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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.
³ blinks slowly when
button is released (set)
and during 20 min.
exercise period.
³ 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.
³ stays on after engine
stops (exerciser is
enabled for weekly
operation)
SECTION 2 SEQUENCE OF OPERATION
2 --- 1
Transfer To Emergency
Thesequenceforloadtransferto
emerg en c y source begins automatic al-
ly when normal source voltage falls
below the preset dropout point or
when Tra nsfe r Test button is pressed.
An und er voltag e co n ditio n on any
phase of the normal source is de-
tected by the sensor .
When the normal
sour c e voltag e fails or
the Transfer Test
button is pressed, the
SE relay de-energiz es
and relay NR begin s
its timing cycl e (1 or 3
seconds, momentary
norma l source outage
delay). The NR relay is provid ed with a time delay on
dropout to override mom entar y outages and prevent
nuisance starting of the engine-driven generator. If the
normal source voltage returns above the sensor dropout
setting b efore the time delay expires, the NR relay timing
cyc l e is reset to zero and relay SE energizes.
If the normal source voltag e does not return above the
sensor dropout setting before the time delay expires, the
NR relay de-energizes and signal s the engine-driven gen-
erator to start. A t the same time, a voltag e and frequen-
cy sensor begins monitoring the emergency source. The
sensor will accept the emergency source only when both
vol tag e and frequency reac h preset picku p points. U su al-
ly about ten seconds elapse from dropout of the NR relay
to acceptance by the sensor. This time span occurs be-
caus e the engine-d riven generator must cr ank, start, and
run up to nom in al picku p points . For this reason, if the
Tra n sf e r Test button is pressed it must be held for 15 sec-
onds. If the emerg en c y source is available imm ediatel y,
the sensor may acc ept 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. F or immediate transfer
press Bypass Time Delay button.
ER rela y ener giz es , the TS coil is energ iz ed , the trans f er
switch operates, and all switch contacts (mains, controls,
auxil iarie s) rever se position. The transfer switc h is now
supplying the load from the emergency source.
ThetransferswitchwillremainintheEmergency
position until the normal source is restored. 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 press Bypass Time Delay button. SE relay i s
provided with a time delay on pickup to prevent
immediate load retransfer to t he 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 and 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 swit ch is now supplying t he load
from the normal source again.
Upon retransfer to the normal source, NR relay begins
its timin g cy cl e (unloade d r unning delay , engine cooldown).
NR rel ay is p rovid ed with a 5 min. time del ay on picku p
to keep the eng ine 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.
Activationof standardcontrol featuresshown inSection 5will
alter the sequenceof operation and introduceadditionaltime
delays during transfer operations.