Hello Jim,
See below
--- On Tue, 10/27/09, Knighten, Jim L <jim.knigh...@teradata.com> wrote:
From: Knighten, Jim L <jim.knigh...@teradata.com>
Subject: certifying overall products vs. certifying individual
constituant chassis
To: emc-p...@ieee.org
Cc: "Rowson, Stuart" <stuart.row...@teradata.com>
Date: Tuesday, October 27, 2009, 2:19 PM
I am wondering what the industry experience is regarding basing EMC or
Safety product certification on individual chassis (or subsystems/components)
that may comprise the product, vs. certification at the product level?
Peter: Most manufacturers of rackable systems do tests and
certification at the system level.
In particular, I have some products that are 40U racks containing
multiple chassis, each of which is compliant and has its own certification.
Currently, product certification is done at the entire product level (i.e.,
rack) and there is a product regulatory label on the overall product. I know
that some companies (names withheld) that appear to be certifying only at the
chassis level, rather at the ensemble product level.
Peter: I also have come across some manufacturers that have not
certified at the system level. Some of these manufacturers have been negligent
about safety/emc regulations - others have done their due diligence and have
additionally tested the racks at the system level (even though they have not
submitted the rack system for certification by a third party). The latter may
have tested system level tests for emc (quiet an experience as you mention
below), but also have conducted internal safety tests such as Input Test (to
ensure the overall system ratings are not exceeded), monitored internal
ambient temperature to ensure the internal chassis manufacturer's specified
ambient levels are not exceeded, Leakage Current Test to ensure the cord
connected earthed limit of 3.5 mA is not exceeded (exceptions if product is
marked with a High Leakage Current Marking and provided with a specialized
plug) and for rack systems that are not fixed to the floor, a Stability Test is
conducted.
From the safety standpoint, in the US and other parts of the world, a
local inspector or certification body may not have problems with a rack system
that has internal components that are Listed/Certified having their own power
cords or interconnected by means of a PDU. As such some manufacturers opt for
certification at the subassemly level. As the long as the subassemly is
Listed/Certified, no further action is required. Such manufacturers are putting
themselves at risk if they have not taken precautionary measues to ensure the
system is compliant with all of the applicable safety requirements. Same goes
with emc.
For EMI, I know the physics tto ebeaches us that CE + CE does NOT equal
CE (i.e. one compliant chassis combined with another compliant chassis does not
assure a compliant combination of the two chassis). I have war stories to
corroborate this.
Peter: You are 100% correct and I know a few people in this forum whom
I worked with in the past who can attest to this.
For Safety, there are some tests (heating test is an example) that can
be are run at the product level.
Peter: That is correct, but the manufacturer's specified maximimum
ambient levels must be followed. In other words, if you purchase an ethernet
switch which has been tested to a 25 deg C ambient (you can review the
manufacturer's safety test reports), you cannot use it in your rack system
which may be rated for a 50 deg C ambient.
Country approval documentation requirements vary by country, but
usually there is requirement for a DoC, CB report, etc.
Peter: This is an area where you need to spend time and define the
countries where certification or a type approval is a must, the exceptions and
what documentation (CB, NRTL Listing, FCC, EU EMC) will be required to meet the
country's mandatory certification requirements for safety and/or emc. A system
CB and/or emc report as applicable will go a long way in complying with the
country's mandatory requirements.
I get increasing pressure internally (economically driven) to declare
product certification done if all the constituent chassis are compliant and
certified.
Peter: This could be a great solution for a country that has no
specific regulations for safety and/or emc. For countries suc as the US where
product liability laws are strict, proof of compliance at the system level is
the way to go
What is the experience you guys have?
Thanks in advance,
Jim
__________________________
James L. Knighten, Ph.D.
EMC Engineer
Teradata Corporation
17095 Via Del Campo
San Diego, CA 92127
858-485-2537 – phone
858-485-3788 – fax (unattended)
-
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