“Listed” Sign Information

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The NEC, National Electric Code, Article 600.3, requires that for electrical, structural, and installation safety all electrical signs shall be "Listed" (tested, and labelled with an appropriate Listing Mark.)

Underwriters Laboratories (“UL” Listing Mark) and Intertek (“ETL” Listing Mark – originally Edison Testing Laboratory founded by Thomas Edison) are the premier certification organizations and 80% of all things electrical are tested by them.

Both these certification organizations have testing laboratories in Plano.  MET Labs, another OSHA approved electrical testing laboratory, has a testing facility in Austin.

ISO (International Organization of Standardization) Standards, such as ISO 9001, are NOT electrical safety listings (similar to a UL, MET, or ETL Listing.)

There are different test standards for a LED electronic message center (EMC) compared to all other electrical signs.

Unlike all other Listed signs, components used in an EMC are not Listed, except potentially the power supplies.  Even so they are not a Class 2 power supply.  NO Outdoor EMC sign meets the Class 2 Power-Limited Circuits standards of NEC Article 725-III.  Their electrical system has fire and electrocution hazard potential.  No Outdoor EMC sign can currently be rated as an “enclosure” so exposed wiring is not allowed, even inside Listed EMC signs, unless the circuit meets Class 2 standards.

All LED Electronic Message Centers are separately Listed, and the signs separately Marked.

A sign structure that has any other type of lighted sign in conjunction with an LED Electronic Message Center will have at least 2 Listing labels (every cabinet a separate Listing label, the EMC a separate Listing label.)  The listing labels might be from different certification laboratories.

There are about 50 Listed electrical sign manufacturers in North Texas.  Only a FEW that manufacture Listed lighted signs also manufacture Listed electronic message centers (EMC.)

Many sign companies and sign installers, including Listed sign companies, are importing Chinese signs that are not Listed.

Virtually all actual manufacturers of EMC’s in the USA manufacture Listed signs.

In some cities the AHJ, according to their electrical ordinance adopting and possibly waiving parts of the NEC, must decide if non-Listed EMC Signs can be installed and serviced while maintaining effective safely.

Most non-Listed EMC signs are not “Marked” (labelled per Article 600.4) with the manufacturer’s name, input voltage, and current rating information, making evaluation difficult.

Their internal wiring is not to Code, especially since they are not Class 2, but most are even wired as if they are a rated enclosure (exposed internal primary wiring, exposed secondary wiring leading from the power supplies, none of the wire rated for wet location use.)  They are also not usually internally wired to meet the NEC 600.5(B)2 requirement for 20 amp maximum branch supply circuits for all signs except those with neon loads.

Non-Listed signs usually contain none of the OSHA mandated electrical safety information labelling or installation instructions.

Non-Listed EMC signs, if allowed by the AHJ, should have electrical supplied to meet the Markings for ALL the internal components as a “continuous” load, often a 100-200 amp requirement.

Non-Listed signs have obviously not had their structure, wiring, and electronics tested and approved for use in Damp or Wet (Outdoor) locations.  The AHJ must determine their safety.

Listed signs are tested and Marked, usually externally, with their approved input voltage and current rating, and internally with the number of branch supply circuits required, including their required rating and wire size.

Listed EMC signs have modified secondary circuits that meet Class 2 standards, and these circuit modifications have been tested and approved.  The sign does not meet Class 2 standards, but all exposed wiring does.  The sign is proven to present no fire or electrocution hazard.  There’s a lot of exposed wiring inside an EMC.

Listed signs are also internally Marked as to whether or not they have been tested and are approved for use in Damp or Wet (Outdoor) installations, or only approved for Indoor use.  (The many other required safety labels will also be present.)

If you suspect illegal use of Listing labels, a label inappropriately placed on ANY sign, you can contact the Listing laboratory on the label; all labels are traceable and they will pursue unauthorized use of their labels, saving you time.

Additional Information

According to the 2011 and 2014 National Electric Code (NEC) all electrical signs must be “listed” or be installed with the special permission of the AHJ. (NEC 600.3)

Special Permission. The WRITTEN (emphasis added) consent of the authority having jurisdiction.” (NEC Article 100)

New in the 2014 Code, these listed electrical signs must include installation instructions, which they already do as a condition of their being listed.

