Carrier 19DA - Manual (Page 8)

Calibrating Electronic Controls - Honeywell Only (Fig. 4)
Table 4 - Chilled Water Module
SEQUENCE PROCEDURE (Compressor Operating)
1. Set Differential
Adjustment
A. Place capacity control switch (8) in MANUAL position.
B. Set throttling range screw (19) on counterclockwise stop.
C. Operate machine manually until leaving chilled water temperature is
within the range of the chilled water thermostat (35 F to 55 F).
D. Adjust differential screw (15) for a 3/4 F movement of the chilled water
thermostat (4) between the operation of relay CRO (25) and CRC (24).
2. Calibrate Chilled
Water Temperature
Setting
A. Open vanes manually until chilled water temperature reaches design
temperature. Place chilled water thermostat in center of dial. (Lowest
division on left corresponds to 35 F. Each division represents I F . )
B. Adjust calibration screw (17) until relay CRC (24) is closed and relay
CRO (25) is open.
3. Adjust Capacity
Balance
A. Connect an a-c voltmeter across test jack (21) and terminal J28. Use
50- or 60-volt scale.
B. Turn chilled water thermostat (4) clockwise or counterclockwise to
obtain lowest voltage reading on voltmeter.
C. Turn capacity balance screw (16) clockwise or counterclockwise until
voltage decreases further.
D. Repeat above steps to decrease voltage to approximately one volt.
4. Observe Automatic
Operation
A. Place capacity control (8) on THERMO position and thermostat (4) at
design chilled water temperature.
B. Turn throttle range screw (19) clockwise 1/3 of its total travel if chilled
water temperature "hunts.”
C. Recalibrate as in sequences 1 thru 4.
Calibrating Electronic Controls - Barber-Colman Only (Fig. 5)
Table 5 - Chilled Water Module
SEQUENCE PROCEDURE (Compressor Operating)
1. Adjust Capacity
Balance
A. Rotate throttling range screw (17) to counterclockwise position.
B. Operate vanes manually until chilled water temperature drops to design
temperature.
C. Place capacity control switch (15) on HOLD.
D. Set chilled water thermostat (3) to dial center. (Lowest division on left
corresponds to 35 P. Each division represents I E . )
E. Connect COMMON plug of an a-c voltmeter to terminal X on amplifier
and other plug to terminal T. Use 12-volt scale.
F. Adjust temperature bridge calibration screw (18) until voltage becomes
minimum.
G. Adjust capacity balance screw (16) until voltage decreases further. Re­
peat steps above to decrease voltage to one volt or lower.
H. Remove voltmeter.
2. Differential Setting NOTE: A differential resistor is factor^'installed between terminals X
and Y (10) OR the cMlled water amplifier to give approximately 1 F dif- ;
ferential between the operation of microrelays CRC and CRO (19).
3. Observe Automatic
Operation
A. Place capacity control switch (15) on AUTO position.
B. Rotate throttling range screw (17) clockwise 1/3 of total travel if chilled
water temperature "hunts."
NOTE: If timottling range is added, recalibrate as in sequences 1 thru 3.