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Hermetic Absorption Liquid Chillers
MACHINE OPERATION
MACHINE START-STOP SYSTEMS
General - The exact start-stop system for a given machine is established by the customer. Systems can vary from one installation to another. These systems and procedures are meant for general guidelines only.
The three most common types of systems are given below. Review these systems and decide which applies to your machine. Then follow the start-stop procedure given.
NOTE: If machine has been shut down for more than 2 days, follow procedures under Start-Up After Limited Shutdown or Start-Up After Extended Shutdown. In all cases below, when machine starts, the white run light will en ergize. When the machine stops, the light will go out after automatic dilution.
Automatic Start-Stop System - Starting and stop ping with this system is accomplished by an automatic controller such as a thermostat or time clock, etc. Also, an AUTO-MANUAL switch is provided so the machine can be started bypressing machine START button with switch in MANUAL position. All auxiliary equipment is tied in with the machine control circuit and will start when the machine starts. If automatic time delay relays are provided, the machine will start after a preselected time interval.
The operating engineer must make periodic checks to ensure that the machine with auxiliary equipment is operating satisfactorily.
PROCEDURES
1.Place AUTO-MANUAL switch in the AUTOposition for the machine to start or stop automat ically. The automatic controller determines when the machine starts or stops.
2.To start fully automatic machines after limited
or extended shutdown place the AUTO-MANUAL switch in MANUAL and press the START button. Then follow start-up procedures for limited or extended shutdown. Only after man ual start has been completed should the AUTO MANUAL switch be placed in AUTO.
NOTE: When the machine shuts down either
automatically |
or manually, |
the refrigerant |
and solution |
pumps will |
continue to run |
until automatic dilution is completed.
Semiautomatic Start-Stop System - All auxiliary equipment used with this system is tied directly
to |
the control circuit. It is necessary for |
the |
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operating engineer to press |
the START button |
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to |
start the condensing water pump, chilled water |
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pump, machine pumps, and |
cooling tower |
fan |
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(if used). |
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PROCEDURES
1. Press STOP button to stop machine. Press START button to start machine.
NOTE: On shutdown the machine pumps will continue to run until automatic dilution is completed.
Semiautomatic Start-Stop System with Manual Auxiliaries - All auxiliaries must be started manually.
PROCEDURES
1.Start chilled water pump.
2.Start condensing water pump.
3.Start cooling tower fan (if used). (This depends on outside temperature.)
4.Press START button to start machine.
5.To stop machine, press STOP button. Then stop the following:
a.Cooling tower fan (if used).
b.Condenser water pump.
c.Chilled water pump.
NOTE: The refrigerant and solution pumps will continue to run until auto matic dilution is completed.
MACHINE START-UP PROCEDURES
General - Procedures for start-up differ depend ing on how long the machine has been shut down. There are two start-up procedures: Start-up after limited shutdown (3 days to 3 weeks), and start-up after extended shutdown (over 3 weeks).
Start-Up After Limited Shutdown
PROCEDURES
1. Start the machine as outlined for your system
under Machine Start-Stop Systems. |
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2. Check the leaving |
chilled |
water temperature. |
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If temperature drops to design, then |
steps 3 |
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and 4 are not necessary. If the temperature |
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does not drop to design, noncondensables are |
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probably present |
in the |
machine. |
Proceed |
with steps 3 and 4. |
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3. Determine the amount of noncondensables by taking an absorber loss reading (the temper ature difference between the refrigerant and solution vapor). To determine absorber loss, refer to Carrier Standard Service Techniques, publication SM-16. A machine with absorber loss of less than 6 F can normally be started without the machine solution becoming solid ified. If absorber loss is greater than 6 F, auxiliary evacuation is recommended. A ma chine fully evacuated will normally have an absorber loss of 2 F or less. Instructions for auxiliary evacuation are in Carrier Stand ard Service Techniques, publication SM-16.
Carrier Corporation 1968 |
Printed in U.S.A. |
1-68 |
16JA-1SO |
To prevent solidification while purging:
a.Place reclaim switch to MANUAL.
b.Throttle back steam control valve.
(1)Electronic Control - Turn the control point adjustor up approximately ten degrees (ten divisions).
(2)Pneumatic Control - Turn the chilled water thermostat set point up ten degrees.
4.Evaluate machine tightness with a noncon densable accumulation rate check. Refer to Carrier Standard Service Techniques, publica tion SM-16.
Start-Up After Extended Shutdown - This pro cedure is critical since accumulated noncon densables may allow the machine solution to solidify if the following precautions are not taken,
PROCEDURES
1. Start the machine as outlined for your system under Machine Start-Up Procedures. Make sure steam valve is closed. If absorber solu tion level is high (above 9 in.) and refrigerant pump is noisy, open steam valve until absorber level indicator shows approximately 9 in. of solution, then close steam valve. Place refrig erant pump switch in ON position.
2. Determine absorber loss by following proce dures outlined in Carrier Standard Service Techniques, publication SM-16.
a.If absorber loss is less than 6 F, open steam valve and allow machine to go into automatic operation.
b.If absorber loss is 6 F or greater, auxil iary evacuation is required. Use instruc tions for auxiliary evacuation provided in Carrier Standard Service Techniques, pub lication SM-16.
