Start-Up and Shutdown
64
RTAF-SVX001K-EN
Running (Lead Compr/Circuit Start - Run)
The figure below shows a typical start and run sequence
for the lead compressor and its circuit.
Figure 42.
Sequence of operation: running (lead compressor/circuit start nd run)
Hold EXV Pre-position
(10 Seconds)
Lead
Compressor
Running
Chiller and Lead Circuit
Mode is “Running” - Lag
Circuit Mode is “Auto”
Hold EXV of Lead
Circuit at pre-
position for 10 sec
De-energize
Oil Heaters
Of Lead Circuit
Control Lead Circuit
Condenser Fans for
Optimum Differential
Pressure,
ƒ(Cprsr Spd, OA Temp)
6
6
6
/
/
/
/
6
6
6
6
6
6
1
1
1
2
2
2
/
/
/
/
2
2
2
2
2
2
2
2
2
0
0
0
1
1
1
2
2
2
-1
1
1
2
2
2
/
/
/
/
2
2
2
2
2
2
1
1
1
1
1
1
/
/
/
/
1
1
1
2
2
2
0
0
0
1
1
1
2
2
2
Enforce All Running Mode Diagnostics for Chiller, Lead Compressor and its Circuit
Modulate EXV for
Pressure Control
Modulate
Compressor
for Limit
Control
Modulate Compressor
for
Capacity Control
Modulate Compressor
for
Capacity Control
6
6
6
/
/
/
/
6
6
6
6
1
1
1
/
/
/
/
/
/
2
2
2
/
/
/
/
2
2
2
2
2
2
/
/
/
/
/
0
0
0
1
1
1
2
2
2
-
7
7
7
/
/
/
/
7
7
7
2
2
2
/
/
/
/
/
4
4
4
/
/
/
/
4
4
4
2
2
2
/
/
/
/
/
0
0
0
1
1
1
2
2
2
Running
6/
6
6 13/
/
3
3 2012
7
7
7
/
/
/
/
/
/
/
7
7
7 2
2
2
2
2
/
//
/
/
/
/
3
3
3
/
/
/
/
3
3
3
2
2
2
/
/
/
/
/
0
0
0
1
1
1
2
2
2
-
8
8
8
/
/
/
/
8
8
8
1
1
1
/
/
/
/
/
/
4
4
4
/
/
/
/
4
4
4
2
2
2
/
/
/
/
/
0
0
Running
7/
7
7 24
2
2 /
/
4
4 2012
8/
//
8 1
// 4/
//
4 2
// 012 - 9/
//
9 1
// 1/
//
2
// 012
Running
Lead Circuit:
Running Limit
8/
8
8 15/
/
5
5 2012
6/
/
/
6
6 1
1
1
1
1
1
3
3
3
3
/
/
/
/
/
3
3
3
3
3
2
2
2
2
2
2
2
2
0
0
0
0
0
0
0
0
1
1
1
1
1
1
2
2
2
2
2
2
Milest
s
s on
n
n
n
n
n
e
e
e
e
D
D
D
D
e
e
e
e
e
e
e
e
e
e
D
D
D
D
D
D
D
D
D
s
s
s
s
c
c
c
c
s
s
s
s
s
s
r
r
r
r
i
i
i
i
i
p
p
p
p
p
t
t
t
t
p
p
p
p
p
i
i
i
i
i
o
o
o
o
n
n
n
n
9
9
9
/
/
/
/
9
9
9
1
1
1
/
/
/
/
/
/
0
0
0
/
/
/
/
0
0
0
2
2
2
/
/
/
/
/
0
0
0
1
1
1
2
2
2
-
1
1
1
0
0
0
/
/
/
/
0
0
0
2
2
2
/
/
/
/
/
9
9
9
/
/
/
/
9
9
9
2
2
2
/
/
/
/
/
0
0
0
1
1
1
2
2
2
Running
9
r
/
/
/
9
9
9
9
11/
/
1 2012
Exit
Limit Mode
Enter
Limit Mode
Stage On
Setpoint Met*
0/
//
0 2
// 8/
//
8 2
// 012 - 12/
//
2 1
// 1/
//
2
// 012
Running
Lag Circuit:
Waiting to Start
1
1
1
r
0
0
0
/
0
0 29
2
2 /
9
9 2012
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
12/
2
2 11
1
/
/
1
2012
*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: A 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. Variable speed
compressors will always be the first compressors to start and last compressors to stop.
