Start-Up, Operation, and Maintenance Instructions
Start-Up, Operation, and Maintenance Instructions
Start-Up, Operation, and Maintenance Instructions
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
PIC II System Functions<br />
NOTE: Words not part of paragraph headings <strong>and</strong> printed in all<br />
capital letters can be viewed on the CVC/ICVC (e.g., LOCAL,<br />
CCN, RUNNING, ALARM, etc.). Words printed both in all<br />
capital letters <strong>and</strong> italics can also be viewed on the CVC/ICVC<br />
<strong>and</strong> are parameters (CONTROL MODE, TARGET GUIDE<br />
VANE POS, etc.) with associated values (e.g., modes, temperatures,<br />
pressures, percentages, on, off, enable, disable, etc.).<br />
Words printed in all capital letters <strong>and</strong> in a box represent soft-<br />
keys on the CVC/ICVC (e.g., ENTER <strong>and</strong> EXIT<br />
). See<br />
Table 2 for examples of the type of information that can appear<br />
on the CVC/ICVC screens. Figures 14-20 give an overview of<br />
CVC/ICVC operations <strong>and</strong> menus.<br />
CAPACITY CONTROL FIXED SPEED — The PIC II controls<br />
the chiller capacity by modulating the inlet guide vanes in<br />
response to chilled water temperature deviation from the CON-<br />
TROL POINT. The CONTROL POINT may be changed by a<br />
CCN network device or is determined by the PIC II adding any<br />
active chilled water reset to the SET POINT. The PIC II uses<br />
the PROPORTIONAL INC (Increase) BAND, PROPOR-<br />
TIONAL DEC (Decrease) BAND, <strong>and</strong> the PROPORTIONAL<br />
ECW (Entering Chilled Water) GAIN to determine how fast or<br />
slow to respond. CONTROL POINT may be viewed or overridden<br />
from the MAINSTAT screen.<br />
CAPACITY CONTROL VFD — The PIC II controls the<br />
machine capacity by modulating the motor speed <strong>and</strong> inlet<br />
guide vanes in response to chilled water temperature deviation<br />
from the CONTROL POINT. The controller will maintain the<br />
highest inlet guide vane setting at the lowest speed to maximize<br />
efficiency while avoiding surge. The CONTROL POINT<br />
may be changed by a CCN network device or is determined by<br />
the PIC II adding any active chilled water reset to the to the<br />
SET POINT. CONTROL POINT may be viewed or overridden<br />
from the MAINSTAT screen. The PIC II uses the PROPOR-<br />
TIONAL INC (Increase) BAND, PROP DEC (Decrease)<br />
BAND, <strong>and</strong> the PROPORTIONAL ECW (Entering Chilled<br />
Water) GAIN to determine how fast or slow it takes the system<br />
to respond. The VFD GAIN allows for additional adjustment of<br />
the VFD response. At start-up, the inlet guide vanes (IGV)<br />
start in the closed position <strong>and</strong> the VFD ramps to its minimum<br />
speed setting.<br />
The PIC II controller then initiates the Capacity Control algorithm<br />
to maintain the chilled water temperature at the CON-<br />
TROL POINT. During operation when the CONTROL POINT<br />
is not met, the controller will establish a GUIDE VANE DELTA<br />
which will either affect a percentage change to the GUIDE<br />
VANES or the VFD TARGET SPEED. Any change that will be<br />
made to the IGV position or the VFD SPEED will depend on<br />
whether the GUIDE VANE DELTA is positive or negative, <strong>and</strong><br />
the status of the Surge Control Algorithm. The Surge Control<br />
Algorithm determines if the chiller should operate in Normal<br />
Mode or Surge Prevention Mode. The logic for how the IGV’s<br />
<strong>and</strong> VFD SPEED will be affected by the GUIDE VANE DEL-<br />
TA <strong>and</strong> the Surge Control Algorithm can be seen below:<br />
GUIDE VANE<br />
DELTA<br />
NORMAL<br />
CONTROL<br />
MODE<br />
SURGE<br />
PREVENTION<br />
MODE<br />
IGV VFD IGV VFD<br />
From +0.2 to +2.0 1st 2nd 2nd 1st<br />
From –0.2 to –2.0 2nd 1st 1st —<br />
Normal Control mode occurs when ACTIVE DELTA T ><br />
SURGE/HGBP DELTA T.<br />
Surge Prevention Mode occurs when ACTIVE DELTA T<br />
≤ SURGE/HGBP DELTA T.<br />
The TARGET VFD SPEED, ACTUAL VFD SPEED <strong>and</strong> the<br />
