8 inch system with smaller exaust pipes

Hello all...

I was searching the forum trying to find an answer to my questions but I had no luck.

I am trying to build a Rocket mass heater for my workplace here in Greece and due to economic crisis I have a limited budget. I currently own a couple of 200 liter steel drums (55 galons), enough refractory brics to build the RMH, insulating materials like stonewool and glasswool (if I am translating right) which I gather through some time and almost 15 meters (50 feet) of stove pipe from my old wood stove.

I will use as a thermal mass a bench with stone walls and cob or pebbels in the middle. The stove pipes that will run through the L shaped bench will be 6 meters long(a little less than 20 feet) . The workplace is big so I am thinking to build an 8 inch RMH. My problem is that the most common wood stove pipes in Greece are 5 inch and I have more than enough from my old wood stove. Is it possible to use them on a larger rocket mass heater? What problems will I face?

My workplace is 40 feet by 13.5 feet and 8.5 feet hight and not very well insulated. (I am working on insulation too). Is it possible to avoid buying 8 inch pipes?

Thank you very much in advance!

P.S. When I start building I will post photos if you like and I am sorry for my mistakes, my english is a little rusty.







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Stergios Polyzoudis : a lot of material to go through here to best help you ! With your Mediterranean Climate you actually basically need

Late night and Early morning heat to reduce and manage the chill of high humidity ! Pipe size is a problem- especially as the C.S.A.

the Cross-Sectional Area should remain constant through the whole build ! I usually resist suggesting trying to make any Rocket Mass Heater

RMH in a sub 6'' system for any 1st build attempt -but a 5'' system is possible- a tall Final vertical chimney after the thermal mass will help

that system work. If your Workshop is open and not divided by walls into sections or bays or coves this should work for you, install the RMH

as close to the center of your workshop as possible. ( close up holes starting at the ceiling and work down, then insulate !

If you can get what we call Rockwool your stone wool we are in good shape, glass wool will melt anywhere close to the rockets Core !

Think on this a while I am sure many of Your other fellow members will add their thoughts too. For The Craft. Big AL

Hello Big Al, thank you for the quick reply.

I live in the northen part of Greece where the climate is very cold usually during winter (not Alaskan cold but we have snow and everything). Even though I have a very good insulated house (125 square meters or 1345 square feet) with a very high quality energy efficient fireplace and also a wood and pellet burning central heating system also top quality, I still manage to consume 10 cubic meters of wood (350 qubic feet or 5 tons in weight).

I estimate that I will need an 8 inch system for the workplace. It is not divided by walls and as I said I am working on insulating the ceiling at the moment. I will have to invest in buying 8 inch pipes otherwise those money will be spent in wood as extra heat for the old stove to warm up this place in January alone.

Yes the word was rockwool not stonewool, I am always translating the greek words in my head!

I live 10 miles away from a rockwool manufacturer very popular brand in europe, they even exporting to the united states and they have some kind of a scrap yard there, where they store and sell almost for free the bad shaped products from the factory to the locals.

I wanted to ignore for my convinience the bernulli equation that it is described clearly in the RMH principals.

Later I will build a 5 inch system just for fun or for the experience in the man-cave or the in the small greenhouse. Who knows if I will build RMH well maybe it will become my new profession during the recession here in Greece.

I want to build this RMH so it performs well and maybe the wife realises how good it is and then I will be allowed to build one for the house.

Thanks again for the suggestions.