rmh with propane backup

I am beginning to haul field stones to make a mass to heat up. I am most likely going to use a rocket stove as the primary source of combustion. I had a propane furnace with forced air that died on me. I want to make a heat exchanger to pull hot air off the mass and route thru the ducts. It is all still in the planning stages. I am running into an impasse when it comes to backup heat. I live alone and also like to travel. So I am trying to figure out if I could heat up my mass with propane in case I break a limb or have someone house sit that is unfamiliar with wood heating or just elderly. Is this doable? Or should i get a replacement propane furnace for backup. Thanks!

Davis B. : To answer your last question first ! There are many significant features of a Rocket Mass Heater RMH, that I would not put into the hands of my
brother-in-law, or the village idiot if he were closer to hand !

Consider what would happen IF someone inexperienced with a Rocket Mass Heaters RMHs, normal operation, decided to place bricks or pavers across the
top of the Feed Tube to attempt to block off the Air and put out the fire ! - A normal response with most "traditional'' or air tight wood stoves !

If this happened, the extremely hot temperatures within the RMHs combustion core would continue to pyrolyse wood gases, and continue to keep those gases
trapped within the RMHs Combustion core! These gases would only need the small increase of oxygen created by the raising of the seal on top of the Burn
Tunnel to create a ''Flash back'', this would -as a minimum, burn off ALL of that Persons Body and Scalp Hairs, but probably most of his clothing as well !

The ducting within the Thermal mass needs no further air flow to increase the performance of the RMH, which works entirely within the Radiant/Infrared heat
energy band! To ask this mass to provide the high energy temperatures necessary for Air to Air heat exchange is to work against the best performance
of the RMH !

A pre-heater insulated against the more extreme temperatures of the RMH could make lighting a fire within the RMH a very easy effort ! However only a gun
type gas or oil furnace that sprays into the combustion chamber the correct mix of fuel and air could generally be asked to safely preform as a back-up for the
rmh!

This is an under-explored field of RMH use, and as a further Tool to make the use of all RMHs more Mainstream could/should certainly be considered! As such,
any efforts you can make to create such a functioning unit works for the future good of all Rocket Mass Heaters RMHs ! For the Good of the Craft! big AL

davis; Its never a bad idea to have a backup source of heat. I would put a direct vent wall mount gas heater nearest to your water pipes , then you can leave without your pipes freezing . Depending on conditions your mass will hold heat for days. In the event you break a limb ,although spendy you could heat your mass with a propane torch.

Thanks you for clearing things up. I am understanding now that it would be pretty hard to move the heat around the house from the mass because of its radiant qualities. I have decided to rely on electric space heaters to keep things thawed out if I am away and unable to feed the dragon.

Its good to know that it could be possible to heat the mass with a propane torch. My friend does the initial heating of his wood fired pottery kiln with one. I'm wondering if it may be a good idea to use the torch to warm the mass a bit for the first firing in order to facilitate some heat draw going up the house chimney.

I guess this question is beginning to open some doors in regards to alternative fuels.

Al L. : I am not sure if this exactly what you had in mind but when I was reading your last post i began thinking of waste oil burners. The babington burner to be more specific. I am a novice pyro, but I could see one of these being mounted in the front of a rocket so it would be more of an L tube than a J tube. I wouldn't want to haul oil into my living space, but if this could work it would be really handy in a shop or garage. I am imagining someone with one of these and a mass underneath the workbench to save space and have nice warm tools all through the winter.

http://www.aipengineering.com/babington/Babington_Oil_Burner_HOWTO.html

Davis Bonk : Thank you ! I'm sure that you have seen the water sprinkler with two bent arms that rotates at some speed while flinging water around.

There was at one time a type of oil burner older than the Babington that attempted to atomize oil into a fine mist with this use of centrifugal force !

I actually worked on one of them, the Babington survives in a few tinkerers shops, other than that they were quickly abandoned and ignored !

As a conjurors trick they are interesting but almost impossible to keep burning cleanly ! IF that was my only option I would rather save my oil for
re-cycling/re-manufactored motor oils, it would be much greener.

It was an embarrassment to the heating fuels industry new! Some technology should only be in textbooks!

For Pre-heating the RMH, if you placed a torches flame head just down into the Burn Tunnel from the Feed Tube, and let it run while you went to the
last clean out at the base off your final vertical chimney/stovepipe , popped the cap off and placed a couple of shredded sheets of newspaper into the
'' T '' at that location, and then lit them on fire, and carefully closed up that clean out cap, by the time you get back to your RMHs Feed Tube, it should
be ready for you to build and light your fire !

