Carrier 040-420 User Manual

Page 38

Example 2

Reading Current Operating Modes

KEYPAD

DISPLAY

ENTRY

RESPONSE I

COMMENTS

TUE

Keypad has not been used for at

LOCAL ON

least 10 minutes Rotating summary

C O O L 1

display appears on screen

0 A L A R M S

2 MODES

There are 2 modes currently in effect

c l

LOCAL ON

Unit is on by chiller on/off switch

c l

M O D E 8

Temperature reset is in effect

(Stage)

This subfunction displays the capac-

ity stage number. See Tables

for compressor load-

ing sequence. To enter the STAGE subfunction, press

and use the

to display the stage number.

Additional

provides the following information:

Percent of total unit capacity being utilized.
Percent of each circuit capacity being utilized.
Demand limit set point in effect (can be any value be-
tween 0% and 100%).

Load limit set point in effect. This is a CCN function for

controlling operation of multiple units between 0% and

100% of total capacity of all units combined.

Status

of each compressor relay. When a compressor is

on, the number of that compressor is displayed. If a com-
pressor is off, a 0 is displayed. For example: In a given
circuit, if compressors 1 and 3 are running, and 2 and 4
are not running, 0301 is displayed for that circuit.
Load/Unload factor for compressors. This factor is an in-
dication of when a step of capacity is added or sub-
tracted. Its value can range from slightly less than -1 .O
to slightly more than 1 .O. When load/unload factor
reaches + 1.0, a compressor is added. When the load/
unload factor reaches -1 .O, a compressor is subtracted.
If compressor unloaders are used, at

a compressor is

unloaded and at

a compressor is loaded up.

(Set Point)

This subfunction displays leaving

water temperature and leaving chilled water set point. If
unit is programmed for dual set point, the chilled water set
point currently in effect (either occupied or unoccupied) is
displayed. If reset is in effect, the unit operates to the mod-

ified chilled water set point. This means the leaving water
temperature may not equal the chilled water set point The
modified chilled water set point can also be displayed in the
Status function. To enter the set point subfunction, de-

press

and use the

to display modified leaving

chilled water set point followed by leaving water set point

and actual cooler leaving fluid temperature.

(Temperature)

The temperature subfunction dis-

plays the readings at temperature sensing thermistors.

To read a temperature, enter

, then scroll to de-

sired temperature using the

key. See Table 9 for the

order of readouts.

(Pressure)

This subfunction displays suction,

discharge and net oil pressure at lead compressor of each
circuit of unit.

(Analog Inputs)

This subfunction displays

analog inputs, if any. Enter

, then use the

. The

transducer supply voltage, 4-20

reset signal can be dis-

played. This is useful for problem diagnosis prior to using
the test function.

( I n p u t s )

This subfunction displays status

(ON/OFF) of input switch where applicable. Status of dual
set point switch, and demand limit switches 1 and 2 can be
displayed. This is useful for problem diagnosis prior to us-
ing the test function.

(Outputs)

This function displays ON/OFF sta-

tus of alarm relay, all fan relays, and chilled water pump
relay. It also displays ON/OFF status of compressor unload-
ers (if used). The position of each EXV (in percent open)
can be displayed.

TEST FUNCTION The test function operates the diag-
nostic program. To initiate test function, the LOCAL/
ENABLE-STOP-CCN switch must be in STOP position.

To reach a particular test, enter its subfunction number,

then scroll to desired test by pressing the

key. Press

to start a test. Press

to terminate or

exit a test. Pressing the

key after a test has started ad-

vances system to next test, whether current test is operating
or has timed out, Once in the next step, you may start

test by pressing

or advance past it by pressing

While the unit is in test, you may leave test function and

access another display or function by pressing appropriate

keys. However, a component that is operating when an-

other function is accessed remains operating. You must

re-enter test function and press the

key to shut down

the component. Components with a timed operating limit
time

out

normally even if another function is accessed.

Keypad entry

allows the operator to make the

following checks by using

LID display check.

is 8.8.8.8.8.8.8.8 .

Operation of remote alarm.
Operation of condenser fans.
Operation of chilled water pump.
Operation of

To drive EXV fully open, enter

(100% open). To drive EXV fully closed,

ter

(0% open).

K e y p a d e n t r y

accesses the compressor and

compressor unloader

tests.

During compressor operational tests, compressor starts
and runs for 10 seconds. Compressor service valves must
be open. Energize crankcase heaters 24 hours prior to
performing compressor tests.

Since test function checks only certain outputs, it is good

practice to also check all inputs and outputs accessible

through the status function. These are located at

and

(see Table 9). If keypad is not used

for 10 minutes, unit automatically leaves test function and
resumes rotating display. See Example 3.