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C C o o n n t t r r o o l l s s
Table 20. Operating modes — circuit (continued)
Circuit Modes
Run Inhibit
Diagnostic Shutdown – Auto Reset
Low Oil Flow Cool Down Time mn:sec
Restart Inhibit min:sec
Low Evap Rfgt Temp (Inh-bit)*
Auto
Calibrating EXV
Waiting to Start
Start Inhibited Waiting For Oil
Running
Establishing Min(imum) Cap(acity) – Low Diff
(erential) Pressure
Establishing Min Cap – High Disch Temp
Establishing Min Cap – Low Vi Min Speed
Maximum Capacity
Running - Limit
(High) Condenser Pressure Limit
(Low) Evaporator (Rfgt) Temperature Limit
EXV Capacity Limit
Noise Reduction (Fan Limit)
Flooded or Hot Start Capacity Limit
Demand Limit
Shutting Down
56
Description
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.
The circuit has been shutdown on a diagnostic that may clear automatically.
See oil flow protection spec
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.
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.
The circuit is not currently running but can be expected to start at any moment given that the
proper conditions are satisfied.
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.
The circuit is going through the necessary steps to allow the lead circuit to start.
The compressor (and thus its circuit) will wait up to 2 minutes in this mode for oil level to
appear in the oil tank.
The compressor on the given circuit is currently running.
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.
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.
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.
The individual circuit is running at the maximum speed possible – no more capacity is
available from this circuit.
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
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.*
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.
*
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.
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.
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.
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.
The circuit is preparing to de-energize the compressor.
AC-SVX001A-EN
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