Trane IntelliPak with Symbio 800 Programming Manual page 38

TD7 Display
Table 12. Circuit operation-top level mode - waiting to start
Circuit
Top Level Mode
Waiting to Start
Waiting to Start Sub Modes
Prepositioning EXV
Table 13. Circuit operation-top level mode - running
Circuit
Top Level Mode
Running
Running Sub Modes
Comfort Purge
Dehumidification Purge
Table 14. Circuit operation-top level mode - running-limit
Circuit
Top Level Mode
Running – Limit
Running – Limit Sub Modes
Coil Purge
Compressor Involute Pressure Limit
Compressor Startup Speed Limit
Discharge Pressure Limit
Frost Protection Limit
High Discharge Pressure Limit
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Description
The circuit is going through the necessary steps to allow the lead circuit to start.
The circuit will wait for the time it takes the EXV to get to its commanded pre-
position prior to starting the compressor. This is typically a relatively short delay
and no countdown timer is necessary (less than 15 seconds).
Note: This does not occur during EXV pre-position but is not necessarily required
as the time is short and the top level mode is adequate to explain that the startup
sequence is in process.
Description
The compressor on the given circuit is currently running.
A Comfort Purge cycle is entered when compressors have been running on the
reheat circuit but no reheat is commanded. Therefore, reheat has been inactive
and the reheat modulating valve has been closed.
A Dehumidification Purge cycle is entered when compressors have been running
on the reheat circuit, "standalone" dehumidification control is active and reheat
has been active with the modulating valve having been opened.
Description
The circuit is currently running however the operation of the unit/compressors
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.
A 3 minute Coil Purge is in process to reclaim any logged oil from the condenser
or reheat coils.
If compressors on the circuit are energized and the compressor involute pressure
differential limit is in the hold region or unload region.
This applies to the variable speed compressor and enforces a maximum speed
limit for a fixed time period following startup. During normal operation, the speed
range limits are determined based on unit type, efficiency, capacity stage and
other limit controls. The maximum speed limit following every startup is treated
as a special case to help provide the best possible oil quality.
The circuit capacity is prevented from loading or has unloaded due to high
discharge pressure.
This is a circuit level protection and is active whenever one or more compressors
on a circuit are running. Each circuit will compare its Saturated Suction
Temperature to various criteria. Depending on the severity of the coil frost
potential this protection will limit loading or unload the circuit capacity in an
attempt to minimize the frost.
This circuit-level feature prevents a circuit shutdown when the discharge
pressure approaches the high-pressure cutout switch setting by decreasing
compressor capacity. Limit control action modifies the normal capacity
modulation and staging commands to decrease capacity by reducing compressor
modulation or staging off compressors on circuits with high discharge pressure.
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