THOMSON TS 880 User manual

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TS 880
AUTOMATIC TRANSFER SWITCHES
INSTALLATION, OPERATING &
SERVICE MANUAL
PM064 REV 8 10/01/25

TS 880 TRANSFER SWITCH
PM064 REV 8 10/01/25 Thomson Technology
TABLE OF CONTENTS
1. PRODUCT REVISION HISTORY 1
2. EQUIPMENT STORAGE 1
2.1. ENVIRONMENTAL CONDITIONS 1
2.1.1. EQUIPMENT STORAGE 2
2.1.2. EQUIPMENT OPERATING 2
3. NOTES TO INSTALLER 2
3.1. UPSTREAM CIRCUIT PROTECTIVE DEVICES/ELECTRICAL CONNECTIONS 2
3.2. TRANSFER SWITCHES WITH INTEGRAL OVER CURRENT PROTECTION 3
3.3. TRANSFER SWITCHES WITH MULTI-TAP VOLTAGE CAPABILITY 3
3.4. SYSTEM PHASING-HIGH LEG DELTA SYSTEMS 4
3.5. REMOTE START CONTACT FIELD WIRING5
3.6. DIELECTRIC TESTING 6
3.7. MOUNTING OF ENCLOSED TRANSFER SWITCHES 6
4. GENERAL DESCRIPTION 9
4.1. PRODUCT MODEL CODE 10
4.2. TYPICAL COMMISSIONING PROCEDURES 11
5. GENERAL THEORY OF OPERATION 11
5.1. STANDARD AUTOMATIC TRANSFER SWITCH 11
5.1.1. NORMAL SEQUENCE OF OPERATION -OPEN TRANSITION 11
5.1.2. NORMAL SEQUENCE OF OPERATION -CLOSED TRANSITION 12
5.2. SERVICE ENTRANCE AUTOMATIC TRANSFER SWITCH 16
5.2.1. NORMAL OPERATION 16
5.2.2. OVER CURRENT TRIP 17
5.2.3. SERVICE DISCONNECT PROCEDURE 17
5.2.4. ADDITIONAL PROCEDURES 19
5.3. TEST MODES 21

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6. OVER CURRENT PROTECTION 21
6.1. STANDARD TS 880 AUTOMATIC TRANSFER SWITCH 22
6.2.OPTIONAL TS 880 AUTOMATIC TRANSFER SWITCH WITH INTEGRAL OVER
CURRENT PROTECTION 22
7. SERVICING TRANSFER SWITCH MECHANISMS 23
7.1. SERVICING –100A-250A S STYLE MOLDED CASE SWITCH TYPE TRANSFER
MECHANISMS 23
7.1.1. GENERAL DESCRIPTION 23
7.1.2. EQUIPMENT INSPECTION 24
7.1.3. MANUAL OPERATION 24
7.1.4. RECOMMENDED MAINTENANCE 25
7.2. SERVICING–400A-1200A MOLDED CASE TYPE TRANSFER MECHANISMS 26
7.2.1. GENERAL DESCRIPTION 26
7.2.2. EQUIPMENT INSPECTION 27
7.2.3. MANUAL OPERATION 28
7.2.4. RECOMMENDED MAINTENANCE 28
7.3. SERVICING –800A –4000A INSULATED CASE TYPE TRANSFER MECHANISMS
29
7.3.1. GENERAL DESCRIPTION 30
7.3.2. EQUIPMENT INSPECTION 30
7.3.3. MANUAL OPERATION 31
7.3.4. RECOMMENDED MAINTENANCE 32
8. FRONT VIEW (TYPICAL) 3 POLE 100A-250A S STYLE TRANSFER MECHANISM
33
9. FRONT VIEW (TYPICAL) 3 POLE 400A-1200A T STYLE TRANSFER MECHANISM
34
10. FRONT VIEW (TYPICAL) 3 POLE 800A-4000A INSULATED CASE TYPE
TRANSFER MECHANISM 35
11. CONNECTION CONFIGURATION OPTIONS 36
12. CABLE TERMINAL INFORMATION 37
13. REQUIREMENTS FOR UPSTREAM CIRCUIT PROTECTIVE DEVICES 38

