Book - School of Science and Technology

Equipment for room stores 131number of sheathed elements enclosed within blocks of either refractory or Feolite, toform the heated core. This core is surrounded by insulation material which may be fittedin contact with the exterior casing or, in some more advanced patterns, held away from itto provide an airway.The surface temperature of the casing reaches a maximum of about 80 C at the end ofthe charging period and this declines to about 40 C during the following day. Output isboth radiant and convective in almost equal proportions and Figure 5.4 illustrates the 24hour pattern of output, the half-life indicated being the point in time when output hasfallen to 50% of the maximum.Ratings vary with different makes but are usually 1.7, 2.55 and 3.4 kW, the seeminglyodd figures being related to rounded 7 hour charge acceptances of 12, 18 and 24 kWh.Dimensions of typical radiators are listed in Table 5.8. Those types provided with airwaysand a damper may provide control of up to about 20% of the convective output.Storage fan heatersIn most respects these are similar in construction to storage radiators, the differencesrelating to increased insulation, the design of air passages in the core and the addition ofa small fan. In order to provide a uniform air-outlet temperature, irrespective of the storeremaining, the casing may incorporate a chamber in which heated air from the core is mixedwith room air via a thermostatically controlled damper. Output is about 75% convective.Table 5.8 storage radiators ± typical particulars (Dimplex)Input rating (kW)Item 0.851.7 2. 5 3.4Performancecharge acceptance (kWh) 5.95 11.9 17.85 23.8half-life (h)a15.4 15.0 15.2Outputmaximum (W)a775 1000 1350minimum (W)a250 320 470Dimensionsheight (mm) 710 710 710 710width (mm) 332 560 788 1016depth (mm) 150 150 150 150Weightin situ (kg) 41 77 110 145Notea Not quoted by manufacturers.Ratings are in the range of 2±6 kW, from heaters of the type illustrated in Figure 5.5,and leading particulars of one make are listed in Table 5.9. Approximately 40% of totaloutput may be controlled.Booster heatersIt is of interest to note that, in recognition of the fact that the capacity of all types of roomstore is barely adequate for domestic use, most manufacturers now provide a facility for