Section 3: Equipment Description; Introduction; Options; Standards - Eaton Cutler-Hammer RTHMFDA20100WSU Instructions Manual

I.B. ATS-RM05

SECTION 3: EQUIPMENT DESCRIPTION

3.1 INTRODUCTION

The Cutler-Hammer Residential Automatic Transfer
Switch is assembled and tested at the factory. It is
designed to be used in conjunction with standby power
distribution equipment to provide an alternate source of
power to critical circuits in the event that a primary
power source is interrupted.
This switch monitors both normal and standby power
sources and automatically transfers critical load circuits
between the two sources depending upon which source
is available. The normal source is preferred and will
remain connected to the switch if it is available.

3.2 OPTIONS

The following section describes the standard features in
the RTHM Transfer Switch. The time delays are not
adjustable.
1. Time Delay Normal to Emergency (TDNE)
This feature delays the transfer from the normal power
source to the emergency power source in order to over-
ride momentary normal power source outages and/or
fluctuations. Timing begins when the emergency power
source becomes available. It does not affect initiation of
the engine start circuit. Should the normal power source
fail, the engine start contact will close and, if connected
to an engine generator, will initiate an engine start-up in
10 seconds. The TDNE timer is set for 3 seconds.
2. Time Delay on Engine Starting (TDES)
This feature is used only where the emergency power
source is an engine generator. It delays initiation of the
engine start circuit in order to override momentary nor-
mal power source outages and/or fluctuations. It does
not affect the ability of the transfer switch to transfer
from the normal power source to the emergency power
source. The TDES timer is set for 10 seconds.
3. Time Delay Emergency to Normal (TDEN)
This feature delays transfer from the emergency power
source to the normal power source to allow the normal
power source to stabilize before the transfer is initiated.
Timing begins when the normal source becomes avail-
able. If the emergency power source fails during timing,
the time delay is overridden and an immediate transfer
to the normal power source will occur. The TDEN timer
is set for 7 minutes.
Effective 6/01
Failsafe
Failsafe refers to the condition whereby the transfer
switch is connected to the Emergency Source. In the
event that the Emergency Source fails and the Normal
Source is available, an immediate retransfer to the Nor-
mal Source shall occur.
4. Time Delay Engine Cool-Off
This feature allows the engine generator to run after the
transfer switch returns to the normal power source with-
out load. The TDEC timer is set for 5 minutes.
5B. Undervoltage /Underfrequency Sensing for
Emergency Source
This feature enables the logic to constantly monitor the
emergency power source. The logic prevents transfer
from the normal power source to the emergency source
until the emergency power source has reached an
acceptable operating voltage and frequency. Drop-out
is set at 80% of nominal voltage and pick-up is set at
90% of nominal voltage. Frequency drop-out is set at
58Hz and pick-up is set at 59 Hz.
23. Plant Exerciser
This feature is a 7-day timer and provides automatic
testing of the emergency source once each week, 15
minutes no load.
26. Undervoltage Sensing for Normal Source
This feature enables the logic to constantly monitor the
normal power source. The logic prevents transfer from
the emergency power source to the normal source until
the normal power source has reached an acceptable
operating voltage. Drop-out is set at 80% of nominal
voltage and pick-up is set at 90% of nominal voltage.

3.3 STANDARDS

Cutler-Hammer transfer switch equipment enclosed in a
NEMA 1 enclosure is listed for application by UL and
UL-C. In addition, Cutler-Hammer automatic transfer
switches are listed in File E38116 by Underwriters
Laboratories, Inc. under Standard UL 1008. This stan-
dard covers requirements for automatic transfer switch-
es intended for use in ordinary locations to provide light-
ing and power as follows:
a. In emergency systems, in accordance with articles
517 and 700 in the National Electrical Code,
ANSI/NFPA 70 and the National Fire Protection
Association No. 76A and/or
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