VFD GAIN can be viewed <strong>and</strong> modified in the CAPACITY<br />
33<br />
display screen. The TARGET VFD SPEED can be manually<br />
overridden by the operator from the COMPRESS screen. The<br />
VFD MINIMUM SPEED, MAXIMUM SPEED, VFD GAIN<br />
<strong>and</strong> INCREASE STEP can be viewed <strong>and</strong> modified in the<br />
SETUP2 display screen. TARGET <strong>and</strong> ACTUAL VFD SPEED<br />
can be viewed in the COMPRESS screen.<br />
ECW CONTROL OPTION — If this option is enabled, the<br />
PIC II uses the ENTERING CHILLED WATER temperature to<br />
modulate the vanes instead of the LEAVING CHILLED<br />
WATER temperature. The ECW CONTROL OPTION may be<br />
viewed on the TEMP_CTL screen, which is accessed from the<br />
EQUIPMENT SERVICE screen.<br />
CONTROL POINT DEADBAND — This is the tolerance<br />
range on the chilled water/brine temperature control point. If<br />
the water temperature goes outside the CHILLED WATER<br />
DEADBAND, the PIC II opens or closes the guide vanes until<br />
the temperature is within tolerance. The PIC II may be configured<br />
with a 0.5 to 2 F (0.3 to 1.1 C) deadb<strong>and</strong>. CHILLED<br />
WATER DEADBAND may be viewed or modified on the<br />
SETUP1 screen, which is accessed from the EQUIPMENT<br />
SERVICE table.<br />
For example, a 1° F (0.6° C) deadb<strong>and</strong> setting controls the<br />
water temperature within ±0.5° F (0.3° C) of the control point.<br />
This may cause frequent guide vane movement if the chilled<br />
water load fluctuates frequently. A value of 1° F (0.6° C) is the<br />
default setting.<br />
DIFFUSER CONTROL — On 19XR FRAME sizes 4 <strong>and</strong><br />
5 compressors equipped with a variable discharge diffuser, the<br />
PIC II adjusts the diffuser actuator position (DIFFUSER<br />
ACTUATOR on the COMPRESS screen) to correspond to the<br />
actual guide vane position (ACTUAL GUIDE VANE POS on<br />
the COMPRESS screen).<br />
The diffuser control can be enabled or disabled from the<br />
SETUP2 screen. See Table 2, Example 19. In addition, the diffuser<br />
<strong>and</strong> guide vane load points may be viewed <strong>and</strong> modified<br />
from this screen. These points must be correct for the compressor<br />
size. The diffuser opening can be incremented from fully<br />
open to completely closed. A 0% setting is fully open; a 100%<br />
setting is completely closed. To obtain the proper settings for<br />
Diffuser Control, contact a Carrier Engineering representative.<br />
PROPORTIONAL BANDS AND GAIN — Proportional b<strong>and</strong><br />
is the rate at which the guide vane position is corrected in proportion<br />
to how far the chilled water/brine temperature is from<br />
the control point. Proportional gain determines how quickly the<br />
guide vanes react to how quickly the temperature is moving<br />
from the CONTROL POINT. The proportional b<strong>and</strong>s <strong>and</strong> gain<br />
may be viewed or modified from the SETUP2 screen, which is<br />
accessed from the EQUIPMENT SERVICE table.<br />
The Proportional B<strong>and</strong> — There are two response modes, one<br />
for temperature response above the control point, the other for<br />
the response below the control point.<br />
The temperature response above the control point is called<br />
the PROPORTIONAL INC BAND, <strong>and</strong> it can slow or quicken<br />
guide vane response to chilled water/brine temperatures above<br />
the DEADBAND. The PROPORTIONAL INC BAND can be<br />
adjusted from a setting of 2 to 10; the default setting is 6.5.<br />
The response below the control point is called the PRO-<br />
PORTIONAL DEC BAND, <strong>and</strong> it can slow or quicken the<br />
guide vane response to chilled water temperature below the<br />
deadb<strong>and</strong> plus the control point. The PROPORTIONAL DEC<br />
BAND can be adjusted on the CVC/ICVC from a setting of 2 to<br />
10. The default setting is 6.0.<br />
NOTE: Increasing either of these settings causes the guide<br />
vanes to respond more slowly than they would at a lower<br />
setting.