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Altitude a concern for RMH ?

Peter gallo


Joined: Dec 11, 2011
Posts: 35
My location is Albuquerque, New Mexico... Approximately 5,000 ft above sea level.

My reason for posting with this concern is that I've head rumors that a RMH built for workshop at Lama Foundation by Ianto Evans didn't work out so well. Not sure of the details, but altitude was listed as a possible problem. Lama is above Taos, NM which i believe is approx 8,000 ft.

-Peter
Ernie Wisner
volunteer

Joined: Oct 16, 2009
Posts: 788
Location: Tonasket washington
    
  23
There where other problems with that build and most of the stoves problems had nothing to do with the stove and lots to do with other factors.
I have not observed any altitude problems. you will need to site the stove in the house properly and make sure you take into account the prevailing wind. you will also want a little taller heat riser than the normal formula.
so i belive on an 8 inch it's 44 or so inches and for the altitude i would guess you will want 48 to 50 inches of well insulated heat riser. Mind the gap so you get it right in the 2 and 1/2 inch range.


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Ernie and Erica
Wood burning stoves, Rocket Mass Heaters, DIY,
Stove plans, Boat plans, General permiculture information, Arts and crafts, Fire science, Find it at www.ernieanderica.info


Peter gallo


Joined: Dec 11, 2011
Posts: 35
Thanks for the tip. Will getter done!
Aaron Oakley


Joined: Jan 05, 2012
Posts: 18
Location: Snowmass, CO
Ernie, will you discuss the relationship between altitude and heat riser length, and the theory as to why it needs to be longer? Thanks!


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Yone' Ward


Joined: Feb 14, 2012
Posts: 135
Location: Springdale, WA USA - Cold Mediterranean Climate
A rocket stove functions on air density differences. I suspect with less air density to work with, you need a little more hardware to make it work.


Just call me Uncle Rice.
17 years in a straw bale house.
Ernie Wisner
volunteer

Joined: Oct 16, 2009
Posts: 788
Location: Tonasket washington
    
  23
the pump action on the stove needs to be a little stronger at elevation. several factors are involved but the key to them is to get the riser height and exhaust cycle balanced with the intake air.

A faster rocket when balanced correctly will work just fast enough to give a total burn and good exhaust pressure. instead of trying to make a little smaller feed and burn tunnel (gives the appearance of a faster flow). the best way to do this is to adjust both the heat riser height and the gap between the barrel and the top of the heat riser. other considerations for elevation is how fast the barrel radiates but thats a non starter for most applications.
Peter gallo


Joined: Dec 11, 2011
Posts: 35
8" system: Barrel height is 35", so heat riser is 33". I should increase the heat riser by how much?

Ernie Wisner wrote:There where other problems with that build and most of the stoves problems had nothing to do with the stove and lots to do with other factors.
I have not observed any altitude problems. you will need to site the stove in the house properly and make sure you take into account the prevailing wind. you will also want a little taller heat riser than the normal formula.
so i belive on an 8 inch it's 44 or so inches and for the altitude i would guess you will want 48 to 50 inches of well insulated heat riser. Mind the gap so you get it right in the 2 and 1/2 inch range.
Ernie Wisner
volunteer

Joined: Oct 16, 2009
Posts: 788
Location: Tonasket washington
    
  23
A couple of inches should do it. you will have to see in the test bed if you need to change things a little bit.
As always build yourself a test system first and run it for a while to get the feel for the stove. Dont make any modifications till you have built the stove by the numbers first. then you can add a little bit of height and keep the gap 1" and 3/4 to 2" and 1/4. you only have 1/4 inch on each side of 2" to adjust the gap. the indications you are looking for that will tell you when it is right are white, wet exhaust with almost no smell. (your eyes wont burn if you stick your face in the exhaust). this is what you are looking for in a good clean burn.
 
I agree. Here's the link: http://stoves2.com
 
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