About the only time you should need to use this technique is when your house has not had a fire in it for a few days, the whole house is very chilly,
and the outside air temps are higher ! Good luck For the Crafts ! Big AL

what about a burner from a fish cooker, placed in under the riser? would that be enough heat to warm the mass? im sure a wall mount ventless would be more efficient though. i have also seen cans, with oil and sawdust in them, made to be placed in a rocket stove. i think it was van powell on youtube. i know it wouldnt be as hot as a wood fire but seems fees-able.

Ronald B. with a top or front load batch burner it probably would work a treat, otherwise, without a clear picture of what you are suggesting I will say go ahead and try
it! I doubt that you can flow enough gas cleanly through most propane heaters that would fit in that space to ever cause damage to your RMH. Please if you do try this
document everything and include pictures ! For the good of the Craft ! Big AL

i was pondering this while in the clouds today. lol was wondering what temps could come off propane. checked it out just now. found a table that states -1,977c--3590f so the temp would be there. fuel cost would be the killer i think. made me wonder about putting some mass around my furnace duct though. lol also an incandescent light is 100-300c--212-572f. wonder how hot a light can get a grease can? be a great night light/heater. lol

as for the cans of oil and sawdust. i believe he shows the barrel temps with a 2 hour burn.


please correct my thinking if wrong. wouldnt you need the higher temps to make a rocket work correctly? would it actually flow with a light bulb in it? i imagine it like trying to cook a pot of stew with a match.

Ronald B. the J-bend shape of our most common Rocket Mass Heater RMH, works almost exactly like the '' P '' trap under a vanity type sink, preventing a continuing
loss of Room heat out through the RMHs Thermal Mass and out its final vertical chimney.

As an example, at about this time of the year after a few days away from home and no fires the House has cooled down into the 40s-50s, or colder and arriving home
in the early evening you might step into the house from afternoon temperatures of 60s-70s or higher, with out the j-bend in place there definitely would be a serious
back draft of cold air ! The chimney will not draft well because of an absence of warm air to rise up the chimney.

A handheld propane torch placed within the burn tunnel from the feed tube will eventually provide some heat for the system! If, you then go to the last clean out at the
base of the final vertical chimney and stuff in a couple sheets of shredded newspaper, lite them, clap the clean outs cap into place and briskly load up your feed tube and
light a small hot fire you should have overcome the temperature differences between inside and out side and removed the blockage to a good draft !

A 100 watt lightbulb would work if given enough time I hope I have given you a clear mental picture of the RMH and the additional fuel savings inherent within the J-Bends
construction, also note that while most Batch burning RMHs are front/horizontally loaded, they can have a top loading or at least drafting feature that restores the J-bend
seal ! For the Craft ! Big AL

i set a can(11"dia.-19"tall) over a lamp, with a 100w bulb. the highest i could get the can was 127f. thats pretty low. i cant imagine thaat even working as a heater. i think it would take a string of bulbs all the way down a mass, to even think of warming it. you mite have to start your heater in sept., to get it warm by nov. lol wood is truly amazing stuff.


still, i find my mind wanting to explore this propane deal. please dont hate me. LOL

Ronald B. : Wood is an evil incarnate thing that stores carbon as a totally indigestible form of sugars except when induced by heat to release that carbon
as short and medium length hydrocarbons :::--> wood gases ! Wood gases are Angles sent down down from heaven as light and heat, making night better
and safer than day and allowing our ancestors to flee Africa !

And in spite of our partnership with light and heat we still find ourselves barking our shins on the damn stuff, figuratively and literally as we stumble around
in the dark doing really dumb things like warming air that rises to the ceiling instead of producing radiant heat to directly warm ourselves

A BTU is a wonderful thing that we all take for granted, basically we all radiate about as much heat energy second by second as that 100watt lightbulb, try
taking that lightbulb with you under the covers where it is insulated and you can easily set fire to them ! For the craft! Big AL!

ronald bush wrote:i set a can(11"dia.-19"tall) over a lamp, with a 100w bulb. the highest i could get the can was 127f. thats pretty low. i cant imagine thaat even working as a heater.

Guess you never hung out and baked with the girls as a kid in this lightbulb heated oven:

lol no i didnt cj. i guess, if i had a miniature house, it mite be a heater. the clay pots over a candle deal gets hotter than 125f.

Ron Bush : What is actually happening is the thermal mass of your combustion core is demonstrating its ability to conduct heat through itself, with just the lightbulb
the temperature had stabilized at 127dF. More BTUs at a faster rate higher temps !

Years ago all mechanics had were incandescent lightbulbs in drop lights, Daily skin burns were common while trying to work in difficult places! (now more and more-
they can whip out a well charged cell phone and simultaneously light up the exact trouble spot, AND take a before and after picture - I see this nearly every week
day ! Big AL