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Subject: Re: Desperate for help on a UL1950 interpretation
Author: [email protected]
List-Post: [email protected]
Date: 9/29/00 4:47 PM
Here is another take(along the same lines of George's answer). If the foam
is more than 13mm from any source of power less than 15VA, then HB flame
rating is required. If the foam is within 13mm of a source of power equal
to or greater than 15VA then, it must be HF-2(derived from 4.4.3.6 and
4.4.4.) Unfortunately, there is very little room in the standard for
allowing materials with no known flame rating. Also remember, the material
may pass the tests of Annex A. Often times material like foam isn't
classified as the manufacturer sells it to industries that don't deal with
UL requirements. Again, this doesn't mean it fails, it just means it hasn't
been checked by anyone.
Good luck and let me know if you decide to go ahead with the gas
impregnated paper enclosure, it sounds like a good one.
georgea@lexma
rk.com To: [email protected]
Sent by: cc: [email protected]
owner-emc-pst Subject: Re: Desperate for help on
a UL1950 interpretation
[email protected]
09/29/00
02:02 PM
Please
respond to
georgea
Doug,
Here is my personal opinion on your product. View the product as a
box within a box. The smaller box is the limited power source (per
2.11). This box must have a fire enclosure. If the small foam spacer
is within this box, it must be of HF-2 or better, or exempted per
4.4.3.3 as a "small part which would contribute negligible fuel to a
fire".
The larger box contains the fire enclosed limited power source, and
the rest of the electronics. Per 4.4.5.2 it does not require a fire
enclosure. If the small foam spacer is outside of the power source,
but within the larger box, there is no required flammability rating,
because it is "outside" the voilume requiring a fire enclosure.
My opinion.....
George
massey_d%[email protected] on 09/29/2000 12:37:00 PM
Please respond to massey_d%[email protected]
To: emc-pstc%[email protected]
cc: (bcc: George Alspaugh/Lex/Lexmark)
Subject: Desperate for help on a UL1950 interpretation
Hello All -
I desperately need some opinions on an interpretation of a particular
clause
in UL1950. The background: I have an investigation underway to UL1950 of a
portable handheld computer, powered by battery and other power options, all
of which meet the requirements for inherently LPS.
Clause 4.4.3.1 states, "Components inside a FIRE ENCLOSURE........", and
continues into flammability requirements of materials and components.
Clause 4.4.5.2 addresses components not requiring a fire enclosure, and
states, "....-components in a SECONDARY CIRCUIT supplied by a limited power
source complying with 2.11, provided that...."
The product in question absolutely meets the requirements of clause
4.4.5.2,
which I interpret to mean that a fire enclosure is not required. However,
the test house performing the evaluation is applying all of the criteria of
clause 4.4.3.2. Unfortunately, I have a relatively small foam spacer inside
that does not meet the flammability class HF-2 or better as specified in
4.4.3.2.
The test house tells me that yes, the product meets the requirements for
the
exemption allowed in 4.4.5.2, but that I cannot literally interpret the
statement in 4.4.3.1 to mean that the substance of clause 4.4.3 regards
only
component and material flammability ratings inside a fire enclosure.
I guess I'm a literal type guy - I can't see any other way to interpret the
standard. Can anyone shed some light on this interpretation so that I can
read between the lines and understand the real requirements? I'm not trying
to make an enclosure of gasoline-impregnated paper, and with the exception
of a small (but critical) piece of foam, everything else meets the
requirements without the exclusion allowed by 4.4.5.2.
HELP !?!?
Doug Massey
Safety Approvals Engineer
LXE, Inc.
Norcross, GA., USA
Ph. (770) 447-4224 x3607
FAX (770) 447-6928
e-mail: [email protected]
Cruise our website at: http:\\www.lxe.com
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