IB00405002E
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Instructional Booklet
Effective: August 2007
Page
3
O & M Manual for the CHGENLC Automatic
Transfer Switch with ATC-100 Control
1.2 General Information
ATSs are used to protect critical electrical loads against loss of
power. The load’s utility power source is backed up by a genera-
tor power source. An ATS is connected to both the utility and
generator power sources and supplies the load with power from
one of these two sources. In the event that power is lost from the
utility power source, the ATS transfers the load to the generator
power source. Once the utility power is restored, the load is auto-
matically transferred back to the utility power source (Figure 2).
Figure 2. Typical Load Transfer Switch (Contactor) Schematic.
An intelligence system initiates the transfer when the utility power
source fails or falls below a preset voltage. An engine start is
then initiated and the ATS transfers to the generator power source
when sufficient generator voltage is available. When the utility
power source is restored, the ATS automatically transfers back
and the generator will shut down after a time delay. In the event
the utility power source fails and the generator power source
does not appear, the ATS remains connected to the utility power
source until the generator power source does appear. Conversely,
if connected to the generator power source and the generator
power source fails while the utility power source is still unavail-
able, the ATS remains connected to the generator power source.
ATSs automatically perform the transfer function, and include
three basic elements.
1. Main contacts to connect and disconnect the load to and from
the source of power.
2. Solenoids to make the transfer of the main contacts from
source to source.
3. Intelligence/supervisory circuits to constantly monitor the con-
dition of the power sources and thus provide the intelligence
necessary for the switch and related circuit operation.
1.2.1 Design Configuration
The Eaton Residential ATS is a rugged, compact design that uti-
lizes contactors to transfer essential loads from one power source
to another (see Figure 3). The Residential ATS contains suitable
mechanical and electrical interlock switches to eliminate the possi-
bility of connecting the utility service to the generator output. In
addition, a manual override lever is provided for the transfer func-
tion
Figure 3. CHGENLC ATS (100 A).
1.2.2 Optional Service Entrance Feature
The ATS can be ordered in either a standard or service entrance
(SE) configuration. When ordered as an SE, integral overcurrent
protection is built into the switch. Therefore, the ATS can be
installed at the point of service entrance without the need for an
upstream disconnect device. Also the switch comes with a gener-
ator breaker on the generator (source-2) side of the contactor (see
Figure 5). The generator breaker can be switched OFF to prevent
the transfer of power from the generator source to the load, if the
service entrance breaker is switched OFF manually. (not an over-
load condition)
Utility
Generator
Load
WARNING
DO NOT MANUALLY TRANSFER THE SWITCH WHILE UNDER LOAD.
