Hold 15sec.to
start the engine
generator and to
transfer the load
to emergency.
Press to cancel the
active exercise period
(stopsengine nowor
after cooldown) See
page 5–1.
Hold 5 sec.toset
20 min. engine exercise
period immediately(engine
starts) and weekly thereafter.
³blinks slowly when
button is released (set)
and during 20 min.
exercise period.
³blinks 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.
³stays on after engine
stops (exerciser is
enabled for weekly
operation)
SECTION 2 SEQUENCE OF OPERATION
2 --- 1

TransferTo Emergency

Thesequenceforloadtransferto
emergency source begins automati-
cally when normal source volt age
falls below the preset dropout point
or when Transfer Test button is
pressed. An under voltage condition
onany phase of the normal source is
detected by the sensor.
When the normal
source voltage fails or
the TransferTestbutton
is pressed, the SE relay
de-energizes and relay
NR begins its timing
cycle (1 or 3 seconds,
momentary normal
source outage delay).
The NR relay is providedwith a ti me delayon dropoutto
override momentaryoutages and prevent nuisance starting
ofthe engine-dri ven generator. If the normal source voltage
returns above the sensor dropout settingbefore the time
delayexpires, the NR relay timing cycle is resetto zeroand
relay SE energizes.
If the normal source voltage does not return above the
sensor dropout setting before the time delay expires,the
NR relay de-energizes and signals the engine-driven
generator to start. At the same time, a voltage and
frequency sensor begins monitoring the emergency source.
The sensor will accept the emergen cy source only when
both voltage and frequency reach preset pickup points.
Usually about ten se conds elapse from dropout of th e NR
relay to acceptance by the senso r. This time span occurs
becauset heengine-driven generator must crank, start, and
run up to nominal pickup points. For this reason, if the
TransferTestbuttonis pressed i t must be held for 15 seconds.
Ifthe emergency source is available immediately,the sensor
may accept it as soon as NR relay drops out.
When the emergency sourceis 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 emerge ncy source. For immediate transfer
press Bypass Time Delay button.
ER relayenergizes, the TS coil is energized, the transfer
switch operates, andall swit ch contacts (mains, contr ols,
auxiliaries) reverseposition. The transfer switch is now
supplying the load from the emergency source.
The transfer switch will remain in the Emergency
position until the normal source is restored. If the
Transfer Test button is used, the transfer switch will
remain on emergencyuntil the ret ransfert o 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. Thevoltage level must
rise above the preset pickup point on all phases before
the sensor will acceptthe normal source.
Whenthenormalsourceisacceptedbythesensor,relay
SE begins its timing cycle (adjustable1 sec. to 30 min.,
retransfer to normal delay). For immediate retransfer
pressBypass Time De lay button. SE relay isprovided with
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
timingcycle is reset to zero. If the emergency source fails
formore than 4 seconds duri ng the timing cycle, ER relay
drops out and the load is immediately retransferredto
the normal source, if that s ource 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 switch is now supplying t he load
from the normal source again.
Uponretransfer to the normal source, NR relay begins its
timing cycle (unloaded running delay [engine cooldown] ).
NRrelay is provided witha 5 minute time delay on pickup
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 a nd introduce
additional time delays during transfer operations.