Question: for most Batch Box systems I’ve seen, I think the exit slot from the box is off to one side, so there’s swirl in the burn chamber, especially for circular burn chambers. I can’t quite tell from your cut-away—is yours centered for smoother flow with rectangular passages?
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The original Batch Box system was straight out the back, some folks built a version out the side, called a Sidewinder. Same principles, no advantage to it except shallower depth for tight spaces.
I didn’t draw the riser at all. Regardless, the swirl is a double vortex “ram’s horn” pattern created by a narrow tall slot. These vortexes swirl and rise their way up to the upper chamber then turn horizontal. There is a “stumbling block” mounted in the ceiling of the upper chamber to trip up the gasses and create more turbulence. By the time it exits the top slot, combustion is complete and only hot gases remain.
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I think Al has a point there to be able to bypass the system (make pizza in a hot summer evening)
I also wonder if the second bell with the water tank in it is closed off between the tank and the back wall to force fluegasses to go around the tank, otherwise I would think it would be a laminar flow there mostly passing the tank. Second thought in there is if it would benefit to close off part of the gas channel to the second bell, i.e. a ’lid’ on top of the channel (preferrably so the gasses come in to the bell in the corner) to create a low pressure zone over the ’lid’ and create a vortex of sorts to mix the cold and warm gasses again to utilize as much heat as possible to the tank.
Also I think temperatures need to be taken into consideration so you don’t get condensation in your chimney, never lower than 180f three feet down in your chimney to be safe. This is hard to figure out on paper though
Perhaps this is all old news but I thought it was worth mentioning anyway 
Edit: I see you already touched this while I was writing 
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Chris, Peter Berg is indeed the WK level, and very accessible. Send him a mail and he will get back to you in short time. My first thoughts are that you take to much heat away, but it is up to Peter. He will see it right away.
Clever thinking of the waterheating, thanks.
No time to read the rest, just wanted to say to mail Peter.
Btw, if someone want to make digital drawings, I cant find the time, he might need some help.
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Good points about the tank, however I’m not wanting to absorb lots of heat at that point. That’s the job of the heat exchanger on the first bell. It’s more about not needing to keep an external insulated tank elsewhere. If it’s inside the heater, it can act as part of the thermal mass and not worry about “losing” heat. Of course it’s never lost if we’re in heating season and the tank is indoors… But this way all heat loss from the tank is simply reabsorbed by the masonry to be radiated again to the room. Conversely, if the tank begins to lose temperature faster than the masonry, it can reabsorb a bit of heat from the warm side of the bricks (maybe).
Pizza in summer I’m not worried about. This is a winter-time only appliance. But I could still have that function, I would open the bypass and waste some heat up the flue.
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From a mantaince perspective i perfer a insulated tank outside the house insulated to r50 or R60 with an edpm liner and a plastic float valve from a cattle energy free waterer. The thing to me is leaks. I would rather have 700 or more gallons not leak out inside my house when it inevitably fails with age. That was how i setup my tarm wood boiler with a 700 gallon tank outside under my deck. I never noticed the thermal loss of having it outside given the high insulation and i always slept better as that house had half the basement finished as 2 bedrooms and a bathroom.
It just looked like too much of a flood risk to have that much water inside my house. The tarm boiler running at 190 would heat the tank to 180. Best would be radiant floor that will work at something like 80f as apposed to baseboard heaters that need 160f at the very coldest. I know i test them below that i just didn’t get enough heat to make air circulation through them.
But if you could go from 180 to even 120f you get alot more unable thermal storage from the same mass.
The other thing i would consider for a thermal mass built today would be electric heater that could run directly off solar panels as an opportunity load. That is still on my to do list here.
My plan is simply a edpm liner that i can cut out a square in and insert a stainless steel bulkhead to pass through the heating coils for floor heating and DHW plus have the electric heating coils in the same bulkhead simply sealed by clamping a outer fram to the bulkhead on the inside with the edpm liner squeezed as the gasket. A simple T on the DHW coil will provide the place to attach the float to keep the water level full at all times. Those plastic float valves never fail in my cattle waterer unless the cows get it open then they break everything.
Anyway that is the one suggestion i would have i understand your desire to use the thermal mass of the water tank but i am too scared of leaks to put that in finished space.
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There are too many differences between the all masonry system Chris wants to build and the Hybrid, metal/ stone/concrete heating system I have to make comparisons but I have learned a few things in the 24 winters I’ve run my system. Two stories. Hydronic heated floors on both. Tons of thermal mass. Floor water heated with pipe grids in a steel firebox surrounded by Concrete and stone with a convoluted smoke path to the flue. I have about 50 gallons of storage above the heater/open to the atmosphere, to allow it to thermosyphon. That is ample water storage for my system and allows the pumps to only work intermittently. Each pump uses 130 watts so not something you want running constantly. Each pass though the floors will drop the 170f water in the tanks back to below 80f as it enters the first floor grid. That floors is 8 inch thick concrete not insulated beneath, but that’s another story. I would certainly do that differently. I am not understanding how the grid of two inch pipes works in the article posted above.
