78
RTHD-SVX01L-EN
Table 23. Main processor diagnostics (continued)
Diagnostic Name
Affects
Target
Severity
Persistence
Active Modes
[Inactive Modes]
Criteria
Reset
Level
High Evaporator
Water Temperature
Chiller
Warning
and Special
Action
NonLatch
Only effective if
either 1)Evap Wtr
Flow Overdue, 2)
Evap Wtr Flow Loss,
or 3)Low Evap Rfgt
Temp,-Unit Off,
diagnostic is active.
The leaving water temperature exceeded the high evap
water temp limit for 15 continuous seconds. The evaporator
water pump relay will be de-energized to stop the pump but
only if it is running due one of the diagnostics listed on the
right. The diagnostic will auto reset and the pump will return
to normal control when the temperature falls 5°F below the
trip setting. The primary purpose is to stop the evaporator
water pump and its associated pump heat from causing
excessive waterside temperatures and waterside pressures
when the chiller is not running but the evap pump is on due
to either Evap Water Flow Overdue, Evaporator Water Flow
Loss , or Low Evap Temp – Unit Off Diagnostics. This
diagnostic will not auto clear solely due to the clearing of
the enabling diagnostic.
Local
High Pressure
Cutout
Chiller Immediate Latch All
A high pressure cutout was detected. Note: Other
diagnostics that may occur as an expected consequence of
the HPC trip will be suppressed from annunciation. These
include Phase Loss, Power Loss, and Transition Complete
Input Open.
Local
High Refrigerant
Pressure Ratio
Chiller Immediate Latch
Service Pumpdown
Only
The system pressure ratio exceeded 5.61 for 1 contiguous
minute. This pressure ratio is a fundamental limitation of the
compressor. The pressure ratio is defined as Pcond (abs)/
Pevap(abs).
Remote
Loss of Oil at
Compressor
(Running)
Chiller Immediate Latch
Starter Contactor
Energized
In running modes, Oil Loss Level Sensor detects lack of oil
in the oil tank feeding the compressor (distinguishing a
liquid flow from a vapor flow)
Local
Loss of Oil at
Compressor
(Stopped)
Chiller
Immediate
and Special
Action
Latch
Compressor Pre-
start [all other
modes]
Oil Loss Level Sensor detects a lack of oil in the oil tank
feeding the compressor for 90 seconds after EXV
preposition is completed. Note: Compressor start is delayed
while waiting for oil to be detected.
Local
Low Differential
Refrigerant Pressure
Chiller Immediate Latch
Chiller Energized
The system differential pressure was either below 15 Psid
for more than 164 Psid-sec, or below 23.0 Psid for 3000
Psid-sec. The latter integral’s value is not cleared for any
reason including diagnostic trip, manual reset, or power up
reset (ie. Integral is saved non-volatile on power down). The
integral will decay while circuit is running at a max rate of
-10 PSID, and while stopped at a rate of -0.4 PSID. This
same integral is associated with the operating mode
“Compressor Cool Down”. Also see diagnostic below
Remote
Low Discharge
Superheat
Chiller Normal Latch
Any Running Mode
While Running Normally, the Discharge Superheat was less
than 12 °F ± 1°F for more than 6500 degree °F seconds. At
startup the UCM shall ignore the Discharge Superheat for 5
minutes.
Remote
Low Evaporator
Liquid Level
Chiller
Warning
NonLatch
Starter Contactor
Energized [all Stop
modes]
The liquid level sensor is seen to be at or near its low end of
range for 80 contiguous minutes while the compressor is
running.
Remote
Low Evaporator
Refrigerant Pressure
Chiller Immediate Latch
Chiller Prestart and
Chiller Energized
The Evaporator Refrigerant Pressure dropped below 10
psia just prior to compressor start. The pressure fell below
10 psia while running but before the 3 minute ignore time
had expired or fell below 16 Psia after the 3 minute ignore
time had expired.
Local
Diagnostics
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