• I think it just gets bigger because it has more circuits.  And bigger buildings have multiple panels.

Hope this helps!

Rebekka O'Melia, B.Arch, M. Ed, Registered Architect, NCARB, ​​Step Up ARE Coaching​​​

• Daniel, I'll share with you an similar example problem to help. . .

Note the arrow. Which equipment could that breaker switch be serving? Select the best answer.

Double-pole, single-throw residential oven

Single-pole, double-throw ten-story elevator

Single-pole, double-throw commercial kitchen light fixture

Explanation

Single-pole breaker switches—like the ones in the photo marked for 15 or 20 amps—protect single-phase 120-volt circuits (electrical outlets and small- and medium-sized building lighting) or single-phase 277-volt circuits (lighting in very large buildings). They switch off (trip) when the wires heat up from a short-circuit.

Double-pole breaker switches, like the one with the arrow, protect single-phase 240-volt circuits (single-family detached residential air conditioning units, ovens, clothes dryers and other large appliances).

Three-pole breaker switches (click here to see one), protect three-phase 208-volt or 480-volt circuits (medium- or large-building elevators, air conditioners and motorized equipment)

The number of poles describes the number of wires; the number of throws determines how many different “on” positions are available.

Need help remembering?

Lighting

Skyscraper: 277-volt (cheaper)

Everything else: 120-volt (safer)

Motors (A/C, Fans, Elevators)

House: 240-volt (cheaper)

Skyscraper: 480-volt (stronger and smoother-operating)

Everything else: 208-volt (smoother-operating)

Fully explaining the different flavors of power delivery and what is meant by the "throws" and "poles" is probably beyond my capabilities on this forum (it represents at least 15 minutes of animated videos in my Amber Book course). I've included a diagram I made that may help if you already have a bit of a background. . .

• Thank you for your thorough explanation

• Such a helpful explanation, happy to see the photo examples! Thank you Michael Ermann!