If I were retrofitting an existing house I would run the PEX in the walls and heat them rather than baseboard heaters. Having run this system for a quarter of a century I have a lot of “wish I knew then what I know now’s” but it’s kept us warm. Just like the 75 per cent of running a wood gas vehicle, there is a learning curve.
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Are you using the water directly or running a copper coil through the tank? This is something I’ve seen debated for safety vs effectiveness, and I’m not decided either way.
I am glad to hear 50 gal is plenty of storage, the tank as drawn holds around 200 gal but it may need to shrink as I draw things to scale.
Are you referring to the heat exchanger in my drawing? It’s meant to thermosyphon to the tank above it. So essentially it’s just an extension of the storage tank, but the pipe grid arrangement increases the surface area significantly.
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Leaks are a concern. However I’ve been around water heaters and plumbing all my life, I’ve never seen a bucket-dump type event, just broken pipes, loose fittings, or rusted out tanks with pinhole leaks. A 700 gallon tank leaking is no different than a burst pipe, either way you will have 700 gallons on the floor within hours, but not instantly.
I need to ensure a) that all leaks are detectable and b) that I provide a drain path that won’t ruin the house. Something like a water heater pan with a drain hole - I use these on all my water heaters and they do work, if you plumb them correctly. I will probably pony up for a stainless water tank inside the masonry heater, since it will be difficult to service. That should eliminate corrosion issues.
I’m more concerned with the additional weight. I will need a very solid foundation for the masonry already, and adding 1500+ pounds of water to that calls for special considerations.
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Chris the tarm boiler would raise 700 gallons of water from 160 to 180 with a single full burn of the fire box about two armloads of wood. That was enough heat to heat the 30x30 saltbox open concept house with 2 full floors of space for about 12 hours here in NH. When it got about -15f i would probably have to fill the boiler a 3rd time. But the water was the only thermal mass in my system.
As the the hours comment you are correct but it has been my luck that such events happen when no one is home for hours and you return to a big mess. Not saying it is inevitable it was just a risk i didn’t want to take when i had an easy alternative. If i had a full basement that wasn’t finished i wouldn’t worry about the tank there. Just my two cents.
The point i wanted to share is the thermal mass needs to equal the burn load energy of the fire box. This is the ultimate goal to burn fast and store the heat. In your case the water and stone combination will require some knowledge to size the fire box. Also is that your hot water for the summer? If so it would probably heat the house.
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On i forgot to say i saw a design for a masonry heater with the water coil and a regular stone thermal mass but you could choose which way the smoke went to heat. I really liked that design as you could heat the hot water in the summer without heating the mass of the heater. They said the only down fall was you burned 2 loads of the fire box if you needed to heat both the storage tank and the room with the mass heater. But both where sized to the same burn volume of wood.
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For hot water I’m planning to use PV electric to run a regular water heater, with preheat from the masonry system in winter time. I feel like during summer it’s an easy load-shed for excessive solar once batteries are charged. In winter, it won’t have as much work to do because of the preheat.
I did consider thermal solar panels, but the cost is high vs the equivalent PV panels, and electricity is more versatile once the water’s hot. Plus the necessary drainback systems and additional storage tanks etc, just too complex for me at this point with no clear advantage.
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Hi ChrisKY
I linked back to your post #54 Nov 1 post.
Something there like fingernails on a chalk board to me.
I’ve slept on it.
Gone back and reviewed my four comments on this topic back in Febuary so’s not to repeat cautions, pictures, my own life stories.
You are combining too many needs to be fulfilled into one system.
And basing too much of that system on the one-concept of “rocketing” turbulence combustion.
as a do-all, for-all superior. It is not.
Here is a good Life’s rule-of-thumb to develop.
A Rule of Threes.
If a tool is made that will have more than three primary uses it will then compromise too much all needs.
There are reasons a fellow like WayneK has three different farm tractors.
I have evolved to three different primary use chainsaws.
Having a wife people hauler car/vehicle. A work commuter/light hauler rig. A hauling-towing real truck-truck. Like many fess up to having here.
Wood fueled for heat energy is the same.
You will benefit best by having three dedicated, using wood-for-fuel; use-seasonally systems.
A wood fueled dedicated cooking stove that can heat water too.
A whole house wood fueled heating system that can heat water too.
An outside summer BBQ/oven/smoker/slow cooker/pleasure fire system. It does not have to heat water directly.
