More education needed - The good, the bad and the ugly

OK, here is an example......from a very well meaning guy......of what NOT to do. Has installed and is learning use of a Liberator.




Some random observations..........

First, even though they have been working on design for a bit, if this is current state of art, it appears to have problems. This owner felt compelled to install a cookie sheet heat shield as was concerned about how hot the pellet bin was getting. And with good concern. Pellets do get hot and catch fire. I've used them in the bottom of a gas grill for supplemental smoke.....in what looked to be a protected area several inches below burners.......and they still catch fire. I have no idea what would happen if a large pellet load caught fire in that bin, but it would not be good.

With no massive heat sink downstream of burn barrel, under some conditions, stove putting out too much heat, so owner was attempting to damper burn. Blocked off air intakes with tin foil and yam can to slow fire down. Thus ending the clean burn attributes. This install needs a massive heat sink or bell, as most certainly flu temps remain very high meaning a whole lot of heat from very expensive pellets being lost to the outside.

Speaking of pellets, seems to me to defeat the purpose, but is a source of fuel. "Pellet" concept however, has a whole lot of appeal. Massive amount of appeal. Instead of pellets.......use a wood chunker to make huge stockpiles of baseball to softball sized wood chunks that can be handled and fed mechanically to a continuous burn setup.

Owner did a great job on his install, with one exception. What is distance to the combustible wood trim on top of his corrugated metal heat shield?

This stove appears to have an easy to use ash removal method, which is often glossed over with most designs. Ash is a byproduct of wood heat and has to be dealt with. Remarkably, I can't really describe how that works with either a RMH or masonry heater, as that part of design is hardly ever mentioned.

So semi-related.......most RMH or masonry heaters I've seen are batch load. Single hot burn.

I have some experience with gas fired boilers for central heat systems, and those prefer a low and slow constant heat source to level out the peaks and valleys.

Has anyone given consideration to a similar approach in a RMH? A fire......but about once ever 10 min or so, a single chunk of wood is dropped to refresh burn? Keeps it warm and flowing on a continuous basis? Still peaks and valleys, but smoother or lower amplitude?

For those of you not familiar with a wood chunker........here is an Einstein in bib overalls. That is a "pellet" stove operation I could get behind.

Hi Eugene;
I am not quite sure what answer you are seeking.

Nice video of the liberator.
Indeed the liborator can have a smaller mass added.
That particular buyer chooses not to build one.
The liberator is a cool stove with the added benefit of being UL listed for installation in homes as well as the pellet feeder option.
Comparing it to a batch box is like comparing a VW beetle to a Ferrari, they are two different beasts.

So your question about tossing chunks in a batch box every ten minutes or so?
After a full load has been burned down to glowing coal, THEN you could toss in a chunk every little bit to maintain the heat.
If you were thinking of only building a tiny fire and slowly adding chunks, then you will not be getting a clean burn.

Are you wanting a fire to burn in your RMH all day?

You asked about ash with an RMH.
Yes, they need cleaning.
I clean ash from my batch boxes maybe once a month.
The ash in the box is easy to scoop out, a bit gets in on the floor of the riser and a vacuum will clean that out.
That's it if using a bell system.
When burned as intended the bell itself can go years without cleaning.

A piped mass should be inspected/cleaned once a season.

Original post about the Liberator not so much a question as an observation. Appears that owner is trying to run it as a conventional wood stove, vs. what it is. That was "more education needed" part.......at least that was my observation after seeing him installing his damper systems. Having never run one, however, it may be doing fine as is.  I need to study these more as have only recently come across them. Happy to see they are made in MO.

Second part that was more of a question.......what happens or would happen if a RMH was run more or less on a continuous basis vs. a batch? At some point it would seem the heat would build to an equilibrium. Idea being contemplated is if a small heater could heat a big space that way.  More of a theoretical question for now.

The other question was about fire management. Between full load burns, would it be better to keep a fire going.......by dropping a new piece of wood as the previous one is reduced to spent coals...........or stick with large batch burn.......and let it die out to to another cold start?  Even out the peaks and valleys? Also considered more of a theoretical question.