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PM064 REV 8 10/01/25 Thomson Technology
13.1. WITHSTAND CURRENT RATINGS (ALL MODELS WITHOUT INTEGRAL
OVERCURRENT PROTECTION OPTION) 38
13.2. INTERRUPTING CAPACITY CURRENT RATINGS (ALL MODELS WITH INTEGRAL
OVERCURRENT PROTECTION OPTION) 39
14. GROUND FAULT SITE TEST REQUIREMENTS 39
14.1. PERFORMANCE TEST 40
15. TROUBLESHOOTING (100A-1200A MOLDED CASE SWITCH TYPE ATS) 40
16. TROUBLESHOOTING (800A-4000A INSULATED CASE SWITCH TYPE ATS) 43
17. POWER SWITCHING DEVICE TROUBLESHOOTING (800A-4000A INSULATED
CASE SWITCH TYPE ATS)45
18. POWER SWITCHING DEVICE DRAWING 47
19. DRAWOUT CHASSIS ENGINEERING DRAWING 48
20. ELECTRICAL DIAGRAMS 49
21. REPLACEMENT PARTS 52
22. PRODUCT RETURN POLICY53
23. NOTES 54
24. PERFORMANCE TEST FORM55

TS 880 TRANSFER SWITCH
PM064 REV8 10/01/25 1Thomson Technology
1. PRODUCT REVISION HISTORY
The following information provides an historical summary of changes made to this product since
the original release.
Operating & Service Manual Version
Rev 0 04/11/15 Original release.
Rev1 04/12/21 Additional information for Closed Transition Operation
Rev 2 05/03/08 Changes to incorporate reversing style ATS motor for 100-250A
transfer switches
Rev 3 05/05/11 Changes to Section 5 & Section 21.
Rev 4 06/05/08 Changes to Section 13.
Rev 5 07/02/01 Changes to Section 13.
Rev 6 07/02/27 Changes to Section 12, Cable Terminal Information
Rev 7 08/03/05 Changes to Incorporate new S-Style mechanism (100A, 150A,
200A, 250A)
Rev 8 10/01/25 Changes to Incorporate Seismic Certification and Mounting
Requirements
Contact Thomson Technology, to obtain applicable instruction manuals or if in doubt about any
matter relating to installation, operation or maintenance. Soft copy of the most current version is
available at www.thomsontechnology.com.
NOTE: All information contained in this manual is for reference only and is subject
to change without notice.
2. EQUIPMENT STORAGE
The following procedures are required for correct storage of the transfer switch prior to installation.
2.1. ENVIRONMENTAL CONDITIONS
CAUTION!!!
Failure to store and operate equipment under the specified environmental conditions may
cause equipment damage and void warranty.

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2.1.1. EQUIPMENT STORAGE
The transfer switch shall be stored in an environment with a temperature range not
exceeding -4° to +158° Fahrenheit (-20°to +70° Celsius) and a humidity range not
exceeding 5%-95% non-condensing. Before storing, unpack sufficiently to check for
concealed damage. If concealed damage is found, notify the ATS supplier and the
Carrier immediately. Repack with the original, or equivalent packing materials.
Protect from physical damage. Do not stack. Store indoors in a clean, dry, well
ventilated area free of corrosive agents including fumes, salt and concrete/cement
dust. Apply heat as necessary to prevent condensation.
2.1.2. EQUIPMENT OPERATING
The transfer switch shall be operated in an environment with a temperature range
not exceeding +5° to +122° Fahrenheit (-15°to +50°Celsius) and a humidity range
not exceeding 5%-95% non-condensing.
3. NOTES TO INSTALLER
DANGER!!!!
Arc Flash and Shock Hazard. Will cause severe injury or death.
Do not open equipment until ALL power sources are disconnected
This equipment must be installed and serviced only by qualified electrical
personnel utilizing safe work practices and appropriate Personal Protective
Equipment (PPE). Failure to do so may cause personal injury or death
3.1. UPSTREAM CIRCUIT PROTECTIVE DEVICES/ELECTRICAL
CONNECTIONS
To ensure satisfactory installation of this equipment be sure to observe "Cable Terminal
Information” regarding power cable connection tightness and "Requirements for Upstream
Circuit Protective Devices" located in this manual.
All mechanical and electrical connections must be checked for tightness prior to placing this
equipment in service to ensure proper operation and to validate applicable warranty
coverage.