Regards
Steve Unruh
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I like the plan of solar PV using a storage tank as an opportunity load. I would just make both thermal loads use the same tank. If you have a mass of water you can have a heating zone thermal coil and a separate DHW coil. The last time i checked was about 15 years ago but code here was two copper walls of isolation between antifreeze and drinking water. So if the tank was full of just water you could run antifreeze in the heating loop if you wanted. I ran water in everything figuring if it got cold enough to freeze i would have long since adressed the cold house or would have much bigger problems.
But if you do solar PV in the same tank even in winter if the batteries are charged there will be days you get free heat from the panels in a common thermal mass.
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Steve, I appreciate the wisdom here. I also have multiples of nearly everything… three tractors (plus the walkbehind BCS), three vehicles, two (working) chainsaws, etc. My running joke is I have to have two of everything - except a wife! She’s as good two of me, anyhow.
You’re assuming this is my do-all system but it is not. This is why I removed the cooktop function, I really don’t want to fire this thing up every time I need to cook all summer. I will probably install a separate metal wood cookstove at some point, but until then (and even then) I will have a boring propane range, like normal people. Water heating will not be reliant on this, only for preheat. Even home heating will not fully rely on this system, I will also have a mini-split for A/C which can do some supplemental heating in the spring/fall if needed.
This heater has one purpose - heating the entire house through the winter. Pizza making is a distant second, fun byproduct (and yes I’ll build a real pizza oven outdoors for summertime. Along with a grill / smoker / outdoor kitchen area).
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Yes but in summer the tank would shed heat into the cold masonry. I am counting on that staying cold for passive cooling purposes.
I have a better idea, why not put a heating element straight in the masonry storage tank? then I can control it separately, still do the load-shedding in winter if I want to. Keeping a standard electric water heater (with a warranty!) is too simple to ignore. Like Steve said, we should avoid combining too many things in one system.
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Good. Good.
I make the same comment about only having the one-Wife. My only do-all reliance.
And I will not apologize about disliking the Rocketing combustion concept.
Here:
This morning: just started house heating fire.
Started on thumb-sized forest floor picked up dry sticks. A bit of consumer paper. With two old covers removed books on the side walls. A single chunk of corrugated box cardboard on top.
“Rocket” velosity, turbulence zoom-zoomed up to be as smoke-less as possible heating ASAP.
Get the chimney updraft flowing good.
Then the fire transitioned over to slow, slow long duration combustion with cut up furniture woods boned out of box-springs mattresses; upholstered chairs and some old tables. Screws, nails, hanging springs and hog-ringed bits of fabrics still attached.
Last night it was big solid cottonwood dry chunks/splits.
I’ve previously pictured double craft paper bagged heating with hand compacted cubes of wood shed floor chips, sawdusts and wood debris in my bulk wood stoves.
Rocket stoving is quick-use; sticks-woods; one-shots does it all. One dimensional like the Drizzer fellow. Like a Wankle engine as a do-all. Not. Never be a do-alls, for all uses.
Stupid to idealize around one dimensional fuel type/forms dependencies.
Leaving you vulnerable to manipulations, and beyond your control “market-forces”.
Grow and use your own woods. ALL forms of woods.
S.U.
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Chris there are many ways to solve the same problem. If you want 2 separate tanks you would probably be better off to use coils to exchange heat between them. Seems to me getting electricity into the masonry heater would be problematic. You already have a heating coil in there. I was just saying with the tarm boiler i had a separate tank that had a separate coil for DHW and it worked very well. I was able to heat the tank with either my oil or wood boiler and today i want to build a tank that can be heated with either a boiler or electric elements but provides both hot water and heating.
To me one common tank is just easier outside of the thermal mass of the masonry heater. That is what i like about the coil in the heating path it keeps the impacts of the thermal mass out of the smoke path and separate from the Mansony heater. This is probably me having struggled with the headache of cold starting a tarm boiler. When the water jacket was below 140f that boiler was so bad i would burn the oil furnace to heat the wood boiler. In the end that made me love the idea of separate water thermal mass from the fire box. I don’t think the tank will be a problem in the heater you want i just am guessing a single larger tank outside would be more useful year around.
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Did you think about solar hot air panels, aka solar furnace? You can make them yourself, so low cost. They won’t leak and ruin your shingles or anything like that. If used with a thermal mass system, like you propose, I suspect they will make a low cost, low labor, safe and efficient system.
Rindert
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I did consider those. At least they can’t freeze.
My plan is to use the south facing window wall to heat up the masonry directly. I can control the solar gains using curtains in the summer or overnight in winter.
Solar air panels heat up air, which is great for convection heating. However I’m trying to maximize radiant heat, and trying to heat the masonry using hot air is difficult.
Using the warm air directly could be a good supplement, maybe down the road a bit. For now I’m focusing on the core.
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