Installation
36
SS-SVX002B-EN
receiver is used to store the extra refrigerant when the
condenser is not using it.
Note:
Systems utilizing air cooled condensers, (D2A
models), must not have a refrigerant line pressure
drop over 14 psig across the condenser and the
interconnecting piping to the condenser sections.
See the line sizing tables in
.
Head Pressure Control-Water/Glycol
Cooled Systems
Condensing temperature is maintained by liquid flowing
through a regulating valve and then into the condenser.
The regulating valve opens to increase the liquid flow as
the refrigerant pressure rises (or closes as the refrigerant
pressure falls).
CyberAir DX units have two refrigeration circuits. Each
circuit has its own pressure transducer. The system
controller monitors a signal from each pressure
transducer to determine how far to open the regulating
valve. The controller automatically changes the control
valve position to maintain head pressure based on the
difference between the set point value and the actual
measured value. The controller transmits a proportional 0
to 10 Vdc signal to the regulating valve with 10 Vdc
corresponding to the valve opening 100%.
The system controller is factory set for the correct
condensing pressure however, it can be adjusted to
increase or decrease the pressure. Adjustment is made by
entering the Factory menu in the E² controller. Refer to the
E² controller IOM manual provided under separate cover
for the system controller before making adjustments to
the controller.
Adjustments should be made in small increments.
Adequate time must be allowed between adjustments for
the valve to fully respond to the control signal and for the
changes in system operation to be observed.
Electronic Expansion Valve
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
Compressor Damage!
Do not exceed 20°F superheat. Exceeding this
temperature may cause failure of the compressor.
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.
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 traveling to the condenser and directs it to the
reheat coil which is mounted directly downstream of the
evaporator coil. The controller can be adjusted to increase
or decrease the reheat temperature. Adjustment is made
by entering the Service menu.
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.
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.
