56
AC-SVX001A-EN
Table 20.
Operating modes — circuit (continued)
Circuit Modes
Description
Run Inhibit
The given circuit is currently being inhibited from starting (and running), but may be allowed
to start if the inhibiting or diagnostic condition is cleared.
Diagnostic Shutdown – Auto Reset
The circuit has been shutdown on a diagnostic that may clear automatically.
Low Oil Flow Cool Down Time mn:sec
See oil flow protection spec
Restart Inhibit min:sec
The compressor (and therefore, its circuit) is currently unable to start due to its restart
inhibit timer. A given compressor is not allowed to start until 5 minutes (adj) has expired
since its last start, once a number of “free starts” have been used up.
Low Evap Rfgt Temp (Inh-bit)*
A start of the circuit had been requested, but the circuit is inhibited from starting due to a
high value of the Low Evaporator Refrigerant Temperature Integral from the last cycle. If the
alternate circuit is available, it will be substituted. Delaying a start in this situation, avoids a
latching diagnostic of the running Low Evaporator Refrigerant Temperature Cutout
protection.
Auto
The circuit is not currently running but can be expected to start at any moment given that the
proper conditions are satisfied.
Calibrating EXV
This submode is displayed when the EXV is performing a calibration. A calibration is only
performed when the chiller is not running and never more frequently than once every 24
hours.
Waiting to Start
The circuit is going through the necessary steps to allow the lead circuit to start.
Start Inhibited Waiting For Oil
The compressor (and thus its circuit) will wait up to 2 minutes in this mode for oil level to
appear in the oil tank.
Running
The compressor on the given circuit is currently running.
Establishing Min(imum) Cap(acity) – Low Diff
(erential) Pressure
The circuit is experiencing low system differential pressure and its compressor is being force
loaded, irrespective of the Chilled Water Temperature Control, to develop pressure sooner.
Establishing Min Cap – High Disch Temp
The circuit is running with high discharge temperatures and its compressor is being forced
loaded to its step load point, without regard to the leaving water temperature control, to
prevent tripping on high compressor discharge temperature.
Establishing Min Cap – Low Vi Min Speed
The compressor is being forced to a higher speed than desired for capacity control, in order
to maintain compressor bearing reliability while in the low Vi state.
Maximum Capacity
The individual circuit is running at the maximum speed possible – no more capacity is
available from this circuit.
Running - Limit
The circuit, and compressor are currently running, but the operation of the chiller/
compressor is being actively limited by the controls. Further information is provided by the
sub-mode.* See the section below regarding criteria for annunciation of limit modes
(High) Condenser Pressure Limit
The circuit is experiencing condenser pressures at or near the condenser limit setting.
Compressors on the circuit will be unloaded to prevent exceeding the limits.*
(Low) Evaporator (Rfgt) Temperature Limit
The circuit is experiencing saturated evaporator temperatures at or near the Low Refrigerant
Temperature Cutout setting. Compressors on the circuit will be unloaded to prevent tripping.
*
EXV Capacity Limit
The EXV is near or beyond 95% wide open, or is predicted to get to that position if the
compressor was to run at full speed, and the capacity of the circuit (compressor speed) is
being held or reduced in order to prevent loss of oil return or insufficient drive cooling.
Noise Reduction (Fan Limit)
The condenser fans of the circuit are potentially being limited by an active chiller-level Noise
Reduction Request to a lower maximum possible speed in order to limit the noise levels.
Flooded or Hot Start Capacity Limit
This mode will occur at circuit start, if the evaporator is sensed to be full of liquid, or if the
evaporator entering water temperature is greater than 65F while the outdoor air
temperature is greater than 70F. This transient starting mode implies the compressor has
begun operation at a speed below the configured “normal” minimum compressor speed, in
order to avoid carryover.
Demand Limit
The compressor is running and is being capacity limited by a high demand power draw in
excess of the compressor’s share of the active Demand Limit Setting for the entire chiller.
Shutting Down
The circuit is preparing to de-energize the compressor.
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