Double Insulation; Spacings - Century UL 1086 Manual

FEBRUARY 1, 1996 HOUSEHOLD TRASH COMPACTORS - UL 1086 29

21 Double Insulation

21.1 An appliance may be provided with an acceptable system of double insulation in accordance with
the applicable requirements in the Standard for Double Insulation Systems for Electrical Equipment, UL
1097, in place of a means for grounding.
21.2 An appliance provided with an acceptable system of double insulation shall not be provided with a
means for grounding.

22 Spacings

22.1 Spacings at field-wiring terminals shall not be less than the values specified in Table 22.1. See
11.2.3.2 and 22.5.
22.2 The spacing between uninsulated live parts of opposite polarity, and between an uninsulated live
part and a dead metal part, shall not be less than the value specified in Table 22.2. If an uninsulated live
part is not rigidly fixed in position, by means other than friction between surfaces, or if a movable dead
part is in proximity to an uninsulated live part, the construction shall be such that the minimum acceptable
spacings will be maintained. See 22.5.
Exception No. 1: The spacing requirements given in Table 22.2 do not necessarily apply to the inherent
spacings of a component of the appliance, such as a snap switch. Such spacings are to comply with the
requirements for the component in question if they are less than the values specified in Table 22.2.
Exception No. 2: At closed-in points, such as the screw-and-washer construction of an insulated terminal
mounted in metal, a spacing of not less than 3/64 inch (1.2 mm) is acceptable.
Exception No. 3: Within a thermostat, except at contacts, the spacing between uninsulated live parts on
opposite sides of the contacts may be not less than 1/32 inch (0.8 mm) through air and 3/64 inch (1.2 mm)
over the surface of insulating material if the construction is such that the spacings will be permanently
maintained.
Table 22.1
Spacings at field-wiring terminals
Minimum spacings, inch (mm)
Between field-wiring terminals of opposite polarity, and between a field-wiring Between a field-wiring terminal and
terminal and a dead metal part other than the enclosure the enclosure – through air or over
surface
Through air Over surface
1/4 (6.4) 3/8 (9.5) 1/2 (12.7)