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Installation
blower and motor pulleys when a firm pressure is
placed on the side of the blower belt. Adjust the blower
belt tension by raising (to tighten) or lowering (to
loosen) the nuts on the adjustment rods of the motor
base.
NOTICE
Belt Tension!
If the belt tension is too tight, it will cause premature
blower and/or motor bearing failure. If the belt is too
loose, the belt will slip and cause belt squeals and
eventual belt failure.
9. Restore power to the system.
10. Check the current draw on the blower motor to make
sure it does not exceed the nameplate rating of the
motor.
11. If current draw exceeds the nameplate rating of the
motor, repeat
Step 1
through
blower speed. If the motor pulls too much current, slow
the blower down by opening the adjustable sheave
one half turn at a time until the motor current is at or
below the nameplate FLA.
12. Check the motor overload on the blower starter to
confirm its setting is correct for the FLA of the motor.
EC Fan (Optional)
The speed of the EC fan is controlled via a 0 to 10 Vdc signal
from the system controller. The controller is set by the
factory and should not require adjustment. If it is
determined that the airflow needs adjustment, this may be
done using the controller's programming menu
selections. Refer to the operator's manual provided under
separate cover for the system controller.
Thermal Expansion Valve
CeilAir units using DX refrigerant have a thermal
expansion valve (TEV). The TEV maintains constant
superheat of the refrigerant vapor at the inlet of the
evaporator by metering the flow of refrigerant into the
evaporator. Superheat is the difference between the
refrigerant vapor temperature and its saturation
temperature at a given suction pressure. By controlling
superheat, the TEV keeps nearly the entire evaporator
surface active while preventing liquid refrigerant from
returning to the compressor. As a standard, superheat is
factory set at 10-15°F and should not need adjustment.
Hot Gas Reheat (Optional)
The hot gas reheat feature incorporates a hot gas reheat
solenoid valve and a hot gas reheat coil. Under normal
operation when no reheat is required, the hot gas reheat
valve is de-energized and hot gas flows directly from the
compressor discharge to the condenser. When there is a
call for reheat, the controller energizes the hot gas reheat
solenoid valve. The hot gas reheat solenoid valve diverts
hot gas to the reheat coil, mounted directly downstream of
34
Step 9
to decrease
the evaporator coil, before it travels to the condenser. No
adjustment to the valve is necessary.
Hot Gas Bypass (Optional)
The two most common systems provided by Trane for hot
gas bypass are snap acting and full floating, described
below.
Snap Acting Hot Gas Bypass
The snap acting hot gas bypass system provides for some
modulated capacity control and freeze protection. The hot
gas bypass system includes a discharge bypass valve that
allows some hot gas from the compressor discharge line
to pass into the evaporator coil to maintain a preset
suction pressure. The compressor cycles on demand from
the controller.
The snap acting hot gas bypass system also provides
freeze protection for the evaporator coil by limiting the
minimum refrigerant pressure, preventing the surface
temperature of the evaporator coil from dropping below
32°F.
The normal control setting for suction pressure is 75 psig
(R407C) read from the suction (low) side of the compressor
as it operates in full hot gas bypass operation. The valve is
factory set and no adjustment should be necessary. If
adjustment is required, block one half of the coil and
remove the adjustment cap from the end of the valve.
Using a 5/16 in. allen wrench, turn clockwise to increase
pressure or counterclockwise to lower the pressure.
Full Floating Hot Gas Bypass
A full floating hot gas bypass system is provided for
capacity control and freeze protection. The hot gas bypass
system may include a quench solenoid valve, a quench
solenoid coil, a quench expansion thermal valve, a hot gas
(dis- charge) solenoid valve, a hot gas (discharge) solenoid
coil, and a hot gas bypass valve. To ensure a constant
running compressor, the hot gas and quench solenoid
valves open and the liquid line solenoid valve cycles on the
demand of the controller.
The hot gas bypass valve allows refrigerant to flow from
the discharge line directly to the suction line. Hot gas
entering the suction side of the compressor would raise
the operating temperature of the compressor to a point
where failure could occur. To prevent this, a small amount
of liquid refrigerant passes through the quench valve and
mixes with the hot gas entering the compressor,
maintaining normal compressor suction pressure and
temperature.
The full floating hot gas bypass system provides freeze
protection for the evaporator coil by limiting the minimum
refrigerant pressure, preventing the surface temperature
of the evaporator coil from dropping below 32°F. The hot
gas (discharge) regulating valve has a normal suction
pressure control setting at 75 psig (R407C) and read from
the suction (low) side of the compressor as it operates in
full hot gas bypass mode. The valve is factory set and no
adjustment should be necessary. If adjustment is required,
AH-SVX008C-EN
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