4
Application Notes:
700-00028-0, DFC-4 Fan Driver Unit.
Fan drive systems ( FDS ) are an important part of the protection needed for the engine and associated
peripheral components to ensure maximum reliability, productivity and long term operation. The FDS
offered by Parker will save fuel, reduce emissions ( particle and noise ) and increase application
productivity by only operating the fan when required and matching the fan speed to the heat load that
requires dissipation.
For fail-safe operation, Parker strongly recommends that the hydraulic valves used are of the ‘Negative
logic’ variety. This means that the valve gives less pressure for an increasing drive current. This choice
results in full pressure and therefore defaults to full fan speed in the event of the electronic controller being
dis-connected or disabled.
There are situations where full fan speed with no drive current may not be optimal so the controller in this
manual allows the user the choice of either ‘negative logic’ or positive logic ( Increasing pressure with
increasing current ) valves by a simple link selection under the units protective cover.
Because the controller is designed to connect directly to the engine ECU, all the decisions on ramp rates,
proportionality, slope angle e.t.c. are already calculated for us. This means that adjustment of the controller
is simple with only three potentiometers –
Dither frequency ( which is needed to ensure correct, repeatable and smooth valve operation ).
I Min ( which sets the Max fan speed on Negative logic valves or Min fan speed in positive logic circuits ).
I Max (which sets the Min fan speed on Negative logic valves or Max fan speed in positive logic circuits).
To maintain operational integrity and prevent unauthorized adjustments once set, the assembly of the
driver is such that the enclosure containing the electronics ( electronic printed circuit board and
components are fully isolated from the casing ) must be firstly securely attached to the unit lid by the 4 x
countersunk screws provided. Once this is done, the entire controller can then be mounted to the
designated flat surface using the 4 x slotted openings in the lid.
The controller electronics are fully encapsulated in black flame proof resin to allow continuous operation in
adverse conditions while protecting them from vibration and external environmental influences.
This unit has been designed to meet all the current EMC requirements and is a well proven control circuit
with many years of field and time proven operation.
Important Note:-
Please be aware that fan systems can start without warning
and may cause personal injury if precautions are not taken
and safe working practices observed.
