Auxiliary Preheating System (Option); Preheater Fuel Filter; Operation; Preheating System Timer - PREVOST H3-41 Maintenance Manual

SECTION 22: HEATING AND AIR CONDITIONING
8. AUXILIARY PREHEATING SYSTEM
(OPTION)
The Auxiliary Preheating System is used for
preheating and maintaining the heat of water-
cooled engines by the means of an independent
water heater using the same diesel fuel as the
engine.
The preheater operates independently from the
vehicle engine. It is connected to the cooling and
heating circuits, the fuel system and the
electrical system of the vehicle.
FIGURE 89:PREHEATER (30 KW)
The heater can be used to pre-heat the engine
coolant in cold weather to ease engine start-up
and to provide heat faster in the cabin.
It can also be used with engine running to
maintain coolant heat and maintain the set
temperature inside vehicle.
The heater "On" symbol
when the preheater is switched on.
Refer to the Eberspacher
Troubleshooting and Repair manual under 2
Function for cutaway views, control diagrams
and a detailed description of the function of the
heater unit.
8.1

PREHEATER FUEL FILTER

The preheater fuel filter is located beside the
preheater.
MAINTENANCE
Replace preheater fuel filter every 50,000 miles
(80 000 km) or once a year, whichever comes
first.
72 PA1621 Maintenance Manual All Series | Revised February 2019
appears on the timer
Hydronic LII
8.2

OPERATION

Switch on the preheater. The heater "On"
symbol appears on the timer display. A
component test is performed (3sec.), then the
water pump is started and the nozzle preheater
is switched on for a maximum of 15 min. 60 sec
after, the preheater motor starts, driving the fan
and fuel pump.
After approximately 10 seconds, the ignition
circuit is switched on and the fuel solenoid valve
opens, injecting fuel. The ignition creates a high
voltage spark, igniting the fuel air mixture.
The flame monitor recognizes the flame and
switches off the spark generator. Combustion
continues by itself. At this moment, the
preheater is working and producing heat.
If the preheater is switched off, the solenoid
valve interrupts fuel supply, combustion stops
and the heater "on" indicator
Combustion air fan still blows air, cleaning the
combustion chamber of any fumes and cooling
down the combustion
circulation continues for 3 minutes, protecting
the preheater against overheating.
The control thermostat will switch off the
preheater when coolant reaches 172°F (78°C)
and will turn it on at 163°F (73°C).
When the preheater is switched off by the
thermostat, the heater indicator
pump remain on although
combustion in the preheater. Combustion air fan
blows air for 3 minutes and then turns off.
8.3

PREHEATING SYSTEM TIMER

The timer, located on L.H. lateral console is
used to program the starting and stopping time
of the preheating system. The heater "on"
indicator appears when the system is
functional.
8.3.1

Preheater Timer Instructions

Basic instructions are provided in the Prevost
operator's manual. For more details, refer to the
7 day timer operating instructions, found on your
Technical Publications USB flash drive, and on
the Technical Publications Website.
disappears.
chamber. Coolant
and coolant
there is no