Introduction to the Glow Wire Test

The Glow Wire Test (GWT) is a critical flammability assessment method used to evaluate the fire resistance of materials and components in electrical and electronic equipment. It simulates thermal stress caused by overheated or faulty components to determine whether a material will ignite, propagate flames, or self-extinguish. The 850°C Glow Wire Test, in particular, represents one of the most stringent evaluations under IEC 60695-2-10 to 2-13 and other regional standards such as UL 746A and GB/T 5169.10-2017.

This article examines the technical principles of the 850°C Glow Wire Test, its industry applications, and the role of advanced testing equipment such as the LISUN ZRS-3H Glow Wire Test Apparatus in ensuring compliance with international safety standards.

Technical Principles of the 850°C Glow Wire Test

The test involves heating a standardized Nichrome (80% nickel, 20% chromium) wire to 850°C using an electrically controlled furnace. The glowing wire is then pressed against a test specimen for 30 seconds under a defined force (1.0 ± 0.2 N). Post-application, the specimen is observed for:

• Ignition Time: Duration before flames appear.
• Flame Duration: Time flames persist after removing the glow wire.
• Dripping Behavior: Whether molten material ignites a tissue paper substrate.

A material passes if:

• Flames extinguish within 30 seconds after removal of the glow wire.
• No ignition of the tissue paper occurs due to dripping particles.

The test replicates real-world thermal faults, such as short circuits in connectors, overheating in switches, or insulation breakdown in wiring systems.

Key Standards and Regulatory Frameworks

The 850°C Glow Wire Test is mandated across multiple industries, with compliance governed by:

The LISUN ZRS-3H Glow Wire Test Apparatus

The LISUN ZRS-3H is a precision-engineered glow wire test instrument designed for compliance with IEC 60695-2-10 and related standards. Its key features include:

Technical Specifications

• Temperature Range: 300°C to 1000°C (± 2°C accuracy).
• Heating Element: High-purity Nichrome wire (Ø 4.0 mm).
• Test Force: 1.0 ± 0.2 N (adjustable via calibrated weights).
• Timer: Digital countdown (0–999.9 s) for precise test duration.
• Safety Features: Overheat protection, automatic shut-off, and fume extraction compatibility.

Competitive Advantages

1. Automated Calibration – Reduces human error in temperature and force application.
2. Multi-Standard Compliance – Validated for IEC, UL, GB/T, and EN standards.
3. Enhanced Repeatability – PID-controlled heating ensures consistent thermal output.
4. Modular Design – Supports additional fixtures for needle flame and horizontal/vertical flame tests.

Industry Applications of the 850°C Glow Wire Test

1. Electrical and Electronic Equipment

Components such as circuit breakers, relays, and terminal blocks must resist ignition under fault conditions. The test ensures enclosures and insulating materials do not propagate fire.

2. Household Appliances

Switches, thermostats, and motor housings in appliances (e.g., washing machines, microwaves) are subjected to GWT to mitigate fire risks from electrical overloads.

3. Automotive Electronics

With increasing electrification, connectors, battery housings, and infotainment systems must pass 850°C GWT to meet ISO 20653 and LV 124 standards.

4. Lighting Fixtures

LED drivers, plastic diffusers, and thermal management materials undergo testing to prevent ignition from prolonged operation.

5. Industrial Control Systems

PLC enclosures, contactors, and wiring ducts are tested to ensure fire safety in high-temperature industrial environments.

6. Telecommunications Equipment

Fiber-optic terminals, server racks, and power supplies must resist ignition due to short circuits or overheating.

7. Medical Devices

Compliance with IEC 60601-1 requires that enclosures and internal wiring in medical equipment do not contribute to fire hazards.

8. Aerospace and Aviation Components

Cabin electronics, wiring harnesses, and insulation materials undergo GWT to meet FAA and EASA flammability requirements.

9. Electrical Components (Switches, Sockets)

Consumer-grade electrical accessories must self-extinguish to prevent household fires.

10. Cable and Wiring Systems

Insulation materials are tested to ensure they do not ignite or propagate flames along cable runs.

11. Office Equipment

Printers, power strips, and surge protectors are evaluated for fire safety under prolonged electrical stress.

12. Consumer Electronics

Chargers, battery packs, and plastic housings in smartphones/laptops must resist ignition from internal faults.

Case Study: Enhancing Compliance in Automotive Connectors

A Tier 1 automotive supplier utilized the LISUN ZRS-3H to validate the fire resistance of nylon-based connectors for electric vehicle battery systems. Testing at 850°C confirmed compliance with LV 124-2, ensuring that molten material did not ignite adjacent components.

Conclusion

The 850°C Glow Wire Test is indispensable for verifying material safety across industries where thermal faults pose fire risks. Advanced testing systems like the LISUN ZRS-3H provide the precision, repeatability, and compliance assurance needed to meet global standards. Manufacturers investing in rigorous flammability testing mitigate liability, enhance product safety, and gain a competitive edge in regulated markets.

FAQ Section

Q1: What is the difference between the 750°C and 850°C Glow Wire Test?
The 750°C test evaluates materials for lower-risk applications, while the 850°C test is required for high-stress environments (e.g., power distribution systems).

Q2: How often should the LISUN ZRS-3H be calibrated?
Annual calibration is recommended, with routine verification before critical tests to ensure temperature and force accuracy.

Q3: Can the ZRS-3H test non-planar specimens?
Yes, custom fixtures can accommodate irregularly shaped components (e.g., connectors, housings).

Q4: Does the test account for material thickness variations?
Yes, but specimens must be tested at their end-use thickness to ensure valid results.

Q5: Is the ZRS-3H compatible with fume extraction systems?
Yes, an optional extraction kit can be integrated to remove hazardous combustion byproducts.