For more information visit: www.cutler-hammer.eaton.com
IB01602007E
Instruction Bulletin
Page
4
Effective: June 2003
O&M Manual for
Non-Automatic Transfer
Switches (30 – 1200 Amperes)
Section 1: Introduction
1.1 Preliminary Comments and Safety Precautions
This technical document is intended to cover most aspects
associated with the installation, application, operation and
maintenance of transfer switch equipment with ratings
from 30 – 1200 amperes. It is provided as a guide
for authorized and qualified personnel only. Please refer
to the specific WARNING and CAUTION in
Section 1.1.2
before proceeding. If further information is required by the
purchaser regarding a particular installation, application
or maintenance activity, an Eaton/Cutler-Hammer represen-
tative should be contacted.
1.1.1 Warranty and Liability Information
No warranties, expressed or implied, including warranties
of fitness for a particular purpose of merchantability, or
warranties arising from course of dealing or usage of trade,
are made regarding the information, recommendations
and descriptions contained herein. In no event will the
Cutler-Hammer business be responsible to the purchaser or
user in contract, in tort (including negligence), strict liability
or otherwise for any special, indirect, incidental or conse-
quential damage or loss whatsoever, including but not lim-
ited to damage or loss of use of equipment, plant or power
system, cost of capital, loss of power, additional expenses
in the use of existing power facilities, or claims against the
purchaser or user by its customers resulting from the use
of the information and descriptions contained herein.
1.1.2 Safety Precautions
All safety codes, safety standards and/or regulations
must be strictly observed in the installation, operation and
maintenance of this device.
1.2 General Information
Transfer switches are used to protect critical electrical loads
against loss of power. The load’s normal power source is
backed up by a secondary (emergency) power source. A
transfer switch is connected to both the normal and emer-
gency power sources and supplies the load with power from
one of these two sources. In the event that power is lost
from the normal power source, the transfer switch transfers
the load to the secondary (emergency) power source. Trans-
fer can be automatic or manual, depending upon the type of
transfer switch equipment being used. Once normal power
is restored, the load is automatically or manually transferred
back to the normal power source, again depending upon the
type of transfer equipment being used (
Figure 2
).
1.2.1 Transfer Switch Types
Four types of basic transfer switch equipment are available:
Automatic Transfer Switch
Automatic transfer switches automatically perform the
transfer function. They consist of three basic elements:
1. Main contacts to connect and disconnect the load to and
from the power source.
2. Intelligence/supervisory circuits to constantly monitor
the condition of the power sources and thus provide
the intelligence necessary for the switch and related
circuit operation.
3. A transfer mechanism to effect the transfer of the main
contacts from source to source.
Basic Transfer Switch
The basic transfer switch is designed for use with customer
furnished controls. It is similar in design to the automatic
version except the intelligence circuit (logic panel) and
voltage selection panel are omitted. All automatic sensing
devices, relays or solid-state devices are the customer’s
responsibility.
Figure 2. Typical Load Transfer Switch (Circuit Breaker Type)
Schematic
WARNING
THE WARNINGS AND CAUTIONS INCLUDED AS PART OF
THE PROCEDURAL STEPS IN THIS DOCUMENT ARE FOR
PERSONNEL SAFETY AND PROTECTION OF EQUIPMENT
FROM DAMAGE. AN EXAMPLE OF A TYPICAL WARNING
LABEL HEADING IS SHOWN ABOVE TO FAMILIARIZE
PERSONNEL WITH THE STYLE OF PRESENTATION. THIS
WILL HELP TO ENSURE THAT PERSONNEL ARE ALERT
TO WARNINGS, WHICH APPEAR THROUGHOUT THE
DOCUMENT. IN ADDITION, CAUTIONS ARE ALL UPPER-
CASE AND BOLDFACE.
CAUTION
COMPLETELY READ AND UNDERSTAND THE MATERIAL
PRESENTED IN THIS DOCUMENT BEFORE ATTEMPTING
INSTALLATION, OPERATION OR APPLICATION OF THE
EQUIPMENT. IN ADDITION, ONLY QUALIFIED PERSONS
SHOULD BE PERMITTED TO PERFORM ANY WORK
ASSOCIATED WITH THE EQUIPMENT. ANY WIRING
INSTRUCTIONS PRESENTED IN THIS DOCUMENT MUST
BE FOLLOWED PRECISELY. FAILURE TO DO SO COULD
CAUSE PERMANENT EQUIPMENT DAMAGE.
Normal
Source
Emergency
Source
Load
