IB70-8671
For more information visit: www.eaton.com
Instructional Booklet
Effective: July 2008
Page
3
O & M Manual for the EGS AutomaticTransfer Switch
with RTC-50 Control and Integral Loadcenter - 100 Amp
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 by the generator and the ATS transfers to the gener-
ator 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
unavailable, 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 power contactors to transfer essential loads from one power
source to another (see Figure 3). The Residential ATS contains
suitable mechanical and/or electrical interlock switches to elimi-
nate the possibility of connecting the utility service to the genera-
tor output. In addition, a manual override lever is provided for the
transfer function.
Figure 3. EGS100L24R (100 A).
1.2.2 Load Shed Contacts
Two sets of contacts are available and can be used to control
large connected loads on the generator (i.e. air conditioners, hot
tubs, etc.). The contacts are rated for 250 Vac, 5 amps maxi-
mum.
1.3 Transfer Switch Catalog Number Identification
ATS equipment catalog numbers provide a significant amount of
relevant information pertaining to a specific piece of equipment.
The Catalog Number Identification Table (see
Table 1
) provides
the required interpretation information.
Utility
Generator
Load
WARNING
DO NOT MANUALLY TRANSFER THE SWITCH WHILE UNDER LOAD.
