Carrier 30GN040-420 operating instructions Example 3 Ð Using Test Function, Reset Set Points

Keypad entry allows the operator to make the

following checks by using :

·LID display check. Proper display is 8.8.8.8.8.8.8.8.

·Operation of alarm relay.

·Operation of condenser fans.

·Operation of chilled ¯uid pump.

·Operation of liquid line solenoids.

·Operation of the hot gas bypass relays.

·Operation of EXVs. To drive EXV fully open, enter

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

ter (0% open).

·Operation of each remote alarm.

·Operation of Motormaster signals.

Keypad entry accesses the compressor and compressor unloader operational 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.

Example 3 Ð Using Test Function

KEYPAD	DISPLAY		COMMENTS
ENTRY	RESPONSE
	COMP		Factory/®eld test of compressors
			subfunction of test function
	CPA 1	OFF	Circuit A, Compressor 1A test
	CPA 1	ON	Pressing ENTR starts the test:
			when the compressor should be running
			the display shows CPA1 on
	CPA 1	OFF	If the test is allowed to time out (10 sec-
			onds) the display will show CPA1 off
	CPA 2	OFF	Pressing the down arrow key advances the
			system to Circuit A, compressor 2 test
NOTE: Once a compressor has been run using the				function,

it is not allowed to run again for 30 seconds.

accesses the transducer calibration subfunction.

All transducers must be calibrated in order for the unit to operate. Refer to Pressure Transducers section on page 60 for calibration procedure.

HISTORY FUNCTION Ð Pressing and dis-

plays total unit run time, total run time for each circuit, and total run time for each compressor.

Pressing and displays total unit starts, the total starts for each circuit, and total starts for each com-

pressor. Pressing and displays the last 10 alarms

along with a description of each alarm.

SET POINT FUNCTION Ð Set points are entered through the keypad. Set points can be changed within the upper and lower limits, which are ®xed. The ranges are listed below.

Chilled Fluid Set Point

Water:

38 to 86 F (3.3 to 30 C)

Medium Brine:

14 to 86 F (±10 to 30 C)

Pulldown Set Point

0.2 to 2.0 F (0.11 to 1.1 C)/min.

Reset Set Points

Maximum Reset Range:

±30° to 30° F (±17° to 17° C)

External Temperature Reset ±40 to 240 F (±40 to 118 C)

Chiller Fluid DT: 0° to 15° F (0° to 8° C)

External Signal Reset 4 to 20 mA

Demand Limit Set Points

Switch Input:

Step 1 Ð 0 to 100% Capacity Reduction

Step 2 Ð 0 to 100% Capacity Reduction

External Signal:

Maximum Demand Limit 4 to 20 mA

Minimum Demand Limit 4 to 20 mA

Loadshed Demand Delta: 0 to 60%

Maximum Loadshed Time: 0 to 120 min.

Set points are grouped in subfunctions as follows:

Subfunction displays chiller ¯uid set points.

a.The ®rst value shown is the occupied chilled ¯uid set point.

b.The next value displayed depends on how the sched- ule function has been programmed. (See pages 44- 47.) If dual set point has been selected, the next set

point after has been pressed is the second chilled ¯uid set point. If single set point or inactive sched-

ule	has been	selected in	the	schedule	function,
then	when	is pressed,	the	display	shows the

head pressure set points, one for each circuit. These are utilized only if the set point controlled method of

head pressure control is selected in .

c. The ®nal value displayed when the is pressed

is the cooling ramp loading rate. This is the maximum rate at which the leaving chilled ¯uid is allowed to drop, and can be ®eld set from 0.2 to 2.0 F (.11° to 1.1° C)/minute. This value is not displayed unless the function is enabled (see Adjustable Field Con®gura- tions on page 44).

Reading and Changing Set Points Ð Example 4 shows how to read and change the chilled ¯uid set point. Other set points can be changed by following the same procedure. Refer to Table 9 for the sequence of display of set points in each sub- function.

38