What is the reason for installing all grounded and ungrounded conductors of a common circuit together in the same metal raceway?

Installing all grounded and ungrounded conductors of a common circuit together in the same metal raceway primarily serves the purpose of minimizing inductive heat. When conductors are arranged together, any magnetic fields generated by the alternating current can effectively cancel each other out, thereby reducing the overall heat produced within the conductors. This is particularly important in fire alarm systems, where excessive heat could compromise the integrity and operation of the system.

Additionally, keeping the conductors together helps ensure that they share a common electromagnetic field. This arrangement is beneficial in minimizing the potential for unwanted inductive coupling that can lead to interference or other issues. Though controlling voltage drop and preventing electromagnetic interference (EMI) are important considerations in electrical design, the primary effect of arranging conductors together in a metal raceway is to manage the heat generated by the currents flowing through them efficiently.