McQuay TGZ 040A

OMM TGZ-1 TGZ 040A through TGZ 190A 31
When the alarm occurs due to this trigger, it can auto reset the first two times each day, with
the third occurrence being manual reset.
For the auto-reset occurrences, the alarm will reset automatically when the evaporator state
is Run again. This means the alarm stays active while the unit waits for flow, then it goes
through the recirculation process after flow is detected. Once the recirculation is complete,
the evaporator goes to the Run state which will clear the alarm. After three occurrences, the
count of occurrences is reset and the cycle starts over if the manual reset flow loss alarm is
cleared.
If active via trigger condition 2:
If the flow loss alarm has occurred due to this trigger, it is always a manual reset alarm.
Condenser Flow Loss
Alarm description (as shown on screen): Condenser Flow Loss
Trigger:
1: Condenser Pump State = Run AND Condenser Flow Digital Input = No Flow for time >
Cond Flow Proof Set Point AND at least one compressor running.
2: Condenser Pump State = Start for time greater than Recirc Timeout Set Point AND all
pumps have been tried AND Condenser Flow Digital Input = No Flow.
Action Taken: Rapid stop all circuits.
Reset:
This alarm can be cleared at anytime manually, via the keypad, or via the BAS clear alarm
signal.
If active via trigger condition 1:
When the alarm occurs due to this trigger, it can auto reset the first two times each day, with
the third occurrence being manual reset.
For the auto-reset occurrences, the alarm will reset automatically when the condenser pump
state is Run again. This means the alarm stays active while the unit waits for flow, then it
goes through the recirculation process after flow is detected. Once the recirculation is
complete, the condenser pump goes to the Run state which will clear the alarm. After three
occurrences, the count of occurrences is reset and the cycle starts over if the manual reset
flow loss alarm is cleared.
If active via trigger condition 2:
If the flow loss alarm has occurred due to this trigger, it is always a manual reset alarm.
Low Evaporator Pressure
Alarm description (as shown on screen): Evap Press Low Cir N
Trigger: [Circuit State = Run AND Freezestat trip AND Low OAT Start not active]
OR Evaporator Press < Absolute Low Pressure Limit AND Circuit State = Run
The absolute low pressure limit is 5 psi with R134a, R22, and R407C refrigerants and 20
psi with R410A refrigerant.
Freezestat logic allows the circuit to run for varying times at low pressures. The lower the
pressure, the shorter the time the compressor can run. This time is calculated as follows:
Freeze error = Low Evaporator Pressure Unload – Evaporator Pressure
Freeze time =
[60 – 2.7 x freeze error] with R134a refrigerant, limited to a range of 20-60 seconds
[60 – 1.6 x freeze error] with R22 and R407C refrigerant, limited to a range of 20-
60 seconds
[60 – freeze error] with R410A refrigerant, limited to a range of 20-60 seconds