Non-listed electrical signs can only be installed with the WRITTEN special permission of the AHJ, obviously increasing the potential liability of the AHJ. 

We don’t see how an AHJ can determine that a non-listed, un-tested, electrical sign can be installed and used with equivalent safety, unless a Structural Engineer certifies both the structure of the sign and the installation instructions (per UL 48) and an Electrical Engineer also certifies that the sign meets electrical standards (UL 48), electronic LED standards (UL 8750), and is safe.  Testing laboratories do offer one-time approval services.  There are two in Plano; UL and ETL Intertek.

OSHA-approved testing laboratories, that test and list electrical signs, reach their conclusion after conducting many varied tests.  They approve installation instructions.  They then regularly inspect the production, materials, components, installation instructions, and procedures of listed manufacturers on an un-announced basis to assure continued compliance.

An electrician is in violation when installing a non-listed electrical sign without written special permission from the AHJ. 

Further Information

Components that are approved for use in UL Listed signs have a “UL Recognized” mark:

This mark does NOT mean that the component is approved for free-standing use.

The limits on a component’s conditions of use can be determined using the free link http://iq.ul.com

An example is http://iq.ul.com/ul/cert.aspx?ULID=102233996.  C***** Systems, Inc. makes an LED module component for LED Signs.  Their system includes a bolt-together skeleton frame for holding the modules.


Sign Accessories [guide info]  
Blade 12, Blade 16, Blade 19


Conditions of Use  
1. Environmental Suitability: Damp or Dry Location Only.  
2. This product requires an electrical enclosure.  
3. Input Ratings - Voltage: 110-240Vac; Frequency: 50/60Hz; Max Amps: 1.0A; Max Watts: 65W  
4. The need to conduct ground continuity tests and mold stress test shall be determined in the end product.  
5. The suitability of wiring of these products shall be determined in the end use applications.  
6. These products were tested in open air room ambient temperature with the fans operating continuously. The need to conduct temperature test at elevated ambient shall be determined in the end product.  
7. This product is to be installed in accordance with the manufacturer's instructions.  


According to the Sign Accessories guide info, the components failed the safety tests for use in wet locations (outdoors.)  In fact, this component is approved for use, anywhere, only when it is enclosed in a UL Listed Sign Enclosure.  According to UL48, an “enclosure” for a lighted sign must be manufactured by a Listed manufacturer, be structurally approved, be tested for water exclusion, and contain a flame-resistant (5VA) rated sign face.  Many outdoor rated electrical signs are not rated as an enclosure, which is why all their components must have a “wet” rating.  To require an enclosure for an electrical sign component is rare.

We understand that at least one sign company mistakenly ordered, and the AHJ mistakenly approved, this component as a completed sign for a school district, assuming that the Recognized mark allows their safe stand-alone use outdoors under the NEC.  It does not.

In fact, by failing some of the Listing tests, this product is proven to be a safety hazard when used as a stand-alone sign.


We have been asked for information, several times recently, as to what concerns the AHJ should have regarding the requirement to maintain effective safety when waving the NEC Article 600 requirement that an electric sign be Listed.

We thought this information might be interesting to everyone.

When an electrical sign is tested by an OSHA approved testing agency (UL, ETL, MET, etc.) the sign is required to be subjected to the following inspections and tests, as applicable:

  • Metal thicknesses
  • Gaps, spacing, and clearances in electrical enclosures and wireways
  • Wire material, size, insulation used
  • Components used
  • Disconnect means
  • Maximum temperature achieved
  • Dielectric
  • Strain Relief on cords and supply leads
  • Stability
  • Mounting
  • Gasket Aging
  • Gasket Adhesion
  • Exclusion of Water
  • Drainage
  • Bond Impedance
  • Accessibility Barrier Dielectric
  • Glass Impact Test (LED cover is glass)
  • Lamp containment barrier melt-through test
  • Straight accessibility probe test
  • Torque, bending moment and conduit pullout tests
  • Leakage current
  • Self-threading screw torque test
  • Input tests
  • Abnormal tests
  • Component failure test
  • Output loading test
  • Adhesive support test
  • Environmental test

All of these inspections and tests, testing methods, and required results are stated in ANSI/UL Standard 48 and ANSI/UL Standard 8750.

If an electrical sign is not Listed it has not passed any of the required tests, and the AHJ is responsible to determine that the sign will maintain effective safety if allowed to be installed.