Book - School of Science and Technology

Infra-red heatersDirect systems ± gaseous fuels (primarily radiant) 101Designed primarily for industrial applications in higher buildings (but often misapplied toothers) heaters of this type are pipe-connected to either the public supply or to eitherbutane or propane cylinders. For permanent installations when wall mounted or suspendedfrom a roof, they may be rated at up to 30 kW but a range between 3 and 15 kW ismore common.Construction of one type, Figure 4.4(a), takes the form of a heavy duty rectangularreflector within which refractory elements and a burner array are fitted behind a safetyguard. Another type, Figure 4.4(b), is cylindrical in plan with a shallow conical reflectorover. Portable versions, as in Figure 4.4(c), are mounted on a telescopic stand whichprovides means to secure a propane cylinder as a fuel source.Flue connections cannot usually be provided for heaters of this pattern and responsiblemanufacturers quote minimum rates of outside air ventilation necessary either per unit orper kW rating. In the case of portable units, these are usually sited in temporary positionswithin open buildings, stockyards and construction sites, etc., and the absence of a flue isnot important.Gas supplyShieldElement(a)TelescopicstandGas supplyIgnitionelectrodesSolenoidcontrolvalve(b)(c)Figure 4.4 Gas-fired infra-red heaters (Spaceray/EMC)