Just a practical reson that it may be undesirable to use a multi-pole breaker on a multi-wire circuit...
In commercial or industrial lighting, a fault on one circuit would kill all 3 or both lighting circuits. This could possibly leave a whole plant, or office wing in the dark.
Economically speaking, if you were to run a neutral (or grounded conductor
![[Linked Image]](https://www.electrical-contractor.net/ubb/biggrin.gif)
) for each circuit, you would lose all lighting bids due to excessive material costs.
