Articulate Probe Illustrated of UL 1278 Figure 8.4

Accessibility of Live Parts
An electrical part of a heater shall be so located or enclosed that protection against unintentional contact with uninsulated live parts will be provided, except that this requirement does not apply to a visibly glowing open-wire element and the connections immediately adjacent to the element. See 3.1. 8.2, 33.7 and 33.14. Insulated motor brush caps do not require additional enclosures.

The requirement in 8.1 does not apply to the sheath of an isolated metal-clad element in a heater having provision for grounding the enclosure, although such a sheath is considered to be a bare live part when spacings are being measured

In determining if an opening in an enclosure is acceptable, consideration is to be given to:
a)The proximity of uninsulated live parts (as determined by applying 8.1, 8.2, 8.4, 8.5, and 8.15 and
b) The possibility of the emission of burning insulation, molten metal, and similar materials through the opening (as determined by applying7.3-7.6.)

To reduce the likelihood of unintentional contact that may involve a risk of electric shock from an uninsulated live part or film-coated wire, an opening in an enclosure shall comply with either (a) or (b).
a) For an opening that has a minor dimension (see 8.8) less than 1 inch (25.4 mm), such a part or wire shall not be contacted by the probe illustrated in Figure 8.3.
b) For an opening that has a minor dimension of 1 inch or more, such a part or wire shall be spaced from the opening as specified in Table 8.1.

Exception: An integral enclosure of a motor need not comply with these requirements if it complies with the
requirements in 8.5.

With respect to a part or wire as mentioned in 8.4, in an integral enclosure of a motor as mentioned in the exception to 8.4:
a) An opening that has a minor dimension (see 8.8) less than 3/4 inch (19.1 mm) is acceptable if:
1) Film-coated wire cannot be contacted by the probe illustrated in Figure 8.2;
2) ln a directly accessible motor (see 8.9), an uninsulated live part cannot be contacted by the probe illustrated in Figure 8.4; or
3) ln an indirectly accessible motor (see 8.9), an uninsulated live part cannot be contacted by the probe illustrated in Figure 8.1.

b) An opening that has a minor dimension of 3/4 inch (19.1 mm) or more is acceptable if a part or wire is spaced from the opening as specified in Table 8.1.

The probes mentioned in 8.4 and 8.5 and illustrated in Figure 8.1-Figure 8.4 shall be applied to any depth that the opening will permit; and shall be rotated or angled before, during, and after insertion through the opening to any position that is necessary to examine the enclosure. The probes illustrated in Figure 8.3 and Figure 8.4 shall be applied in any possible configuration; and, if necessary, the configuration shall be changed after insertion through the opening.

UL 1278 Figure 8.4

The probes mentioned in 8.6 and 8.8 shall be used as measuring instruments to judge the accessibility provided by an opening, and not as instruments to judge the strength of a material; they shall be applied with a force of 1 lb (4.4 N) through any opening.

With reference to the requirements in 8.4 and 8.5, the minor dimension of an opening is the diameter of the largest cylindrical probe having a hemispherical tip that can be inserted through the opening.

With reference to the requirements in 8.5, an indirectly accessible motor is a motor:
a) That is accessible only by opening or removing a part of the outer enclosure, such as a guard or panel, that can be opened or removed without using a tool, or
b) That is located at such a height or is otherwise guarded or enclosed so that it is unlikely to be contacted.

A directly accessible motor is a motor:
c) That can be contacted without opening or removing any part, or
d) That is located so as to be accessible to contact.

Lisun Instruments Limited was found by LISUN GROUP in 2003. LISUN quality system has been strictly certified by ISO9001:2015. As a CIE Membership, LISUN products are designed based on CIE, IEC and other international or national standards. All products passed CE certificate and authenticated by the third party lab.

Our main products are Goniophotometer, Integrating Sphere, Spectroradiometer, Surge Generator, ESD Simulator Guns, EMI Receiver, EMC Test Equipment, Electrical Safety Tester, Environmental Chamber, Temperature Chamber, Climate Chamber, Thermal Chamber, Salt Spray Test, Dust Test Chamber, Waterproof Test, RoHS Test (EDXRF), Glow Wire Test and Needle Flame Test.

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