Rumpus Room Fireplace Refit

You see here the fireplace in the rumpus-room. It is working reasonably well, but there is good reason to believe that it never did in the 30 years of the preceding owner's occupation.

Let me start by describing a few things you see at left. The fireplace has a heat exchanging device, consisting of a 50mm iron pipe that has air circulated through it; the fan that blows the air is in a small metal box which is under the bricks at right. The pipe runs under the grate, up the back of the chamber, forward and across from right to left above where the flames are expected, then back down, and out. Of course you cannot see this for the fire at the moment. The air comes out of the slot in the flat black metal strip upon which the beaker sits. In front of the slot you see a shallow pan, in which Kay puts water to humidify the air somewhat.

The front of the fireplace is equipped both with glass doors, and a pair of a sort of iron-mail curtains. These are barely discernible in the photograph behind the left-hand-most glass door panel. The brickwork includes a chamber for the extraction of ash through a 4"x8" trapdoor under the grate out to the outside of the house. There is also a built-in gas feed to a starting mechanism best described as a cast-iron rod under the grate from which can be caused to issue three fierce gas jets that play on the underside of logs. So far so good.

The problems were simple. First, The fire chamber is a "standard size", that is the opening is a standard size, and this fire chamber is carefully built with this in mind. It is way too big to get any intensity in the fire! You would need huge logs to get the heat up, and thus you would end up with a huge inferno before you got either efficient combustion or any decent heat.

We tried simply lighting a fire in the arrangement as was. The draught from the chimney is good, but the opening so large that smoke still leaks out, so the doors must be closed. Even with several logs burning well, the doors remained so cool I could place my hands flat smack on the panels with no ill effects! The exchanger got some heat out - without it the fire was visual but provided absolutely no heat - but the exchanger air barely reached 50C or about 60C with a full-scale inferno in the chamber.
This would be good fireplace design if you lived in the tropics but missed the cosy feeling of a log fire....

The next problem is that the whole frontpiece was never properly attached. In fact, the advantage of the standard size must be the ability to fit whatever front section you need. The front section here has not had proper fittings driven into the brick, and is held in place by its mass and four screws just screwed against the brick. Typical Ralph situation... he never noticed the half-inch gap around the frame.

Here you see the (nearly identical) loungeroom fireplace. This one has a different front, and is equipped with fake logs and a different gas assembly that is designed to make the logs look as if they are burning. It is about as effective at heating as the rear fireplace was, but a whole lot cheaper on wood, and probably the only incarnation that could be smokefree without our redesign or a new and superior front assembly. The CD gives an idea of size... the cavity is large indeed. You can also see the ash hatch below the grate, and the iron-mail curtains. This fireplace has no glass doors.

In fact, it might heat quite nicely if you closed off the chimney (which facility is built into the chimney brickwork damper assembly). This would be possible with gas. I doubt seriously that the fire between Ralph's ears would have been bright enough to suggest this, and why bother when the house is centrally heated? Well, I guess there are Americans who think a few porcelain logs and a bit of gas adds charm... Ralph must have, he always had it on when the house was being inspected.

Anyway, I redesigned the grate, and using 60 or so bricks I have reduced the effective size of the fire cavity. The front is better fitted (you can see at right the fibreglass that seals the front), and the ash removal cavity nicely feeds air to the base of the fire if the grate is propped open to an appropriate degree. You can see the bricks in the first photograph, intruding into the paths of the flames at various points. Chamber temperature is increased, combustion efficiency is up, smoke down, the windows are now normally well above touching temperature (60C?) and the exchanger air regularly reaches 100C, with a peak so far of 138C. An engineer was here. Incidentally, the built-in gas-powered ignition system is a little ripper! This is a design innovation that Aus fireplace designers could usefully adopt.

In comparison with the Canadian-made Osburn closed stove system in Wentworth Falls, this is much less efficient, perhaps less than half as efficient, and the Osburn used convection instead of a fan for the room-side of the exchanger. More ash is left, signifying lower temperatures at some points in the fire, too. Also, there is room to cook on the Osburn, and make coffee, and there is nothing to compare with a coq-au-vin simmered long on a wood fire you were going to have anyway, when it comes to food that satisfies both the epicure and the engineer.

We bought a cord of wood. This turns out to be 128 cubic feet, typically quoted as a 4x4x8 or 2x4x16 foot pile. It's a bloody lot, that's all I can tell you! Here you see Meri posing to give the stack on our front porch some scale. We have already consumed a lot as you can see from the reduction of the stack. Good thing we like wood-burning fires.

The cost is not too bad, either: US$260, eucalyptus or oak, cheaper if you buy before the cold sets in. (This is about 30% more than we paid two years ago in Wentworth Falls.)