IEC 61255-2014 pdf Household electric heating pads – Methods for measuring performance

The test is carried out with the control adjusted to the maximum setting and the temperature rises are measured when steady conditions are established or at the end of a cycle of operation. The average temperature rise is calculated from all the measurements. The difference between the maximum and minimum temperature rises is also calculated. NOTE If there is more than one heated area, the calculations are made for each heated area separately. The uniformity factor is calculated, being the percentage of the heated area which is within ± 2 K of the average temperature rise. The evenness of temperature is expressed as the difference between the maximum and minimum temperature rises, rounded to the nearest 1 K, and the uniformity factor, rounded to the nearest 1 %. 9 Heating-up time and energy consumption The time taken for the temperature rise of a representative measuring point to rise by 20 K during the test of Clause 8 is stated in minutes (min), rounded to the nearest 1 min, as the heating-up time. The ambient temperature is maintained at 20°C ± 2°C and the heating pad is conditioned for at least 24 h at this temperature before starting the test. The temperature rise is measured by means of a thermocouple attached to the centre of a copper plate having dimensions of 65 mm × 65 mm × 0,5 mm, which is placed in the centre of the heated area. The control is adjusted to the maximum setting and the heating pad is operated. The time taken for the temperature of the measuring point to obtain a temperature rise of 20 K is measured. The energy consumption during the heating-up time is determined as well as the energy consumption during a period of operation. The operation is continued and the energy consumption is measured. The test is terminated for heating pads having a time-based operation when it switches off. The energy consumed for heating pads for continuous use is measured after 90 min of operation and between the second and third hour of operation.