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JOHNSON CONTROLS
FORM 100.50-NOM6 (1207)
5
• If the outdoor air temperature is less then the
economizer supply air temperature set point,
compressors will not operate regardless of the
“OUTDOOR AIR TEMP COOLING LOCK-
OUT” set point.
LOW AMBIENT OPERATION
A condenser fan VFD can be installed on condenser
fan # l. When this is installed compressor system 1
(compressors 1A and 1B) can operate down to an
outdoor temperature of 0.0º F. The VFD is located in
an enclosure on the right hand side of the condenser
section, to the right of the system 2 compressors.
To enable low ambient operation when a condenser
fan VFD is installed, the following parameter must be
programmed:
“LOWAMBIENT KITINSTALLED” - is enabled
using Parameter 84 under the PROGRAM key
of the Simplicity Elite control board or under the
EQUIPMENT INSTALLATION tab in the Simplicity
PC software package.
Operation and Pressure Control Range
The VFD controls the speed of the fan based on a
discharge pressure setpoint and a differential range.
When discharge pressure reaches approximately 270
PSIG, the VFD will start the fan if the Unit Controller
is calling for compressor / condenser fan operation. The
binary outputs from the Unit Controller are as shown
in Table 5-1.
TABLE 5-1 – BINARY OUTPUTS
CONDENSER
FAN
CONNECTOR
TERMINAL
#
WIRE
#
CONTACTOR
1A P13 1 423 6M
As soon as the contactor is energized, the VFD will be
activated and will begin to control. As the pressure rises
over the next 80 PSIG (270 – 350 PSIG); the fan speed
will increase to full speed at approximately 350 PSIG.
The VFD control input signal originates from the
discharge pressure transducer for the compressor system
it is controlling. The transducer signal feeds the VFD.
The VFD controls the fan speed based on discharge
pressure.
Confi guration (Jumpers and Potentiometers)
The inverter is confi gured at the factory. The jumpers
must be in the positions shown in Table 5-2.
TABLE 5-2 – VFD JUMPERS
J2 REMOVE -
J3 REMOVE
J4 REMOVE
J5 MIDDLE
J6 MIDDLE
J7 IN
J8 IN
J9 IN FOR 60 HZ REMOVE FOR 50 HZ
Potentiometer settings are also preset at the factory.
The potentiometers should be in the positions shown in
Table 5-3. The potentiometers do not have numerical
settings and are set according to the positions indicated.
DO NOT change potentiometer settings unless they do
not match the positioning of the potentiometers shown
in Figure 5-1. Modifying these settings may cause
damage to the unit, control problems, and/or poor
operating effi ciency.
TABLE 5-3 – POTENTIOMETER SETTINGS
P1 P2
350 PSIG 80 PSIG
6 O’CLOCK 6 O’CLOCK
P1
P2
P1
P2
FIG. 5-1 – CONDENSER FAN VFD POTENTIOMETER
SETTINGS
LD113008