Carrier XRV Spécifications télécharger pdf (Page 90)

COOLER CONDENSER PRESSURE TRANSDUCER

AND OPTIONAL WATERSIDE FLOW DEVICE CALI-

BRATION — Calibration can be checked by comparing the

pressure readings from the transducer to an accurate refrigera-

tion gage reading. These readings can be viewed or calibrated

from the HEAT_EX screen on the ICVC. The transducer can

be checked and calibrated at 2 pressure points. These calibra-

tion points are 0 psig (0 kPa) and between 25 and 250 psig

(173 and 1724 kPa). To calibrate these transducers:

1. Shut down the compressor, cooler, and condenser pumps.

NOTE: There should be no flow through the heat

exchangers.

2. Disconnect the transducer in question from its Schrader

fitting for cooler or condenser transducer calibration. For

oil pressure or flow device calibration, leave the transduc-

er in place.

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 zero without remov-

ing the transducer from the vessel.

3. Access the HEAT_EX screen and view the particular

transducer reading (the EVAPORATOR PRESSURE or

CONDENSER PRESSURE parameter on the HEAT_EX

screen). To calibrate oil pressure or liquidside flow

device, view the particular reading (CHILLED WATER

DELTA P and CONDENSER WATER DELTA P on the

HEAT_EX screen, and OIL PUMP DELTA P on the

COMPRESS screen). It should read 0 psi (0 kPa). If the

reading is not 0 psi (0 kPa), but within ± 5 psi (35 kPa),

the value may be set to zero by pressing the

softkey while the appropriate transducer parameter is

highlighted on the ICVC screen. Then press the

softkey. The value will now go to zero. No high end

calibration is necessary for OIL PRESSURE DELTA P or

flow devices.

If the transducer value is not within the calibration

range, the transducer returns to the original reading. If

the pressure is within the allowed range (noted above),

check the voltage ratio of the transducer. To obtain the

voltage ratio, divide the voltage (dc) input from the

transducer by the TRANSDUCER VOLTAGE REF

supply voltage signal (displayed in CONTROL TEST

menu in the PRESSURE TRANSDUCERS screen) or

measure across the positive (+ red) and negative

(– black) leads of the transducer. For example, the

condenser transducer voltage reference is measured

at CCM terminals J2-4 and J2-6, the condenser trans-

ducer voltage input. The input to reference voltage

ratio must be between 0.80 and 0.11 for the software to

allow calibration. Pressurize the transducer until the

ratio is within range. Then attempt calibration again.

4. A high pressure point can also be calibrated between 25

and 250 psig (172.4 and 1723.7 kPa) by attaching a regu-

lated 250 psig (1724 kPa) pressure (usually from a

nitrogen cylinder). The high pressure point can be

calibrated by accessing the appropriate transducer param-

eter on the HEAT_EX screen, highlighting the parameter,

pressing the softkey, and then using the

or softkeys to adjust the

value to the exact pressure on the refrigerant gage. Press

the softkey to finish the calibration. Pressures at

high altitude locations must be compensated for, so the

chiller temperature/pressure relationship is correct.

The PIC III does not allow calibration if the transducer is

too far out of calibration. In this case, a new transducer must be

installed and re-calibrated. If calibration problems are encoun-

tered on the OIL PRESSURE DELTA P channel, sometimes

swapping the compressor oil discharge pressure transducer and

the oil sump pressure transducer will offset an adverse trans-

ducer tolerance stack up and allow the calibration to proceed.

TRANSDUCER REPLACEMENT — Since the transducers

are mounted on Schrader-type fittings, there is no need to

remove refrigerant from the vessel when replacing the trans-

ducers. Disconnect the transducer wiring. Do not pull on the

transducer wires. Unscrew the transducer from the Schrader

fitting. When installing a new transducer, do not use pipe sealer

(which can plug the sensor). Put the plug connector back on the

sensor and snap into place. Check for refrigerant leaks.

Control Algorithms Checkout Procedure — One

of the tables on the ICVC SERVICE menu is CONTROL

ALGORITHM STATUS. The maintenance screens may be

viewed from the CONTROL ALGORITHM STATUS table to

see how a particular control algorithm is operating.

These maintenance screens show different tables that are

very useful in helping to determine how the control tempera-

ture is calculated and guide vane positioned and also for

observing the reactions from load changes, control point over-

rides, hot gas bypass, surge prevention, etc. See Table 15.

Table 15 — Control Algorithm Status Tables

*The HEAT_EX screen is under the STATUS menu.

SELECT

ENTER

SELECT

INCREASE

DECREASE

ENTER

WARNING

Be sure to use a back-up wrench on the Schrader fitting

whenever removing a transducer, since the Schrader fitting

may back out with the transducer, causing an uncontrolled

loss of refrigerant and possible injury to personnel.

TABLE

EXPANDED

NAME

DESCRIPTION

CAPACITY

Capacity

Control

This table shows all values used to

calculate the chilled water/brine

control point.

OVERRIDE

Override

Status

Details of all chilled water control

override values.

SURGPREV Surge Pre-

vention Sta-

tus

Displays all information used or

supplied by the surge prevention

algorithm.

LL_MAINT

LEAD/LAG

Status

Indicates LEAD/LAG operation

status.

OCCDEFCM

Time

Schedules

Status

The Local and CCN occupied

schedules are displayed here to

help the operator quickly deter-

mine whether the schedule is in

the “occupied” mode or not.

WSMDEFME

Water

System

Manager

Status

The water system manager is a

CCN module that can turn on the

chiller and change the chilled water

control point. This screen indicates

the status of this system.

VFD_HIST

VFD Alarm

History

Displays VFD values at last fault.

LOADSHED

Loadshed

Status

Displays Loadshed (Demand Limit)

status.

CUR_ALARM

Current

Alarm Status

Displays current chiller alarms.

HEAT_EX*

Surge and

HGBP Status

The surge and hot gas bypass

control algorithm status is viewed

from this screen. All values related

to this control are displayed.

1 2 ... 85 86 87 88 89 90 91 92 93 94 95 ... 189 190

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Carrier XRV Spécifications Page 90

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