Horticultural Lighting FAQs
Q: How should the ambient temperature be listed on my product's specification sheet?
All products' specification sheets must show the maximum rated ambient temperature, in Celsius. This information will be used by the reviewer to evaluate component lifetimes.
Q: Why are lamps not allowed in the program?
Allowing lamps, bulbs, or other methods of retrofitting existing legacy non-LED fixtures with LED sources introduces measurement and performance risk. The areas of concern include:
- Identification of approved reference housings
- Sufficient light (and wavelength) extraction from within the housing
- Thermally-driven longevity verification of LED devices and drivers
- Potential for "snap-back" to non-LED sources before the utility-incentivized life of the product has run its course.
The DLC is not inherently biased against this product class and is open to suggestions for how to incorporate it in future policies.
Q: Should optional accessories be powered during fixture testing?
Any removable accessories not required to achieve full light output, such as cameras and sensors, should be removed during whole-fixture flux and efficacy testing. Any non-removable accessories with controllable power states that are not required to achieve full light output, such as microphones or external luminaire power connections, should be disabled or powered down during testing.
Q: How do I scale up multi-bar fixtures, and where is scaling/grouping not allowed?
In the early stages of the horticultural SSL marketplace conversion, the DLC horticultural lighting program is meant to control performance risk. Therefore, the program is not allowing scaling or family grouping. Every fixture will be individually evaluated, since the traditional means of defining a "family" or "group" for general lighting are not applicable across the variables of spectrum, power, size, and flux output.
However, the DLC will allow certain flexibility for product designs that present measurement challenges. For example, if a fixture with a central power supply and two "light bars" extending outward were longer than any available integrating sphere could accommodate, the DLC reviewer will allow the testing to proceed with the two "light bars" mounted parallel to each other, nearly halving the length of the fixture and allowing it to fit within the test equipment. In contrast the DLC reviewer will not allow this same test setup to test only one bar attached to the driver, with the 2-bar performance then determined by multiplying the performance of the test model in an effort to estimate the performance of the "double long" fixture. The total power and flux must be measured at all times.
Similar testing challenges as mentioned above should be discussed prior to application submissions by emailing email@example.com. The DLC reserves all rights to make final judgements.
Q: What is the required spectral content of test reports?
The definition of the lumen curve ("V-lambda") stops at 780nm. Consequently, many products which underwent legacy testing techniques based on human visual metrics do not necessarily contain spectral information for the portion of Far Red between 780-800nm. Since the DLC is collecting information on Far Red flux for informational purposes only, reviewers will allow test reports missing data in this range prior to October 15, 2019.
After October 15th, 2019, if a newly applying product has insufficient data covering the complete Far Red range for flux output or flux maintenance, both fields will be marked as zeros on the horticultural lighting QPL. If the DLC decides to count Far Red flux as eligible for efficacy threshold calculation, this policy will likely become more stringent, and we urge all stakeholders to collect the widest range of wavelengths possible when testing fixtures and components.
Q: I have products with various Product ordering codes. What are the testing requirements?
Lighting products often use an AA-BB-CC-XXX structure for model numbers or Stock Keeping Units (SKUs) that refer to various options and permutations. The horticultural lighting QPL requires individual testing of any permutation that produces different outcomes. For example, two different spectral distributions on the same fixture chassis would require two separate applications and listings, and would not be listed by a [XX] or [AA,BB] on the product's QPL listing.
An [XX] entry implies the DLC approval of all variables represented by this placeholder. Allowable entries include options that do not affect the product's operation or are completely covered by testing (see driver performance details). Examples of this include drivers, cord length, housing color, and similar variables.
If there are specific variables that meet the DLC's requirements, while others that do not, only those approved variables should appear on the SKU entry for the DLC QPL. The reviewer will check specification sheets and marketing brochures to ensure that only approved variables are clearly noted as DLC qualified, and that non-approved variables are clearly noted as not being DLC qualified.
Q: Why am I being asked for PPID and not an IES file or PPFD plot?
The IES file (formally known as a LM-63 document) is a useful format for reporting and modeling light distribution. The file format and its common usage in design software assumes measurements based on human-vision terms of candelas and lumens. While it is possible to place appropriate horticulturally based PPF measurements into the format of an IES file, significant care must be taken to appropriately warn the end user and design software of this modification. To encourage the adoption of easy-to-use formats for the adaptation process (like the new ANSI/IES TM-33) and updated software that will use automate the application of appropriate context in designs, the DLC is using PPID plots as a placeholder while the measurement, testing, and modeling ecosystem adapts to these new standards.
PPFD plots with a "heat map" generated with varying PPF density across an application plane, are useful tools for end users. The DLC is participating in standards development work to define uniform and repeatable ways of measuring and reporting these values, and will consider requiring them to accompany or replace PPID images or TM-33 documents as technical maturity of the sector advances.
Q: What are the warranty requirements?
The DLC does not have a complete set of required terms and conditions and will allow manufacturers significant flexibility relating to common mechanisms of a warranty. The DLC does expect the entire set of warranted products to be covered when used as directed by the manufacturer for a minimum of five years.
Q: What are the steps for getting my products listed on the horticultural lighting Qualified Products List (QPL)?
The first step towards getting your horticultural lighting product listed on the qualified products list is to create a manufacturer account on the DLC’s web portal.
- Start a new application and select "Horticultural" as the application type. Informational prompts and explanations are built into the application to guide you through the process. However, if you have questions or need clarification email firstname.lastname@example.org.
- When all information is complete, submit the application along with any supporting documentation.
- A reviewer will complete a thorough review of your application in the web portal, identifying any issues which require clarification. The web portal stores a complete record of all correspondence tied to each part of the application to make it clear and simple to understand where follow up is required.
