-50-
22.7 (continued)
In addition to the capability to assign each of the setpoints (2 per channel) and the LOAD
INHIBIT and FORCE UNLOAD functions, there are 6 auxiliary control outputs which can be
used to implement corrective actions, sound alarms, etc. These outputs are rated for 60 VDC
and 2 amp maximum. These outputs would typically be connected to solenoid valves or control
relays. The control outputs are transistors which turn on to system ground when a control
setpoint assigned to them is violated. The assignment of the auxiliary output channels is non-
exclusive. That is to say that multiple channels can be assigned to a single output or multiple
outputs to a single channel in whatever combination is desired. In the first example above of
a low injection oil temperature control setpoint on a screw compressor being used to inhibit
loading, an auxiliary control output (#3 for example) could also be assigned to this setpoint
which would energize a heater to increase the oil temperature to allow loading. In the second
example of limited compressor throughput due to cooling capacity, an auxiliary output (#4 for
example) assigned to the high discharge temperature setpoint could be used to turn on a fin-fan
to increase cooling or activate a solenoid valve allowing for an optional coolant routing through
an additional heat exchanger. The control setpoints are active at all times, even if the engine
is not running. This allows for protective or corrective actions controlled by these outputs to be
implemented prior to attempting a startup. The potential applications of the secondary control
setpoints are too numerous to compile here.
22.8 On DE-2500 units programmed using Terminal Program 2.0 or higher, the control setpoint
options have been modified to add more flexibility as detailed below.
Inhibit an output increase - The output of one or more of the control loops can be limited in the
increasing direction only, while allowing the assigned output to freely decrease.
Inhibit an output decrease - The output of one or more of the control loops can be limited in the
decreasing direction only, while allowing the assigned output to freely increase.
Force an output increase - The output of one or more of the control loops can be forced to
increase even if the primary control loop requires a different action.
Force an output decrease - The output of one or more of the control loops can be forced to
decrease even if the primary control loop requires a different action.
In addition to these actions being assignable to the analog inputs, they are also assignable to
the analog outputs. This allows for the output of one control loop to interact with the other
according to a programmed priority. For example, the output of loop #2 can be inhibited until
a certain output value of Loop #1 is reached.
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