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SECTION 26 - VARIABLE GEOMETRY DIFFUSER
FORM 160.54-M1
ISSUE DATE: 10/25/2019
JOHNSON CONTROLS
JCI COMPANY CONFIDENTIAL
26
FIGURE 82 -
VARIABLE GEOMETRY DIFFUSER STATE DIAGRAM
LD15438
CHILLER OFF
or
PRELUBE
VGD Open
STALL
WAITING
Probe wait time
(0.5-15 Min., Default 10)
PRV Offset
(0 to 5%, Default 3)
PROBING
Pulse VGD Open
Until Stall Signal > High Limit
(0.5 to 1.2 V, Default 0.8)
Pulse Open time
(1-5 Sec., Default 2)
STALL
REACTING
Close VGD
Until Stall Voltage < Low Limit
SURGE
WAITING
Hold VGD for Probe Wait Time
Look for 2
nd
Surge and if occurs
set HG Control = True
HOT GAS
OVERRIDE
Hold VGD
Wait timer done
Detect
Stall
Hot Gas Valve
Open
Hot Gas Valve
Open
Hot Gas Valve
Open
Hot Gas Valve
Closed
No Stall
Wait Time Expired
or
PRV position moved
Chiller
Run
Chiller Stop
Variable Geometry Diffuser (VGD)
STATE DIAGRAM
SURGE
REACTING
Close VGD for X second
(X = 1-30 Sec., Default 5)
Detect
Surge
Detect
Surge
Surge Reaction
Time Expired
Detect
Stall
Detect
Surge
Action Arrow Legend
Stall
Surge
Hot Gas Valve
Detect
Stall
Detect
Stall
No Stall and
Surge Waiting Timer
Active
NOTE 1
NOTE 1
(0.3 to 0.80), Default 0.50)
NOTES:
1. Software version C.OPT.01.23.307 (and later),