Generac Power Systems 53187 - Manual (Page 91)

PART 3- ENGINE
LUBRICATION & COOLING SYSTEM
1
SECTION 3.3- COOLING
& VENTILATING AIR
Section 3.3
COOLING & VENTILATING AIR
General
Service technicians who work on the Series NP
(recreational vehicle) and IM (industrial mobile) gener­
ators should be familiar with the air flow requirements
forthese units. Adequate air flow for cooling, ventilation
and engine combustion MUST be provided or serious
problems will result.
Types of Cooling Fans
Engine-generator sets may be equipped with either
(a) a PUSHER type fan, or (b) a SUCTION type fan.
The suction type (squirrel cage) fan may be Installed
on units with either a 10 or 15 inch stator. Pusher type
fans are used primarily on units having a 10 inch stator.
Air Flow- Pusher Fan Units
See Figure 1 below. A blower fan attached to the
generator rotor draws air into the generator interior to
cool generator internal parts. The heated generator
cooling air is expelled through a blower air outlet duct
on the side of the unit. The engine’s pusher fan draws
air around the generator, forces it through the radiator,
and outward, away from the unit.
Air Flow- Suction Fan Units
A centrifugal blower fan rotates with the generator
rotor to cool generator internal parts. The heated gen­
erator cooling air is expelled outward through a blower
air outlet duct on the side of the generator.
The suction type fan is a high capacity 'squirrel
cage" type which draws air in, across the radiator, then
directs the air downward and away from the unit
through an air duct. See Figure 2.
Installation Manual
Additional information on cooling and ventiiating
requirements can be found in the 'INSTALLATION
MANUAL" for water-cooled recreational vehicle gener­
ators. Installation Manuals can be ordered from
Generac Corporation.
Figure 2. Air Flow Suction Fan Units
Air Inlet- Suction Fan Units
When the engine-generator is installed in a com­
partment (as in a recreational vehicle), the following
rules apply to air inlet openings in the compartment;
□ Ideally, the air inlet opening should be close to the
generator's rear bearing carrier. This will allow air to
circulate the full length of the compartment and
around the entire generator.
□ Unrestricted air inlet opening area must be at least
150 square inche (15 Inch stator units): or 300 square
inches (10 inch stator units).
□ If louvers, screening or expanded metal are used to
cover an air inlet opening, the restriction to air flow
offered by such materials must be compensated for.
This is done by making the actual air inlet opening
size proportionally larger.
Other Rules for Suction Fan Units
Some installations provide a compartment, to
house the generator set. In some installations, a floor­
less compartment or no compartment at all may be
P rovided. The following rules apply:
I If a compartment is used, the unit radiator must not
contact the compartment wall. A minimum of at least
3-1/2 inches (90mm) of clearance is recommended
between the front and sides of the radiator and the
compartment walls. Such clearance is required so
the suction fan can draw air around the radiator
edges.
□ If a floorless compartment (or no compartment) is
used, the generator must be protected against road
splash and debris by such means as anti-splash
baffles.
PAGE 3.3-1