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Hold 15 sec.to
start the engine
generator and t o
transfer the load
to emergency.
Press to cancel the
active exercise period
(stops engine now or
after cooldown) See
page 5–1.
Hold 5 sec
.toset
20 min. engine exercise
period immediately (engine
starts) and weekly thereafter.
➤ blinks slowly when
button is released (set)
and during 20 min.
exercise period.
➤ blinks rapidly when
button is held 5 sec.
while being set
Lights show position of transfer switch.
Lights show the sources accepted.
Light for built–in
engine exercise timer:
Seepage5–1
for complete
instructions
Figure 2–1. Membrane controls and indicator lights.
➤ stays on after engine
stops (exerciser is
enabled for weekly
operation)
SECTION 2 SEQUENCE OF OPERATION
2 --- 1
Transfer To Emergency
Thesequenceforloadtransferto
emerg en cy source begins automati-
cally when normal source voltage
falls below the preset dropout point
or when Transfer Test button is
pressed. A n under voltage condition
on any phase of the norm al source is
detected by the senso r.
Whe n the norma l
sour c e voltage fails or
the Transfer Test b utton
is pressed, the SE relay
de-energ iz es and rel ay
NR begins its timing
cycle (1 or 3 seconds,
momen t ar y no rmal
source outage delay).
The NR relay is provid ed with a time delay on dropout to
overr ide m om en tary o utag es and pr even t nu isan c e starting
of the engine-driven generator. If the n ormal s ourcevoltage
retur ns ab ov e the sensor dr op ou t setting before the tim e
delay exp ires , th e NR rela y timin g cycl e is re s e t to ze r o and
relay SE energizes.
If the normal source voltage does not r eturn above the
sensor dr opout setting b efor e the time delay expires, the
NR relay de-energizes and s ign al s the eng ine-driven
gen erator t o s tar t. At t he s am e tim e , a vo l tag e and
frequenc y sensor b egins monitoring the emerg enc y sour c e.
The sensor w ill accept the emergency source only when
both
voltage and frequency reach preset pickup points.
Usually about ten seconds elapse from dropout of the NR
relay to acceptance by the sensor. This time span occurs
bec ause th e eng ine-dr iven g ener ator m us t c rank, star t, and
run u p to no m in al p ic k u p poin ts . For this reason , if th e
Tra n sf e rTest button is pressed it must be held for 15 se conds.
If the e m er g en c y sou r c e isavailabl eimmediatel y, thesensor
may accept it as soon as NR relay drops out.
When the emergency source is accepted by the sensor,
relay ER begins its timing cycle (transfer to emergency
delay). ER relay is provided with an adjustable (0 to 5
minutes) time delay on pickup to delay transfer of the
load to the emergency source. For immediate transfer
press Bypass Time Delay button.
ER relay energizes, the TS coil is energized, the transfer
switch operates, and all switch contacts (mains, controls,
auxiliaries) reverse position. The transfer switch is now
supplying the load from the emergency source.
The transfe r swi tch will remain in the Emergency
positi on until the normal source is re stored. If the
Transfer Test button is used, the transfer switch will
remain on emergency until the retransfer to normal delay
times out.
Retransfer to Normal
The sequence for load retransfer to the normal source
automatically begins when the voltage sensor detects
restoration of the normal source. The voltage level must
rise above the preset pickup point on all phases before
the sensor will accept the normal source.
Whenthenormalsourceisacceptedbythesensor,relay
SE begins its timing cycle (adjustable 1 sec. to 30 min.,
retransfer to normal delay). For immediate retransfer
pressBypass TimeDelay button. SErelay is providedwith
a time delay on pickup to prevent immediate load
retransfer to the normal source. The delay insures that
the normal source has stabilized before reconnection of
vital loads. If the normal source voltage falls below the
present dropout point before the time delay expires, the
timing cycle is reset to zero. If the emergency source fails
for more than 4 seconds during the timing cycle, ER relay
drops out and the load is immediately retransferred to
the normal source, if that source is acceptable.
SE relay energizes a nd ER relay is dropped out. The TS
coil is energized, the transfer switch operates, and all
switch contacts (mains, controls, auxiliaries) reverse
position. The transfer switch is now supplying the load
from the normal source again.
Uponretransferto the normalsource, NRrelay beginsits
timing cycle (unloadedrunning delay [engine cooldown] ).
NRrelay isprovidedwitha 5minutetimedelay onpickup
to keep the engine running for a cool-down period.
NR relay energizes after the time delay and signals the
engine-driven generator to shut down. All circuits are
reset for any future normal source failure.
Activation of standard control features shown in Section 5
will alter the sequence of operation and introduce
additional time delays during transfer operations.