Post by mizwiz on Sept 4, 2009 20:23:48 GMT -8
Hey there,
We're working with Portland (Oregon)'s Alternative Technology Advisory Committee, on making it possible to build a permitted Rocket Mass Heater in an ordinary home.
Although this will be an expensive option and some of you may not be interested, I'd still like to make all the data we submit consistent with the things that work for actual stove owners.
(Meaning I don't want to accidentaly disqualify your perfectly well-working stove, or make it harder to use your favorite materials.)
So this is a survey. Take out my answers and put yours in:
If you have built and operated a Rocket Mass Heater,
- How big is it?
Ducting size & length of run?
(e.g. 6", 25 feet)
Size & shape of the masonry mass?
(L-shaped couch, 30" tall combustion unit, 18" tall bench about 27" wide, flat, 7 feet from combustion unit to corner, then 5 more feet out from that corner.)
- Any idea what the whole thing weighs? Or lbs./square foot?
(I'd guess about 7,000 lbs, or about 150 lbs/sf)
- What are the proportions on your combustion unit?
(47" heat riser: 19" burn tunnel length: 16" feed tube, 35-gallon drum, 2" insulation)
- How hot does it get?
(about 400 F on barrel, maybe 150F on bench, exhaust is up too high to measure, but it tends to drift rather than rise or fall)
- Did you take any special precautions with the foundation, heat-shielding, or clearances to combustibles?
(Bench has 1-2" of insulation between it and the wall, we used woodstove code for the barrel (18" between it and a heat shield, 1" air gap from shield to wall) and spaced the combustion unit 4" from the wall like a masonry heater. We didn't reinforce the concrete-slab floor, which is has stemwalls along both corner walls and an extra one near the middle.)
- Does it work the way you intended, i.e. smoke free indoors and out?
(works great in winter, but is tricky to start in summer when it's cool and the air is warm. We prefer to keep it cool then, anyway.)
- What's your favorite mortar mix? Cob mix?
(We used 4 sand: 1 clay soil, plus about 1/2 of combined ceramic clay and lime, for the mortar. Our cob here runs about 2 sand : 1 soil.)
- Any breakdowns, parts needing replacement, or other maintenance/longevity issues?
(We cleaned it out once so far, first year in operation. No creosote, but some soot, in ducting. Barrel shows a little rust stain where it's in contact with clay, and we're thinking of putting lime mortar on instead. We have a spare barrel if needed. We made a stone tile lid for the burn tunnel, but dropped it on concrete floor and it broke. Works OK broken - more options for air control. Our first brick in the burn tunnel bridge cracked, as they do, but it is holding OK so we haven't replaced it yet.)
I've already checked Ianto's book for general info, and am submitting a few pages with my drawings.
(and yes, I did read the part about avoiding permit officials if possible, but we're quixotic). So I don't need book quotes - just additional data from actual stoves in working conditions.
Thanks for taking the time. Please let me know if there are any other concerns with us doing this - I want to open up more options for people who want to build these, and not close them off.
Thanks,
Erica Wisner
www.ernieanderica.info/rocketmassheaterpermitting
Here are their questions verbatim, what we're submitting soon:
1. Detailed illustration/specifications for a rocket heater with a 6” and 8” flue showing the following:
a. Acceptable size ranges for the heater components and clearances based on best design practices.
b. Anticipated range of maximum temperatures for the burn barrel and the surface.
c. Anticipated weight per square foot for the burn barrel and bench portions of the heater.
d. Total weight range in pounds and kgs for the entire heater unit.
2. Specifications for the earthen mortar mix based on best practices for heat and longevity (i.e. percentage of sand vs. earth).
3. Information addressing the anticipated service life of a typical rocket heater, any periodic maintenance that would need to be performed on the unit over time and where failure of the system is likely to occur.
We're working with Portland (Oregon)'s Alternative Technology Advisory Committee, on making it possible to build a permitted Rocket Mass Heater in an ordinary home.
Although this will be an expensive option and some of you may not be interested, I'd still like to make all the data we submit consistent with the things that work for actual stove owners.
(Meaning I don't want to accidentaly disqualify your perfectly well-working stove, or make it harder to use your favorite materials.)
So this is a survey. Take out my answers and put yours in:
If you have built and operated a Rocket Mass Heater,
- How big is it?
Ducting size & length of run?
(e.g. 6", 25 feet)
Size & shape of the masonry mass?
(L-shaped couch, 30" tall combustion unit, 18" tall bench about 27" wide, flat, 7 feet from combustion unit to corner, then 5 more feet out from that corner.)
- Any idea what the whole thing weighs? Or lbs./square foot?
(I'd guess about 7,000 lbs, or about 150 lbs/sf)
- What are the proportions on your combustion unit?
(47" heat riser: 19" burn tunnel length: 16" feed tube, 35-gallon drum, 2" insulation)
- How hot does it get?
(about 400 F on barrel, maybe 150F on bench, exhaust is up too high to measure, but it tends to drift rather than rise or fall)
- Did you take any special precautions with the foundation, heat-shielding, or clearances to combustibles?
(Bench has 1-2" of insulation between it and the wall, we used woodstove code for the barrel (18" between it and a heat shield, 1" air gap from shield to wall) and spaced the combustion unit 4" from the wall like a masonry heater. We didn't reinforce the concrete-slab floor, which is has stemwalls along both corner walls and an extra one near the middle.)
- Does it work the way you intended, i.e. smoke free indoors and out?
(works great in winter, but is tricky to start in summer when it's cool and the air is warm. We prefer to keep it cool then, anyway.)
- What's your favorite mortar mix? Cob mix?
(We used 4 sand: 1 clay soil, plus about 1/2 of combined ceramic clay and lime, for the mortar. Our cob here runs about 2 sand : 1 soil.)
- Any breakdowns, parts needing replacement, or other maintenance/longevity issues?
(We cleaned it out once so far, first year in operation. No creosote, but some soot, in ducting. Barrel shows a little rust stain where it's in contact with clay, and we're thinking of putting lime mortar on instead. We have a spare barrel if needed. We made a stone tile lid for the burn tunnel, but dropped it on concrete floor and it broke. Works OK broken - more options for air control. Our first brick in the burn tunnel bridge cracked, as they do, but it is holding OK so we haven't replaced it yet.)
I've already checked Ianto's book for general info, and am submitting a few pages with my drawings.
(and yes, I did read the part about avoiding permit officials if possible, but we're quixotic). So I don't need book quotes - just additional data from actual stoves in working conditions.
Thanks for taking the time. Please let me know if there are any other concerns with us doing this - I want to open up more options for people who want to build these, and not close them off.
Thanks,
Erica Wisner
www.ernieanderica.info/rocketmassheaterpermitting
Here are their questions verbatim, what we're submitting soon:
1. Detailed illustration/specifications for a rocket heater with a 6” and 8” flue showing the following:
a. Acceptable size ranges for the heater components and clearances based on best design practices.
b. Anticipated range of maximum temperatures for the burn barrel and the surface.
c. Anticipated weight per square foot for the burn barrel and bench portions of the heater.
d. Total weight range in pounds and kgs for the entire heater unit.
2. Specifications for the earthen mortar mix based on best practices for heat and longevity (i.e. percentage of sand vs. earth).
3. Information addressing the anticipated service life of a typical rocket heater, any periodic maintenance that would need to be performed on the unit over time and where failure of the system is likely to occur.