CyberAiR DX Floor Mounted IOM Manual
2.9.8
Electronic Expansion Valve
STULZ CyberAir precision A/C units utilize an
expansion valve for each refrigeration circuit. The
electronically controlled expansion valve (EEV)
maintains constant superheat at the outlet 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 EEV keeps nearly the
entire evaporator surface active while preventing
liquid refrigerant from returning to the compressor.
Superheat is factory set at 12-15°F and should not
need adjustment. The superheat temperature is
monitored and controlled by the
E²
system controller
mounted inside the electric box. Should adjustment
be necessary, refer to the IOM manual provided
under separate cover for the system controller.
Adjustment is made by entering the Service menu.
CAUTION
Do not exceed 20°F superheat. Exceeding this
temperature may cause failure of the compressor.
2.9.9
Snap Acting Hot Gas
Bypass (Optional)
The snap acting hot gas bypass system provides
some modulated capacity control and freeze
protection. The hot gas bypass system consists of a
discharge bypass valve that allows some hot gas
from the compressor discharge line to flow directly to
the evaporator coil, in order to maintain a preset
suction pressure.
The snap acting hot gas bypass system also
provides freeze protection for the evaporator coil by
limiting the minimum refrigerant pressure, thereby
preventing the surface temperature of the
evaporator coil from dropping below 32°F.
The normal control setting is 120 psig (suction
pressure), 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
3/8 inch wrench, turn clockwise to increase pressure
or counterclockwise to lower pressure.
2.9.10 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 from travelling to the condenser and directs it
to the reheat coil which is mounted directly
downstream of the evaporator coil. The
E²
controller can be adjusted to increase or decrease
the reheat temperature.
Adjustment is made by entering the Service menu.
2.9.11 EC Fans
The speed of the EC fans is controlled via a 0 to
10 VDC signal from the system controller. The
controller is pre-set by the factory for the correct
fan speed configuration and should not require
adjustment. If it is determined that the air flow
needs adjustment, this may be done using the
controller’s programming
menu selections. Refer to the
E²
Controller
Operators Manual provided separately.
2.9.12 Humidifier Adjustment
The humidifier has an adjustable capacity
potentiometer on the humidifier control circuit board.
The potentiometer may need to be field adjusted if
the humidifier is not supplying enough capacity for
current room conditions.
It is recommended that if the humidifier capacity
potentiometer requires adjustment, the adjustment
is made in small increments and verified. Refer to
the humidifier manual sent under separate cover
with your unit for the location of the capacity
adjustment potentiometer.
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