What conductor size and maximum run length are specified for wiring this system?

• A. #16 AWG, max 25 feet
• B. #12 AWG, max 25 feet
• C. #14 AWG, max 25 feet
• D. #14 AWG, max 100 feet

Answer: (C)

Managing voltage drop in the wiring for the escalator’s control circuit is the key idea. For a small control or signaling circuit, you want a conductor that can carry the required current without losing too much voltage over the run length. 14 AWG copper is a common, appropriate size for these circuits because it has enough capacity to handle the current while keeping resistance low enough to limit voltage drop.

Using 14 AWG over a 25-foot run (one-way) keeps the round-trip length and resistance small enough that the voltage drop stays well within typical design limits (often around 3% or less for control circuits). For example, 14 AWG has about 2.525 ohms per 1000 feet; over roughly 50 feet round trip that’s about 0.126 ohms. At a typical control current (e.g., around 15 A), the voltage drop is under 2 volts, a safe margin for control equipment. If the run were much longer, like 100 feet, the drop would become substantial enough to risk under-voltage conditions for the control devices. A smaller wire (like 16 AWG) would increase the drop, while a larger wire (like 12 AWG) would reduce it but isn’t specified as the requirement here.

So, the specified combination of conductor size and maximum run length is chosen to ensure reliable operation of the system’s control wiring by balancing adequate current capacity with acceptable voltage drop over the specified distance.