TP-6734 5/10 27Section 2 Operation
2.10 Model RRT Transfer Switch
Operation
The RDC/DC generator set/transfer switch controller
manages automatic transfer switch (ATS) functions
when connected to a Kohler r model RRT transfer switch
through the ATS interface board.
2.10.1 Source Availability
The Model RRT transfer switch supplies voltage
sensing data to the RDC/DC controller through the ATS
interface board. If the source voltage falls below the
undervoltage dropout setting, the source is considered
to have failed. See Figure 2-8.
Item Setting
Accuracy ±5%
Undervoltage Dropout 90% of Pickup
Undervoltage Pickup 90% of Nominal
Figure 2-8 Voltage Sensing Parameters
2.10.2 ATS Cont rol Sequence of
Operation
See Figure 2-9 for time delay settings.
Preferred Source Fails:
1. The load control contact opens.
2. The engine start time delay times out.
3. The generator set is signaled to start.
4. The generator starts and the emergency source
becomes available.
5. The normal-to-emergency time delay times out.
6. The transfer switch transfers to the emergency
source.
7. The load control contact time delay times out.
8. The load control contact closes.
Normal Source Returns:
1. The emergency-to-normal time delay times out.
2. The contactor transfers to the normal source.
3. The engine cooldown time delay times out.
4. The generator is signaled to stop.
2.10.3 Time Delays
Time delays are factory-set to the values shown in
Figure 2-9. An authorized distributor/dealer can adjust
time delays using a personal computer and Kohlerr
SiteTecht software.
Time delays described in this section operate only when
the controller is connected to a Kohlerr model RRT
transfer switch.
Time Delay Setting Description
Engine Start 3 seconds Time delay after utility source is lost until the engine start cycle begins.
Guards against starting the generator set because of a brief change in
the utility source.
Transfer, Normal to Emergency 3 seconds Time delay after emergency source becomes available until transfer to
emergency source.
Transfer, Emergency to Normal 2 minutes Time delay after the utility source returns until transfer back to normal.
Ensures that the the utility source is stable before transferring from the
emergency source.
Load Control 5 minutes Allows delayed connection of selected loads to the generator set.
Prevents simultaneous starting of large motors after transfer to the
emergency source. Recommended for delayed starting of air
conditioners.
Engine Cooldown 5 minutes Runs the engine with no load after transfer from the generator set.
Engine stops before the time delay expires if the temperature drops
below the cooled-down temperature level, or if the temperature rises
during the cooldown cycle.
Figure 2-9 Time Delays
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