Independent testing of heaters likely

Press, 17 June 1982, Page 20

Independent testing of heaters likely

(Supplied by the Building Research Association of New Zealand.) It seems likely that in the near future all heating appliances will have to be tested for their heat capacity. The building code of practice is under revision and this amendment, if accepted, could be operating within about six months. It could place the responsibility on the manufacturer to ensure that his' product meets independent, testing requirements at the Building Research Association's office in Wellington. At present, the only tests undertaken are those by local authorities to test the amount of smoke emission and tests to ensure that the heater meets safety requirements. Safety is still the most important factor as far as BRANZ is concerned. Free-standing appliances All fires need an adequate air supply — a modern, draught-proof house will not provide this unless an opening is always present. With the increasing range of open or closed free-stand-ing appliances, it is essential to choose the type of fuel and then the appliance to suit. A closed sto've can always be made to burn more fiercely, and because of this the flue design is of greater importance. For adequate safety, open appliances should have a spark guard: The weight of the unit on the floor or hearth should be taken into consideration. Most domestic floors, apart from concrete slabs, are designed to carry no more than

150 kg per square metre. Some very heavy closed-in stoves placed on a concrete hearth are likely to exceed this, and, if in doubt you should consult a builder or building inspector, Some type of heat insulation under the fire is vital. The hearth, particularly a modern factory-made design, can provide some insulation and many fireplaces have heat-shields permanently attached. Modern floors made of particle-board are less heatresistant than wooden floors, and concrete is not a good insulator. Insulation of the conventional concrete slab hearth can be improved by raising the hearth about 25mm above floor level, and supporting it on strips of noncombustible material. The air space will prevent direct conduction of heat from fire to floor surface. To prevent damage to paintwork or decor, the walls may also need a heat shield. It is essential to shield the wall which is exposed to the flue. This can be achieved by using a semi-circular metal shield mounted on metal brackets which is then welded to the stainless steel flue. Alternatively, the wall screen behind the appliance may be continued to the ceiling. Flue design A flue usually consists of two main portions: one part is connected direct to the stove and wholly within the room, and the remaining portion passes through the ceiling and the roof.

In a masonry chimney the connector can be led into the chimney. This must be 25 per cent larger in cross-section than the connector and the old fireplace opening must be completely sealed with non-combustible materials. The chimney should have been checked before this and repaired where necessary. Some appliances are designed for use with, factorybuilt flues and existing chimneys are not suitable.

Before buying and installing a. free-standing space heater consider these points: • Does the floor need extra support? • Does the floor need shielding from the heat? • The walls may also need shielding. • The flue must be suited to the heater, fuel and house. • Choose between wood and coal as the prime fuel and then buy an appliance designed for the choice of fuel.