Charger glow-wire testing is an essential fire-safety evaluation that verifies whether the plastic and insulating materials used in power adapters can withstand contact with an overheated element without igniting or producing flaming droplets. Performed in accordance with the IEC 60695-2 series and product safety standards such as IEC 62368-1 and GB 4943.1, this test is a key requirement for charger certification in major global markets. This article explains the applicable standards, sample types, test items, test methods, and frequently asked questions to help manufacturers develop compliant, market-ready charging products.
Technical Overview
Glow-wire testing is a fire-hazard simulation test that evaluates the resistance of insulating materials to thermal stress. During real-world faults inside a charger—such as an overloaded resistor, a glowing component lead, or a loose solder joint carrying excessive current—adjacent plastic parts can be exposed to intense localized heat. The glow-wire test reproduces this scenario by pressing an electrically heated wire, at a precisely controlled temperature, against the material and observing whether ignition, sustained flaming, or flaming droplets occur.
For chargers, power adapters, and similar low-voltage power supply products, glow-wire testing is primarily governed by the following standards:
- IEC 60695-2-10 / GB/T 5169.10 — Glow-wire apparatus and common test procedure
- IEC 60695-2-11 / GB/T 5169.11 — Glow-wire flammability test method for end-products (GWEPT)
- IEC 60695-2-12 / GB/T 5169.12 — Glow-wire flammability index test method for materials (GWFI)
- IEC 60695-2-13 / GB/T 5169.13 — Glow-wire ignition temperature test method for materials (GWIT)
- IEC 62368-1 / EN 62368-1 / UL 62368-1 / GB 4943.1 — Safety requirements for audio/video, information and communication technology equipment, including chargers and external power supplies
- IEC 61558-1 / EN 61558-1 — Safety of transformers, reactors, power supply units and combinations thereof
- IEC 60335-1 / GB 4706.1 — Household and similar electrical appliances, applicable to certain built-in or dedicated charging products
The exact test temperature and applicability are determined by the governing product safety standard, the function of the part, and its proximity to potential ignition sources. Accredited third-party laboratories routinely perform these tests as part of national certification schemes, product safety assessments, and factory quality control programs.
Testing Samples
Complete Charger or End-Product Parts
For the glow-wire flammability test on end-products, samples are tested in their finished, assembled condition wherever possible. This includes the complete charger housing with all internal components in place, or individual disassembled parts such as enclosure halves tested in their normal orientation of use. Testing the actual end-product provides the most realistic assessment of fire behavior, including the influence of part geometry, wall thickness, internal supports, and nearby components.
Enclosure and External Insulating Parts
External plastic parts are a primary focus of charger glow-wire testing because they contain any internal fire and protect the user. Typical samples include the upper and lower housing shells, output cable entries, indicator-light windows, and any decorative or functional external covers.
Internal Insulating Components
Internal parts that support, secure, or are located near energized components are also evaluated. Common internal samples include printed circuit board mounting clips, transformer bobbins and barrier tapes, winding insulation sheets, connector housings, terminal blocks, strain-relief components, insulating collars, and adhesive-lined sleeves.
Material Plaques for Preselection Testing
For material-level characterization, flat plaques with preferred dimensions of approximately 60 mm × 60 mm, at the same thickness as the finished part or at standard thicknesses, are submitted for GWFI and GWIT testing. A minimum of three specimens per temperature level is generally required. Material-level data is valuable during design and material selection before tooling investment is made.
