CyberOne EC DX IOM Manual
Flooding the condenser reduces the area available for heat
transfer. The desired result is to increase the pressure into the
condenser, maintaining a minimum discharge pressure during
low ambient operation thus ensuring proper condensing
temperature. The head pressure control valve requires no
adjustment.
While the fan is running, the flooded head pressure control
valve modulates the amount of discharge gas entering the
receiver. As the pressure increases, the valve diverts more
discharge gas to the condenser, allowing more liquid to flow
from the condenser to the receiver.
When using this method of head pressure regulation there
must be enough refrigerant in the system to ensure adequate
charge at the lowest expected ambient temperature in which
the system will be operating. A receiver is used to store the
extra refrigerant when the condenser is not using it.
NOTE
Systems utilizing air cooled condensers must
not have a refrigerant line pressure drop greater
than 14 psig across the condenser and the
interconnecting piping to the condenser sections.
2.9.2.6
Flooded Head Pressure Control
(Condenser Model HES-CAA , -30 °F)
Used for indoor installations where ambient condenser air
inlet temperatures may fall to -30 °F. First, familiarize yourself
with Flooded Head Pressure Control as discussed in Section
2.9.2.5. Instead of cycling the fan on and off, the condenser
fan speed is continuous. The head pressure control valve
diverts discharge gas to the receiver causing liquid to back
up in the condenser, as described in Section 2.9.2.5, while
the fan continues to run.
2.9.3
Head Pressure Controls-
Water/Glycol Cooled Systems
In a water/glycol condenser, condensing temperature is
maintained by the liquid flowing through a regulating valve
and then into a liquid-cooled condenser. The regulating valve
opens to increase the liquid flow as the refrigerant pressure
rises (or closes as the refrigerant pressure falls). The system
controller monitors a signal from a pressure transducer
to determine how far to open the 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 condensing pressure. Adjustment is made by entering the
Factory menu in the E²
controller. Contact STULZ Product
Support for a password to enter the Factory menu and for
technical assistance if adjustment is necessary.
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.
2.9.4
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 the 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
with your unit for the capacity potentiometer location.
CAUTION
Adjusting the capacity potentiometer too high
may result in the formation of condensate within
the system.
2.9.5
EC Fan
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 air flow 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. It is recommended that STULZ Product
Support be contacted before making adjustments to the
controller.
2.9.6
Thermal Expansion Valve
CyberOne EC units utilize a thermal expansion valve (TEV).
The TEV maintains constant superheat of the refrigerant
vapor 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 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 12-15
°F and should not need adjustment.
2.9.7
Hot Gas Reheat (Optional)
The hot gas reheat option 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
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