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3.2. TRANSFER SWITCHES WITH INTEGRAL OVER CURRENT PROTECTION
For models of transfer switch with integral over current protection, the over current
protection must be set prior to operation. The equipment will be shipped from the factory
with a long-time current setting of 100% (of the equipment rating) and maximum short-
time/instantaneous current and time delay settings.
WARNING!
Do Not Energize this equipment until
device settings have been verified to
ensure proper system protection &
coordination. Failure to do so may
result in equipment failure.
Refer to Section 5.2.2 of this manual for additional information on operation of the Transfer
switch following an over current trip condition.
Refer to information supplied with the transfer switch documentation package for
adjustment procedures on the power switching units over current protection trip unit.
Contact the factory if any additional information is required.
3.3. TRANSFER SWITCHES WITH MULTI-TAP VOLTAGE CAPABILITY
If the transfer switch has programmable multi-tap voltage capability (refer to engineered
drawings), confirm the transfer switch has been configured for the correct system voltage
prior to installation.
WARNING!
Failure to confirm and match transfer
switch voltage with the system voltage
could cause serious equipment damage.
The voltage selections and connections are shown on the engineered drawings attached to
each transfer switch. The factory default settings will be indicated on the calibration label
attached on the inside of the enclosure door (supplied loose on open style models). A
blank label is included to record the applicable settings if the configuration is changed from
the factory default settings.
To change the transfer switch configuration the following must be accomplished:

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qChange voltage taps of the potential transformers (i.e. PT’s) to system voltage (refer to
drawings)
qOnce the voltage taps have been set to correct operating voltage, the “control circuit
isolation plug” on the mechanism, may be reconnected, prior to voltage energization.
qChange TSC 800 programming (refer to the TSC 800 instruction manual (PM049). The
following settings will require reprogramming:
ØSystem voltage
ØUtility under voltage pickup (typically 90% of system voltage)
ØUtility under voltage dropout (typically 80% of system voltage)
ØUtility over voltage pickup (typically 110% of system voltage)
ØUtility over voltage dropout (typically 105% of system voltage)
ØGenerator under voltage pickup (typically 90% of system voltage)
ØGenerator under voltage dropout (typically 80% of system voltage)
ØGenerator over voltage pickup (typically110% of system voltage)
ØGenerator over voltage dropout (typically 105% of system voltage)
Record any changed setting on the TSC 800 Programming Data Sheets for future
reference.
qComplete the blank calibration label and attach to the inside of the transfer switch
enclosure door.
3.4. SYSTEM PHASING-HIGH LEG DELTA SYSTEMS
For systems using high leg delta 240V 3 phase 4 wire systems, connection of supply
conductors must have the correct phasing as shown below.
WARNING!
Failure to match correct system
phasing will result in serious damage
to the TSC 800 controller.

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208V
B
(Orange)
(High Leg)
C
(Yellow)
A
(Red)
N
(White)
PH A
(UA)
Automatic Transfer
Switch (Utility Supply)
PH B
(UB) PH C (UC) Neural (N)
120V 120V
240V 240V
CAUTION!!!
All installation and/or service work performed must be done by qualified
personnel only. Failure to do so may cause personal injury or death.
Where transfer switches are supplied without power isolation transformers (PT1 & PT2) for
ATS control logic it is essential that the orientation of phase conductors of the supply
source be arranged such that the phase of highest potential with respect to ground is not
connected to the power supply inputs to the controller (A Phase for both supplies). Failure
to do so will result in equipment damage.
Per NEC Article 384-3 (f) “The B phase shall be that phase having the higher voltage to
ground on a 3-phase, 4-wire delta connected systems.”
3.5. REMOTE START CONTACT FIELD WIRING
As a minimum, the remote engine start control field wiring shall conform to the local
regulatory authority on electrical installations. Field wiring of a remote start contact from a

