Pressure Transducer Calibration - Carrier AquaEdge 19XRV series Operation, Maintenance And Installation Manual

Table 14 — Control Test Menu Functions
TESTS TO BE
PERFORMED
1. CCM Thermistors Entering Chilled Water
Leaving Chilled Water
Entering Condenser Water
Leaving Condenser Water
Evap Refrig Liquid Temp
Comp Discharge Temp
Comp Thrust Brg Temp
Oil Sump Temp
Comp Motor Winding Temp
Spare Temperature 1
Spare Temperature 2
Remote Reset Sensor
2. CCM Pressure Evaporator Pressure
Transducers Condenser Pressure
Oil Pump Delta P
SRD Delta P
SRD Rotating Stall
Chilled Water Delta P
Condenser Water Delta P
Transducer Voltage Ref
Humidity Sensor Input
Relative Humidity
3. Pumps Oil Pump — Confirm Pressure
Chilled Water — Confirm Flow and Delta P
Condenser Water — Confirm Delta P
4. Discrete Oil Heater Relay
Outputs Hot Gas Bypass Relay
Tower Fan Relay Low
Tower Fan Relay High
VFD Coolant Solenoid
Alarm Relay
Shunt Trip Relay
5. IGV & SRD Open/Close
Actuator If present, split ring diffuser will operate in
coordination with the guide vanes per con-
figured schedule.
6. Head Pressure Increase/Decrease 4-20 mA output
Output
7. Diffuser Actuator* Open/Close (independent of guide vanes)
8. Pumpdown When using pumpdown/lockout, observe
Lockout freeze up precautions when removing
charge:
Instructs operator which valves to close
and when.
Starts chilled water and condenser water
pumps and requests flow confirmation.
Monitors
Evaporator pressure
Condenser pressure
Evaporator temperature during
pumpout procedures
Turns pumps off after pumpdown.
Locks out compressor.
9. Terminate Starts pumps and monitors flows.
Lockout
Instructs operator which valves to
open and when.
Monitors
Evaporator pressure
Condenser pressure
Evaporator temperature during
charging process
Terminates compressor lockout.
10. Guide Vane Automatic, displays guide vane position
Calibration signal voltage. This test is required before
first start-up with new Actuator or Control-
ler.
*Diffuser tests function only on size 4 and 5 compressor with diffuser
control enabled.
NOTE: During any of the tests, an out-of-range reading will have an
asterisk (*) next to the reading and a message will be displayed if
diffuser control is enabled.
PRESSURE TRANSDUCER CALIBRATION — The
transducers measuring single pressure values (such as condens-
er and evaporator pressure) are calibrated individually, while a
pair of transducers measuring a pressure differential (OIL/
PUMP DELTA P, CONDENSER WATER DELTA P, CHILLED
DEVICES TESTED
WATER DELTA P) are calibrated together as a differential. In
units with ICVC controllers, transducers for sensing water side
flow are not provided as standard. These readings can be
viewed and calibrated from the COMPRESS and HEAT_EX
screens on the ICVC controller.
Each transducer or transducer pair can be calibrated at two
points: zero (0 psig or 0 kPa) and "high end" (between 25 and
250 psig, or between 173 and 1724 kPa). It is not usually
necessary to calibrate at initial start-up. However, at high
altitude locations, recalibration may be necessary to ensure the
proper refrigerant temperature-pressure relationship.
Zero Point Calibration — Shut down the compressor, and
cooler and condenser pumps. There must be no water flow
through the heat exchangers, but these systems must be filled.
For differential pairs, leave the transducers installed. For single
value transducers, disconnect the transducer's electrical cable,
remove the sensor from its Schrader fitting, then reconnect the
cable.
NOTE: If the cooler or condenser vessels are at 0 psig (0 kPa)
or are open to atmospheric pressure, the transducers can be
calibrated for the zero point without removal.
Access the HEAT_EX or COMPRESS screen under the
STATUS menu, and view the particular transducer reading.
(OIL PUMP DELTA P is in the COMPRESS screen; all others
are in HEAT_EX.) If the displayed reading is not 0 psi (0 kPa),
press the key to highlight the associated line in the
SELECT
display, then the
ENTER
and
INCREASE DECREASE
ue should change to 0.0.
If the ICVC fails to accept the zero point calibration, the
value will not change to 0.0 and the display will show "Higher
Force In Effect." This indicates that the sensor voltage is out of
the acceptable range. For each single value transducer there are
3 terminals at the CCM: 0 vdc (low), "sensor" voltage, and
5.00 vdc (high). With a base supply voltage of 5.00 volts, the
acceptable range of voltage taken between the low and sensor
terminals for zero point calibration is 0.40 to 0.55 v. For each
transducer differential pair there are two 3-terminal sets at the
CCM. With a base supply voltage of 5.00 volts, the acceptable
range of voltage taken between the sensor terminal for the high
end transducer (water inlet or oil pump discharge) and the
sensor terminal for the low end transducer (water outlet or oil
sump) for zero point calibration is –0.065 to +0.085 v. If this
occurs with a differential pair, one possible remedy is to swap
the high end (e.g., inlet) and low end (e.g., outlet) transducers.
In most cases this puts the sensor voltage within the acceptable
range.
High End Calibration — High end calibration can be per-
formed between 25 and 250 psig (173 and 1724 kPa), compar-
ing the pressure readings in the ICVC display to an accurate re-
frigeration gage. While it normally will have a negligible ef-
fect, it may improve transducer accuracy over the full pressure
range. High end calibration is not recommended for transducer
differential pairs. Pressure can be provided by attaching a regu-
lated 250 psig (1724 kPa) pressure source, such as from a nitro-
gen cylinder, to the transducer.
Access the HEAT_EX screen under the STATUS menu,
and the CONDENSER PRESSURE or EVAPORATOR
PRESSURE to the reference pressure gage. To change the dis-
played reading, press the
ated line in the display, then the
key to set the new value, then the
value can be changed to any value within ±15% of a nominal
value.
78
key. (For zero point calibration, the
keys have no effect.) The val-
key to highlight the associ-
SELECT
or
INCREASE DECREASE
key. Generally, the
ENTER