Trane Ascend ACR C Series - Load

AC-SVX003A-EN
85
Lead Circuit Running — Increasing Load
The following diagram shows a typical start and run
sequence for the lead compressor and its circuit.
Figure 31. Sequence of events: lead circuit running — increasing load
Hold EXV Pre-position
Lead
Compressor
Running
Chiller and Lead Circuit
Mode is “Running” - Lag
Circuit Mode is “Auto”
Hold EXV of Lead
Circuit at pre-
position
Control Lead Circuit
Condenser Fans for
Optimum Differential
Pressure,
ƒ(Cprsr Spd, OA Temp)
Enforce All Running Mode Diagnostics for ChillerEnforce All Running Mode Diagnostics for Chiller
Modulate EXV for
Pressure Control
Modulate
Compressor
for Limit
Control
Modulate Compressor
for
Capacity Control
Modulate Compressor
for
Capacity Control
RunningRunning RunningRunning
Running
Lead Circuit:
Running Limit
Running
Lead Circuit:
Running Limit
RunningRunning
Exit
Limit Mode
Exit
Limit Mode
Enter
Limit Mode
Enter
Limit Mode
Stage On
Setpoint Met*
Running
Lag Circuit:
Waiting to Start
Running
Lag Circuit:
Waiting to Start
Prepare to Start
Lag Compressor,
Check for Oil,
Check for LPC
EXV moving to preposition
0 to 25 Seconds
Start Control of
Condenser Fan Flow
on Lag Circuit
Send Start Command
to Lag Compressor
Continue
Running
Pre-Position EXV of
Lag Circuit
*Note: The decision to stage on or off another compressor is determined by
the Average Running Compressor Load Command, Water Temperature Error, and Time Since Last Stage
Circuit X Lead: XA compressor on the selected circuit will lead followed by a compressor on the alternate circuit, given an appropriately increasing chiller
load. Additional compressors will alternate between lead and lag circuits.
On a manifolded circuit, GP4 will be the first to start and last to stop; GP2 will not run by itself.
Hold EXV Pre-position
Lead
Compressor
Running
Chiller and Lead Circuit
Mode is “Running” - Lag
Circuit Mode is “Auto”
Hold EXV of Lead
Circuit at pre-
position
Control Lead Circuit
Condenser Fans for
Optimum Differential
Pressure,
ƒ(Cprsr Spd, OA Temp)
Enforce All Running Mode Diagnostics for Chiller
Modulate EXV for
Pressure Control
Modulate
Compressor
for Limit
Control
Modulate Compressor
for
Capacity Control
Modulate Compressor
for
Capacity Control
Running Running
Running
Lead Circuit:
Running Limit
Running
Exit
Limit Mode
Enter
Limit Mode
Stage On
Setpoint Met*
Running
Lag Circuit:
Waiting to Start
Prepare to Start
Lag Compressor,
Check for Oil,
Check for LPC
EXV moving to preposition
0 to 25 Seconds
Start Control of
Condenser Fan Flow
on Lag Circuit
Send Start Command
to Lag Compressor
Continue
Running
Pre-Position EXV of
Lag Circuit
*Note: The decision to stage on or off another compressor is determined by
the Average Running Compressor Load Command, Water Temperature Error, and Time Since Last Stage
Circuit X Lead: XA compressor on the selected circuit will lead followed by a compressor on the alternate circuit, given an appropriately increasing chiller
load. Additional compressors will alternate between lead and lag circuits.
On a manifolded circuit, GP4 will be the first to start and last to stop; GP2 will not run by itself.
De-Energize Oil
Heater(s) of
Energized Circuit(s)
Start-up and Shutdown