VMAC – Vehicle Mounted Air Compressors
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3.2.1 Remote ON/OFF Connections
Connect the yellow remote wire on the harness coming out of the
PREDATAIR to one side of a switch or remote control relay module.
Connect the other side of the switch or relay to a chassis ground.
The PREDATAIR will turn on when the circuit between the yellow
wire and ground is completed by the switch or relay. The
PREDATAIR will turn off when the switch or relay opens the circuit.
The display box can be used to see messages, but if the system is
operated using the remote wire, the push buttons on the display box
are disabled. The PREDATAIR can be operated without a display
box by using the remote wire but messages and diagnostics will not
be available.
3.3 Speed Control
The PREDATAIR has the ability to signal for a higher engine speed
under high air demand conditions and for a lower engine speed
under low air demand conditions.
Most work trucks either have a built in electrically activated idle up
system or an after-market product may be available which will
provide this function.
It is not essential that the two speed feature be used, it is entirely
acceptable to run the PREDATAIR constantly at a fixed engine rpm
and pump GPM. There are, however, several advantages to the two
speed feature which should be considered when deciding whether to
go with two speed or single speed operation.
Two speed operation offers these advantages:
•
lower fuel consumption.
•
lower
noise.
•
lower wear rate on engine, hydraulic pump and compressor.
•
greater latitude for flexible service intervals.
•
better cold start behavior.
The preferred approach for speed control is to keep the hydraulic
flow as low as possible when the PTO first starts, then when the
PREDATAIR is engaged, the engine idles up for the desired
performance.
For single speed operation, the throttle would idle up to achieve the
desired CFM when power to the PREDATAIR is turned on (Figure 8).