Trane IntelliPak SCRF 25, Инструкция по установке, эксплуатации и обслуживанию

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60 SCXF-SVX01Q-EN
connected to the changeover input on the RTM. Supply
air static pressure is maintained.
Supply Air Setpoint Reset (VAV Units
Only)
Supply air reset can be used to adjust the supply air
temperature setpoint on the basis of a zone
temperature or outdoor air temperature. Supply air
reset adjustment is available at the HI panel for supply
air heating and supply air cooling control.
Reset Based on Outdoor AirTemperature
Outdoor air cooling reset is sometimes used in
applications where the outdoor temperature has a
large effect on building load. When the outside air
temperature is low and the building cooling load is low,
the supply air setpoint can be raised, thereby
preventing subcooling of critical zones. This reset can
lower usage of mechanical cooling, thus savings in
compressor kW, but an increase in supply fan kW may
occur.
Outdoor air heating reset is the inverse of cooling, with
the same principles applied.
For both outdoor air cooling reset and heating reset,
there are three user defined parameters that are
adjustable through the human interface panel:
• Beginning reset temperature
• Ending reset temperature
• Maximum amount of temperature reset
Reset Based on zone temperature
Zone reset is applied to the zone(s) in a building that
tends to overcool or overheat. The supply air
temperature setpoint is adjusted based on the
temperature of the critical zone(s).This can have the
effect of improving comfort and/or lowering energy
usage. The user-defined parameters are the same as
for outdoor air reset.
Supply AirTempering (Hot Water and
Steam VAV Units Only)
When supply air temperature falls below the supply air
temperature deadband low end, the heating valve
modulates open to maintain the minimum supply air
temperature setpoint.
Daytime Warm-up (Units with Supply Air
Temperature Control Only)
During occupied mode, if the zone temperature falls to
a preset, user-defined zone low limit temperature
setpoint, the unit is put into daytime warm-up. The
system changes over to CV heating, the VAV boxes
drive full open. However, unit airflow modulation
control operates to maintain duct static setpoint, and
full heating capacity is provided until the daytime
warm-up setpoint is reached. The unit is then returned
to normal occupied mode.
Supply AirTempering
Supply air tempering is available on units without
volume control and with hot water, steam, or electric
heat or units with supply air temperature control with
steam or electric heat. When the unit is in heat mode
but not actively heating, if the supply air temperature
drops to 10°F (5.5°C) below the occupied zone heating
temperature setpoint, electric heat will stage on or the
hydronic valve will modulate to maintain a minimum
supply air temperature. The unit transitions out of heat
mode if the supply air temperature rises to 10°F (5.5°C)
above the occupied zone heating temperature setpoint.
Changeover
This mode only functions on units with supply air
temperature control with hydronic heat. When the
changeover binary input is closed the unit will control
to a discharge air heating setpoint. This setpoint is
entered from the HI, and can be a higher temperature
than the supply air cooling setpoint. This function
maintains duct static pressure.
Thermostatic Expansion Valve
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Refrigerant system reliability and performance is
heavily dependent upon proper superheat. The
importance of maintaining the proper superheat
cannot be overemphasized. Accurate measurements of
superheat will provide the following information:
• How well the expansion valve is controlling the
refrigerant flow.
• The efficiency of the evaporator coil.
• The amount of protection the compressor is
receiving against flooding.
The expected range for superheat is 14-20°F at full load
conditions. At part load, expect a properly adjusted
expansion valve to control to 8-12°F superheat.
Systems operating with lower superheat could cause
serious compressor damage due to refrigerant
floodback.
Compressors
Units use two sizes of hermetic scroll compressors, 10
and 15 hp, and have from two to six compressors.
When viewing the front of the unit, compressors are
identified A through F from left to right. The second
compressor from the left, or B compressor, is always
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