When all issues have been resolved, and all materials have been accepted, an invoice will be generated through the web portal. Once paid, your product will be posted on the horticultural lighting QPL within 24hrs. You may now market the product as DLC® qualified. Please refer to the DLC’s Logo Guidelines for instructions on proper marketing of a DLC qualified product.
Q: Which LED should be used for ISTMT?
The measured and reported LED temperature in an ISTMT must be for the hottest LED of that model or type in the fixture. Guidance on how to determine the hottest LED is provided by the IES in Annex A of LM-84. The DLC reviewer will use the worst-case thermal condition, and will generally look for the LED chosen for ISTMT instrumentation to be in the middle of an array surrounded by the most neighboring LEDs. If the instrumented LED is not in this area, the DLC reviewer may ask for additional explanation, understanding that driver placement, structural elements, and other variables may change thermal flow for a product.
Q: Is a LM-80 report applicable to multiple LEDs?
For phosphor-converted “white” LEDs, the DLC reviewer will reference the ENERGY STAR program rules for applicability of LM-80 data. In sections 4.2 and 6.b.i.2 of this document, the ENERGY STAR rules only allow cross-applicability of LM-80 data to LEDs that perform within the chromaticity quadrangles defined in ANSI C78.377-2015.
In “single-emitter” or “narrow-band” LEDs, such as 440-nm “blue” or 660-nm “red” packages, a die produces a relatively narrow band of wavelengths. Their photons are not going through a phosphor conversion step and their chromaticity (if plotted) would be outside the ANSI quadrangles allowed to “share” LM-80 data. LM-80 data will be expected for each package in question. The DLC will follow ENERGY STAR program guidance on assessing assertions of series and successor identity for LEDs which share an emission profile, but have varying series, model, name and part numbers.
As the horticultural lighting program evolves the DLC reserves the right to modify this guidance as greater understanding and technical justification of applicability is provided. Attempts to claim cross-applicability of data via the ENERGY STAR guidance will be thoroughly scrutinized.
If LEDs are relatable per ENERGY STAR guidance, then only one question set entry in the application form is needed since the single "worst case" temperature of the LED package will be evaluated. For record keeping and auditing, applicants will need to provide the model number or ordering code for each relatable LED using this approach.
The DLC reviewer will be identifying the highest ISTMT of all observed LEDs that are classified as relatable and using this value for TM-21 projections. This may be any of the relatable models. The reviewer reserves the right to ask for proof and reasoning if only some of the LED types have undergone ISTMT and not others.
Q: What are the application requirements for photosynthetic photon flux (PPF) maintenance?
If a fixture uses LED device-based projections to meet the PPF maintenance requirement [Q90 must be at least 36,000 hours], the DLC will currently allow LM-80 data to be extrapolated with the TM-21 calculation method for the following units:
- Lumens or radiometric watts will be accepted in new applications until October 15th, 2019.All fixtures using LEDs with LM-80 reports denominated in lumens or radiometric watts will be contacted by the DLC by December 31st, 2019 to request updated LM-80 reports in PPF units for these LEDs. There will be no extra fee associated with this request and verification. If the LEDs' LM-80 reports are updated, their fixtures will maintain their listing through April 15th, 2021, which is the DLC hort program's first two year cycle, including grace period. If the LEDs' LM-80 reports are not updated, their fixtures will be removed from the DLC horticultural lighting QPL on April 16th, 2020.
- Lumens or radiometric watts, converted to PPF with a one-time measurement of spectral content at the start of the device's operating life will be accepted in new applications until October 15th, 2019. Fixtures using these LEDs will maintain their listing through April 15th, 2021, which is the DLC horticultural lighting program's first two year cycle, including grace period.
- Starting on October 15th, 2019, the DLC will only accept LM-80 reports denominated in PPF units for its Q90 threshold. The DLC may decide at its discretion to accept LM-80 reports that are clearly within the PPF range of 400-700nm based on the LED’s spectral signature, but are described in general terms of photon flux.For LEDs with emissions in both the PPF and Far Red bands (700-800nm), the DLC will require LM-80 reports to evaluate Q90 of PPF to be explicitly labeled appropriately with a separate reporting table for Far Red flux maintenance. In these cases, the descriptive term "photon flux" will be insufficiently specific and will be returned by the reviewer.
Driver and Power Supplies
Q: What are the driver testing requirements for efficiency and lifetime?
The horticultural lighting QPL allows multiple driver options for a single listed product to accommodate differing voltages and also to allow fixture manufacturers to manage supply chain complexity with multiple driver original equipment manufacturers (OEMs). When operating at its full power, each driver has slightly different electrical efficiencies at different ends of its input voltage range. The most accurate way to ensure that the lowest-efficacy operating state of the fixture is known would be to require full-fixture testing for each driver, at all input voltage extremes. However, this would be prohibitively expensive in both time and money.
As a compromise, the driver testing requirements call for fixture manufacturers to perform "benchtop" electrical testing of all drivers when operating at the fixture's maximum designed power state and report the accumulated performance data. See this file for a suggested format.
The driver and input voltage combination that results in the single lowest electrical efficiency out of the global set in the benchtop report will be the test condition that should be examined in full-fixture LM-79 performance testing.
Other variables from the benchtop testing, like total harmonic distortion (current) and power factor, are also collected. Reviewers will search for the single highest and lowest value, respectively, in the data set, and ensure that these are listed for the fixture on the horticultural lighting QPL. Reviewers will examine both the benchtop report, and any LM-79 reports, to ensure that the most accurate data is provided.
Evaluation of a driver's lifetime also follows a similar approach. The key difference is that the DLC cannot assume that different drivers have similar designs, components, and temperature tolerances. Therefore, each unique driver available for the fixture must feature ISTMT data and an OEM-provided time-at-temperature lifetime projection.