ESIE10-01 Functional Control
Part 2 – Functional Description 2–25
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2.2.1 Unit Enable
There are different ways to start and stop a unit. Enabling and disabling the chiller is accomplished
using set points and inputs to the chiller. The unit switch, remote switch input, and Unit Enable Set
Point all are required to be 'on' for the unit to be enabled when the control source is set to 'local'. The
same is true if the control source is set to 'network', with the additional requirement that the BMS
request must be 'on'.
Unit is enabled according to the following table.
Note: An "x" indicates that the value is ignored.
All these normal methods for disabling the chiller (no alarms) should cause a normal shutdown,
discussed later on, of any running circuits.
When the controller is powered up, the Unit Enable Set Point should be initialized to 'off' if the Unit
Status After Power Failure Set Point is set to 'off'.
Unit Switch
Control Source
Set Point
Remote
Switch Input
Unit Enable
Set Point
BMS
Request
Unit Enable
Off x x x x Off
x x x Off x Off
xxOffxxOff
On Local On On x On
xNetwork x x OffOff
On Network On On On On
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