Adjustable RMH - Heat mode vs Storage mode

I keep wondering if it would be beneficial or downright awesome to be able to adjust a RMH to go from "heat now" mode to "store it in the mass" mode.  Currently that adjustment is built into the design and you can't change it.  This was especially obvious when staying in the red cabin before the insulation and sealing upgrades.  It was primarily "heat now" so you'd get it up to 80 degrees and all the heat would be gone in 4 hours.

I believe the ratio of bell/drum to the mass determines how much heat is shot out into the room with radiant action versus dumped into the mass for slow release.

Some situations where you want fast heat:
- Spring and Fall where you just want to take the chill off
- Forgot to run the RMH for a bit and need to get the house warmer fast
- Normal guests are coming who would enjoy it a bit warmer

Some situations where you want slow heat:
- Steady running in the depths of winter
- You want even temps in your house without fluctuating bursts of heat off the barrel

SO.....  Can we come up with a design that allows you to adjust it from one mode to another?

One thought would be to have the barrel be two barrel-like things that telescope inside each other.  When the upper barrel is down low, you have less radiant barrel exposed (plus two layers of metal to get through).  When you slide it up you get more radiant barrel surface exposed and it's a single layer of metal.  Yes, sealing between the two and moving them would take some brain power.

Another would be a thicker steel (or masonry?) piece that can rotate or clam-shell around the fixed barrel to block some of the heat in the steel piece.  So if you want fast heat, move the heat blocker out of the way, if you want slow heat, engage the blocker.

Any other ideas?  Might this be the thing that makes RMHs more popular?  I sure prefer a design that has some adjustment in it after it's built.

Hi Mike;
There is such a thing!  It is called a bypass, with the bypass open over 50% or more of your heat is going directly up the chimney.
Close the bypass and 100% is heating your mass.
My bypasses are 1/2 the diameter of my outlet chimney.
A larger bypass could be incorporated to let more heat escape up the chimney.

Thanks Thomas but I don't want to waste the heat by bypassing it up the chimney.

I want to be able to turn a knob (figuratively) to switch between:
1. normalish RMH, perhaps a bit heavy on the barrel like the auditorium heater at WL.  This would kick out heat fast when you need to heat up a place fast
2. rocket MASS heater that puts most of its heat into the mass.  Maybe more like a Peter Van den Berg design with a brick bell or a RMH with cob covering much of the barrel.  Most of the heat is stored to keep the average temp more steady

Hey Mike,
Had that same thought a while back but because it was not as simple to do as installing a bench bypass, I just left it alone.
I like your ideas though.
The only thing I would be watchful for though is not allowing the barrel to get too hot while in ‘bypass mode’ as it may then start to spall/degrade a lot more rapidly than if it was allowed to shed the heat quickly.
Would be a nice feature to have though. Look forward to see what other ideas people come up with.

Mike, It seems as though you are searching for a "passive" but "built-in" method. I think the heat-shielding around the bell would reduce the direct output, and likely allow more heat to continue on to the mass. It might behave more like a bell than the plain barrel, and be less "rockety" if the barrel sheds less heat?

Another way to approach is to make a masonry bell that might charge more slowly, but add a heat exchange channel and a small fan (could be one of those stove fans? or a 12v computer fan on solar/battery?) for when you would like some of the heat NOW.

Or... a masonry bell and a barrel except that the barrel would not have the heat riser inside, the barrel would be just be a secondary bell with a bypass/damper to exclude it from the path or not.

I like those ideas Kenneth!  Having a secondary barrel with a bypass would be a neat trick.  Or the air channel idea if you don't want to look at a barrel.  I do like the look of a masonry bell instead of a 55 gallon drum...

Gerry, I didn't know about the barrel overheating being an issue so that's definitely worth keeping in mind...

Ooh, the "secondary barrel" could be a white oven similar to the rocket oven (though possibly square?) that you could switch on/off via damper. It could have hinged or removable insulation panels. Panels ON and it is a rocket oven, panels OFF and it is a heater! Damper CLOSED and it isn't heated.

I've thought about this in the past. If you incorporated a glass stove cooktop into your design like Matt Walker and had yourself a panel of ceramic fiber board, maybe you could simply cover the cooktop to force the heat to stay in the bell when desired. Remove to let heat radiate out fast.

That’s a great idea too Matt except I wonder how the glass would hold up with the cf board on it?
Like the barrel, it was meant to shed that heat as quickly as it came. Remove that ability and it might just crack or shatter. Worth a try though for a rocket scientist!

If the standard diverter is used, the pipe between the barrel and the ceiling can be a special heat exchanger. Ideally, a fan could blow air over the exchanger when in instant heat mode to make the exchanger work as quickly as possible. Without power, the exchanger would need to be a more efficient design. Possibly the heat exchanger may need to be covered/insulated when in mass heat mode to prevent stalling the draft.

Alternatively, you could have two exhaust paths. One through a mass, and the alternate through a bare pipe. This would provide radiant heat, while the former would heat the air.

Yet another option might be a masonry bell (no barrel) and a stovepipe heat reclaimer on the flue. The bell and mass would charge slowly, and the fan on the heat reclaimer could be run or not... depending on if you need a boost of heat now. It might also be more gentle since by then the flue gasses would be cooler by the time they get there.

Hopefully this wouldn't cause draft issues? Just how cool can you get the chimney and still have a safe amount of draw?? Is it being too greedy to try for that one last bite at the apple?

Kenneth Elwell wrote:.Hopefully this wouldn't cause draft issues? Just how cool can you get the chimney and still have a safe amount of draw?? Is it being too greedy to try for that one last bite at the apple?

Between 150 - 200F is a good target to shoot for. Occasionally your going to get spikes up in the 300F range, but you don't want to go much lower than 150F otherwise its much easier for backdrafting to sneak up on you when your not looking!