019 – Rocket mass heaters

What this episode covers

Paul interviews Ernie and Erica Wisner about Rocket Mass Heaters . Paul discusses the videos he made where he makes a RMH. Ernie and Erica review Paul’s portable rocket mass heater design concept of putting a RMH on a trailer pulled by bicycles. Paul asks Ernie to critique his design in a constructively praise like manner. Ernie and Erica discuss the bucket heater. Paul explains that his set up took just about an hour and fifteen minutes to build. Paul explains why he is using rocks in place of sand. Ernie talks about the temperature differential required for long runs versus short runs of duct work. Erica explains outside versus inside temperature differential and the impact on the draft. Shorter runs of pipe will change the draft. Paul mentions the 6″ pipe and five people foot rule for each 90 degree bend. Paul suggests a review of a standard RMH. Erica goes through a brief history of stove efficiency and how master mason worked on these. The cost of these today could be as much as 30 to 100k. Erica explains how smoke indicates unburned fuel and how this is not good for people and the environment. Erica explains the basic parts of a RMH and how each part interacts with the heater exhaust and heat exchange. The different types of exhaust alignments is discussed. Ernie explains some of the criteria important to efficiency ratings. Erica explains that there are three different formulas used to determine efficiency. RMHs are incredibly efficient. wood stove are not allowed to put out exhaust below the dew point which gives RMHs another advantage. Typical temperatures leaving a Wood stove are 300 to 600 degrees versus 80 to 100 degrees for a RMH. Exhaust temperature also effects what gets left in the chimney like creosote and tar build up found with wood stoves. Erica explains how clean and cool the exhaust is when leaving a RMH. Paul discusses the recent video put out showing a person smelling the exhaust. Erica recommends not breathing the exhaust. Paul discusses mixed results of the earth day burns. Ernie explains how warming the heat riser is an important first step. cob is explained by Erica and Paul. Sand and clay and a little straw makes up Cob. Paul likes to discuss his position on RMHs and how to do it without Cobb. Paul explains the advantages of making a RMH portable and some temperatures readings they measured. Ernie explains why he uses an attachable magnetic thermometer. Erica explained how insulating the barrel is a bad idea. Paul explains how all other RMH designs have the heat riser on top of the core. Paul’s design is different. Paul thinks his design increases the pump. Erica explains how the brick burn tunnel works better than a smooth pipe. Paul’s entire j tube was round duct just at the end. Ernie explains his rifled j tube and how cleaning it can be a problem. Breaking up the flame profile is discussed. RMHs have lots of options and Ernie explains how each one is a little different. RMHs are great for people who want to tinker. Some of the questions coming from premise.com are best explained if the person builds a test stove in their backyard. Paul discusses the RMH book and how inexpensive...

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