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transfer switch to a control panel should conform to the following guidelines to avoid
possible controller malfunction and/or damage.
3.5.1. Minimum #14 AWG (2.5mm2) wire size shall be used for distances up to
100ft (30m)1). For distances exceeding 100 ft. (30m) consult Thomson Technology
3.5.2. Remote start contact wires should be run in a separate conduit.
3.5.3. Avoid wiring near AC power cables to prevent pick-up of induced voltages.
3.5.4. An interposing relay may be required if field-wiring distance is excessively
long (i.e. greater than 100 feet (30m)) and/or if a remote contact has a resistance of
greater than 5.0 ohms.
3.5.5. The remote start contact must be voltage free (i.e. dry contact). The use of a
“powered” contact will damage the transfer controller.
3.6. DIELECTRIC TESTING
Do not perform any high voltage dielectric testing on the transfer switch with the TSC 800
controller connected into the circuit as serious damage will occur to the controller. All AC
control fuses and control circuit isolation plugs connected to the TSC 800 must be removed
if high voltage dielectric testing is performed on the transfer switch.
3.7. MOUNTING OF ENCLOSED TRANSFER SWITCHES
Model TS840, TS870 and TS880 Automatic Transfer Switches and Automatic
Transfer and Bypass Isolation Switches in "standard" enclosures are seismic
certified under AC156 building code for non-structural components.
"Standard" enclosures are all transfer switch enclosures Thomson Technology offers
in NEMA 1, NEMA 2, NEMA 3R and NEMA 4X for the above listed product. If a
customer requests a custom enclosure it would not be covered under the generic
certificate; if certification were a requirement Consult factory before ordering.
The Automatic Transfer Switches are qualified to the highest known level in North
America; based on site class D. Specifically this is a spectral acceleration of 342%.
The transfer switch must be installed per the anchoring details provided for seismic
qualification. The equipment can be mounted in alternate means and still qualify if a
qualified Civil Engineer designs the alternate method of anchoring.

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Anchoring Notes:
1. Anchoring must be designed according to IBC 2006 or latest version.
2. The anchoring details shown are recommended according to the seismic
certification; design Engineer may use alternate anchors within the scope of IBC.
3. Wall anchors in concrete; use a typical concrete anchor as necessary.
4. Expansion anchors as shown. To be installed according to manufacturer's
recommendation.
5. The 800-1200A NEMA 3R ATS enclosure may be floor/wall mounted or it may be
free standing (floor mounted only); If free standing it must be a minimum of 12"
(305mm) away from pipes, conduits or other obstructions to allow for sway during a
seismic event.
.

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4. GENERAL DESCRIPTION
Thomson Technology TS 880 series of Automatic Transfer Switches employ two mechanically
interlocked enclosed contact power switching units and a microprocessor based controller to
automatically transfer system load to a generator supply in the event of a utility supply failure.
System load is then automatically re-transferred back to the utility supply following restoration of
the utility power source to within normal operating limits.
The standard TS 880 series Automatic Transfer Switch is rated for 100% system load and requires
upstream over current protection. The TS 880 Automatic Transfer Switch may be supplied with
optional integral over current protection within the enclosed contact power switching units for
applications such as Service Entrance Rated equipment. Refer to Section 6of this manual for
detailed information on over current protection.
The TS 880 series transfer switches employs a TSC 800 microprocessor based controller which
provides all necessary control functions for fully automatic operation. The TSC 800 controller is
mounted on the door of the transfer switch enclosure and operating status is shown via LED lights
and LCD display module. For further information on the TSC 800 Transfer Controller, refer to
instruction manual PM049.
100A-1200A rated molded case power switching devices used for the utility and generator sources
are operated by an electrically driven motor mechanism in the transfer switch. 800A-4000A rated
insulated case power switching devices used for the utility and generator sources are operated by
internal drive motor operators. The transfer switch mechanism utilizes the power from the source to
which the electrical load is being transferred. The mechanism provides a positive mechanical
interlock to prevent both power switching units from being closed at the same time, which allows an
interrupted open transition “break-before-make” transfer sequence. For transfer switches supplied
with Closed Transition transfer option, the mechanical interlock is removed thereby allowing a
“make-before break” transfer sequence when both sources of power are available. The TSC 800
transfer controller provides a standard neutral position delay timer for open transition transfer
sequences to allow adequate voltage decay during transfer operation to prevent out of phase
transfers.
Note: For the purpose of this manual, the following standard nomenclature is utilized:
qUtility: to indicate the source of primary power
qGenerator: to indicate the source of standby power
qPower switching device: to indicate the automatic transfer switch power switching device

