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componenT FuncTionS
High Pressure Switch (HPS) - A high-pressure switch
is factory-installed and located in the liquid line internal
to the outdoor unit. The switch is designed to protect the
system when very high pressures occur during abnormal
conditions. Under normal conditions, the switch is closed.
If the liquid pressure rises above 575 psig, then the switch
will open and de-energize the outdoor unit. The switch will
close again once the liquid pressure decreases to 460
psig. Please note that the switch interrupts the thermostat
inputs to the unit. Thus, when the switch opens and then
closes, there may be a 5 minute short cycling delay before
the outdoor unit will energize.
applicaTion noTeS For uSing T4QD reFrigeranT
legenD
Shaded boxes indicate flooded conditions.
Rated design values. The suction pressure
will be lower than design value if outdoor air
flow, entering dry bulb, or entering wet bulb
temperatures are lower than design.
• This equipment's cooling system contains refrigerant under high pressure. always use safe and
environmentally sound methods when handling refrigerant handling or servicing the unit. review the
factory literature and safety warnings prior to servicing.
• When repairing system leaks, always use a nitrogen (inert) gas to protect the refrigerant system and pressure
check the repair before re-charging. Always replace the filter-dryers when performing any repair to the refrigeration
system with one capable of acid removal. After completing the repairs, evacuate the system to 350 - 500 microns
and weigh in the refrigerant to the amount specified on the unit rating label.
• The refrigerant charging charts and tables are valid for a variety of indoor, return air conditions and are most
influenced by the outdoor ambient temperature, outdoor fan operation and the unit operating voltage. Before using
these tables and charts, make sure the unit is in a stable operating mode. As shown in Tables 4 - 6 (page 9) and
Figures 3 - 8 (pages 10 - 12), the ideal system sub-cooling can vary over the range of operation. Reference the
tables to determine the ideal amount of sub-cooling for a given liquid pressure. Units charged to other values will
not perform at the rated unit efficiency (EER) or rated Coefficient of Performance (COP) in heating mode.
• To inspect a systems operation using quality instruments, match the measured liquid temperature to the units
chart. The measured liquid pressure reading should be within 3% of the charts value for most installations.
• For systems that are operating with more than a 5% deviation, inspect the unit for the proper voltage and phase
balance and the refrigeration system for leaks.
• Units that are operating at less then 95% of the nominal voltage or with a 2% phase imbalance may see a more
significant deviation than the amount stated above.
• Do noT use the charts in systems that have a fan cycling under low-ambient control. Refer to the low-ambient
kit instructions for more information. (If applicable)
8
cHarging cHarTS & TableS - cooling only
application notes on the use of charging charts
Low Pressure Switch (LPS) - A low-pressure switch is
factory-installed in select models only. If provided, this
located in the suction line internal to the outdoor unit. The
switch is designed to protect the compressor from a loss
of charge. Under normal conditions, the switch is closed.
If the suction pressure falls below 5 psig, then the switch
will open and de-energize the outdoor unit. The switch
will close again once the suction pressure increases
above 20 psig. Please note that the switch interrupts the
thermostat inputs to the unit. When the switch opens and
then closes, there will be a 5 minute short cycling delay
before the outdoor unit will energize.
noTeS:
1. All pressures are listed psig and all temperatures in °F
2. Discharge temperatures GREATER than charted values
indicate an UNDERCHARGED system.
3. Discharge temperatures LESS than charted values
indicate an OVERCHARGED system.
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