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Can I convert my boiler . . . and I'm not talking religion

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We have a 1800 sq ft, one level house built over a crawl space in Central Minnesota. Currently it is heated by a propane fueled boiler system that heats water in copper pipes that run through the crawlspace and pop up in the rooms. We bought the house about 8 months ago after moving from Florida to MN, and having never lived in a cold climate we were shocked at the price of heating in the winter. We originally thought of a wood stove, but then came across the idea of the mass heater. The efficiency is what we are after.

So we were thinking . . . since the boiler basically heats the water in the copper pipes and uses that heated water to heat the house, could we use the mass heater to heat the water instead of the propane? Then we could bypass messing with the current infrastructure.

We have no clue how to go about doing this, but we need to do something on the cheap, and preferably before winter. In a perfect world we'd love to keep it in the place where the boiler is stowed away now -- the utility room.

Has anybody done this . . . or know if it would work?

My husband is a carpenter by trade with some electrical and plumbing experience, but we've never attempted anything like this. Any ideas?
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Location: Southern alps, on the French side of the french /italian border 5000ft elevation
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Location: S.W. Missouri, Zone 6B
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"Boom Squish" is the popular phrase describing this. Boom goes the steam heating, squish go the people, and house. There is a tremendous amount of energy available in steam, as well as expansion rates. If you are not a trained boilermaker, I would not do this. There is a level of complexity and safety concerns that I do not think you are likely to manage in a few short months. If you really want to pursue this, plan on taking your time and research it thoroughly. Ernie Wisner has written about it here, and he speaks to it in the first 4 DVD series; in fact one of the DVDs is devoted to that topic, so that would be a very good place to start.

Instead, I would recommend building a standard rocket mass heater, be that the J-style or batch. Safer, by far, and easier to build. That is a project you may reasonably expect to have in place before winter hits.

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Location: Northern New York Zone4-5 the OUTER 'RONDACs percip 36''
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Leanne T. : I Strongly second Erik's comments, The 'Expansion Rates' Erik mentions occur at the speed of an explosion! Think Boston Marathon Bombing with MORE Deaths,

MORE Full thickness, Full body Burns, ( Family ) !

It is possible to prove to yourself that a Full sized mock-up of a working Rocket Heater is technically within your grasp -literally within the same day you get your bricks !

An alternate much more modest proposal to use a Rocket Mass Heater RMH to heat and store hot water in an open/un-pressurized tank, and use that stored energy to

supplement your existing Boiler (In a manner nearly identically to a system of water heating solar panels, and holding Tanks) would still require several months of full time

study to allow you to understand how this system designed and installed by professionals would work !

Again, your heating season is less than 4 months away, here is another vote to scale down your project !

Think like Fire, Flow like a Gas, Don't be the marshmallow ! For the good of the Crafts ! Big AL
Erik Weaver
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Location: S.W. Missouri, Zone 6B
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This is the DVD set I mentioned (which I have, and recommend). There are a number of purchase/viewing options. It is a pretty quick and easy way to get up to speed on many points concerning RMHs:


I would also recommend buying "the book" by Evans, Rocket Mass Heaters (2014 edition):


It's only 120 pages and a quick read. Page 28 offers a great summary/overview as I recall. Also, study the appendixes. This is the best way I know of to get up to speed on this material. If you don't care to spend $20 and an afternoon reading, then building your own RMH is most likely not for you conversely, if you devour this info and want more, a RMH may very well be right up your alley!

The one topic it does *not* cover is the batch style RMH as developed by Peter VDB. Fortunately, that is discussed quite thoroughly over at Donkey's forum:


Although, there are some threads on Peter's design here too:


You'll also need to look into building on a wood framed floor. The Wisner's have at least one set of plans for doing that. Air movement to draw away the heat from the floor is key. Or, if you have more money, you can install a pier and / or foundation below the mass, as per a more conventional masonry heater, and build on top of that. Either way, you need to look into this and start drawing up some plans, and consider the pros and cons of the various options.

Also plan on a full chimney, meaning one that properly runs out of the roof and has at minimum a 2-foot height above anything within 10-foot radius of the pipe/chimney. Evans' book talks about routing the stove pipe out the wall, near floor level and exiting more like a drier vent than a wood burning chimney. Unfortunately that does *not* seem to work for many persons. Most likely you will need a pipe/chimney just like you would for any other wood burning stove.

I'd also pick up a copy of ASTM-E1602-03, which details safe clearances. This is one of the go-to references when designing masonry heaters.

Also, look up some building details on heat shielding. It'll be easy for your husband, given the back ground you mention. He'll just need a good reference so he can build it to safe specs. (It boils down to sheet metal and an air space behind the metal, and not direct route for heat transmission into the wall/ceiling.)

YouTube has a number of videos and clips done by or showing the Wisner's projects. I'd look at those too. Just be careful about what you see on YouTube, because not everyone there builds safely or reports their results after having used the system they built for at least one heating season (more longer, is more better, of course heheh). So take YouTube with a grain of salt, and give preference to those hosted by reputable persons experienced with RMH builds.

In any event, that ought to be enough to get you started. Browse around the above forums and see what you like.
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