76
AC-SVX002C-EN
Table 31.
Main process diagnostics (continued)
Diagnostic
Name
Affects
Target
Severity
Persistence
Active
Modes
[Inactive
Modes]
Criteria
Reset
Level
High
Evaporator
Water
Temperature
Chiller
Info and
Special Action
NonLatch
Only effective if
either
1) Evaporator
Water Flow
Overdue
2) Evaporator
Water Flow
Lost
3) Low Evap
Water Temp:
Unit Off,
diagnostic is
active.
4) Heating
mode
Either the leaving or the entering water temperature
exceeded the high evap water temp setting (TU
service menu settable – default 40.5°C (105°F)) for
15 continuous seconds. The evaporator water pump
relay will be de-energized to stop the pump, but only
if it is running due to one of the diagnostics listed on
the left. The diagnostic will auto reset and the pump
will return to normal control when both the entering
and leaving falls 2.778°C (5°F) below the trip
setting. The primary purpose is to stop the
evaporator water pump and its associated pump heat
from causing excessive water-side temperatures and
water-side pressures when the unit is not running
but the evap pump is on due to either Evaporator
Water Flow Overdue, Evaporator Water Flow Lost , or
Low Evap Water Temp – Unit Off diagnostics. This
diagnostic will not auto clear solely due to the
clearing of the enabling diagnostic.
*at unit installation, especially reversible units, high
evap water temp setting will need to be written. The
value should be approximately 65.5°C (150°F) for
heat pumps
Remote
High Suction
Rfgt Pressure
Chiller
Immediate
NonLatch
All
Any circuit’s suction pressure has risen above 95% of
the high pressure cutout setting. The evaporator
water pump relay will be de-energized to stop the
pump regardless of why the pump is running. The
diagnostic will auto reset and the pump will return to
normal control when all circuits’ suction pressures
fall below 85% of the high pressure cutout setting.
The primary purpose is to stop the evaporator water
pump and its associated pump heat from causing
refrigerant side pressures close to the relief valve
setting when the chiller is not running, such as could
occur with Evaporator Water Flow Overdue,
Evaporator Water Flow Lost, or Low Evap Water Temp
– Unit Off diagnostics. This condition is unlikely
unless a discharge isolation valve is installed and
closed.
Remote
High Pressure
Cutout
Circuit
Immediate
Latch
All
The high pressure cutout switch recognized a high
pressure. See Condenser High Pressure Protection
spec for more details.
Local
High Discharge
Refrigerant
Pressure
Circuit
Immediate
Latch
All
Discharge pressure exceeded the high pressure
cutout se 100 kPa. Likely cause: failed or
incorrectly set high pressure cutout switch. Prevents
release of refrigerant through relief valve.
Local
Emergency
Stop Feedback
Input
Chiller
Immediate
Latch
All
Emergency Stop input is open. See Auto Stop and
Immediate Stop spec
Local
Starts/Hours
Modified - xy
Cprsr
Warning
NonLatch
All
A counter for a given compressor starts or hours has
been modified by TU. This diagnostic is immediately
and automatically cleared and thus can only be seen
in the historic diagnostic list.
NA
Evaporator
Pump 1 Starts/
Hours Modified
Chiller
Warning
NonLatch
All
A counter for evaporator pump 1 starts or hours has
been manually modified. This diagnostic is
immediately and automatically cleared and thus can
only be seen in the historic diagnostic list.
NA
