Section 1 - General Information; Generator; Transfer Switch; Automatic System Operation - Generac Power Systems Guardian 004988-1 Owner's Manual

1.1

GENERATOR

This equipment is a liquid-cooled, engine-driven gen-
erator set. The generator is designed to supply elec-
trical power that operates critical electrical loads
during utility power failure. The unit has been facto-
ry-installed in a weather resistant, all metal enclosure
and is intended for outdoor installation only. Use this
generator as a source of electrical power for the oper-
ation of 120 and/or 240VAC, single-phase loads.
If this generator is used to power electrical load
!
circuits normally powered by a UTILITY power
source, it is required by code to install a trans-
fer switch. The transfer switch must effectively
isolate the electric system from the utility distri-
bution system when the generator is operating
(NEC 701). Failure to isolate an electrical system
by such means results in damage to the genera-
tor and may also result in injury or even death
to utility power workers due to backfeed of
electrical energy.
1.2

TRANSFER SWITCH

This generator system may include a matched auto-
matic transfer switch which is intended to be used in
conjunction with the Generac generator. It is supplied
in either a NEMA 1 enclosure or a NEMA 3R enclo-
sure. The NEMA 1 enclosure is intended for indoor
use only. The NEMA 3R enclosure is weather proof
and can be used indoors or outdoors. Follow these
rules:
• Install the transfer switch on a firm, sturdy sup-
porting structure.
• To prevent switch distortion, level the switch if nec-
essary. This can be done by placing washers
between the switch enclosure and the mounting
surface.
• Never install the switch where water or any corro-
sive substance might drip onto the enclosure.
• Protect the switch at all times against excessive
moisture, dust, dirt, lint, construction grit and cor-
rosive vapors.
If a transfer switch is not included, one may be pur-
chased separately from a Generac Authorized Dealer.
Model Rating
004948-0 27,000 NG
30,000 LP
4 Generac ® Power Systems, Inc.

Section 1 - General Information

Guardian Liquid-cooled 27 kW and 30 kW Generators
Figure 1.2 - Main Circuit Breaker
Phase
1
1
* Amp Rating of C/B structured under model.
1.3

AUTOMATIC SYSTEM OPERATION

When this generator, along with a transfer switch, has
been installed and interconnected, a circuit board in
the generator panel constantly monitors UTILITY
power source voltage. Should that voltage drop below
a preset value, and remain at such a low state for a
preset amount of time, the generator cranks and
starts. After the generator starts, the transfer switch
transfers load circuits so the generator can power
them.
When UTILITY source voltage has been restored, the
switch re-transfers back to the UTILITY source volt-
age and the generator then shuts down.
Please reference the transfer switch manual for spe-
cific information.
1.4 GENERATOR AC CONNECTION
SYSTEMS
The generator was shipped from the factory with its
stator AC output leads connected in a single-phase,
three-wire generator AC connection system (Figure
1.1). The stator assembly in this system consists of a
pair of stationary windings, with two leads brought
out of each winding. Each single winding can supply
120VAC, 60 Hertz. When the two windings are con-
nected in series, a 240VAC, 60 Hertz AC output
results. Typically the two HOT leads in the circuit are
wires 11 and 44. The NEUTRAL leads are the junc-
tion of Wires 22 and 33. The NEUTRAL is not
grounded.
Figure 1.1 - Generator AC Connection System
1.5

MAIN CIRCUIT BREAKER

The generator's main circuit breaker is included with
the unit as shipped from the factory. The breaker for
each unit is described in Figure 1.2.
Actual Current
112.5
125.0
C/B Rating* Circuit Breaker
150 150A QN2
150 150A QN2