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4.1. PRODUCT MODEL CODE
The type of TS 880 series transfer switch supplied is identified by way of a 21 digit product
code which appears on the equipment rating plate (MODEL) on the door of the transfer
switch, and on the transfer switch drawings. The model code structure and definitions are
as follows:
1 2 4 6 7 8 9 10 11 12 13 14 15 17 18 19 20 21
TS8
1-3. SERIES 15 . VOLTAGE (CONTINUED) 18. UTILITY SWITCHING DEVICE (CONT'D)
TS - TRANSFER SWITCH 3
f
4 WIRE (GROUNDED NEUTRAL) V - INSULATED CASE DRAW-OUT SWITCH
E - 120/208
1
C/W ELECTRONIC TRIP (800 - 4000A)
4 & 5. MODEL F - 127/220 W - INSULATED CASE, DRAW-OUT SWITCH
88 - 880 SWITCH
G - 120240
1
(DELTA)
C/W ELECTRONIC & GF TRIP (800-4000A)
H - 220/380
2
X - SPECIAL
6. POLES J - 240/416
2 - 2 POLE K - 254/440 19. GENERATOR SWITCHING DEVICE
3 - 3 POLE M - 277/480
1
K - MOLDED CASE SWITCH (100 - 1200 A)
4 - 4 POLE
N - 347/600
1
M - MOLDED CASE SWITCH C/W THER-MAG
3
f
3 WIRE TRIP (100-200A)
7. CONFIGURATION TYPE P - 208
N - MOLDED CASE SWITCH C/W ELECTRONIC
A - ATS Q - 220 TRIP (250-1200A)
B - BYPASS/ISOLATION ATS R - 240
P - MOLDED CASE SWITCH C/W ELECTRONIC
X - SPECIAL
S - 380
2
& GF TRIP (250-1200A)
U - 416 Q - INSULATED CASE, FIX MOUNT SWITCH
8 - 11. AMPERAGE V - 480 (800A-4000A)
0100 W - 600 R - INSULATED CASE, FIX-MOUNT SWITCH
0150 X - SPECIAL C/W ELECTRONIC TRIP (800-4000A)
0200 T - INSULATED CASE, FIX-MOUNT SWITCH
0250 16. CONTROLLER C/W ELECTRONIC & GF TRIP (800-4000A)
0400 2 - TSC800 U - INSULATED CASE DRAW-OUT SWITCH
0600 7 - NONE (MANUAL) (800 - 4000A)
0800 V - INSULATED CASE DRAW-OUT SWITCH
1000 17. ENCLOSURE TYPE C/W ELECTRONIC TRIP (800 - 4000A)
1200 A - NEMA1, ASA #61 GREY W - INSULATED CASE, DRAW-OUT SWITCH
1600 B - NEMA2, ASA #61 GREY C/W ELECTRONIC & GF TRIP (800-4000A)
2000 C - NEMA12, ASA #61 GREY X - SPECIAL
2500 D - NEMA3R SD, ASA #61 GREY
3000
E - NEMA3R/4 DD, ASA #61 GREY
3
20. POWER CONNECTIONS
4000 F - NEMA3RX/4X DD A - STANDARD
(306 STAINLESS STEEL)
3
X - SPECIAL
12. APPLICATION G - NONE (OPEN STYLE)
A - STANDARD H - NEMA 3RXDD (ALUMINUM)
21. ATS CONNECTION CONFIGURATION
5
B - SERVICE ENTRANCE
ASA#61 GREY
4
A - STANDARD
C - DUAL SOURCE X - SPECIAL B - ALTERNATE B (400-1200A)
X - SPECIAL C - ALTERNATE C (400-1200A)
18. UTILITY SWITCHING DEVICE D - ALTERNATE D (400-1200A)
13. OPERATION TYPE K - MOLDED CASE SWITCH (100 - 1200 A) E - ALTERNATE E (800-4000A)
1 - OPEN TRANSITION M - MOLDED CASE SWITCH C/W THER-MAG F - ALTERNATE F (800-4000A)
2 - MANUAL ELEC. OP. TRIP (100-200A) G - ALTERNATE G (800-4000A)
3 - CLOSED TRANSITION (MOMENTARY) N - MOLDED CASE SWITCH C/W ELECTRONIC X - SPECIAL
4 - CLOSED TRANSITION (SOFT LOAD) TRIP (250-1200A)
X - SPECIAL
P - MOLDED CASE SWITCH C/W ELECTRONIC
NOTES
& GF TRIP (250-1200A)
1
MULTI-VOLTAGE CAPABLE.
14 . SAFETY STANDARD Q - INSULATED CASE, FIX MOUNT SWITCH
2
FOR 50 Hz APPLICATION.
A - UL 1008 (800A-4000A)
3
STANDARD ENCLOSURE RATING IS N3R
B - CSA C22.2 NO 178 R - INSULATED CASE, FIX-MOUNT SWITCH AT 800A AND ABOVE AND N4 AT 600A
X - NOT APPLICABLE C/W ELECTRONIC TRIP (800-4000A) AND BELOW.
T - INSULATED CASE, FIX-MOUNT SWITCH
4
ONLY AVAILABLE 800A AND ABOVE.
15 . VOLTAGE C/W ELECTRONIC & GF TRIP (800-4000A)
5
FOR BYPASS SWITCH APPLICATIONS
1
f
3 WIRE U - INSULATED CASE DRAW-OUT SWITCH REFER TO FACTORY
D - 120/240
(800 - 4000A)
5 16
8

