McQuay SWT C Series, Руководство по установке и обслуживанию

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Refrigerant Charge
Units are shipped with a full operating charge of refrigerant
and oil. However, in the event of a leak in the system, some
added charge may be required. If an undercharged situation
occurs, any of the following may be experienced:
1. If a circuit is slightly undercharged, bubbles will show
in the sightglass.
2. If a circuit is moderately undercharged, it may trip on its
frost protection sensor.
3. If the circuit is severely undercharged, it may trip on its
low pressure safety.
If any of these conditions occur, first identify and correct the
source of the leak and then follow the charging procedure
described below.
Using the liquid line sight-glass as the sole means of meter-
ing additional refrigerant charge into a self-contained unit, or
any AC unit, will not always provide the desired result.
Depending on the load conditions experienced by the equip-
ment during the charging process, adding refrigerant until
the sight-glass is clear of all bubbles may over charge the
system and cause future operating issues. The better way to
charge a circuit is to use liquid sub-cooling and suction line
superheat as indicators, using the following procedure:
1. Verify that superheat is set per the System Check, Test
& Start procedures in this manual.
2. Measure the discharge pressure reading and convert it to
a discharge temperature.
3. Measure and record the circuit's liquid line temperature.
4. Measure and record the entering condenser water tem-
perature using the MicroTech II display.
5. Calculate liquid subcooling: subcooling = discharge
temperature - liquid line temperature
6. If the calculated subcooling value is less than 8ºF, refrig-
erant needs to be added.
7. Monitoring discharge pressure and liquid line tempera-
ture, add refrigerant until the discharge temperature
minus the liquid line temperature is equal to 8ºF ± 2ºF.
If the system is running at light load conditions, sub-
cooling should be at the low end of the range. If the sys-
tem is running near design conditions, subcooling
should be near the upper end of the range.
8. Verify that superheat is still in the prescribed range. Fol-
lowing this method should prevent over charging of the
circuit.
Figure 26. Water and Refrigerant Piping Schematic
Note: Water Temperature Sensor to be installed by others
in field after the condenser water connections are
made.
RELIEF
VALVE
ISOLATION
VALVE
FILTER
DRIER
SIGHT
GLASS
ISOLATION
VALVE
EXPANSION
VALVE
SUCTION
VALVE
DISCHARGE
VALVE
COMPRESSOR NO. 1
CONDENSER
RECEIVER
EQUALIZER
CAPILLARY
EVAPORATOR
A- A
RELIEF
VALVE
ISOLATION
VALVE
FILTER
DRIER
SIGHT
GLASS
ISOLATION
VALVE
EXPANSION
VALVE
SUCTION
VALVE
DISCHARGE
VALVE
COMPRESSOR NO. .2
CONDENSER
RECEIVER
EQUALIZER
CAPILLARY
EVAPORATOR
A- A
RELIEF
VALVE
ISOLATION
VALVE
FILTER
DRIER
SIGHT
GLASS
ISOLATION
VALVE
EXPANSION
VALVE
SUCTION
VALVE
DISCHARGE
VALVE
COMPRESSOR NO. 3
CONDENSER
RECEIVER
EQUALIZER
CAPILLARY
EVAPORATOR
A- A
RELIEF
VALVE
ISOLATION
VALVE
FILTER
DRIER
SIGHT
GLASS
ISOLATION
VALVE
EXPANSION
VALVE
SUCTION
VALVE
DISCHARGE
VALVE
COMPRESSOR NO. 4
CONDENSER
RECEIVER
EQUALIZER
CAPILLARY
EVAPORATOR
A- A
MODERATING
VALVE
WATER FLOW SWITCH
BYPASS
VALVE
WATER SENSORS
LOW
HIGH
E.S.
WATER
COIL
CONDENSER
WATER
OUT
CONDENSER
WATER
IN
SUCTION
LINE
EXPANSION
VALVE
BULB
CAPILLARY
12'
SECTION A - A
30°