t> or check for previous versions at the Internet Archive. Yahoo! is not affiliated with the authors of this page or responsible for its content.
Transfer switch LT III open or delayed transition, automatic ©2007|Cummins Power Generation Inc.|All rights reserved|Specifications subject to change without notice|Cummins Power Generation
and Cummins are registered trademarks of Cummins Inc. Our energy working for you. is a trademark of Cummins Power Generation.
S-1272k (1/08)



Transfer switch LT III
open or delayed
transition, automatic



Description
The LT III automatic transfer switch combines reliability
and flexibility in a small, economical package for
transferring loads between a utility and a generator set.
Available in 3-pole with solid neutral models.
When utility power fails or is unsatisfactory, the control
starts the generator set and transfers the load from the
utility to the generator set. Once utility power returns, the
switch automatically transfers the load back to the utility.
All transfer switches are thoroughly inspected both
mechanically and electrically under simulated operating
conditions prior to shipment.

All switches are UL 1008 Listed with UL Type
Rated cabinets and UL Listed CU-AL
terminals.

All switches are certified to CSA 282
Emergency Electrical Power Supply for
Buildings, up to 600 VAC.

All switches comply with NEMA ICS 10.

This transfer switch is designed and
manufactured in facilities certified to ISO9001.


Features
Transfer action - Independent break-before-make
action positively prevents dangerous source-to-source
connections.
Positive interlocking - Mechanical and electrical
contactor interlocking prevents source-to-source
connection through power or control wiring.
Auxiliary contacts - One Form A and one Form B
contact (for each source) are provided for customer use.
Rated at 10 A continuous and 600 VAC maximum.
Electronic control - Reliable digital electronic control
system with surge voltage isolation, under-voltage
monitoring on each power source, four standard
normal/emergency source time delays, and diagnostic
LEDs. Two control packages are available.
Easy service/access - The unit is equipped for ease of
service and accessibility. These features include
convenient plug connections, door mounted controls,
ample access space and compatible terminal markings
Product lines, accessories and services -
Cummins Power Generation offers a wide range of
accessories and services to suit your requirements.
Warranty and service - Backed by a comprehensive
warranty and worldwide distributor network.











30 - 260 Amp
Our energy working for you.

www.cumminspower.com
©2007|Cummins Power Generation Inc.|All rights reserved|Specifications subject to change without notice|Cummins Power Generation
and Cummins are registered trademarks of Cummins Inc. PowerCommand and Our energy working for you. are trademarks of Cummins
Power Generation. Other company, product, or service names may be trademarks or service marks of others.
S-1272k (1/08)


Control packages
A choice of two control packages allows flexibility for determining the most suitable level of control for a given
application:
Package A control (C021)
Package B control (C022)
Time delay start: 3 sec (fixed)
Time delay start: 0 to 15 sec (adjustable)
Transfer time delay: 3 sec (fixed)
Transfer time delay: 2 to 120 sec (adjustable)
Retransfer time delay: 5 min (fixed)
Retransfer time delay: 6 sec to 30 min (adjustable)
Stop delay: 5 min (fixed)
Stop delay: 2 sec to 10 min (adjustable)
Undervoltage sensing:
Single phase on normal and emergency
- Pickup 85% of nominal
- Dropout 75% of pickup
Remote test terminals
Undervoltage sensing:
Three phase differential sensing on normal, single phase
on emergency
- Pickup: 85 to 100% of nominal (adjustable)
- Dropout: 75 to 98% of pickup (adjustable)

LED status indicators: for source available and switch
position on normal and emergency
Remote test terminals
Momentary test switch
Retransfer bypass switch
7-day exerciser clock: with or without load
Auto/manual retransfer
Time-delay functions
Engine start: Prevents nuisance genset starts in the event of momentary power system variation or loss.
Normal to emergency transfer: Allows genset to stabilize before application of load. Prevents power interruption if
normal source variation or loss is momentary.
Emergency to normal retransfer: Allows the utility to stabilize before retransfer of the load. Prevents needless
power interruption if return of normal source is momentary.
Engine stop: Maintains availability of generator set for immediate reconnection in the event that the normal source fails
shortly after retransfer. Allows gradual generator set cool down by running unloaded.
Delayed (programmed) transition: Controls the speed of operation of the transfer switch power contacts to allow
load generated voltages from inductive devices to decay prior to connecting a live source. Adjustable 0-10 seconds,
default 0 seconds.
Control options
Delayed (programmed) transition (027 or J028)
Available on switches rated from 100 to 260 Amps, this option helps prevent fuse blowing and circuit breaker tripping
when transferring inductive loads such as large motors and transformers. Extends transfer time of the transfer switch
mechanism to allow load induced voltages to decay prior to connection to the oncoming source.
Battery chargers (K001 or KB59 or KB60)
2A, 15A/12V, or 12A/24V battery chargers are available as factory-installed options to reduce field wiring expense.
Three-wire start module (M002)
This option modifies the standard LT III two-wire start circuit to a three-wire start system required by some generator
sets.
Manual override switch (N014)
This key selector switch provides a manual transfer capability. The manual override switch uses the power from the
source to which the switch will transfer, in order to bypass the control and transfer load.

