Carrier XRV Spécifications télécharger pdf (Page 48)

Kilowatt Output — An output is available on the CCM

module [Terminal J8-1 (+) and J8-2 (–)] to represent the power

consumption of the chiller. The 4 to 20 mA signal generated by

the CCM module can be wired to the building automation or

energy management system to monitor the chiller’s energy

consumption. Output is 2 mA with the chiller off, and it

varies linearly from 4 mA (representing 0% rated kilowatt

consumption) to 20 mA (representing 100% RATED LINE

KILOWATTS). The rated peak kilowatt consumption is

configured by the user in the VFD_CONF display screen by

setting the RATED LINE KILOWATTS from the machine elec-

trical data nameplate.

Remote Reset of Alarms — A standard feature of the

PIC III controls is the ability to reset a chiller in a shutdown

alarm state from a remote location. If the condition which

caused the alarm has cleared the chiller, the chiller can be

placed back into a normal CCN operating mode when the

REMOTE RESET OPTION (ICVC_PWD menu) is set to

ENABLE. A variety of Carrier Comfort Network

software

systems including ComfortVIEW™ or Network Service

Tool™ can access the PIC III controls and reset the displayed

alarm. Third party software from building automation systems

(BAS) or energy management systems (EMS) can also access

the PIC III controls through a Carrier DataLINK™ module and

reset the fault displayed. Both methods would access the

ICVC_PWD screen and force the RESET ALARM? point to

YES to reset the fault condition. If the PIC III controls have de-

termined that it is safe to start the chiller, the CCN MODE?

point (ICVC_PWD screen) can be forced to YES to place the

chiller back into normal CCN operating mode. The only excep-

tions are the following alarms that cannot be reset from a

remote location: Alarm/Alert STATE 100, 200, 201, 204, 206,

217-220, 233, 234, 247, and 259. To view alarm codes, refer to

Troubleshooting Guide, Checking Display Messages, page 89.

After the alarm has been reset, the PIC III control will incre-

ment the STARTS IN 12 HOURS counter by one upon restart. If

the limit of 8 starts in a 12-hour period is reached (Prestart/

Alert state 100), this must be reset at the local chiller control

panel (ICVC).

Condenser Pump Control — The chiller will moni-

tor the CONDENSER PRESSURE and may turn on the con-

denser pump if the condenser pressure becomes too high while

the compressor is shut down. The COND PRESS OVERRIDE

parameter is used to determine this pressure point. COND

PRESS OVERRIDE is found in the SETUP1 display screen,

which is accessed from the EQUIPMENT SERVICE table.

The default value is 125 psig (862 kPa).

If the CONDENSER PRESSURE is greater than or equal to

the COND PRESS OVERRIDE, and the ENTERING CON-

DENSER WATER temperature is less than 115 F (46 C), the

condenser pump will energize to try to decrease the pressure

and Alert 151 will be generated. The pump will turn off when

the condenser pressure is 3.5 psi (24.1 kPa) less than the

pressure override and the CONDENSER REFRIG TEMP is

within 3 F (1.7 C) of the ENTERING CONDENSER WATER

temperature.

Condenser Freeze Prevention — This control algo-

rithm helps prevent condenser tube freeze-up by energizing the

condenser pump relay. The PIC III controls the pump and, by

starting it, helps to prevent the water in the condenser from

freezing. The PIC III can perform this function whenever the

chiller is not running except when it is either actively in pump-

down or in pumpdown/lockout with the freeze prevention

disabled.

When the chiller is off and CONDENSER REFRIG TEMP

is less than the CONDENSER FREEZE POINT, the

CONDENSER WATER PUMP will be energized (Alert State

154) However, if the chiller is in pump down, and when it

entered pump down mode, the CONDENSING REFRIG

TEMP was more than 5 F (2.7 C) above the CONDENSER

FREEZE POINT, the same low temperature condition will

generate Alarm State 244 and the CONDENSER WATER

PUMP will be energized. In either case, the fault state will clear

and the pump will turn off when the CONDENSER REFRIG

TEMP is more than 5 F (2.7 C) above the CONDENSER

FREEZE POINT and the entering condenser water temperature

is greater than the CONDENSER FREEZE POINT. If the chill-

er is in Recycle Shutdown Mode when the condition occurs,

the controls will transition to a non-recycle shutdown.

Evaporator Freeze Protection — When the EVAP-

ORATOR REFRIG TEMP is less than the EVAP REFRIG

TRIPPOINT plus the REFRIG OVERRIDE DELTA T (configu-

rable from 2 to 5 F or 1.1 to 2.8 C), Alert State 122 will be dis-

played, and a capacity override will occur. (See Table 7.)

When the unit is running or in recycle, if the EVAPORATOR

REFRIG TEMP is equal to or less than the EVAP REFRIG

TRIPPOINT (33 F or 0.6 C for water, configurable for brine),

Protective Limit Alarm State 232 will be displayed, the unit

will shut down, and the CHILLED WATER PUMP will remain

on. The alarm will be clearable when the leaving chilled water

temperature rises 5°F (2.8°C) above the CONTROL POINT.

When the unit is off, if the EVAPORATOR REFRIG TEMP

is less than the EVAP REFRIG TRIPPOINT plus 1° F (0.6 C),

Alarm State 243 will be generated and the CHILLED WATER

PUMP will be turned on. The alarm can be reset when the

EVAPORATOR REFRIG TEMP rises 5 F (2.8 C) above the

EVAP REFRIG TRIPPOINT.

Tower Fan Relay Low and High — Low condens-

er water temperature can cause the chiller to shut down when

refrigerant temperature is low. The tower fan relays, located in

the VFD, are controlled by the PIC III to energize and deener-

gize as the pressure differential between cooler and condenser

vessels changes. This prevents low condenser water tempera-

ture and maximizes chiller efficiency. The tower fan relay can

only accomplish this if the relay has been added to the cooling

tower temperature controller.

TOWER FAN RELAY LOW is turned on whenever the

condenser water pump is running, flow is verified, and the

difference between cooler and condenser pressure is more than

30 psid (207 kPad) for entering condenser water temperature

greater than 65 F (18.3 C).

TOWER FAN RELAY LOW is turned off when the condens-

er pump is off, flow is stopped, or the EVAP REFRIGERANT

TEMP is less than the EVAP REF OVERRIDE TEMP for

ENTERING CONDENSER WATER temperature less than

62 F (16.7 C), or the difference between the CONDENSER

PRESSURE and EVAPORATOR PRESSURE is less than

25 psid (172.4 kPad) for ENTERING CONDENSER water less

than 80 F (27 C).

TOWER FAN RELAY HIGH is turned on whenever

the condenser water pump is running, flow is verified and

the difference between EVAPORATOR PRESSURE and

CONDENSER PRESSURE is more than 35 psid (241.3 kPa)

for ENTERING COND WATER temperature greater than the

TOWER FAN HIGH SETPOINT (SETPOINT menu, default

75 F [23.9 C]).

The TOWER FAN RELAY HIGH is turned off when the

condenser pump is off, flow is stopped, or the EVAPORATOR

REFRIG TEMP is less than the EVAP REF OVERRIDE TEMP

and ENTERING CONDENSER WATER is less than 70 F

(21.1 C), or the difference between EVAPORATOR PRES-

SURE and CONDENSER PRESSURE is less than 28 Psid

(193 kPa), and ENTERING CONDENSER WATER tempera-

ture is less than TOWER FAN HIGH SETPOINT minus 3 F

(–16.1 C).

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Carrier XRV Spécifications Page 48

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