RXT Transfer Switch Manual

TP-6807 1/1632 Section 3 Operation
System Configuration in SiteTecht. See Figure 3-6
and TP-6701, SiteTech Software Operation Manual.
The load management function will operate if the rating
setting is not changed, but loads will be shed at a kW
level based on the factory default rating, rather than the
rating of the reconfigured generator set.
1
1. Genset Power Rating setting
2. Genset Fuel Type setting
2
Figure 3-6 Genset Power Rating in SiteTech
3.5.2 Load Shed
Less important (larger priority number) loads are shed
when the generator is unable to support them. This
permits more important loads to continue to receive
power from the generator. The less important loads are
re-added after the generator loading has gone down
enough to support them again. The load management
board sheds less important loads before the power
quality of the generator suffers from the overload.
Loads are shed in two ways – Overload and Under
Frequency.
3.5.3 Overload Shed
Loads are shed on a time scale which is based on the
total generator overload. The loads will shed slowly
when the generator is not heavily overloaded. Loads
are shed much more quickly when the overload is
higher. The timing variation allows consistent overloads
to be removed, instantaneous excessive overloads to
be very quickly removed and normal overloads (such as
motor inrush) to remain online until the transient
overload condition is removed.
Figure 3-7 shows the overload shed timing for a 20 kW
generator set with the generator overloaded percent set
to the default setting of 85%. If the overload condition
persists, the load shed timing can be affected by load
shed acceleration. See Section 3.5.5.
The Generator Overload Percent setting is the
maximum load that the load management board will
accept without shedding. The setting is adjustable using
a laptop computer connected to the RDC2 or DC2
controller and Kohler SiteTech software. See Section
3.5.6. Set the Generator Overload Percent at least 10%
higher than the Generator Maximum Percent Capacity.
Generator
Overload
(%)
Load (%)
Load (kW) for
a20kW
Generator
Time
(seconds)
0% <85% <17 kW Never Shed
0% 85% 17 40
10% 95% 19 28
13% 98% 19.6 24
15% 100% 20 22
20% 105% 21 17
>35% >120% >24 kW 0.5
Figure 3-7 Overload Shed Timing for a 20 kW
Generator
3.5.4 Under Frequency Shed
Loads are shed on a time scale which is based on the
generator frequency droop. The loads will shed quickly
when the frequency droop is high (output frequency is
lower), and more slowly when the generator is running
close to rated frequency. The timing variation allows
large overloads to be shed very quickly, while allowing
the generator to ride through normal transients (such as
starting an AC compressor).