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4.2. TYPICAL COMMISSIONING PROCEDURES
CAUTION!!!
Commissioning procedures must be performed by qualified
personnel only. Ensure the Automatic Transfer Switch
(ATS) Isolation Plug is disconnected prior to energizing the
supply sources. Manually place the transfer switch
mechanism in the neutral position prior to applying power.
Failure to do so may result in equipment failure or personal
injury.
Note: The TYPICAL AUTOMATIC TRANSFER SWITCH COMMISSIONING
PROCEDURES MODEL SERIES TS 880 (attached as “APPENDIX A”) is provided for
general information only pertaining to typical site installations and applications. Contact
Thomson Technology for further information as may be required.
5. GENERAL THEORY OF OPERATION
5.1. STANDARD AUTOMATIC TRANSFER SWITCH
5.1.1. NORMAL SEQUENCE OF OPERATION -OPEN TRANSITION
TYPE TRANSFER SWITCHES
When utility supply voltage drops below a preset nominal value (adjustable from
70% to 99% of nominal) on any phase, an engine start delay circuit is initiated and
the transfer to utility supply signal will be removed (i.e. contact opening). Following
expiry of the engine start delay period (adjustable from 0 to 60 sec.) an engine start
signal (contact closure) will be given.
Once the engine starts, the transfer switch controller will monitor the generator
voltage and frequency. Once the generator voltage and frequency rises above
preset values (adjustable from 70% to 99% of nominal), the engine warmup timer
will be initiated. Once the warmup timer expires (adjustable from 0 to 60 min.), the
transfer to Generator Supply signal (contact closure) will be given to the transfer
switch mechanism. The load will then transfer from the utility supply to the generator
supply via the motor operated mechanism. Note: A neutral delay timer circuit will
delay the transfer sequence in the neutral position (i.e. both power-switching devices
open) until the selected time expires (adjustable from 0 to 60 sec.).

