Most chain is not rated because the factories never conduct metallurgical testing for reliable results.
UL states that you must perform a deflection test.
A split-chain deflection test (or load test) involves applying the maximum anticipated load to measure the chain's deformation (deflection) and structural integrity.
In UL 1598, the standard for luminaries, a split-link chain used for support is generally allowed to deform up to one thickness of the wire from which the link is made. This limit ensures the mechanical integrity of the suspension system during structural testing.
Deformation Limits and Measurement
The requirements are typically evaluated during the Support Test or Loading Test as follows:
- Maximum Allowed Deformation. A split-link chain must not open or deform such that the gap between the ends of the wire exceeds one wire thickness.
- No Structural Failure. The chain and its associated mounting hardware must support the load without breaking or suffering permanent distortion that would compromise safety or reduce electrical spacing.
- Measurement Method.
- Initial State. The width of the gap in the split link is noted before testing.
- Load Application. A test load—typically 4 times the luminaire's weight—is applied to the chain for a specific duration (often 1 minute).
- Post-Test Measurement. After removing the load, the gap in the split link is measured again. The difference (deformation) is compared against the thickness of the chain's wire to determine compliance.
General Mechanical Requirements
- Secure Mounting. The standard requires that all mounting methods, including chains, must be capable of supporting the fixture's weight under both normal and "abnormal" mechanical stress.
- Material Integrity. Testing also confirms that no parts of the mounting assembly crack or break during the application of the specified safety factor load.