Testing Items
Charger glow-wire evaluation typically comprises the following test items, selected according to the applicable product standard:
- Glow-wire flammability test for end-products (GWEPT) — performed on the finished charger or its component parts at temperatures commonly ranging from 550 °C to 960 °C
- Glow-wire flammability index (GWFI) — a material property characterizing the highest temperature, from a defined series between 550 °C and 960 °C, at which the material meets the pass criteria
- Glow-wire ignition temperature (GWIT) — the temperature 25 K above the highest temperature at which the material does not ignite, or self-extinguishes, within the specified time without igniting the indicator tissue
Representative temperature assignments for charger parts under common product safety schemes include the following, noting that the governing standard always prevails:
- 550 °C — general insulating parts that do not maintain live parts in position
- 650 °C to 750 °C — internal parts that support or maintain energized components, and parts located close to potential ignition sources
- 750 °C to 850 °C — enclosure and external parts, particularly for equipment intended for continuous or unattended operation
- 850 °C to 960 °C — severe-duty parts, such as certain switch components and highly stressed insulating supports
Testing Methods
The test method is defined by IEC 60695-2-10, which specifies the apparatus and common procedure used across the entire glow-wire test series:
- Apparatus — a glow-wire made of nickel-chromium (80/20) alloy, 4 mm in diameter, bent into a standardized loop and heated by electric current to the specified temperature
- Temperature measurement — a fine-gauge sheathed K-type thermocouple installed at the tip of the loop, with the system verified against the melting point of silver (960 °C) at specified intervals
- Test atmosphere — conducted in an essentially draft-free environment at standard laboratory conditions; specimens are conditioned beforehand, typically for at least 24 hours
- Specimen setup — end-product parts are mounted in their normal position of use, while material plaques are clamped with the test surface vertical; a single layer of soft tissue paper laid on a pine board is positioned approximately 200 mm below the contact point to detect burning droplets
- Contact procedure — the heated glow-wire tip is pressed horizontally against the specimen surface with a contact force of 1.0 N ± 0.2 N for a duration of 30 seconds, with mechanical penetration limited to a maximum of 7 mm
During and after contact, the laboratory records the ignition time, flame extinguishing time, flame height, whether glowing continues, whether burning or glowing drops fall, and whether the tissue paper is ignited. The evaluation criteria for a passing result are:
- No ignition of the specimen occurs, or any flaming or glowing self-extinguishes within 30 seconds after removal of the glow-wire
- The underlying tissue paper is not ignited by flaming or glowing particles or droplets
- For material indices, the GWFI and GWIT values are determined from the series of tested temperatures and compared against the minimum values required by the product standard
Following completion, accredited third-party laboratories issue test reports documenting the apparatus parameters, temperatures applied, observations, photographs, and conformity conclusions, which can be used to support certification applications and customer declarations.
Applications
Glow-wire testing is applied throughout the charger product lifecycle and across a broad range of charging devices:
- Consumer chargers — mains-powered adapters for smartphones, tablets, laptops, cameras, wearable devices, and multi-port USB wall chargers
- Network and infrastructure power supplies — PoE injectors, router and gateway adapters, smart-home device power units, and LED driver power supplies
- Wireless and specialty charging — inductive charging pads, charging docks, industrial charging stations, and battery-pack charging accessories
- Regulatory market access — supporting national certification schemes such as China Compulsory Certification under GB 4943.1, CE marking under the Low Voltage Directive via EN 62368-1, North American listing programs referencing UL 62368-1, and other regional market entry requirements
- Research, development, and quality control — comparing flame-retardant material formulations, validating supplier lots of plastics, supporting halogen-free material transitions, and performing root-cause analysis after field failures or audit findings
By verifying material fire performance early in development and during mass production, manufacturers reduce certification risk, avoid costly tooling changes, and strengthen the overall fire safety of their charging products.
FAQ
Why do chargers need glow-wire testing?
Chargers are permanently connected to mains voltage and can experience internal overheating faults. Glow-wire testing demonstrates that enclosure and insulating materials will not ignite or propagate fire under such faults, protecting users and property. It is also an explicit requirement in most charger safety standards and certification schemes worldwide.
What temperatures are used for charger glow-wire tests?
Test temperatures typically range from 550 °C to 960 °C. The exact value depends on the part function and the applicable standard: general insulating parts are commonly tested at 550 °C, parts maintaining or supporting live parts at 650 °C to 750 °C, and enclosures or severe-duty components at 750 °C to 960 °C.
What are the pass criteria?
A specimen passes if it does not ignite, or if any flaming or glowing extinguishes within 30 seconds after the glow-wire is removed, provided the tissue paper placed below the specimen is not ignited by falling burning particles or droplets.
What is the difference between GWFI, GWIT, and GWEPT?
GWEPT is performed on the finished end-product or its parts and evaluates the assembled device. GWFI is a material index equal to the highest tested temperature at which the material meets the flammability criteria. GWIT characterizes the ignition sensitivity of the material and is expressed as 25 K above the highest temperature at which no sustained ignition occurs.
How many samples are required?
For material-level GWFI and GWIT tests, a minimum of three specimens per temperature level is typically required, plus spare specimens in case of retest. For end-product tests, the complete charger or the relevant component parts in their normal use condition are submitted, ideally with several units to cover all tested locations.
How long does testing take?
Excluding specimen conditioning, the glow-wire contact itself lasts 30 seconds per location. Including conditioning, setup, multiple temperature levels, and reporting, projects are usually completed within several working days, depending on the number of parts and temperatures involved.
What can be done if a material fails the glow-wire test?
Manufacturers can select a higher flame-retardant grade of the polymer, increase the wall thickness at the contact area, reposition the part away from potential ignition sources, or add barriers and additional insulation. Retesting at an accredited third-party laboratory confirms whether the design change achieves compliance before submission for certification.