UL 82:2007 pdf download – Electric Gardening Appliances.
77.1.3 If the physical arrangement of the motor and enclosure permits. an appliance is to be subjected to an overload by means of a dynanlometer, eddy-current braie, or the like.
77.1.4 For an adjustable line grass trimmer, the load is to be adjusted by varying the line length. To obtain the rated load setling, the length of line is to be extended until cut by the line limiter provided on the appliance Each period of operation is to consist 0115 minutes of operation with the appropriate load. without operation at no-load.
77.1.5 For a fixed line length grass trimmer, the load is to be adjusted by attaching various fixed length line segments to result in the desired incremental overload. Each period of operation is to consist of 15 minutes of operation with the appropriate load, without operation at no-load.
77.1.6 The exterior temperatures of the motor housing are to be monitored during the test by means of thermocouples. If the temperature of the motor housing exceeds 90CC (194°F) during operation during load, the appliance is to be operated at no-load other than the mechanical load provided by the loading device until the housing temperature is stabilized: and upon stabilization, the test is to be resumed at the same load increment for the balance of the 14-1/2-minute load period. The loading cycle is to be resumed as indicated in 77.1.2 until the end result occurs or the appliance has been operated for 6 hours.
77.1.7 The leakage current is to be monitored continuously as the appliance reaches the end result, using the methods described in 25.2 — 25.5, utilizing both positions of switch S2 and with the appliance switching and control devices in all intended operating positions.
77.1,8 During the running-overload operation, any protective device provided with the appliance that can be reset, replaced. repaired, or otherwise modified by the user, is to be short-circuited, and the branch circuit protection is to be of high enough capacity to withstand the test currents without opening the circuit. The obective of the test is to determine the integnty of the appliance insulation and not the effectiveness of a protective device, other than a thermal-cutoff type specified in 77.1.9.
77.1.9 A one-shot nonresenable or nonreplaceable thermal cut off that is permanently embedded in the motor may be used to limit the end result of the test specified in 77.1.2 if opening of the thermal cutoff renders each motor part it is intended to protect permanently inoperative and requires that these parts be replaced In order to return the appliance to a functional condition.
77.110 If a material other than metal is used for an accessible enclosure or part of an enclosure, the leakage current is to be measured using a single layer of metal foil applied tightly around the appliance. The foil is to be applied around the appliance in such fashion so as not to restrict ventilation and to minimize the effect of the foil on the operating temperature of the appliance. The foil is to be kept in place for the running overload test described in 77.1.2.
77.2.2 If flame occurs, it is to be extinguished immediately.
77.2.3 If the appliance stalls but will run at rated load, the load is to be reapplied at the highest level the appliance will operate under until failure of the appliance to operate occurs. At the moment the end result occurs, switch S1 in the circuit of Figure 25.1 is to be opened and the leakage current monitored until stabilization.