Carrier PIC 5+ - Capacity Control

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analog input signal provided from any external sensor,
controller, or other device which is appropriately congured.
At this type, Degrees Reset At 20 mA shall be congured in
RESETCFG table.
RESET TYPE 2: REMOTE TEMPERATURE RESET
Reset Type 2 is an automatic water temperature reset based
on a remote temperature sensor input signal. This function
can be accessed by the following congurations:
- Congure the remote temperature at no reset occurs
(Remote temp –> NO RESET).
- Congure the remote temperature at full reset occurs
(remote temp –> FULL RESET).
Finally, enter the amount of reset (Deg reset water DT full).
RESET TYPE 3 — CONTROLLED WATER TEMP
DELTA RESET
Reset Type 3 is an automatic controlled water temperature
reset based on heat exchanger temperature difference. This
function can be accessed by the following congurations:
- Congure the Controlled water temperature delta T at
no reset occurs (Controlled Water DELTA T NO
RESET).
- Congure the Controlled water temperature delta T at
full reset occurs (Controlled Water DELTA T FULL
RESET).
- Finally, enter the amount of reset (Deg reset water DT full).
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Capacity control shall provide chilled or condenser water temperature control by modulating the position of the inlet guide
vane 1, and VFD speed for variable speed compressor based.
If VFD OPTION is set to with VFD, when need to increase capacity, the control will rst try to increase IGV TARGET
POSITION if it has not reached the travel limit, otherwise increase VFD TARGET SPEED; when need to decrease capacity,
the control will rst try to decrease VFD TARGET SPEED if it has not reached the minimum VFD speed, otherwise decrease
IGV TARGET POSITION.
100TRAVEL LIMIT
GUIDE VANES % POSITION
GUIDE VANES AT MAX.
MODULATE VFD
VFD AT START-UP SPEED.
MODULATE GUIDE VANES
STARTUP;
VFD TO START-UP SPEED,
GUIDE VANES CLOSED
GUIDE VANESVFD
STA RT
MIN.
MAX.
VFD% SPEED
0
Guide vane control
The control regulates the guide vane position as determined
by the Capacity Control function in normal condition and
other functions in abnormal conditions which include
capacity inhibit request, capacity decrease request. The guide
vane actuator is driven by guide vane target position and
comparing to the actual feedback value.. Guide vane actual
position is limited to between zero and “GV1 TRAVEL
LIMIT” which is congured at “Service Conguration” menu.
When chiller is shutting down or off, guide vane is always
driven to zero.
VFD speed control
If VFD option is set to NO VFD, or compressor relay is not
closed, VFD TARGET SPEED will be 0.
From compressor relay is commanded to be closed to the
end of ramp loading, VFD TARGET SPEED will be set to
startup speed.
When chiller is running normally, the control will get input
from capacity control to see whether to change VFD
TARGET SPEED and how much to change.
When chiller is in shut down process, VFD TARGET SPEED
will be set to minimum VFD speed.
After the compressor relay is cut off, VFD TARGET SPEED
will be set to 0.