(minor yet effective) fireplace improvements

It has appeared in the background of some of my blog posts but, particularly in winter, my small wood burning heater features at the center of life inside at night.

Like all things, almost nothing is designed for Australian conditions (even much of the commercial stuff here which is often just slavishly copied from Northern Hemisphere conditions). One such thing is my wood heater.

Its a fairly ordinary heater for its type (and already seen a bit of use too) and its about 60cm square with an inside compartment about 40cm deep behind the door.

So while not big, is certainly big enough for the room its in (and my adjoining bedroom).

It has an added "benefit" that it has a small electric fan that sucks air (you can see the grill at the bottom and the switch and lead on the right) from the floor and circulates it through the back of the heater and comes out the vent at the top. This can really help warm the room faster, but its best not left on long or it will strip heat out of the furnace too fast and result in incomplete burns with Australian hardwoods (design issue #1).

Actually Australian hardwoods like Eucalypts (or known locally as gum trees) are harder and heavier woods than the common northern hemisphere woods (like pine, birch or spruce) and require much hotter temperatures to get going. As a result they burn into coals more readily and long after the large flames have gone there remains intense heat coming from the mass of coals.

Unless the furnace sheds the heat too fast, like the fan tends to do. If you use the fan too long you'll rob the system of energy needed to sustain combustion, and you'll have heaps of unburnt charcoal left in the morning (and the temperatures will fall sooner).

Its also actually difficult to start hardwood burning in these furnaces and requires (more) tending (than I'd like) to get the fire going. Not least of the issue is that it does require more air flow than softwoods require to get going and stay going.

I've noted also in my fire stoking this last winter (southern hemisphere, means its winter here now folks) that the coals burn and crush under the weight and choke the air flow and thus the heat coming from above (which is the wood).

Having seen a few hearths in my time I've noted various attempts at making a fireplace cradles to hold the burning wood and coals and achieve better air flow (ash falling away).  While in some ways in a fireplace they are also designed to increase radiation, in a furnace like mine its un-needed.

I've also seen gates held up above the floor of the furnace, but they are also make it a pain in the arse to clean the furnace out. My furnace is easy to scrape out with a small shovel.

So I came up with this idea, some simple lengths of 50mm box section which contains the coals, allows air to pass beneath the log and through the coals and no matter what allows some air to get to the back of the furnace (and the hot air exits the top from the front too).

In this photo above you can see that I've cleaned the floor, left the larger unburnt coals (and actually now with this system there really are less coals in the morning and more ash - meaning better completion of transfer of energy from the wood into my house).

The one on the right looks odd at first glance because it has a 45° cut in it and I'm going to weld on a short section to prevent logs rolling off the cradle (and snuffing out). This will still leave the bottom open to carry air through.

This also makes it easier to start with a mixture of woods too. I'll start from the bottom:

1. coals from the previous night, with wood splinters and some small off cuts sprinkled atop the coals (from checkering the slats I put on the house (earlier blog post) (waste not want not).
2. two small chunks of fire starter (hexamine), each is about ¼ of a piece as it really starts quickly
3. a layer of pine (scrap 4x2) cut into small sticks and to act as a pyre and get the coals going too
4. cross angled shorter pieces of 4x2 hardwood (gum) scrap wood (I got this from a re-roofing done locally for free) which will then fall (burning) onto the coals when the pine is gone
5. a chunk of hardwood of medium size to get the ball rolling.

This will go for about an hour with what you see and bring my room up to 24°C when outside is 8 or so.

So if you're an Australian (or Kiwi) using Gum you may feel free to try this design out and see what works for you.

Oh, and the steel was sourced free from a local guy making cattle races.

Win Win