FORM 160.77-O2
ISSUE DATE: 11/15/2011
JOHNSON CONTROLS
16
SECTION 1 - YKEP CHILLER OVERVIEW
ing the load on the chiller, by reducing the ow, or
decreasing the inlet temperature. This will cause
the capacity control system to back the vanes in
an unload sequence.
• If the chiller surges before the Hot Gas valve be-
gins to open, then the anti-surge line must move
right on the map.
• If the chiller never surges down to minimum load,
then the anti-surge parameters are adequate for
protection, but may not be most efcient.
• During the unload sequence, record the operating
head as VPD2
• Increasing and decreasing the parameter MVP2
will move the anti-surge line right and left on the
map. Listen for a surge, and move the anti-surge
line right several percent, to increase refrigerant
ow, by supplementing hot gas.
The plant condenser water control system will deter-
mine the actual high and low head conditions depending
on the range of condenser water temperature allowed.
If actual operating conditions are different than those
shown above, you must enter the new values for the an-
ti-surge parameter calculation to produce the required
output signals.
The “ANTI-SURGE MIN PRV POS” output (Y%) is
calculated based on the actual calculated differential
pressure (head) as follows:
PD (Head) = (Compressor Discharge Pressure) – (Evaporator Pressure)
Y% = (PD-PD2) x (MVP1-MVP2) / (PD1-PD2) + MVP2
Hot Gas Control Tuning
The “HOT GAS CONTROL” operates to open the
valve as a decreasing load causes the “CHILLED WA-
TER TEMP. CONTROL” output to drop below the
“ANTI-SURGE MIN. PRV POSITION”.
ANTI-SURGE, SPEED
Chillers which employ a variable speed drive for the
primary compressor motor also use a speed anti-surge
subsystem. This system is based on a 4-segment line
approximation of the compressor full-open PRV surge
curve. The specifics can be visualized on the Primary
Anti-Surge Screen. Any required adjustments to the
speed anti-surge tuning should be performed before
adjusting the PRV anti-surge line.
Anti-Surge (Speed) Tuning
• With the chiller running in automatic, take the
condensing conditions to the highest inlet tem-
perature attainable in the system (without tripping
on high discharge pressure). Increase tower inlet
temperature or reduce tower ow.
• At the highest condensing temperature, start re-
ducing the load on the chiller, by reducing the
ow, or decreasing the inlet temperature. This
will cause the capacity control system to back the
primary compressor speed in an unload sequence.
• If the chiller surges before the PRV’s throttle
closed, then the anti-surge line must move right
on the map.
• If the chiller never surges down to minimum load,
then the anti-surge parameters are adequate for
protection, but may not be most efcient.
• During the unload sequence, record the operating
head as SPD1
• Increasing and decreasing the parameter MSP1
will move the anti-surge line right and left on the
map. Listen for a surge, and move the anti-surge
line right several percent, to increase speed.
• Repeat the procedure for low head operation.
• At the lowest condensing temperature, start reduc-
ing the load on the chiller, by reducing the ow, or
decreasing the inlet temperature. This will cause
the capacity control system to back the primary
compressor speed in an unload sequence.
• If the chiller surges before the PRV’s throttle
closed, then the anti-surge line must move right
on the map.
• If the chiller never surges down to minimum load,
then the anti-surge parameters are adequate for
protection, but may not be most efcient.
• During the unload sequence, record the operating
head as SPD5.
• Increasing and decreasing the parameter MSP5
will move the anti-surge line right and left on the
map. Listen for a surge, and move the anti-surge
line right several percent, to increase speed.
• Repeat the process as needed for head and mini-
mum speed points SPD2, SPD3, SPD4 and MSP2,
MSP3, MSP4 between the endpoints to further
dene the surge line.
To Next Page
Loading...
Need help?
General
