DLC SHM: Family Grouping Variability
and Evaluation of Worst Case
August 4, 2015
Summary:
The DLC's family grouping policy has remained mostly unchanged since its inception into the program in late
2010. How can the policy evolve to better address an evolving market, specifically to allow for greater
variability in products allowed in a given family and reduce burden on both industry and DLC reviewers, while
still providing member program -- and their regulators and evaluators -- necessary assurance that all products
within the group meet the minimum Technical Requirements? This session will review the backbone of the
family grouping policy and discuss suggestions received to evolve the policy, including driver variations, LED
sourcing, and more simplified and streamlined guidance on testing "worst case". Participants will be asked to
share innovative ideas that balance evolution of variability while still ensuring the integrity of the
qualification process.
DLC Technical Committee Participants:
Cristian Suvagau - BC Hydro
Kyle Kichura - Focus on Energy
Dan Mellinger - Efficiency Vermont
Current Policy:
 The primary purpose of the family grouping policy is to allow qualification of products that have
relatable, scalable performance without needing to test every product
 The generalized approach is to provide sufficient testing to demonstrate that the entire group meets
the requirements
 This is done by limiting the variations that can be present within the group, and to identify and
require testing on the worst-case members of the group in various parameters
 The logic is that if the worst-case product with respect to a critical parameter passes the
requirements, the other products in the group also meet the requirements (because they are
"better" than the worst-case member)
 The DLC's family grouping policy can be found here:
http://www.designlights.org/content/QPL/ProductSubmit/FamilyGrouping
Key Issues:
 How to expand allowances in product lines, to simplify qualification and make it less
burdensome on industry.
o Drivers, LEDs, shape
 How to simplify worst-case guidance to make it more streamlined and open for
interpretation/argumentation.
o Worst-case with respect to CCT (especially thermal performance)
o How to deal with LED binning
o Test worst-case vs. "test close enough"
 How to each of these things while maintaining confidence in qualification process and listed
performance.
Key Questions:
Allowable variations
 Many variations are allowable within the family grouping policy such as number of LEDs, drive
current, optics, and size. Are the allowable variations appropriate? If not, how should they be
restricted?
 Some design variations are restricted such as drivers, LEDs, and shape. How can performance across
these parameters be assessed?
Worst-case testing guidance
 Requirements for family groups include:
o A logically sound, technically-defensible methodology for determining rated performance
o Testing for:
 Worst-case light output
 Worst-case efficacy
 Worst-case thermals (ISTMT)
 Worst-case power quality (THD/PF)
 Representative highest CCT
 Representative IES files for each optical distribution
o Is it possible to come up with standardized methods for determining expected performance?
Should the DLC attempt to? Are there suggestions for what this could look like?
 Current policy asks manufacturers to identify their worst-case performers, and justify with
engineering/technical logic, design information, and test data as needed, especially in cases where
the claimed worst-case performer is other than what DLC would normally expect.
 Is it possible to come up with formulaic rules about which product will be worst-case within the
group on various parameters?
 Current worst-case expectations are many, but include:
o Light output
 Lowest wattage
 Fewest # of LEDs
 Lowest drive current
 Worst-case optical efficiency
 Needs to be determined and supported
 Lowest CCT
 Highest CRI
 Hottest thermal conditions?
 Other parameters staying equal
o Efficacy
 Hottest thermal conditions
 Wattage
 Highest drive current
 Worst loading condition of the driver?
 Works opposite wattage (drive current/thermal conditions)
 Worst-case optical efficiency
 Needs to be determined and supported
 Lowest CCT
 Highest CRI
 Other factors?
o Thermals
 Highest wattage
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Highest drive current
Smallest housing size
 Other parameters staying equal
Proximity of other heat sources
Lowest CCT
Highest CRI
Influence of optics?
 Optical efficiency?
 Thermal resistance of optical materials?
Other factors?
CCT variations in Single Product applications
 Historic policy decision that is difficult to explain and not supported by a strong technical rationale.
Family Grouping applications were originally created to allow for performance affecting variations to
be evaluated within the same application. Single Product applications were maintained for situations
where simple evaluations were possible. The allowable CCT variation within Single Product
applications requires an additional LM-79 evaluation akin to the Family Grouping application
evaluation process. A trend has emerged where multiple Single Product applications are being
submitted where one Family Grouping application would be more appropriate, creating
administrative burden.
 The DLC is considering restricting Single Product applications to non-performance affecting variations
only, requiring CCT variations to be allowed under the Family Grouping application process only.
Does this make technical sense? Is there any reason to maintain the allowance for CCT variations in
Single Product applications?