Generac Power Systems Nexus smart, Technical Manual

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1.1 INTRODUCTION
This manual has been prepared especially for the purpose of famil-
iarizing personnel with the design, application, installation, opera-
tion and servicing of the applicable equipment. Read the manual
carefully and comply with all instructions. This will help to prevent
accidents or damage to equipment that might otherwise be caused
by carelessness, incorrect application, or improper procedures.
Every effort has been expended to make sure that the contents
of this manual are both accurate and current. The manufacturer,
however, reserves the right to change, alter or otherwise improve
the product at any time without prior notice.
1.2 UNPACKING
Carefully unpack the transfer switch. Inspect closely for any dam-
age that might have occurred during shipment. The purchaser must
file with the carrier any claims for loss or damage incurred while in
transit.
Check that all packing material is completely removed from the
switch prior to installation.
1.3 EQUIPMENT DESCRIPTION
The automatic transfer switch is used for transferring critical
electrical loads from a UTILITY (NORMAL) power source to a
GENERATOR (STANDBY) power source.
The transfer switch prevents electrical feedback between the
UTILITY and GENERATOR sources. For that reason, electrical
codes require a transfer switch in all standby electric system
installations.
When the transfer switch is connected to the engine generator
control panel, the control panel constantly monitors the UTILITY
voltage and controls the operation of the transfer switch.
This switch is suitable for control of motors, electric discharge
lamps, tungsten filament and electric heating equipment and the
tungsten load does not exceed 30% of the switch rating.
This UL listed transfer switch is for use in optional standby sys-
tems only (NEC article 702).
The Load Shed module is designed to prevent an overload on the
generator when it is supplying the customer loads. See figure 1.1.
Up to six loads can be managed by the LSM; 2 air conditioner
loads and 4 other loads. The LSM manages the loads by “shed-
ding” the connected loads in the event of a drop in generator
frequency (overload). Loads to be “shed” are grouped in 4 priority
levels on the LSM.
• Priority 1 and 2 has connections for both one air conditioner
and one contactor. Both an air conditioner and a contactor
can be used at the same time if desired. To control an air
conditioner, no additional equipment is required. Internal relays
interrupt the thermostat 24VAC control signal to disable the air
conditioner load.
• Priority 3 and 4 have connections for one contactor only.
• Four LEDs, located on the load shed module, will indicate when
a load priority level is enabled.
• Any loads, including central air conditioners, can be controlled
via a contactor that must be purchased separately. Up to four
contactors can be controlled by the load shed module. The LSM
supplies the 120 Vac to energize each contactor coil.
• Generator overload condition is determined by generator fre-
quency. Loads are shed when the frequency is <58Hz for 3
seconds or <50Hz for ½ Second (For 60Hz).
The LSM has a Test button which forces the unit to act as if an
overload has occurred. This button operates even when the trans-
fer signal is inactive.
Figure 1.1 — Load Shed Module
0 Ground
194 +12V
23 Transfer
T1
NEUTRAL
AIR 1
AIR 2
CONTACTOR
1
CONTACTOR
2
CONTACTOR
3
CONTACTOR
4
Priority 1
Priority 2
Priority 3
Priority 4
0 Ground
194 +12V
23 Transfer
T1
NEUTRAL
AIR 1
AIR 2
CONTACTOR
1
CONTACTOR
2
CONTACTOR
3
CONTACTOR
4
Priority 1
Priority 2
Priority 3
Priority 4
Air Conditioner Connections:
Up to two A/Cs can be
controlled via low voltage
thermostat wires
Status LEDs: Shows
which loads are
currently allowed
to run.
Load Connections: Up to four loads of any type can
be controlled via these connections. (A separate
contactor module is required.)
1.4 TRANSFER SWITCH DATA
DECAL
A DATA LABEL is permanently affixed to the transfer switch enclo-
sure. Use this transfer switch only with the specific limits shown
on the DATA LABEL and on other decals and labels that may be
affixed to the switch. This will prevent damage to equipment and
property.
When requesting information or ordering parts for this equipment,
make sure to include all information from the DATA LABEL.
Record the Model and Serial numbers in the space provided below
for future reference.
MODEL #
SERIAL #
General Information