Aluminum Branch-Circuit Wiring
Rules on terminations and listed connectors after 1960s–70s aluminum wiring caused overheating at connections.
Why this code exists
Copper shortages drove builders to solid aluminum branch wiring. Aluminum expands, creeps and oxidizes differently than copper; connections loosened and overheated, causing fires.
The response was material-rated terminations (CO/ALR devices), antioxidant compounds, and later listed repair connectors (e.g., COPALUM). The episode is why terminal and conductor materials must be compatible under 110.14.
When it applies
Any time you land aluminum branch-circuit wire on a device or splice, the termination has to be rated for it. Old-style 15 and 20 amp receptacles and switches were never built for aluminum, and that mismatch is what cooked connections in a lot of 1960s and 70s houses. Look for CO/ALR devices or listed connectors, and use the antioxidant compound the connector calls for.
Common mistakes
- Landing solid aluminum on a plain brass-screw receptacle that only says copper.
- Skipping the oxide-inhibitor paste on lugs, then wondering why the lug turns dark and loose.
- Over-torquing or under-torquing terminals instead of using a calibrated driver to the label value.
- Mixing copper and aluminum on the same terminal without a listed dual-rated connector.
Aluminum is fine when it is landed right. It is the lazy termination that starts fires, not the metal itself.
Every so often I open a 1970s panel and there it is — aluminum branch wiring going dark at the lugs. I don't touch it without the right terminations and antioxidant.
See full history
- 1965 — Aluminum branch wiring widely installed.
- 1971 — CO/ALR device marking introduced.
Related codes
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