Generac Power Systems NP-40G - Manual (Page 81)

Section 5.2- ENGINE COOLING SYSTEM
General
The engine and generator are alr-cooled. It is
absolutely essential that an adequate flow of air for
cooling, ventilation and combustion be supplied to
the RV generator. Without sufficient air flow, the
engine-generator will quickly overheat. Overheat­
ing can result in serious damage to the equipment,
as well as fire and possible Injury. Air must be
drawn into the generator compartment of the recre­
ational vehicle at a sufficiently high rate. The air
must then be exhausted from the compartment at
a sufficiently high rate.
Generator Air Flow
A cooling fan is attached to the generator’s per­
manent magnet rotor. This pressure fan draws air
Into the top of the generator, into the side of the
control panel, and across the engine-generator and
electronic components.
A suction fan is attached to the engine crank­
shaft. This fan draws the heated air Into a collector
pan at the bottom of the engine-generator, where It
Is
directed across the exhaust muffler and then
deflected out to ambient air.
Air Flow into Generator Compart­
ment
GENERAL:
The installer of an RV generator Into a vehicle
must provide air openings that will supply the
needed air for cooling, ventilation and combustion.
Technicians who service the engine-generator
must not do anything that will restrict this air flow.
Any one or a combination of several different meth­
ods may be used to deliver the required air flow.
The method used by the installer will depend on the
method used to mount the generator In the vehicle,
as follows:
1. If the generator set Is mounted In a compartment above
the vehicle frame, air openings can be provided In the
compartment door.
a. Ideally, three openings should be provided In such a
door as shown In Figure 2.
(1) One opening of 40 square Inches (unre­
stricted) as shown.
(2) Two 10 square inch openings (unrestricted)
as shown.
NOTE: If screening, louvers or expanded metal are
used to cover air openings, It must be remembered
that such materials will restrict air flow. This re­
striction must be compensated for by making the
actual air opening size proportionately larger. See
"Compensating for Restrictions".
NOTE: If the generator Is Installed In a compart­
ment. at least 1-1/2 Inches of clearance must be
provided between the generator and the compart­
ment and any Insulation or metal lining the com­
partment walls. Provide at least two (2) Inches of
clearance between the top of the generator and the
compartment celling.
Figure 2. Air Inlet In Door
2. If the generator Is suspended below the vehicle frame,
any one of several methods can be used to supply re­
quired air flow.
a. A door in the vehicle skirt having the required
air inlet openings (Figure 3).
b. By using ductwork. Air must be available at top
of the engine-generator. See Figure 4.
c. By providing an opening in the vehicle skirt
and at least 2 Inches of space above the engine-
generator (Figure 5).
Compensating for Restrictions
Materials such as screening, louvers and ex­
panded metal will restrict the free flow of air. When
such materials are used to cover air openings, they
must be compensated for by making the actual air
opening size proportionately larger.
Some materials may offer only a 60 percent "free
inlet area". More efficient materials may offer a 90
percent "free inlet area". The percentage of free air
inlet opening can usually be obtained from the
manufacturer of the material.
Page 5.2-1