Ok, that clarifies it for me.

1) The liberator is a good compromise between a box stove and an electric pellet stove.
A quality American-made product for mainstream consumers needing a UL-listed wood burner.

2) Each size batch box has a corresponding maximum size bell it can utilize while maintaining a draft.
This has been discussed with Matt Walker during the stove chat show.
He stated that it is possible to have a series of bells inter-connected, that could be opened as the previous one comes up to full temperature.
To accomplish that you would be burning back-to-back full loads.
Side note)  with welding gauntlets on, you can open a batch at full burn to toss in more wood... but why, it's better to let them calm down a bit.

3) This one is easy!
In a home, once an RMH is warmed up, there are no cold starts for the rest of the winter!
In either a heated or unheated space, a bypass allows for easy cold starts.

Having studied the Liberator features a bit, a few more observations. Ditch the pellet feeder option and this is basically an off the shelf ready to go J tube core. Adding either an upright or horizontal bell bench for thermal mass storage and you are set!

As for the video, to critique the owner's install, he could improve upon it by again, ditching the pellets in favor of real wood, and do that for a couple reasons, starting with he would be able to moderate his heat better by being able to vary his wood load, and wood eliminates his concern about pellet temperatures, not to mention being cheaper.

As noted before, the owner is treating this as a wood stove. He would likely get better outcome by running exhaust thru a bell of some type.........and would benefit even further by replacing the corrugated metal wall cover with non flammable stacked bricks or stone for a radiant heat sink, with a polyiso foil faced insulation board behind those to reflect absorbed heat back into the room.  End result could be more retained heat and much less fuel consumption.

But as for the Liberator itself, to have an off the self UL approved option, this is one of the most encouraging developments I've seen in the RMH concept. A good chance to expose the concept to the mainstream for widespread adoption.

Since more education is needed, the FAQ thread might be a good place to start:

https://permies.com/t/191801/Building-Ultimate-Rocket-Mass-Heater

Eugene, you may have some points but, at the end of the day the owner in question seems delighted with his stove!

Fox James wrote:Eugene, you may have some points but, at the end of the day the owner in question seems delighted with his stove!

True, but he would probably be even more excited if he used it to it's full potential. BTW, that wasn't his first video. He has been working with it for some time. My concern there is what instructions and background were included with his stove? Are those good? Bad? Ugly?

Thomas: thanks for the comment. I was not aware that a RMH could eventually max out on heat absorption and stall (my expression). So unless one used a series of bells sized to to the source, it is not possible or a good idea to do a continuous burn. Good to know. For a variety of reasons.

Edited to include: continuous burn not easy to do with batch box, but very much possible with a J tube.

Good news!

It turns out that the owner's manual is available on the Liberator's website. Not only that, but if you read thru it there is a section on installing the stove INCLUDING the use of a thermal mass storage device. Basically a cob bench. Including sketches. Even references Ernie and Erica's book

So that pretty much does make it an off the shelf UL approved RMH option.

Owners Manual:

https://drive.google.com/file/d/18C23FQc9skGm4-rU56DQ5cFeYyeCTWB5/view

Hey Eugene;
You misunderstood what I tried to say. (I tend to ramble)
"I was not aware that a RMH could eventually max out on heat absorption and stall"
That's not what I was trying to say.
A 6" batch has a maximum bell size that it can fill when cold and reliably still draft.
If you burn a 6" all day, it will just make more of the bell warmer.
External brick temps on a single skin bell can be 200-300F near the top.
However, your exhaust temps can go higher than we like to see.

Next, there is nothing wrong with back-to-back burns in an uninsulated building.
We burn the 6" batch in Liz's uninsulated greenhouse/ studio all day every day from September thru April.
No fire all night and it maintains 45-50F while teens are outside.

"continuous burn not easy to do with batch box, but very much possible with a J tube."
Not true, you can burn back-to-back with either.