 comments:
My biggest complaint about my wood burning insert is the size of the firebox. I have to cut and split the wood pretty small. But I have a feeling yours will require even smaller sizes. But if things work right, you shouldn't need very much.
It is amazing to see how you and Dan figure things out and accomplish them. Hope you're doing well.
Ed, I've never had a fireplace inset, but I have to imagine they have to be fed the same as an open fireplace . Or a conventional woodstove. Of course, with any of those, the goal is to heat the room. The masonry heater is typically only fired up twice a day, and does use smaller wood, the idea being to heat the thermal mass.
One of the reasons Dan wanted a masonry stove is to ease up on the amount of firewood cutting and splitting that our old woodstove required. We wanted larger pieces of wood to keep the fire going. The masonry heater can do really well on branch sized wood and coppiced trees. It will still require cutting, but no splitting.
Sue, good to hear from you! Thankfully, there's a lot of really good information out there that has helped with every step. :)
One advantage an insert has over a conventional fireplace is that is utilizes the space between the insert and the conventional fireplace box much like your masonry stove to the brick surround except instead of the heat radiating out from the brick, there is a small fan attached that blows the air in-between out into the room. It heats the room quite well that was but does require electricity to do so.
Ed, it sounds like a really good option if one already has a fireplace. We have an Ecofan, which is thermoelectric and runs by the construction of the fins when they get warm. But we keep it on top of the stove, but you probably don't have a top to your inset. It's nice though, that it still runs even when the electricity is out.
We have had a fireplace insert for 12 years. It produces 80k btu’s and takes 20in logs. We have configured the chimney to capture the heat and gravity feed it to the bonus room above the garage. Previously this was the only room that was not comfortable when the fireplace unit was in use. The biggest deterrent for an insert is the inability to cook when all other power sources are no longer functioning. Thank you for sharing your journey! It has been a joy and encouragement to read of the productive endeavors of the homestead for many years.
Anonymous, sounds like you worked out a great solution! Thank you for sharing. The cooking aspect is a real nice bonus, if it's practical.
That is looking so good! Will be looking forward to the maiden run.
Rosalea, so are we!
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