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The generator will continue to supply the load until the utility supply has returned.
The retransfer sequence is completed as follows: when the utility supply voltage is
restored to above the preset values (adjustable from 70% to 99% of nominal) on all
phases, a utility return delay circuit will be initiated. Following expiry of the Utility
Return Timer (adjustable from 0 to 60 min.), the Transfer to Generator Supply signal
will be removed (contact opening), and then the Transfer to Utility Supply signal
(contact closure) will be given to the transfer switch mechanism. The load will then
retransfer the load from the generator supply back to the utility supply. Note: A
neutral delay timer circuit will delay the transfer sequence in the neutral position (i.e.
both power switching devices open) until the neutral delay time period expires
(adjustable from 0 to 60 seconds).
An engine cooldown timer circuit will be initiated once the load is transferred from
the generator supply. Following expiry of the cooldown delay period (adjustable
from 0 to 30 minutes), the engine start signal will be removed (contact opening) to
initiate stopping of the generator set.
5.1.2. NORMAL SEQUENCE OF OPERATION -CLOSED TRANSITION
TYPE TRANSFER SWITCH OPTION
For transfer switches equipped with the Closed Transition transfer option, the ATS is
configured to operate as follows:
Under normal closed transition operating conditions, the transfer switch operates
automatically during a failure and restoration of utility power and does not require
operator intervention.
When utility supply voltage drops below a preset nominal value (70 -99% of rated
adjustable) on any phase, an engine start delay circuit will be initiated and the
transfer to utility supply signal will be removed (i.e. contact opening). Following
expiry of the engine start delay period (0 -60 sec. adjustable) an engine start signal
(contact closure) will be given.
Once the engine starts, the transfer switch controller will monitor the generators
voltage and frequency levels. Once the generator voltage and frequency rises
above preset values (70 –99% nominal adjustable) a warmup time delay will be
initiated. Once the warmup timer (0-60 Min adjustable) expires, the transfer to

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generator supply signal (contact closure) will be given to the transfer switch
mechanism. The load will then transfer from the utility supply (i.e. opening the utility
power switching device) to the generator supply (closing the generator power
switching device) via motor driven mechanism to complete a “break-before-make”
open transition transfer sequence.
The generator will continue to supply the load until the utility supply has returned
and the retransfer sequence is completed as follows: When the utility supply voltage
is restored to above the present values (70 -99% of rated adjustable) on all phases,
a re-transfer sequence will be initiated once the Utility Return timer expires. The
utility will close its power switching device when it is in synchronism with the
generator supply via external logic device. The generator power switching device will
immediately trip open approximately 50-100 milliseconds after the utility power
switching device closes to complete the “make-before-break” re-transfer sequence.
An engine cooldown timer circuit will be initiated once the load is transferred from
the generator supply. Following expiry of the cooldown delay period (0 -60 min.
adjustable) the engine start signal will be removed (contact opening) to initiate
stopping of the generator set.

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Closed Transition Operation Sequence Diagram
(Normal Power Failure & Return Sequence)
The following operating sequences and time delays are associated with closed
transition type transfer switches which momentarily parallel two sources of supply for
less than 100 milliseconds. For closed transition type transfer switches, which utilize
extended parallel operation for soft-loading operating sequences, refer to separate
instruction manual.
1. Transfer Control Switch (Open/Closed Transition): A two position selector switch
is provided on the front of the transfer switch for operator section of desired
operation. The 2 positions are as follows:
§OPEN TRANSITION: The transfer switch will operate in a “break-
before-make” open transition sequence during load transfers. A
programmed neutral delay period will occur during the transfer
sequence to ensure voltage decays on the load bus before load is
re-applied. The two sources will not be paralleled at any time
during operation in this mode.
§CLOSED TRANSITION: When both sources of supply are
available, the transfer switch will operate in a “make-before-break”
closed transition sequence during load transfers. Note: If only
one source of supply is available during an initiated transfer
sequence, the control system will automatically revert to an open
transition transfer sequence.
2. Synchronizing Protection: To ensure both sources are in synchronism prior to
initiating a closed transition transfer sequence, a sync check relay is used
(Device 25). The synch check relay is door mounted and proved a LED light
Synchroscope to monitor phase angle of the two sources. The synch check relay
will block a closed transition transfer sequence until both sources phase angle
and voltages are within programmed limits. The synch check relay settings are
field programmable (+-5 to 20 Deg Phase Angle (rw) and 1-10% voltage
difference (rU) and they must be set at time of final equipment commissioning
for desired values. The factory settings are as follows: