Carrier 16JT Series Start Up & Operation Manual Download Page 35

Page: 35 / 44

Adding Octyl Alcohol —

Octyl alcohol may be re-

quired when leaving chilled water temperature starts to rise
above design temperature without alteration of the control
set point. Since the rise in temperature can also be caused by
fouled tubes or other problems, use the following procedure
to determine whether a lack of octyl alcohol is the cause:
1. Remove a sample of solution from the solution pump serv-

ice valve (see Solution or Refrigerant Sampling section,
page 34). If the solution has no odor of alcohol (very pun-
gent), add about

⁄

gal. (2 L) of octyl alcohol.

The addition of octyl alcohol also may be required after
the machine has been evacuated or after an extended pe-
riod of operation.

Use only octyl alcohol. Other types of alcohol have
a detrimental effect on machine performance.

2. Fill a length of flexible tubing with water and connect

one end to the solution pump service valve (see
Fig. 29). Insert the other end in a container of octyl al-
cohol. Stop the solution pump. The pump can be stopped
without a dilution cycle by pressing the trip bar on the
pump starter overload, then pressing the Stop button and
the overload reset. Then open the service valve to allow
alcohol to be drawn into the machine. Close valve before
air can be drawn into the hose. Restart the chiller and
solution pump.

Removing Lithium Bromide from Refrigerant
—

During normal operation, some lithium bromide may be

carried over into the refrigerant. Lithium bromide in the re-
frigerant is automatically transferred back to the absorber by
the Cycle-Guard™ valve when it is needed. The refrigerant
flows through the Cycle-Guard valve into the solution cir-
cuit and separation is made in the generator in the normal
manner.

Lithium bromide recovery can also be initiated by placing

the Cycle-Guard switch in MANUAL position while the ma-
chine is running and the capacity control valve is open. When
the refrigerant specific gravity drops below 1.02, return the
Cycle-Guard switch to AUTO. to close the Cycle-Guard valve.

Refrigerant Charge Adjustment —

Check the evapo-

rator refrigerant (water) charge after every 6 months of op-
eration. An increase in the amount of water in the machine
indicates tube leakage. Furthermore, the correct refrigerant
charge must be maintained for accurate operation of the Cycle-
Guard system.

For charge adjustment, refer to Initial Start-Up, Final Re-

frigerant Charge Adjustment section, page 25.

Capacity Control Adjustment —

Check the leaving

chilled water temperature. If design temperature is not being
maintained, reset the control set point in the machine control
panel (see Check Capacity Control Operation section,
page 23).

If machine still fails to maintain design temperature, re-

fer to the Troubleshooting section entitled Problem/Symptom
— Leaving Chilled Water Temperature Too High or Too Low,
page 41.

Low-Temperature Cutout Adjustment —

This ma-

chine safety serves to prevent freeze-up damage to the evapo-
rator tubes. Check the cutout periodically to confirm trip at
the selected setting.
NOTE: If the cutout sensor has been exposed to tempera-
tures above 120 F (49 C), the control must be recalibrated.
1. Remove the control sensing element from its well in the

chilled water pipe. Immerse the element in a container of
cool water. Slowly stir crushed ice into the water so that
the temperature goes down at a rate not exceeding 1° F
(0.5° C) per minute.

2. Observe the cutout temperature. It should be 9° F (5° C)

below design leaving chilled water temperature or a mini-
mum of 36 F (2 C). If control fails to cut out by 36 F
(2 C), stop machine immediately and recalibrate control
as

described

Check

Low-Temperature

Cutout

section, page 22.

3. When control cuts out, machine shuts down immediately

without going through dilution cycle. Control cuts in when
sensing element warms up 7.2° F (4° C).
If necessary, reset cutout adjustment knob and recali-
brate. Restart machine by depressing the Stop button and
then the Start button. Replace sensing elements in wells.

Cycle-Guard™ System Operation —

To check op-

eration, place Cycle-Guard switch in MANUAL position. The
Cycle-Guard transfer valve energizes. The flow of refriger-
ant will cause the transfer line between valve and solution
pump inlet to feel cold to the touch. This line should not feel
cold when the transfer valve is closed (not energized). If the
line is cold when valve is deenergized, the valve is leaking
and must be repaired. Return Cycle-Guard switch to AUTO.
position.

During normal operation, the Cycle-Guard valve is con-

trolled by a thermoswitch (26SH), which senses the strong
solution temperature as it flows to the absorber spray header
and by 2 refrigerant level switches (33RH and 33RM), lo-
cated in the evaporator.

For nominal operating conditions, switch 26SH closes on

temperature drops below 118 F (48 C). Special operating con-
ditions may require special settings.

Level switches 33RH and 33RM close with rising refrig-

erant levels that correspond to increasing solution concen-
trations of approximately 59.5% and 60.0% respectively, for
nominal full load operating conditions. (See Maintenance Pro-
cedures entitled Refrigerant Charge Adjustment and Thermo-
switch Adjustment, pages 35 and 36.)

Cycle-Guard system malfunction makes the machine sus-

ceptible to solution crystallization. See Troubleshooting Guide,
Solution Crystallization During Operation, page 42.