Carrier 16JT Series Start Up & Operation Manual

Carrier 16JT Series Start Up & Operation Manual Manual pdf 35 page image

Adding Octyl Alcohol — Octyl alcohol may be re-quired when leaving chilled water temperature starts to riseabove design temperature without alteration of the controlset point. Since the rise in temperature can also be caused byfouled tubes or other problems, use the following procedureto 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 1 ⁄2 gal. (2 L) of octyl alcohol.The addition of octyl alcohol also may be required afterthe machine has been evacuated or after an extended pe-riod of operation.Use only octyl alcohol. Other types of alcohol havea detrimental effect on machine performance.2. Fill a length of flexible tubing with water and connectone end to the solution pump service valve (seeFig. 29). Insert the other end in a container of octyl al-cohol. Stop the solution pump. The pump can be stoppedwithout a dilution cycle by pressing the trip bar on thepump starter overload, then pressing the Stop button andthe overload reset. Then open the service valve to allowalcohol to be drawn into the machine. Close valve beforeair can be drawn into the hose. Restart the chiller andsolution pump.Removing Lithium Bromide from Refrigerant— During normal operation, some lithium bromide may becarried over into the refrigerant. Lithium bromide in the re-frigerant is automatically transferred back to the absorber bythe Cycle-Guard™ valve when it is needed. The refrigerantflows through the Cycle-Guard valve into the solution cir-cuit and separation is made in the generator in the normalmanner.Lithium bromide recovery can also be initiated by placingthe Cycle-Guard switch in MANUAL position while the ma-chine is running and the capacity control valve is open. Whenthe refrigerant specific gravity drops below 1.02, return theCycle-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 machineindicates tube leakage. Furthermore, the correct refrigerantcharge 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 leavingchilled water temperature. If design temperature is not beingmaintained, reset the control set point in the machine controlpanel (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 atthe 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 thechilled water pipe. Immerse the element in a container ofcool water. Slowly stir crushed ice into the water so thatthe 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 controlas described in Check Low-Temperature Cutoutsection, page 22.3. When control cuts out, machine shuts down immediatelywithout going through dilution cycle. Control cuts in whensensing element warms up 7.2° F (4° C).If necessary, reset cutout adjustment knob and recali-brate. Restart machine by depressing the Stop button andthen the Start button. Replace sensing elements in wells.Cycle-Guard™ System Operation — To check op-eration, place Cycle-Guard switch in MANUAL position. TheCycle-Guard transfer valve energizes. The flow of refriger-ant will cause the transfer line between valve and solutionpump inlet to feel cold to the touch. This line should not feelcold when the transfer valve is closed (not energized). If theline is cold when valve is deenergized, the valve is leakingand 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 strongsolution temperature as it flows to the absorber spray headerand by 2 refrigerant level switches (33RH and 33RM), lo-cated in the evaporator.For nominal operating conditions, switch 26SH closes ontemperature 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, fornominal 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 42.35