Well, that one I've pictured was most correctly termed a 'donkey boiler' or 'hot water donkey', back in its day. It is a 'recirculating water heater', driven by the 'thermosyphon principle', and operates at 'gravity feed' [i.e. around 3 metres water gauge] water pressure. A lot of people confuse the terminology, these days. See below for what a true 'chip heater' was.
That donkey at the Benambra homestead would take reasonable sized pieces of firewood, but was still very efficient in its wood consumption per volume of water heated. It was hooked up to a 40 gallon [~180L] hot water tank, which would easily stay hot overnight, after the donkey had been fired up the previous evening, even when the outside air temp got well below zero, by Oz standards [i.e. double figures below zero, Celsius].
The donkey and main tank were located in an enclosed rear veranda, so weren't fully exposed. This was intentional design - so that the water in the pipes wouldn't freeze, despite lagging.
I've also encountered a true chip heater when I was a kid, in a 19th Century miner's cottage in Wandiligong, Vic., where we used to stay with friends occasionally. The original owner must have been pretty successful in his gold mining, because the cottage was solid brick. We also visited the mine he operated, about a mile walk up the hill behind the house - but that's another story; it was very intact in the 1970's, almost as if he'd only knocked off a short time ago...
This is an actual 'chip heater', used to heat bath water;
![[Linked Image]](https://www.outdoorking-forum.com.au/forum/uploads/usergals/2017/02/full-5630-33225-chip_heater_bath.jpg)
Pic credit: Newcastle City Council's Collections,
http://collections.ncc.nsw.gov.au/keemu/pages/nrm/Query.php 'Chip heater' because it needed to be run on small, fast-burning pieces of fuel. Chips, twigs, pine cones...
It was run by filling it up with water via the funnel visible in the pic [in the Wandiligong cottage, there was a tap connected to the house rainwater tanks positioned over the funnel], then lighting the fire. The heater is not pressurised at all.
When the water started to boil, it would spew out of the outlet spout a bit. Then you would run cold water into the funnel [which had a dip tube on it, that ran to the bottom of the heater tank] to displace the hot water out, via the outlet spout.
I used to love the 'choofing' sound that thing made; very like a steam locomotive!
I can still taste the burnt toast that hung off the long wire fork over the fire.
Ah yes, the old open fire toast... Fond memories here, too. I grew up with a wood combustion stove in the kitchen, and an open fire in the lounge.
Gadge, I have had some in depth discussions with a friend who is a retired master plumber, about how to rig up hot water to this AGA, but I think the trouble to do so would outweigh any benefits - & you are completely correct, vermiculite is to be the insulating material with a ceramic blanket over the top and the sides that will be exposed in the rebuild. The diatomaceous earth has been added to the various gardens and back lawn (which has suffered somewhat in our summer heat) as it has been removed from the cooker. It's amazing how much moisture that stuff holds onto
Yes; Kieselguhr is known for its absorbent properties. Alfred Nobel [another inventive Swede] used it to absorb nitroglycerine [NG] to create 'dynamite', patented 1867, the first safe-to-use NG-based explosive. It also sees a lot of use as a 'filter aid', to create a permeable filter cake, for materials that would normally block up filters for process liquids.
Vermiculite is way superior as an insulating material, and certainly a lot easier to handle.
Pity you aren't a bit closer; I have a couple of 25mmTx610mmW rolls of high-temp Fiberfrax ceramic fibre blanket here, that I won't need anywhere near all of...
