UL 1278-2020 pdf free download

UL 1278-2020 pdf free download.Movable and Wall-or Ceiling-Hung Electric Room Heaters.
22.1 The supports for an open-type healing element shall be positively secured in position if loosening of the element may result in reduction of electrical spacings between a heating element and a dead metal part. See Spacings. Section 35. The securement of the supports shall not be dependent on tension or pull by the heating element as evaluated by 22.2.
22.2 Element supports are evaluated by assuming an expansion of the heating element from its normal position, to any position that will not cause contact of the element with the exposed dead metal parts. The heater is then moved to various positions in an attempt to dislodge an element support.
23 Electrical Insulation
23.1 Insulating washers, bushings, and the like that are integral parts of a heater, and bases or supports for the mounting of live parts shall be of a moisture-resistant material that will not be damaged by the temperatures to which they will be subjected under conditions of actual use. Molded parts shall be constructed so that they will have the mechanical strength and rigidity necessary to withstand the stresses of actual service.
23.2 Insulating material employed in a heating appliance is to be judged with respect to its particular application. Materials such as mica, some molded compounds, and certain refractory materials are usually acceptable for use as the sole support of live parts; and some other materials that are not for general use, such as magnesium oxide, may be acceptable if used in conjunction with other less hygroscopic insulating materials or if located and protected so that they are not subject to mechanical damage and are resistant to the absorption of moisture. When it is necessary to investigate a material to determine whether or not it is acceptable, consideration is to be given to its mechanical strength, dielectric properties, insulation resistance (see 49.1), heat-resistant qualities, the degree to which it is enclosed or protected and any other features having a bearing on the likelihood that a risk of fire, electric shock, or injury to persons may occur, under conditions of actual service. All of these factors are considered with respect to thermal aging
23.3 In the mounting or supporting of small, fragile, insulating parts, screw or other fastenings shall not be tight enough to cause cracking or breaking of these parts with expansion and contraction. Generally, such parts should be slightly loose.
24 Thermal Insulation
24.1 Thermal insulation shall be of such nature and located and mounted or supported so that it will not be adversely affected by any intended operation of the heater.
24.2 Thermal insulation that is not rigid shall be mounted or supported so that it will not sag. Adhesive material employed for mounting thermal insulation shall be acceptable for use at the temperature to which it may be subjected.UL 1278-2020 pdf free download.