Product Manual

Table Of Contents

2. Introduction 7-2019

FIGURE 1. RA112L1 AUTOMATIC TRANSFER SWITCH

2.2 Transfer Switch Application

Transfer switches are an essential part of a building's standby or emergency power system. The utility line

(normal power), is backed up by a generator set (emergency power). The transfer switch connects the

electrical load to the utility or generator set.

The load is connected to the common of the automatic transfer switch, as shown below. Under normal

conditions, the load is supplied with power from the utility (as illustrated). If utility power is interrupted, the

load is transferred to the generator set. When utility power returns, the load is retransferred to the utility.

The transfer and retransfer of the load are the two most basic functions of a transfer switch.

NOTICE

Maximum continuous loads not to exceed 80% of the overcurrent protective device (circuit

breaker and fuses) ratings employed in other than motor circuits, except for those circuits

employing circuit breakers marked as suitable for continuous operation at 100% of their ratings.