Honeywell EXCEL 5000 User Manual page 73

EXCEL CARE CONTROL ICONS
Aux Input Function The auxiliary input, Aux, can prevent integral windup when EPID is used in a limit
application. In this case, you pass a control signal from some other PID controller
through the EPID before going to the controlled device. This control signal passes
through unchanged unless the EPID input rises above its setpoint on a high limit or
falls below its setpoint on a low limit. The auxiliary input mode parameter must be
set correctly depending on whether the EPID is reverse- or direct-acting and on
whether it is imposing a high or low limit. If this parameter is set to +1, then the
auxiliary signal is maximized with the internal PID signal. If the parameter is a -1,
then the auxiliary signal is minimized with the internal PID signal. A parameter value
of zero causes the auxiliary input value to be ignored.
For direct-acting low limit and reverse-acting high limit, set P8 to -1. For reverse-
acting low limit or direct-acting high limit, set P8 to +1.
Example 3 The following diagram is an example of a heating discharge air temperature reverse-
acting low limit application.
Sequence
Example 4 The following diagram is an example of a duct static pressure discharge reverse-
acting high limit application.
Sequence
The space temperature sensor modulates the heating coil
control valve to maintain space temperature setpoint. A heating
coil discharge air temperature low limit controller prevents the
heating coil discharge temperature from falling below 45F.
The static pressure sensor located two-thirds down the longest
duct run modulates the supply fan air volume to maintain duct
static pressure. A duct discharge static pressure high limit
controller prevents the supply fan discharge static pressure from
rising above the high limit setpoint (5 in. wc).
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ALPHABETIC REFERENCE
74-5577–33 (US)
EN2B-0184 GE51 R0518 (Europe)