UL 6500 - SECOND EDITION
(Sub) CLAUSE/ANNEX NUMBER:
Clause 20.2.2 and 20.2.3
(Sub) CLAUSE/ANNEX HEADING:
Fire Enclosures
OTHER RELEVANT (Sub) CLAUSES/ANNEXES (as applicable):
Clause 20.2 and Table 14
DESCRIPTION OF ISSUE:
How are Clauses 20.2.2 and 20.2.3 applied to projection television constructions?
APPLICATION GUIDELINE:
Clause 20.2.3 applies to projection televisions when that product is constructed using an internal fire enclosure. As an example, the internal fire enclosure may be a box of wood or metal constructed around critical components (see below) typically within the bottom of the projection TV chassis. When these internal fire enclosures meet the requirements of Clause 20.2.1 (specifies the parts that need to be contained) and Clause 20.2.2 (no openings that permit accessibility), then the outer shell of the TV may have a flammability rating of HB or better.
Note - critical components as defined by Clause 20.2.1 are
- circuits and their associated components where the available power exceeds 15 watts or
- inductors and windings conductively connected to the mains or
- apparatus with open circuit voltages exceeding 4 kV (peak) ac or dc under normal operating conditions.
RATIONALE:
The above is considered a clarification of the requirements. The internal fire enclosure is used to contain potential ignitions from within the product that allows the outer shells to have a flame rating of HB or better.
OTHER:
none
SEE RELATED PAG:
None.