3.Continue auxiliary evacuation until absorber loss is less than 6 F. Place machine in auto matic operation.
4.After auxiliary evacuation, evaluate machine tightness with a noncondensable accumulation rate check.
WINTER CONDITIONS
General - At the end of each cooling season when the machine is no longer required use one of the following winter shutdown procedures. The choice depends on whether the machine ambient tempera ture will be kept above or below freezing.
Shutdown Procedures
BELOW FREEZING
1. Stop machine and wait until automatic dilution completes and machine pumps stop.
2.Set dilution thermostat to its lowest possible setting.
3.Connect a hose between solution and refrig erant pump service valves. Open both valves.
4. Switch refrigerant pump ON-OFF switch to OFF and solution pump switch to ON.
5. Press START button and allow solution pump to run for approximately 5 minutes.
NOTE: This procedure contaminates the refrigerant with lithium bromide solution lowering the refrigerant freezing point.
6.Press STOP button and reset dilution thermo stat to 140 F (refer to Checking Dilution Ther mostat under Maintenance).
7.Drain water from all chilled water, condensing, steam and condensate circuits. Flush all cir cuits with ethylene glycol.
ABOVE FREEZING
1.Press STOP button.
2.Allow machine to go thru automatic dilution.
When dilution has completed, machine may be left in this condition until spring start-up.
Start-Up Procedures
BELOW FREEZING
1.Refill all water circuits that were drained at shutdown.
2.Follow Start-Up After Extended Shutdown pro cedures.
3.Reclaim lithium bromide from refrigerant circuit. Follow Reclaim Solution procedures given under Maintenance.
4.Restart machine.
ABOVE FREEZING
1.If machine vacuum was broken for maintenance work, etc., follow auxiliary evacuation pro cedures outlined in Carrier Standard Service Techniques, publication SM-16. Then follow Start-Up After Extended Shutdown procedures.
2.If machine vacuum was not broken, follow Start-Up After Extended Shutdown procedures.
PURGE OPERATION
General - The 16JA purge unit automatically per forms the following functions:
1.Removes noncondensables from the machine.
2.Accumulates these noncondensables in the purge storage chamber where they will not affect the machine performance.
3.Provides an indication of the degree of air leakage into the machine.
The 16JA purge unit cannot be used as an auxil iary evacuation device to evacuate the machine.
When the purge exhaust light (red) is energized during machine operation, it indicates that the purge must be manually exhausted. For instruc tions refer to the instruction sticker located on the separation chamber (Fig. 1) or use the following procedure.
STORAGE CHAMBER
SUPPLY LINE
CONDENSER PURGE
SUCTION LINE
PURGE EXHAUST
VALVE
INSTRUCTION
STICKER PURGE
SEPARATION
CHAMBER
PURGE RETURN VALVE
TO GENERATOR OVERFLOW TUBE
SOLUTION PUMP-
Fig. 1 - Purge Exhaust System
Manual Exhaust Procedures
1.Close purge return valve.
2.Wait 10 minutes for storage chamber to pressurize.
3.Slowly open purge exhaust valve. If level in container drops, shut valve and wait 2 minutes. Reopen valve. If bubbles appear, keep valve open until bubbles stop and level in container rises, then close valve.
4.Collect lithium bromide solution to recharge into machine. Recharging procedures are given in Carrier Standard Service Techniques, pub lication SM-16.
SOLUTION DESOLIDIFICATION
General - Should solidification occur, it will occur usually in the shell side ofthe heat exchanger, pre venting the strong solution in the generator from returning to the absorber thru the strong solution line. However, the strong solution will be returned to the absorber thru the generator overflow tube (Fig. 6) thereby desolidifying automatically.
If during a shutdown period solidification has occurred to the extent that the solution pump will not rotate and the motor overloads trip put, desolidify by using the following procedure.
PROCEDURE
1. Heat the pump casing and adjacent lines with steam until the pump will rotate. Be careful not to allow steam and condensate to enter the pump motor and controls.
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2. Confirm pump rotation. Rotation of the her metic pump cannot be viewed directly. Install a compound pressure gage on the solution pump
service valve. With correct pump rotation, the gage will indicate a positive reading above at mospheric pressure. If the pump is solidified, the gage will indicate atmospheric pressure. If the casing is partially desolidified and the pump will not turn, the pressure gage will in dicate a deep vacuum. Continue to heat the casing until the pump is desolidified. Desolid ification of the heat exchanger will take place automatically once the pump starts functioning.
3. Refer to Troubleshooting Guide for possible causes of solidification and their correction.
MAINTENANCE
INTRODUCTION
General - The following are routine steps nec essary for normal preventive maintenance on 16JA Hermetic Absorption Liquid Chillers.
To ensure the continued satisfactory perform ance of the machine, these schedules must be closely adhered to.
We recommend the suggested steps be per formed as often as indicated, and that an accurate log be kept to aid in diagnosing any troubles.
Certain components and operations should be checked on an individual basis as needed.
