ColinPBriggs said:... My father had a Tubulous boiler that also ran for 25-30 years. My problem with them is the design doesn't look too have changed in the 30 years. I guess it just reflects that the market for this type of heating in Oz is small so no one wants to spend the dollars on research and design.
You're exactly right. John Larking died nearly 30 years ago, and that also coincided with the beginning of the decline in suburban interest in wood-fired heaters. Remember the brief resurgence in the '80s when every second person had a Coonara. The Tubulous boilers haven't changed much since then. But the design was already proven.
John and his brother did a lot of development work with improved combustion air-feed, waste heat recovery, thermostatic control of secondary air feed for better combustion of the wood gases, and so on. They experimented with heat transfer oils instead of water, pressurized closed heat transfer fluid systems, ceramic catalysts in the firebox's gas zone to improve efficiency and emmissions quality, and many other things. Some of these ideas were abandoned because they added marginal or no improvement when tested - just cost and unnecessary complexity. John was also working on techiques for retro-fitting under-floor hydronic heating to a timber floored house.
At the time of his death in 1986, he was working on a refrigeration system that would allow small Pacific island communities with no electricity to run a large absorption refrigerator using waste coconut fibre as fuel.
John ran the business with his brother. His daughter ran the office and his son Andrew was their apprentice. I got to know them in 1981 when I was looking for a boiler and any time I was in the area I would call in. John was always ready for a chat and would fill me in on his latest ideas. He was 30 years my senior, and became a friend.
The business had evolved from the old Collister company that began making laundry and bath "chip heaters" in 1948. These were familiar sights in houses before electric hot water services became common. By the 1970s they were building advanced boilers, some big enough to walk inside the firebox. They also had LPG conversions available.
But the market declined in the late '80s and after his father's untimely death, Andrew continued with the hydronic heating side of the business, only building wood-fired boilers to order. And that is where Tubulous is today.
So don't write off Tubulous without discussing your requirements with Andrew first. I haven't seen Andrew for 20 years, so if this comes across as an advertisement it is only because I know these boilers.
The German and Kiwi wood "gasification" boilers will be very good products, I'm sure, but don't be influenced just by techno-speak or appearances. These things aren't intended to sit in your lounge room. They belong in a boiler room. The Tubulous is bulletproof. It will almost last forever. They are made from cast iron and heavt steel plate, copper waterways and refractory cement lining. The firebox has a heavy cast iron front and door (horizontal models) and the interior is lined with refractory cement within which the copper tubular "skeleton" is imbedded. The fire only comes in contact with the cast iron and cement. The vertical boilers use an annular copper tank lined with refractory cement. But you need to compare the horizontal models with the German and NZ boilers.
With the Tubulous you see the boiler naked. It isn't hidden under a cosmetic skin of painted sheet-metal. They use high quality wax capsule mechanical thermostats to precisely control airflow and the combustion process, rather than a computer and complex electrical devices. It's all exposed and you can see it working. No digital displays, just a large dial thermometer. It will only break if you hit it with something hard, and to replace it involves loosening one screw.
The buzz word gasification is used these days but that's what happens with any wood-fired boiler or heater running on slow combustion. It's the process by which charcoal is formed. If you heat wood and start to break down the cellulose structure, hydrogen and other flammable gases are released. Carbon monoxide is also produced by partial combustion in an oxygen starved environment. Carbon monoxide is highly flammable. These are the gases that burn in the red flames you see in a fire. If a fire can access an unlimited air supply, it burns as fiercely as possible, releases all its energy quickly, and consumes the fuel rapidly. You need to control the fire in order to usefully heat a house. We're all familiar with this. You shut down the air supply to slow down the rate of combustion. By starving the fire of air, much of the available flammable gas isn't burnt and simply goes up the flue with the smoke. Even the smoke contains unburnt carbon particles. It used to be called slow combustion - now it's called wood gasification. Sounds more modern and technical. It has always occurred. The important thing is what happens next. Do you let the gases escape or do you burn them in a controlled manner in a location that extracts the heat but doesn't cause the main fire to burn harder. This is done by the introduction of a secondary air supply.
If you look at a Tubulous boiler, you can see the two thermostats on the right-hand side. These control the primary and secondary air intakes which allow air into the firebox via the ashpan and grate (under the fire) and at the base of the copper booster section of the flue. The intakes are made from heavy cast iron and the mating surfaces of the control flap and the intake housing are machined dead flat. When the thermostat lowers that flap onto the intake housing, it forms an air-tight seal. The firebox door is fitted with the familiar fibreglass rope seal. (Some models have an additional manually adjustable air inlet on the door). The accuracy of the thermostats and air control means that the water temperature will be maintained at whatever you set it for. All done simply with old-fashioned hydraulic and mechanical devices.
Modern wood gasification boilers do all this "behind closed doors" using complicated electronics. Tubulous does it out in the open, simply and mechanically, using techniques that have been around for many decades. It's just air control.
The modern gasification boilers from reputable manufacturers will be excellent products, but they aren't necessarily going to work more efficiently. Wood isn't a new fuel. All I'm saying is, make your decision based on your needs and the available products. Don't be distracted by the bare bones 19th century industrial look versus a modern looking colourful skin and some fancy digital read-outs.
Compare all the options before you commit to buying - particularly if you have to import it yourself. The serviceman is a long way away, and the more complex it is the more likely you are to need him one day.
Posted Friday 4 May 2012 @ 1:51:50 am from IP
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