Reset Type; Demand Limit Control Option; Hot Gas Bypass (Optional) Algorithm (See; Head Pressure Output Reference - Carrier AquaEdge 23XRV Start-Up, Operation And Maintenance Instructions Manual

The ICVC default screen indicates when the chilled liquid
reset is active. TEMPERATURE RESET on the MAINSTAT
screen indicates the amount of reset. The CONTROL POINT
will be determined by adding the TEMPERATURE RESET to
the ECL SETPOINT or LCL SETPOINT.
To activate a reset type, access the TEMP_CTL screen and
input all configuration information for that reset type. Then,
input the reset type number (1, 2, or 3) in the SELECT/
ENABLE RESET TYPE input line.
RESET TYPE 1: 4 to 20 mA (0 to 5 vdc) TEMPERATURE
RESET — Reset Type 1 is an automatic chilled liquid tempera-
ture reset based on a remote temperature sensor input con-
figured for either an externally powered 4 to 20 mA or a 0 to
5 vdc signal. Reset Type 1 permits up to ±30 F (±17 C) of
automatic reset to the ECL SETPOINT or LCL SETPOINT.
The auto, chilled liquid reset is hardwired to CCM terminals
J5-3 (–) and J5-4 (+). Switch setting number 2 on SW2 will
determine the type of input signal. With the switch set at the
ON position the input is configured for an externally powered
4 to 20 mA signal. With the switch in the OFF position the
input is configured for an external 0 to 5 vdc signal. One of the
following modifications are also required when using a 1 to
5 vdc temperature reset signal:
1. Install a 25 ohm resistor in series with the (+) voltage
lead connected to CCM terminal J5-4.
2. Modify the input voltage signal with an external con-
troller software to calibrate the temperature interpreted
by the CCM. The controller should provide 4.54 v at
100% of the controller's output range and 0.91 v at 0%
of the controller's output range.
RESET TYPE 2: REMOTE TEMPERATURE RESET —
Reset Type 2 is an automatic chilled liquid temperature reset
based on a remote temperature sensor input signal. Reset Type
2 permits ±30 F (±17 C) of automatic reset to the ECL
SETPOINT or LCL SETPOINT based on a temperature sensor
wired to the CCM module (see wiring diagrams or certified
drawings). The temperature sensor must be wired to CCM
terminal J4-13 and J4-14.
To configure Reset Type 2, enter the temperature of the
remote sensor at the point where no temperature reset will

occur (REMOTE TEMP
temperature at which the full amount of reset will occur

(REMOTE TEMP FULL RESET). Then, enter the maximum
amount of reset required to operate the chiller (DEGREES RE-
SET). Reset Type 2 can now be enabled.
RESET TYPE 3 — Reset Type 3 is an automatic chilled liquid
temperature reset based on the difference between ENTERING
CHILLED LIQUID and LEAVING CHILLED LIQUID tem-
perature. Reset Type 3 adds ±30 F (±17 C) based on the chilled
liquid temperature difference.
To configure Reset Type 3, enter the chilled liquid tempera-
ture difference (the difference between entering and leaving
chilled liquid) at which no temperature reset occurs (CHL

DELTA T NO RESET). This chilled liquid temperature differ-
ence is usually the full design load temperature difference.
Next, enter the difference in chilled liquid temperature at which
the full amount of reset occurs (CHL DELTA T
SET). Finally, enter the amount of temperature reset (DE-
GREES RESET). Reset Type 3 can now be enabled.
Demand Limit Control Option —
control option (20 mA DEMAND LIMIT OPT) is externally
controlled by a 4 to 20 mA or 1 to 5 vdc signal from an energy
management system (EMS). The option is set up on the
RAMP_DEM screen. When enabled, 4 mA is the 100%
demand set point with an operator-configured minimum
demand at a 20 mA set point (DEMAND LIMIT AT 20 mA).
The auto. demand limit is hardwired to terminals J5-1 (–)
and J5-2 (+) on the CCM. Switch setting number 1 on CCM
SW2 will determine the type of input signal. With the switch
NO RESET). Next, enter the

