CSLB C-10 Electrical ContractorWiring Methods and MaterialsMedium
An electrician terminates aluminum THHN conductors onto a device that is listed and rated for use with aluminum conductors (marked AL-CU). What additional step should be taken at the termination to help prevent oxidation and ensure a reliable long-term connection?
- AIncrease the conductor size by two AWG sizes to compensate
- BWrap the termination with electrical tape only
- CUse only push-in style connections for aluminum conductors
- DApply an approved antioxidant compound to the conductor before making the connection
Show answer & explanationAnswer & explanation
Correct answer: D. Apply an approved antioxidant compound to the conductor before making the connection
Aluminum conductors form an oxide layer when exposed to air, which increases resistance and heat at terminations. Manufacturers and the NEC recommend applying an approved antioxidant compound during termination on devices listed for aluminum use to maintain a low-resistance, reliable connection.
Why the other options are wrong
- A. Oversizing does not eliminate the oxidation problem.
- B. Tape does not address the oxidation issue at the termination point.
- C. Push-in connectors are generally not rated for aluminum conductors and increase failure risk.
Aluminum Termination Antioxidant
Antioxidant compound is applied to aluminum conductor terminations to prevent oxide buildup that increases resistance and heat.
- Aluminum oxidizes quickly when exposed to air
- Antioxidant compound maintains low-resistance connections
- Only use devices listed AL-CU or CO/ALR for aluminum conductors
Memory trick: Grease the aluminum to stop the oxide from growing.