I'm wondering if any list members can explain the rationale behind
62368-1, in sections 6.4.8.2.2 and 6.8.8.4. I'm looking at the 2014
edition.
Clause 6.4.6, Control of fire spread in a PS3 circuit, states that,
"/Fire spread in PS3 circuits shall be controlled by applying all of the
following supplementary safeguards/:". In that clause it includes, "/by
providing a fire enclosure as specified in 6.4.8./"
Clause 6.4.8.2.2, /Requirements for a fire enclosure/, states "/For
circuits where the available power does not exceed 4 000 W (see 6.4.1),
a fire enclosure shall comply with the requirements of Clause S.1./"
That clause then goes on to say that V-1 is acceptable....
Clause (6.4.8.4) is addressing "Separation of a PIS from a fire
enclosure and a fire barrier" and is only requiring the application of
the S.2 flame test, which I believe is less demanding in that only a 60
s flame is applied rather than three steps up to 120 s for the S.1 test
method. Clause 6.4.8.4 then goes on to state that a V-0 material is
excluded from the requirement. So unless I'm mistaken, this clause
6.4.8.4 (which addresses separation) is requiring a lesser flame
requirement than S.1, yet goes on to exclude V-0, but not V-1.
I don't see the rationale. I must be missing something here. The most
fundamental question in my mind here is why does 6.8.8.4 allow the S.2
test method?
Thanks,
Carl
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