Fire but no smoke with magic grate

Press, 15 September 1988, Page 25

Fire but no smoke with magic grate

GARRY ARTHUR

talks with a man

who has invented a more efficient and less polluting open fire.

David Halliday has been playing with fire for 12 years. It started the day he was sitting in his farmhouse kitchen at Leeston and suddenly realised that if firewood was added from the back of the fire instead of the front, it would not block off the heat radiating from the fuel already burning. That is the basic principle behind the Halliday grate, developed to produce an open fire that is more efficient and nonpolluting. Mr Halliday, who is 77, believes that his device could save the traditional and much-loved open fire from the City Council ban planned for January, 1992. The Canterbury United Council is so impressed with his invention that it has urged him to have it developed commercially to the point where it can get a certificate of approval from the Clean Air Council. Then it would become an “approved appliance,” even though it is still an open fire. When developing his grate, Mr Halliday decided that an important factor was air control, and with that in mind he began choosing nice straight pieces of wood to block as much air from going up the chimney at the back as possible. “Then I got the idea of blocking off the back of the fireplace altogether, which I did with a piece of sheet steel. It was then that I knew I had an entirely different, new kind of fire.” At the back of David Halliday’s fire is a steel box the width of the grate and about 150 mm square. It started out as a steelhood to put over the fire when he wanted to dampen it down, either to -reduce the heat or to reduce the burning wood, to charcoal as a fire-starter for the next morning. (“I haven’t chopped kindling for 12 years,” he says.) “By accident one day I put the arch down on its back with the opening to the front, and found that it was a wonderful heat trap. You can control the heat by moving the fire back into the heat-trap.” He has made himself a special tool, a triangular steel scraper with a long handle, for moving the fire back and forth on the flat grate to adjust the heat by adjusting the air supply — forward for more, back for less. It sounds like a lot of work, but

Mr Halliday says that it is just the problem with the council's attitude to open fires. One of its criteria for an acceptable enclosed woodburner is that it should not need adjusting more than every two hours. This is a mistake, in David Halliday’s view. He says fires should be stoked and tended regularly to ensure they burn efficiently. “The more attention you give to reducing the smoke from an open fire, the more successful it

is,” he says, "but you don’t have to fiddle all the time.” With his grate, logs are preheated on the steel hotbox at the back, and burst into flame when rolled forward on to the fire. Experimentation has shown Mr Halliday that the most successful fuel is roundwood thinnings from pine plantations. From this he gets a variety of thicknesses of wood, up to 150 mm in diameter, cut to the

right length for the width of his fireplace. He is trying to convince forest owners like the Selwyn Plantation Board that these thinnings could be made available to fuel improved open fires like his. “I’m convinced that the fuel supply and the grate have to go together,” he says. “You do need graded wood, down to one inch (25mm) diameter for starting the fire. I’ve found round-section wood more efficient than split wood. It gives an even burn.” As for pollution, Mr Halliday’s improved open fire produces virtually no smoke when tended properly. “If it does smoke,” he says, “you can adjust it by moving the wood.” It was the burning efficiency and consequent lack of smoke pollution that inspired him to persevere with his invention. He spent $2OOO trying to patent it but gave up when he ran out of money. A friend who. had a Fulbright scholarship to the University of California at Berkeley to study the subject of energy, sent him a book about open fires. “When I read it, I made the most astonishing discovery — that everybody is testing and considering the open fire as an air heater. But it’s not; it’s a radiant heater, and I find that it can’t be tested for radiant heat because there are no facilities here for that. The D.S.I.R. can’t do it, and the Cawthron Institute can’t do it. “And yet that is the judgment on the open fire — how it heats the air in the room — whereas radiant heat doesn’t have any effect on the air through which it passes.” David Halliday’s hope is that before Christchurch bans the open fire on pollution grounds, it will look at new ways of using the open fire. “If people really want to save the open fire, they can learn from this and use it efficiently.” People all over the world have been trying to improve the open fire, but David Halliday says noone else has come up with anything like his invention. “I’m absolutely sure that the future of Christchurch depends on this contraption,” he says. “If they ban the open fire, they may find that they have not improved the position whatsoever. I want it recognised that there has been a dramatic improvement to the open fire.”

He points out that it is now recognised that even thfe approved enclosed woodburners are guilty of polluting the atmosphere when people damp them down for the night. They burn efficiently only at full blast. The answer, he believes, is in educating the public, both in the proper use of enclosed woodburners, and in the use of his improved open fire grate. Open fires, used his way, can be efficient and non-polluting, and he considers them healthier than electric heating because they rely on a certain amount of draught, which ventilates the room. Canterbury United Council’s air pollution staff went out to Leeston to examine Mr Halliday’s invention, and were impressed. “Technically, it performs very well,” says Dr Chris Kissling;the C.U.C.’s planning services director, “judging by a visual inspection and without a laboratory test.” If used as designed and tended frequently, the Halliday grate “doesn’t appear to be very polluting at , all” as long as it gets

the right sort of fuel. But if not used properly, it pollutes like any other fire, including enclosed woodburners when they are not being used properly. What Mr Halliday needs now, says Dr Kissling, is to have his appliance developed commercially and tested through the Clean Air Council. This is not cheap. It costs upwards of $20,000 for testing by the Cawthron Institute, and Dr Kissling concedes that this is a prohibitive amount for the individual inventor. It may also be hard to get a manufacturer interested in taking it on unless he can be sure there is a commercial market. “So he’s between the devil and the deep blue sea,” says Dr Kissling. The C.U.C. has advised Mr Halliday to go through the testing procedure, because before a local authority can approve his appliance for use by the public, it must have a certificate from the Clean Air Council. Dr Kissling saw the Halliday grate in action and concluded that as open fires go, this one did not smoke. “It performed excep-

tionally well,” he says. The novel idea is the way the logs are preheated on the steel box at the back of the fire, and then they can be rolled forward primed up ready to go, and burst into flames with no smoke. He says this allows the fire to be continually refuelled in a non-

polluting« way. Combustion is very good because of the preheating system. He adds, however, that its fuel efficiency would be the same as for any other open fire. “It would get through the fuel,” he says. “It's nowhere near as costeffective as electricity.”