Carrier 17 Start Up & Operation Manual Download

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Starter faults or optional protective devices within the starter

can shut down the machine. These devices are dependent on
what has been purchased as options.

If compressor motor overload or ground fault occurs,
check the motor for grounded or open phases before at-
tempting a restart.

If the controller initiates a safety shutdown, it displays the

fault on the LID with a primary and a secondary message,
and energizes an alarm relay in the starter and blinks the
alarm light on the control center. The alarm is stored in memory
and can be viewed in the PIC Alarm History table along with
a message for troubleshooting.

To give a better warning as to the operating condition of

the machine, the operator also can define alert limits on vari-
ous monitored inputs. Safety contact and alert limits are de-
fined in Table 3. Alarm and alert messages are listed in the
Troubleshooting Guide section, page 83.

SHUNT TRIP — The optional shunt trip function of the PIC
is a safety trip. The shunt trip is wired from an output on the
SMM to the motor circuit breaker. If the PIC tries to shut
down the compressor through normal shutdown procedure
but is unsuccessful for 30 seconds, the shunt trip output is
energized and causes the circuit breaker to trip off. If ground
fault protection has been applied to the starter, the ground
fault trip will also energize the shunt trip to trip the circuit
breaker.

Default Screen Freeze —

Whenever an alarm oc-

curs, the LID default screen will freeze displaying the con-
dition of the machine at the time of alarm. Knowledge of the
operating state of the chiller at the time an alarm occurs is
useful when troubleshooting. Current machine information
can be viewed on the Status tables. Once all existing alarms
are cleared (by pressing the RESET softkey), the default
LID will return to normal operation.

Motor Cooling Control (Hermetic Motors Only)
—

Motor temperature is reduced by refrigerant entering the

motor shell and evaporating. The refrigerant is regulated by
the motor cooling relay. This relay will energize when the
compressor is running and motor temperature is above
125 F (51.7 C). The relay will close when motor tempera-
ture is below 100 F (37.8 C). Note that there is always a
minimum flow of refrigerant when the compressor is oper-
ating for motor cooling; the relay only controls additional
refrigerant to the motor.
NOTE: An additional motor cooling relay is not required for
Hermetic FA style compressors.

Auxiliary Oil Pump Control (Open Drive
Machines Only) —

The auxiliary oil pump (optional)

is controlled by the PIC. During start-up, if the main oil pump
cannot raise pressure to 18 psid (124 kPa), the auxiliary oil
pump will be energized. During compressor operation, the
auxiliary oil pump will be energized if the oil pressure falls
below the alert threshold (18 psid [124 kPa]). Once running,
the auxiliary oil pump will remain on until the compressor
is turned off and will deenergize with the main oil pump af-
ter the post-lube time period.

Shaft Seal Oil Control (Open Drive Machines
Only) —

All open drive machines require that the shaft

seal be bathed in oil at all times, especially when the

machine is not running. This ensures that refrigerant does
not leak past the seal. The PIC control will energize the oil
pump for one minute if the oil pump has not operated during
the past 12 hours.

It is important to note that if control power is to be turned

off for longer than this period, the refrigerant charge must be
pumped over into the utility vessel. Because the oil heater
will also be off during this time, storing the refrigerant will
also prevent refrigerant migration into the oil.

Ramp Loading Control —

The ramp loading control

slows down the rate at which the compressor loads up. This
control can prevent the compressor from loading up during
the short period of time when the machine is started, and the
chilled water loop has to be brought down to normal design
conditions. This helps reduce electrical demand charges by
slowly bringing the chilled water to control point. However,
the total power draw during this period remains almost
unchanged.

There are 2 methods of ramp loading with the PIC. Ramp

loading can be based on chilled water temperature or on mo-
tor load.
1. Temperature ramp loading limits the rate at which either

leaving chilled water or entering chilled water tempera-
ture decreases by an operator-configured rate. The lowest
temperature ramp table will be used the first time the ma-
chine is started (at commissioning). The lowest tempera-
ture ramp rate will also be used if machine power has
been off for 3 hours or more (even if the motor ramp load
is selected).

2. Motor load ramp loading limits the rate at which the com-

pressor motor current or compressor motor load in-
creases by an operator-configured rate.

The TEMP (Temperature) PULLDOWN, LOAD PULL

DOWN, and SELECT RAMP TYPE may be viewed/modified
on the LID Equipment Configuration table, Config table (see
Table 2). Motor load is the default type.

Capacity Override (See Table 4) —

These can pre-

vent some safety shutdowns caused by exceeding motor am-
perage limit, refrigerant low temperature safety limit, motor
high temperature safety limit, and condenser high pressure
limit. In all cases there are 2 stages of compressor vane
control.
1. The vanes are held from opening further, and the status

line on the LID indicates the reason for the override.

2. The vanes are closed until condition decreases below the

first step set point, and then the vanes are released to nor-
mal capacity control.

Whenever the motor current demand limit set point is reached,

it activates a capacity override, again with a 2-step process.
Exceeding 110% of the rated load amps for more than
30 seconds will initiate a safety shutdown.

The compressor high lift (surge prevention) set point will

cause a capacity override as well. When the surge preven-
tion set point is reached, the controller normally will only
hold the guide vanes from opening. If so equipped, the hot
gas bypass valve will open instead of holding the vanes.

High Discharge Temperature Control —

If the dis-

charge temperature increases above 200 F (93 C), the guide
vanes are proportionally opened to increase gas flow through
the compressor. If the leaving chilled water temperature drops
5° F (2.8° C) below the control point temperature, machine
will enter the recycle mode.