UL 250:2000 pdf download – Household Refrigerators and Freezers
UL 250:2000 pdf download – Household Refrigerators and Freezers.
8.3 Leakage current test — cord-connected refrigerators
8.31 The leakage current of a cord-connected refrigerator shall be no more than 0.75 mA when tested in accordance with Clauses 8.3.6 and 8.3.7.
8,3.2 Leakage current refers to all currents, including capacitively coupled currents, that may be conveyed between exposed conductive suriaces of a refrigerator and ground or other exposed conductive surfaces.
8.3.3 All exposed conductive surfaces are to be tested for leakage currents. The leakage currents from these surfaces are to be measured to the grounded supply conductor. Paris are considered to be exposed surfaces unless guarded by an enclosure providing protection in accordance with Clauses 44.1 and 4.4,3, These leakage current measurements do not apply to terminals of extra-low voltage (Class 2) circuits.
8.3.4 If a conductive surface other than metal is used for the enclosure or part of the enclosure, the leakage current is to be measured using metal foil with an area of 100 x 200 mm (3.9 by 7.9 inches) wi contact with the surface. If the surface is less than 100 x 200 mm (3.9 by 7.9 inches), the metal foil is to be the same size as the surface. The metal foil shall not remain in place long enough to affect normal operation, drainage, and ventilation of the refrigerator.
8.3.5 ‘The measurement circuit for leakage current shall be as shown in Figure 8.1. The measurement instwment is defined in Items (a) — (C) and, unless it is being used to measure leakage from one part of a refrigerator to another, the meter is to be connected between the accessible parts and the grounded supply conductor. The meter that Is actually used for a measurement need only indicate the same numerical value for a particular measurement as would the defined instrument. The meter used need not have all of the following attributes of the defined instwrnenl:
a) the meter is to have an input impedance of 1500 ohms resistive shunted by a capacitance of 0.15 microfarad:
b) the meter is to indicate 1.11 times the average of the full-wave rectified composite waveform of voltage across the resistor or current through the resistor; and
c) over a frequency range of 0 — 100 kHz, the measurement circuitry is to have a frequency response (ratio of indicated to actual value of current) that is equal to the ratio of the impedance of a 1500 ohm resistor shunted by a 0.15 microfarad capacitor to 1500 ohms. At an indication of 0.75 mA, the measurement is to have an error of not more than 5 percent.
8.3.6 A sample of the refrigerator is to be tested for leakage current starting with the asreceived condition
— as-received being without prier energization except as may occur as part of the production-line testing
— but with its grounding conductor, if any, open at the grounding terminal or attachment plug. The supply voltage is to be adjusted to the voltage specified in Table 8.1. If the retngerator is intended to be connected to a water supply, these connections are to be made with nonconductive tubing.
8.3.7 With reference to the measuring circuit in Figure 8.1, the leakage current test sequence shall be as described in Items (a) — (d) below:
a) with switch Si open, the unit is to be connected to the measuring circuit. The leakage current is to be measured using both positions of switch S2 and with manually-operated unit switching devices successive1y placed in each mode (unit thermostat, anticondensation heaters, door switches, and the like);
b) with unit controls set for lowest storage compartment temperature, switch Si is to be dosed to energize the unit. Within 5 seconds, leakage current is to be measured using both positions of switch S2. Following this and using both positions of switch S2, manual switching devices are to be operated as quickly as possible through all modes, but not in the refrigeratoc off” position, to determine the maximum leakage current condition:
C) with switching devices set at the position that causes the highest leakage current, as determined in Item (b), the unit is to be operated continuously through all modes, including defrost and ice making/harvesting, until the measured leakage current stabilizes or decreases. Both positions of switch S2 are to be used.