OMM TGZ-1 TGZ 040A through TGZ 190A 43
• If there are no compressors running when Evaporator Water Flow Loss is indicated
the Unit Status changes to Auto:Wait for flow. The evaporator water pump state
changes to Start and no alarms are indicated.
• If an Evaporator Water Flow Loss occurs while a compressor is running all of the
running compressors will be shutdown. The alarm indicators are turned On and the
Circuit Status for any circuit with running compressors becomes Off: Ready, the Unit
Status becomes Auto: Wait For Flow and the evaporator water pump state changes to
Start
• When flow is reestablished the Unit Status becomes Auto: Recirculate while the
Evaporator Flow Recirculation Timer counts down. If there is continuous evaporator
water flow while the Evaporator Recirculation Timer counts down the Alarm
indicator is turned off, and the unit resumes normal start up procedures based on
water temperature and cycle timers.
• If second Evaporator Water Flow Loss occurs within twenty-four hours the process
described above is repeated.
• If a third loss of flow is indicated in a twenty-four hour time frame the unit will shut
down on an Evaporator Water Flow Loss alarm and it will be locked out until this
alarm is manually cleared.
• The twenty-four hour timer that limits the auto restart is reset when the control clock
rolls over 00:00 each night.
Condenser Pump and Tower Control – Water Cooled
Condenser pump and cooling tower control logic requires that the unit be configured as water-
cooled in order to be active.
Condenser Water Pump State Control (Cond State)
If the unit is configured as water-cooled, then the state-transition diagram shown below
defines the condenser pump control logic.
Off
Run Start
Unit State=Auto AND
Any Circuit Available AND
Stage up now = True]
OR
Cond Refrig Freeze Event
AND No Cond Flow Alarm
Cond Flow Alarm OR
[Unit State = Off OR
No Circuit Available OR
Evap Pump State = Start OR
LWT error < Start Delta]
AND
No Cond Refrig Freeze Event
AND
No Compressor Running
[Cond Pump State = Start
AND Flow Switch Closed]
for time > Cond Pmp
Recirc Time seconds
Cond Flow Alarm OR
Unit State = Off OR
Evap Pump State = Start OR
No Circuit Available OR
LWT error < Start Delta]
AND
No Cond Refrig Freeze Event
AND
No Compressor Running
Condenser Pump State Diagram
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