Ventilation System; Cooling System - Onan DFE Series Installation Manual

IF EXHAUST LINE MUST BE PITCHED UPWARD.
CONSTRUCT A TRAP OF PIPE FITTINGS AT
POINT OF RISE
AVOID
SHARP
BENDS
DRAIN CONDENSATION TRAP
PERIODICALLY
EXS-1046
FIGURE S. EXHAUST CONDENSATION TRAP (TYPICAL)
Shield.or insulate exhaust lines if there is a danger of
personal contact. Allow at least 12 inches (305 mm) of
clearance if the pipes pass close to a combustible wall
or partition.
VENTILATION SYSTEM
Generator sets create considerable heat that must be
removed by proper ventilation. Outdoor installations
rely on natural air circulation but indoor installations
need properly sized and positioned vents for the
required airflow. Refer to Onan Technical Bulletin,
T-030, for additional application information.
Vents and Ducts
For indoor installations, locate vents so incoming air
passes through the immediate area of the installation
before exhausting. Install the air outlet higher than the
air inlet to allow for convection air movement (see Fig-
ure 1 for a typical installation).
Size the vents and ducts so they are large enough to
allow the required flow rate of air. The "free area" of
ducts must be as large as the exposed area of the
radiator. Refer to the DFE series Product Data Sheets for
the airflow requirements.
Wind will restrict free airflow if it blows directly into the
air outlet vent. Locate the outlet vent so the effects of
wind are eliminated.
For operation outside a building, a shelter housing with
electrically operated louvres is available as an option.
Transformers connected across the generator output
supply current to the motors.
When the generator is operating, current in the trans-
formers actuate the motors and open the louvres. The
louvres are held open for the duration of the set opera-
tion, then are closed by return springs when the set is
shut down.
Dampers
Dampers are used in any system to block the airflow
through the vents when the generator set is not running.
This is sometimes necessary in cold climates to keep
the generator enclosure at a normal temperature.
Radiator Set
Radiator set cooling air is drawn past the rear of the set
by a fan which blows airthrough the radiator. Locate the
air inlet to the rear of set and near the floor. Make the
inlet vent opening 1 -1 /2 times larger than the radiator.
Locate the cooling air outlet directly in front ofthe radia-
tor and as close as possible. The effective opening area
should be 1.3 times as large as the radiator area. Length
and shape of the air outlet duct should offer minimum
restriction to airflow. Use a duct of sheet metal and
canvas between the radiator and the air outlet opening
to prevent recirculation of heated air and provide for
flexible connection. ^
Heat Exchanger *
Heat exchanger cooled sets do not use a conventional
radiator. Instead, a constantly changing water flow
cools the heat exchanger which in turn cools the engine
coolant. Sufficient air movement and fresh air must be
available to disperse heat radiated from the heat exchanger.
To provide sufficient airflow, ventilation fans may be
required. Size the fans to remove all heat rejected to the
room by the generator set, exhaust pipes and other heat
producing equipment. Maintaining a temperature dif-
ferential of 20° to 30°F (11° to 17 0 C) is usually
satisfactory.
COOLING SYSTEMS
A set mounted radiator with engine driven fan is stan-
dard on the generator set. Optional cooling systems
include remote radiator cooling and heat exchanger
cooling.
The following sections briefly cover the installation
requirements for each system. Refer to Technical Bul-
letin T-030 for more detailed information.
Standard Radiator Cooling
The standard radiator cooling system (see Figure 1)
uses a set mounted radiator with an engine driven
pusher type fan to cool the generator set. Air is pulled
from the generator end of the set across the engine and
then forced through the radiator. An air duct adapter
flange surrounds the radiator grill to allow mounting of
the air discharge duct. Refer to the section on Ventila-
tion for location and sizing of ducts and vents.