Product Manual B

1 Introduction

1.1 Installation Manual

This manual covers models produced under the Cummins

/Onan

and Cummins Inc. brand names.

This manual provides information necessary for the installation of all product models and specs provided

on the cover of this manual.

1.2 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 automatically

switches the electrical load from one source to the other.

The load is connected to the common of the ATS (Figure 1). 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 (genset). 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.

1.3 Transfer Switch Function

Automatic transfer switches, capable of automatic operation without operator intervention, perform the

basic function of transferring the load to the available power source. The controller monitors each source

for allowable voltage and frequency range.

This automatic transfer switch, capable of automatic operation without operator intervention, is designed

for utility-to-genset applications. In utility-to-genset applications, the transfer switch performs the following

functions:

1. Senses the interruption of utility power.

2. Sends a start signal to the genset.

3. Transfers the load to the genset.

4. Senses the return of utility power.

5. Retransfers the load to the utility.

6. Sends a stop signal to the genset.