Automatic Changeover Switch Connection
An Automatic Transfer Switch (ATS) switches power between the main grid and a backup generator to keep the load running without interruption.
Key Components
- Main Grid → feeds the N (Normal) input of the ATS through an MCB.
- Generator → feeds the R (Backup) input of the ATS through an MCB.
- ATS / Changeover Switch → auto selects Normal or Backup and outputs to load.
- Load MCB → protects the outgoing circuit to the load.
Wiring Overview
- Connect grid phase/neutral to ATS N (Normal) via grid MCB.
- Connect generator phase/neutral to ATS R (Backup) via generator MCB.
- Connect ATS Output to the Load MCB and then to the load.
- Bond earth/ground for grid, generator, ATS, and load according to code.
How It Works
- Grid available: ATS supplies the load from Normal.
- Grid fails: ATS transfers to Backup (generator) automatically.
- Grid returns: ATS re-transfers to Normal.
Safety Notes
- Use correctly sized MCBs and follow local electrical codes (NEC/IEC).
- Prevent backfeed: never tie generator and grid lines directly.
- Test ATS operation periodically and label all feeders clearly.
FREE PRACTICE TOOL
Think you'd pass this on a real exam?
Test what you just read with instant-feedback quizzes built around real code questions — not generic trivia.
5
Code standards
10,000+
Active learners
100%
Free to start
✓
Instant explanations on every answer, right or wrong
✓
NEC, BS7671, AS/NZS, CEC, and DIN VDE covered
✓
Bite-sized quizzes you can finish in 5 minutes
✓
No signup required to try your first quiz
Try a free quiz now →
No account needed · Takes less than 2 minutes
