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UL 1703 Testing of Flat Plate Photovoltaic Modules and Panels

The UL requirements cover flat-plate modules intended for installation on or integral with buildings. As a certified environmental lab, we realize the importance of flat plate module testing. Meeting the environmental UL 1703 compliance requirements can be difficult. We understand the challenges and guide companies through the process.

Keystone Compliance partners with customers to achieve environmental product compliance. Not only do we create an accurate test plan to eliminate expensive over-testing, our proven process helps avoid product launch delays. We are in constant communication throughout the entire test process. We provide comprehensive reports shortly after completion of the standard compliance test. Our expert UL 1703 test engineers take pride in providing the peace of mind that all of your needs will be met.

Request a quote to receive testing services tailored to your specific requirements. Contact us to receive more information on environmental UL flat-plate photovoltaic testing.

Summary of UL Compliance Testing of Photovoltaic Modules and Panels

The UL 1703 standard compliance test also determines requirements for freestanding panels. These laboratory tests are in accordance with the National Electrical Code, NFPA 70, and Model Building Codes.

The maximum voltage of the systems being tested can not exceed 1000 V. The UL 1703 test also considers components able to provide electrical connection to and mounting facilities for flat-plate photovoltaic modules and panels.

The module being tested must be completely assembled when shipped from the manufacturer. 

Scope of UL 1703 Flat Plate Modules and Panels

The same test procedure used for electrical performance measurements is applied. A polymeric material system serving as the enclosure of a part involving a risk of fire must apply to specific requirements. These requirements are concerning flammability, ultraviolet light exposure, water exposure, immersion, and hot-wire ignition.

The Ul 1703 compliance testing standard does not cover:

  • Equipment intended to accept the electrical output from the array, such as power conditioning units and batteries.
  • Any tracking mechanism.
  • Cell assemblies intended to operate under concentrated sunlight.
  • Optical concentrators.
  • Combination of photovoltaic-thermal modules or panels.

The photovoltaic module compliance test contains keywords necessary to understand the standard. Some keywords are defined below:

Module (flat-plate) – The smallest environmentally protected assembly of solar cells and ancillary parts. Such as interconnects and terminals, intended to generate DC power under nonconcentrated sunlight.

Panel (flat-plate) – A collection of modules mechanically fastened together, wired, and designed to provide a field-installable unit.

Rated Operating Voltage – The voltage at which maximum power is available from the module or panel under standard test conditions.

UL 1703 Photovoltaic Test Procedures

Thermal Shock

For thermal shock testing, the module or panel is exposed to 200 cycles of temperature change. When subjecting the unit to thermal shock, the test can not result in:

  • Loss of circuit continuity
  • Accessibility of parts that involve a risk of electric shock
  • A reduction in the resistance between parts involving a risk of electric shock
  • Reduction in the thickness of the wall of a nonmetallic wiring compartment below required values
  • A gap greater than 1/16 inch, or, an increase of 1/16 inch in or more in an existing opening between nonmetallic wiring compartment walls and the cover

Three samples of a module or panel are placed in an air circulating chamber. the temperature and humidity of which can be varied and controlled. Additionally, the humidity is only regulated if required to prevent the accumulation of humidity on the samples.

The samples are mounted or supported in the chamber. This is done to provide free circulation of the surrounding air. The thermal conduction of the mount or support means is to be low, so that the samples are thermally isolated.


For humidity testing, a module or panel is subjected to 10 cycles of humidity freezing. This test can not result in:

  • Loss of circuitry continuity
  • Accessibility of parts that involve a risk of electric shock
  • A reduction in the resistance between parts involving a risk of electric shock
  • Corrosion of metal parts
  • Reduction in the thickness of the wall of a nonmetallic wiring component

Three samples are chosen and placed in a chamber. Similarly to temperature shock testing, the unit must be mounted to provide circulation of the surrounding air. The module or panel samples are to be arranged so that dripping of condensate on a sample is prevented. Each cycle must consist of the following:

  • A transition in the test chamber temperature from 25 C to 85 C
  • A dwell at 85 C for 20 hours
  • A transition from 85 C to -40 C
  • A dwell at -40 C for 30 minutes at minimum
  • A transition from -40 C to 25 C.


Water/spray testing can not result in water or uninsulated live parts or the collection of water in a compartment containing live parts. After conducting the water/spray test the module must comply with:

  • Dielectric Voltage-Withstand test
  • Leakage Current test

The rain test apparatus is to consist of three spray heads. These heads are mounted in a water supply rack.

The water pressure for all tests is to be maintained at 5 psig at each head. There must be exactly 3 feet between the center nozzle and the product. Next, the spray is directed toward the module or panel at an angle of 45 degrees to the vertical.

Exposure time for the test is to be 1 hour. After exposure to the rain/spray, the unit under testing is examined for evidence of water penetration.


The laminate portion of the module or panel is to be immersed in a non-corrosive liquid agent solution. The liquid is to have a temperature of around 22 C. Connectors must be maintained above the solution level. The connectors must be thoroughly wetted by pouring solution over these areas. Uninsulated terminations should not be wetted.

After two minutes of immersion, the insulation resistance between the shorted output terminals and the solution is to be measured.

Expert UL 1703 Compliance Testing of Photovoltaic Modules and Panels

Keystone Compliance strives to give our customers more time and energy on product development instead of testing. In addition to UL 1703 compliance testing, Keystone has a full lab of test equipment which permits us to provide a broad scope of other compliance tests. The tests range from industries such as commercial, aerospace, medical, and eCommerce.

Contact us to receive more information on UL flat plate compliance testing.

For more standards on photovoltaic compliance testing, please visit the following pages below: