Figure 45 - Typical Vfd Location; Figure 46 - Liquid Line Sensing Bulb Location; Figure 47 - Potentiometer Settings; Ycal0019-0028 Low Ambient Fan Control Option - York YCAL0019 Installation, Operation And Maintenance Manual

SECTION 8 – UNIT OPERATION
YCAL0019-0028 LOW AMBIENT FAN
CONTROL OPTION
General
The low ambient option consists of a single phase Vari-
able Frequency Drive (VFD) that controls the speed of
the first fan (Fan 1) in the fan staging sequence. The
VFD is located in the control panel. An example of the
VFD location is shown in Figure 45.
VFD

FIGURE 45 - TYPICAL VFD LOCATION

The VFD will control fan speed based on the liquid
temperature of the system. As liquid line temperature
rises and falls, the fan speed will operate between min-
imum and full speed RPM.
As liquid temperature rises, the VFD will ramp the
speed of the fan from a minimum speed of about 200
Hz to maximum RPM while attempting to control liq-
uid line temperature between 65 and 75° F. If the liq-
uid temperature is below 65 to 75° F, the VFD will shut
off the motor even though the VFD is powered by 7M.
The VFD control signal is sent from a liquid tempera-
ture sensor connected to a condenser coil return bend.
The sensor is connected to S1 and COM terminals of
the VFD in the control panel. The sensor must always
be insulated. The location of the sensor is shown in
Figure 46.
190

FIGURE 46 - LIQUID LINE SENSING BULB LOCATION

The VFD will not only control fan speed in low ambi-
ent conditions, but in all ambients based on the liquid
line temperature. Speed control of the fan will occur
whenever the liquid line solenoid is energized.
Potentiometer Configuration
The VFD is pre-configured from the factory prior to
shipping and should be ready for operation when the
chiller arrives on site. Potentiometers allow adjustment
50093b
of the minimum speed and for selection of the tempera-
ture control range. A quick check of the potentiometer
setting is recommended. The potentiometer settings
should be in the position shown in Figure 47.

FIGURE 47 - POTENTIOMETER SETTINGS

Wiring
VFD wiring is simple and requires only single phase
power in, single phase power out and a 2-wire signal
from the liquid line temperature sensor. No start, stop
or other alternate power requirements are needed to op-
erate the VFD. Figure 48 shows the power and control
wiring schematically as well as the actual connections.
FORM 150.67-NM1
ISSUE DATE: 4/28/2017
BULB
50094
50095
JOHNSON CONTROLS