Rocket heating/stove for indoors - possible to use existing flue?

I am new to retrofitting. Or most types of fittings.  
I have lots of ideas and the season of change is brewing.
So I am beginning to ask many questions.

I am figuring someone savvy will know a more reality based answer than my notion of, "I wonder if"

1)  Is it wise? viable? possible? and can I? re-use an existing heater 'wall furnace' flue for a desired replacement of a Rocket Heater/Stove?  The flue is insitu on an external wall attached and working with the wall furnace. Obviously I cannot have both at the same time. But the wall furnace is from an 1980s instalment, and although they endure well, I over it. It only heats the air and discipates, I would prefer a radiant heat, so I am willing to remove it and keep the flue to then create a rocket heat source and potential stove in the design too.

2) I dont know how to find retrofitters who are savvy to do such a thing - I am in Melbourne Australia, so I dont expect most of you to know a local. but if yes that would be brilliant to get in touch with them.

3) A local person with experience and success and safety of course is ideal but then comes the question.... can we do this? Do we need permission from someone to install our own heating?  what's the  overarching practices with home made appliances? such as a rocket heater/stove?


Any feedback is better than what I have.  Thanks to one and all.
And sorry if this is so common and there are many responses elsewhere.

The first question is, what is the size of the existing flue (diameter), and where does it go? Straight out, or up the wall to above the roof? How cold is your climate? (Probably not very, in Australia )

The flue needs to be the same size as your new system, and 6" diameter equivalent is the most common for milder climate installations. Smaller than that is usually tricky to make function well.

I'm not quite clear about what your "wall heater" is. Does it burn wood/coal? Or is it a natural gas/propane appliance?

The flue piping for the gas appliances cannot handle the heat from a wood burner.

Ah great question, sorry I did not explain the existing 1980s wall furnace.
Thanks for asking for clarity.

The wall furnace as it is commonly known in Australia, is merely piped gas, with electric fan.
Even though it is working and they are a reknown work horse of heater unit, but I realise i prefer radiated heat options, rather than fans that blow the air/dust, and using gas and electric to get the same result is not economically sound for me neither.

It will die one day, however this is the first winter I have chosen not to use it, and where winter clothing inside instead of only outside.
its working so far.  

Because it makes little sense to me to heat the air but not my surrounds wihich the wall furnace only does.
And I am no insulated - - that's on the to do list, in a timely fashion - yes I have many potential projects or moving parts at present - so the hot air just escapes in its own way but mostly  because the cold air over rides it as soon as the heating is turned off,  with nothing to show for my hard earned cash on heating bills.


Thanks again for your message.

Cold climate as it is southern region of Australia.
Not snowing in my usual winter except about 3-4 hrs away.

It leaves the room at the top of the furnace inside the wall  so I dont see it, and goes through to the edge of my flat roof. It goes straight.

The existing flue diameter will need to be measured, from the roof top. From memory it is maybe 4inches or ? 10cms.
But I would definately need to check that.

Thanks for the questions.

If your flue is near 4"/10cm diameter, it will not be big enough to handle anything but a tiny batch box RMH system, not to mention its safety with a wood burning appliance.

You will need to run a new chimney/flue to serve a new RMH. "Cold" is a relative term; if it only gets below freezing occasionally in the winter, that is a mild climate compared to northern US regions where it can be below freezing continuously for weeks or months, and below zero Fahrenheit occasionally. I think you would be well served by a 6" J-tube system with moderate mass, so you can tailor the heating to respond to warmer or colder days. A high-mass system is not so good when the weather can suddenly get warm after building up a reserve of heat inside.

On the other hand, it might be reasonable to build a 4" batch box RMH and use your existing flue, if you do not need a lot of heat or constant heat day and night through the winter. We would need more details about your climate and your house to give the best answer.

If you are inside city limits,there is probably someone who wants you to get approval for anything you build, and may not approve anything that does not come from a factory with an official seal. Such things are so local that you need to talk with someone in your own city to know what you can do. I would confer with a contractor or builder first to see whether you are better off being official or winging it. Insurance may also be a factor - insurance companies are notoriously reluctant to allow anything out of the ordinary.

Cold climate is what they refer to on manifactured seed packets.
I thought it was universal language.

Winter July Aug Sept/Oct/Nov
5-13C give or take 3 degrees.

Summer. Avg. 20-38C give or take 3 degrees C

Type of house

Layout with no hallways:
Four rooms plus utilities on my south(cold) side.
Literally a North room ( sun room),
South Room ( regardless of utilities)
East Room and
West Room.

Ext materials
North room ( front of house) is single brick cladding
Other walls are Hardie plank type rendered walls.


Wall furnace ( gas electric) is in North room which is two steps ip from rest of home. So the hot air stays in there as heat risers and cold keeps getting sicked in from lower rooms.
If i use it i use a curtain to block the double arch between east and north rooms. And i stay in the nirth heated room. But tgats nit practical.

Yes. Sadly such bounds are reatrictive for the creatives.
But safety is necessary too.

Glenn Herbert wrote:You will need to run a new chimney/flue to serve a new RMH.

I think this needs to be emphasized again. An existing gas appliance flue does not have the materials or clearances to safely handle a solid fuel burning heater. There is no shortcut that will make the old flue a safe option. Please factor the cost of a new flue into your calculations.

Douglas,
thanks for the clarity about needing a new flue to match the kit.  I figure I can probably remove the existing flue and install a new one in its place if it works that I can, according to code, install after all.

The reality is will the people in certain positions say YES to having an urban creative install a RMH/Stove?

Does anyone have a successful URBAN experience with CODES (I think that's what you US folk call them), and how long did it take for your code folk to come around to this alternative homemade appliance for heating /cooling your home?

Our local code-folk are advertising how much more green they are going and looking for others who are interesting local greening opportunities.
So I know this may only be a political front, but how awesome it would be if the local code folk really were interested in changing how be regenerative and alternative in creative real ways.

I pray, constantly, formally things, but maybe should start a fair go in seeing realistic alternatives for the local property owners and rental dwellers to adopt in their contexts. Lord hear our cry.