Hi Terry,
To answer your question bluntly, NO, there is no correlation between VW-1 and
UL94V-1,HF-1, etc.
The VW-1 rating is a flame test and rating performed on wire and cable
constructions only. The combination of the wire, plus any insulstion, jacket,
shielding, or taping, and coloring, is tested and given the rating.
The UL94 tests, the same tests as the IEC V-0, V-1, V-2 tests, are tests
performed on samples of insulation material. The test samples are bars of
certain shape tested to a certain method. How the sample bars perform under
controlled conditions determines whether they are rated V-0
(best), V-1, or V-2 (worst).
Furthermore, insulation materials can be tested to various test methods to
determine relative flammability. The rating hierarchy is as follows:
UL94 5V-A (best)
5V-B
V-0
V-1
V-2
HB (worst)
Furthermore, some materials are unfairly biased against by the test methods for
the above tests. These are Very Thin Materials (VTM) and Highly Foamed
Materials (HF). They have special test methods, that correspond to flammability
ratings above:
UL94 VTM-0 = V-0
VTM-1 = V-1
VTM-2 = V-2
UL94 HF-0 = V-0
HF-1 = V-1
HF-2 = V-2
HBF = HB
Note that all of these insulation (plastics) ratings are component (insulation)
tests only, for use as relative data with conditions of acceptabilty, etc. The
construction of the sample shapes are pre-defined specifically for the test.
For the wire and cable tests, actual constructions are tested, ie number of
conductors, insulation, jacket and shileds, tapes etc. are all tested as
actually representative of the constructions being sold. Conditions of
acceptability are determined based on this fact.
What does this mean to 950/1950 examinations? Well, for one, the requirement
"V-1 or better" flammabilty does not apply to the wires and cables in or
connected to your unit. Second, it will be up to the organization who is
performing the testing/giving the certification for your unit to
determine what flame rating is needed for your wires and cables.You may only
need a Horizontal flame test rating for some wires and cables in some areas in
your unit, while other areas and wires and cables may need a VW-1 vertical
rating.
Some areas/constructions/testing agencies may actually not require any flame
rating for the wires in certain constructions!
Finally, you mentioned UL1581 as a wire class - it isn't. UL1581 is the
standard that includes all the basic wire tests and requirements for wire and
cable that are used in various UL wire standards - it is called the Test
Reference Standard for wire and cable. The other numbers you
mentioned are probably UL Style numbers, referencing various wire and cable
construction Recognized by UL with restrictive conditions of acceptability. I
recognize those numbers as some popular internal wiring Style numbers.
I hope this helps.
Regards,
Robert Tims
Compliance Engineer
Ericsson Messaging Systems Inc.Terry Meck wrote: > Hello: > > I have a question about the interpretation of UL 1950 / En 60950 sec 4.4.6 > Fire enclosure construction. > > "The following constructions are considered to satisfy the requirement > without test: > .... openings in the bottom, each not larger than 40 mm sq under: @ > components of FLAMMABILITY CLASS V-1 or better, or FLAMMABILITY CLASS HF > -1 or better, or @ parts made of material of FLAMMABILITY CLASS > V-1 or better, or FLAMMABILITY CLASS HF -1 or better;" > > Is there any correlation between VW-1 wire and UL 94 V-1 FLAMMABILITY CLASS > ? > That is to say if all parts are V-0 or V-1 and wires of VW-1 would this > construction be considered to comply? > > What is the best way to get information on the various wire classes UL 1581, > 1180, 3239 etc. > Your input is appreciated! > > Terry J. Meck > tjm...@accusort.com > > --------- > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to majord...@ieee.org > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to ed.pr...@cubic.com, > j...@gwmail.monarch.com, ri...@sdd.hp.com, or > roger.volgst...@compaq.com (the list administrators).
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