FULL RE-
The demand limit
set at the ON position the input is configured for an externally
powered 4 to 20 mA signal. With the switch in the OFF
position the input is configured for an external 1 to 5 vdc sig-
nal. One of the following modifications are also required when
using a 1 to 5 vdc DEMAND LIMIT signal:
1. Install a 25 ohm resistor in series with the (+) voltage
lead connected to CCM terminal J5-2.
2. Modify the input voltage signal with an external con-
troller software to calibrate the temperature interpreted
by the CCM. The controller should provide 4.54 v at
100% of the controller's output range and 0.91 v at 0%
of the controller's output range.

Hot Gas Bypass (Optional) Algorithm (See

If a hot gas bypass solenoid valve is present
Fig. 31-33) —
and the HGBP OPTION in the OPTIONS table is set to 1 or 2,
this operator configurable feature can determine if load condi-
tions are too low for the compressor and corrective action can
be taken.
When the HGBP OPTION = 0: the HGBP algorithm is
disabled.
When the HGBP OPTION = 1, the algorithm determines if
corrective action is necessary by checking the chiller operating
point against an operator configured threshold. The threshold is
calculated from a combination of the difference between Enter-
ing and Leaving Chilled Liquid temperatures and the differ-
ence between CONDENSER PRESSURE and EVAPORATOR
PRESSURE. The operator configured data points are the MIN
LOAD POINT(T1/P1) and the FULL LOAD POINT (T2/P2).
These points have default settings defined in the OPTIONS
screen and on Table 3. A line is drawn between these points as
shown in Fig. 31 and 32. The default Load Points (to prevent
compressor stall) are shown.
Whenever the ACTIVE DELTA T (actual temperature differ-
ence between the LEAVING CHILLED LIQUID and ENTER-
ING CHILLED LIQUID) is on the left side of the line plotted
in Fig. 31 and 32, the algorithm will energize the hot gas by-
pass valve to falsely load the chiller. If ACTIVE DELTA T falls
to the right side of the line plotted in Fig 31 and 32 by more
than the HGBP DEADBAND, the hot gas bypass valve is de-
energized. The HGBP valve is also deenergized if ACTIVE
DELTA P (actual difference between CONDENSER PRES-
SURE and EVAPORATOR PRESSURE) falls to below HGBP
DELTA P1. Instructions to configure the MIN LOAD
POINT(T1/P1) and FULL LOAD POINT(T2/P2) are on
page 76.
When the HGBP OPTION = 2, the option energizes the Hot
Gas Bypass relay solely based on the VFD TARGET SPEED.
Evaluation of the VFD TARGET SPEED begins at the comple-
tion of ramp loading. If the VFD TARGET SPEED is less than
the Minimum Speed plus the HGBP ON DELTA SPEED for 3
seconds then the Hot Gas Bypass is energized. When the VFD
Target Speed is greater than the Minimum Speed plus the
HGBP ON DELTA SPEED and the HGBP OFF DELTA
SPEED for 3 seconds then the Hot Gas Bypass relay is de-en-
ergized. See Fig. 33.
Head Pressure
The PIC III controls output a 4 to 20 mA signal
Fig. 34) —
for the configurable Delta P (CONDENSER PRESSURE –
EVAPORATOR PRESSURE) reference curve shown in Fig. 34.
The DELTA P AT 100% (default at 50 psi), DELTA P AT 0%
(default at 25 psi) and MINIMUM OUTPUT are configurable
in the EQUIPMENT SERVICE-OPTIONS table. When con-
figuring this output, ensure that minimum requirements for
proper condenser FLASC orifice performance are maintained.
The 4 to 20 mA output from VFD TB1 terminals 17 and 18 can
be used as a reference to control a tower bypass valve, tower
speed control, or condenser pump speed control. The head
54
Output Reference (See