EACH MONTH
Reclaim Solution - During normal operation it is possible that some lithium bromide might carry over into the refrigerant circuit.
To determine if contamination exists, remove a refrigerant sample from the machine using refrigerant and solution sampling procedures out lined in Carrier Standard Service Techniques, publication SM-16. Measure the specific gravity of the sample. If the value exceeds 1,02, the solu tion must be reclaimed.
RECLAIM PROCEDURE FOR CONTINUOUS OP ERATION
1. Place reclaim valve switch in MANUAL posi tion. Wait for approximately 15 minutes. This causes refrigerant to flow into the solution circuit where the lithium bromide solution is reclaimed.
2, Place reclaim switch in AUTO position, de energizing the refrigerant solenoid valve, thus stopping refrigerant flow.
RECLAIM PROCEDURE FOR FREQUENT SHUT DOWN - When the machine is shut down, the re claim valve will automatically reclaim the lithium bromide salt solution.
NOTE: If the reclaim solenoid valve does not energize during the reclaim procedure (aud ible click, and typical rattling noise of refrig erant passing thru the valve) contact your nearest Carrier representative for assistance.
Check Machine Tightness - The most important maintenance item on the absorption machine is maintaining vacuum tightness within acceptable limits. Check machine tightness by determining the noncondensable accumulation rate. Use pro cedures given in Carrier Standard Service Tech niques, publication SM-16.
EVERY 2 MONTHS
Check Dilution Thermostat - The dilution thermo stat should be open when the strong solution drops to 140 F. If temperature cutout point is not 140 F, insert screwdriver in slot on face of thermostat (located on strong solution line) and turn adjust ment dial until cutout occurs at 140 F.
Check Low-Temperature Cutout - Remove lowtemperature cutout sensing element from sep
arable |
well |
in the evaporator shell. Place it in |
an ice |
bath. |
Low-temperature cutout should trip |
at 5 F below design leaving chilled water tem perature or a minimum of 36 F. The actual cutout point is the dial setting less 3 F differential. When the control trips, the machine will shut down immediately without going thru a dilution cycle.
NOTE: The chilled water pump will continue to run if hooked up in the standard wiring arrangement.
EVERY 6 MONTHS
Check Evaporator Water Charge-Check the evap orator water charge to determine if the reclaim valve has energized. If valve has energized then either tube leakage or excess refrigerant is indicated.
Reclaim should start at full load (corresponds to approximately 62 percent lithium bromide in absorber for standard nominal conditions). Check as follows:
1.Operate machine at full load with design en tering condensing water and design leaving chilled water.
2.Remove a sample of evaporator water from refrigerant pump service valve and check the
specific gravity. If specific gravity is below 1.02 proceed with step 3. If specific gravity is above 1.02 reclaim solution (see instruc tions for Reclaim Solution, page 3) until specific gravity is below this point, then proceed with step 3.
3. Evaluate absorber loss. Should be 2 F or less. If more, purge air from machine.
4. Check reclaim line by feel. Listen for refrig erant flow (audible). If reclaim line is already cold, with audible refrigerant flow, remove refrigerant until reclaim valve closes (audible click) and refrigerant flow ceases.
If machine is operating under light load, it will be necessary to concentrate the absorber weak solution to 62 percent. To do this, raise entering
condenser water temperature. Turn down control point adjuster below design leaving chilled water temperature setting. Repeat steps 1 thru 4.
Continual removal of water indicates leakage in one of the tube bundles. Leak test by using proce dures outlined in Carrier Standard Service Tech niques, publication SM-16.
Check Capacity Control Valve - Check to see if leaving chilled water is being maintained at design temperature. If not, adjust the electronic or pneumatic control.
TO ADJUST ELECTRONIC CONTROL
1.Move control point adjuster clockwise to in crease temperature, or counterclockwise to decrease temperature. If this fails to bring leaving chilled water within design temper ature, perform step 2.
2.Replace vacuum tubes in control motor. Make sure that new tubes are installed in correct
plugs. |
If this |
fails to bring leaving chilled |
water |
within |
design temperature, proceed |
with step 3, |
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3. Clean relay contacts with stiff paper. If this fails to correct problem, contact Carrier immediately.
TO ADJUST PNEUMATIC CONTROL
1.Reset control point setting to design.
2.If above fails to correct problem, contact Carrier immediately.
Check Cooling Tower Bypass Control - If control is not maintaining design entering condensing water temperature, recalibrate the control ther mostat. For information, contact the valve (or control) manufacturer.
EVERY YEAR
Check for Absorber and Condenser Scale - Check absorber and condenser tubes to see if cleaning is required. Soft scale may be removed with tube cleaning brushes. When hard scale has formed, it may be necessary to chemically clean the tubes. If a scale problem occurs, contact a water treat ment representative. Annual tube cleaning may not be required if adequate water treatment is maintained.
Recharge Lithiunn Bromide - Recharge lithium bromide when the purge exhaust bottle becomes filled.
PROCEDURES
1.Open the exhaust valve and allow solution to be forced back into the purge,
2.Close the exhaust valve when the level nears the end of the tube. Do not allow air to be drawn into the tube.
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