* Note: Some options may not be available on all models - consult factory for availability.







Our energy working for you.

www.cumminspower.com
©2007|Cummins Power Generation Inc.|All rights reserved|Specifications subject to change without notice|Cummins Power Generation
and Cummins are registered trademarks of Cummins Inc. PowerCommand and Our energy working for you. are trademarks of Cummins
Power Generation. Other company, product, or service names may be trademarks or service marks of others.
S-1272k (1/08)


UL withstand and closing ratings
The LT III transfer switch must be protected by an overcurrent device, of the type and size specified, which will protect
the switch when used on a circuit capable of delivering not more than the symmetrical RMS amperes listed in the table.
Fuse protection


Transfer
switch ampere
WCR @ volts max. with
current limiting fuses
Drawing reference
30 A
100,000 A (600 VAC)
60 A, Class J or T
60 A
100,000 A (600 VAC)
100 A, Class J or T
100 A
100,000 A (600 VAC)
225 A, Class J or T
150 A
100,000 A (600 VAC)
250 A, Class J or T
200 A
100,000 A (600 VAC)
400 A, Class J or T
260 A
100,000 A (600 VAC)
450 A, Class J or T

Enclosures
The transfer switch and control are mounted in a key-locking enclosure. Wire bend space complies with 2008 NEC.
Dimensions - transfer switch in UL type 1 enclosure
Depth
Height Width Door closed
Door open
Weight
Amp rating
in mm
in mm
in mm
in
mm lb
kg Outline
drawing
30
29.0
735
18.0 455
11.3 285 28.1 715 120
55
310-0924
60
29.0
735
18.0 455
11.3 285 28.1 715 120
55
310-0924
100
29.0
735
18.0 455
11.3 285 28.1 715 120
55
310-0924
150
29.0
735
18.0 455
11.3 285 28.1 715 120
55
310-0924
200
34.0
865
21.5 545
11.3 285 31.6 805 155
70
310-0925
260
34.0
865
21.5 545
11.3 285 31.6 805 155
70
310-0925
Note: Add 1.75 in (44.45 mm) to 'Door closed' dimension for handle clearance.

Dimensions - transfer switch in UL type 3R enclosure
Depth
Height Width Door closed
Door open
Weight
Amp rating
in
mm
in
mm
in
mm
in
mm
lb
kg
Outline drawing
30 33.8
859
26.25
667
13.75
350
36.25
921
125
57
0310-0453
60 33.8
859
26.25
667
13.75
350
36.25
921
125
57
0310-0453
100 33.8
859
26.25
667
13.75
350
36.25
921
125
57
0310-0453
150 33.8
859
26.25
667
13.75
350
36.25
921
125
57
0310-0453
200 33.8
859
26.25
667
13.75
350
36.25
921
125
57
0310-0453
260 33.8
859
26.25
667
13.75
350
36.25
921
125
57
0310-0453
Transfer switch lug capacities
Amp rating
Size
30
10 to 3 AWG CU
60
10 to 2 AWG CU
100
14 AWG to 2/0 CU/AL
150
6 AWG to 3/0 CU/AL
200
6 AWG to 300 MCM CU/AL
260
6 AWG to 400 MCM CU/AL










Our energy working for you.

www.cumminspower.com
©2007|Cummins Power Generation Inc.|All rights reserved|Specifications subject to change without notice|Cummins Power Generation
and Cummins are registered trademarks of Cummins Inc. PowerCommand and Our energy working for you. are trademarks of Cummins
Power Generation. Other company, product, or service names may be trademarks or serv