Hold15 sec.to
startthe engine
generatorand to
transfer the load
toemerg ency.
Pressto cancel th e
activeex ercise period
(stopsengine now or
after cooldown) See
page 5–1.
Hold5 sec.toset
20min. engineex ercise
periodimmediately (engine
starts)and w eekly thereafter.
³blinksslowly when
button is released (set)
andduring 20 m in.
exercise period.
³blinksrapidly when
button is held 5 sec.
whilebeing set
Lights show position of transfer switching device. Lights show the sources accepted.
Light for built–in
engineex ercise timer:
Seepage5–1
forcomplete
instructions
Figure 2–1. Membrane controls and indicator lights.
³stayson af ter engine
stops(ex erciser is
enabled for weekly
operation)
SECTION 2 SEQUENCE OF OPERATION
2--- 1

TransferTo Emergency

Thesequenceforloadtransferto
emergency source begins
automatically when normal
source voltage falls below the
preset dropout point or when
TransferTestbutton is pressed. An
under voltage condition on any
phase of the normal source is
detectedby the sensor.
When the normal
source voltage fails
or the TransferTest
buttonis pressed, the
SE relay de-ener-
gizes and relay NR
begins its timing
cycle (1 or 3 seconds,
momentary normal
sourceoutage delay). The NR relay is providedwith a time
delay on dropout to override momentary outages and
preventnuisance starting of the engine-driven generator.
If the normal source voltage returns above the sensor
dropout setting before the time delay expires, the NR
relay timing cycle isre set tozero and relay SE energizes.
If the normal source voltage does not return above the
sensordropout 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 emergency source only
when both voltage and frequency reach preset pickup
points.Usually about ten seconds elapse from dropout of
theNR relay to acceptance by the sensor.This time span
occurs because the engine-drive n generator must crank,
start, and run up to nominal pickup points. For this
reason, if the TransferTest buttonispresseditmustbe
held for 15seconds. If the emergency source is available
immediately,the sensor may accept it as soon as NRrelay
drops out.
Whenthe emergency source is accepted by the sensor,
relay ERbegins 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 so urce. For immediate transfer
press Bypass Time Delay button.
ER relay energizes, the TS coil is energized, the
transfer switching device operates, and all switch
contacts(mains, controls, auxiliaries) reverseposition.
The transfer switch is now supplying the loadfrom the
emergencysource.
The transfer switching device will remain in the
Emergencypositionuntilthe normal source is restored.
Ifthe TransferTestbutton is used, the transfer switching
devicewill remain on emergency until the retransfer to
normaldelay times out.

Retransfer to Normal

Thesequence for load retransfer to the normal source
automatically beginswhen the voltage sensor detects
restoration of the normal source. The voltage level
must rise above the preset pickup point on all phases
beforethe sensor will accept the normal source.
When the normal source is accepted bythe sensor,
relaySE begins its timing cycle (adjustable 1 sec. to 30
min., retransfer to normal delay). For immediate
retransferpress Bypass Time Delay button. SE relay is
provided with a time delay on pickup to prevent
immediate load retransfer to the normal source. The
delay insures that the normal source has stabilized
beforereconnection ofvital loads. If the normalsource
voltagefalls be low the present dro pout point befo re the
time delayexpires, the timing cycle is reset to zero. If
the emergency source fails for more tha n 4se conds
duringthetiming cycle, ER relay drops out and the load
is immediately retransferred to the normal source, if
that source is acceptable.
SErelay energizes and ER relay is dropped out. The TS
coil is energized, the transfer switching device oper-
ates, and allswitch contacts (mains, controls, auxilia-
ries)reverse position. The transfer switching device is
now supplyingt he loadfrom the normal source again.
Uponretransfer to the normal source, NR relay begins
its timing cycle(unloaded running delay [engine cool-
down] ). NR relay i s provided with a 5 minute time
delay on pickup to keep the engine running for a
cool-downperiod.
NRrelay energizes aft er the time delay and signals the
engine-drivengenerator to shut down. All circuits are
reset for any future normalsource failure.
Activation of standard control features shown in Section
5 will alter the sequence of operation and introduce
additional time delays duringtransfer operations.