JOHNSON CONTROLS
173
SECTION 8 – UNIT OPERATION
FORM 150.67-NM2
ISSUE DATE: 01/31/2019
8
Wiring
VFD wiring is simple and requires only 3-phase power
in, 3-phase power out, and a 2-wire signal from the
transducer. No start, stop, or other alternate power
requirements are needed to run the VFD. Figure 57
on page 173 and Figure 56 on page 173 show the
power and control wiring schematically as well as the
actual connections. The VFD controlled fan will oper-
ate whenever the liquid line solenoid on the respective
system is energized.
Programming
Condenser fan control type must be programmed un-
der both the OPTIONS and PROGRAM keys when a
VFD is installed on the chiller. Under the OPTIONS
key, FAN CONTROL must be programmed for DIS-
CHARGE PRESSURE CONTROL only. This will as-
sure condenser fan control of the chiller is solely by
discharge pressure, with no ambient control.
Under the PROGRAM Key, the FAN CONTROL
ON PRESSURE should be programmed for 425
PSIG and the FAN DIFFERENTIAL OFF PRES-
SURE must be programmed for 125 PSIG.
FIGURE 56 - INVERTER POWER WIRING SCHEMATIC
150A L1 T1 150
151A L2 T2 151
152A L3 T3 152
CONDENSER
FAN NO. 1
SPEED
CONTR.
7M
250A L1 T1 250
251A L2 T2 251
252A L3 T3 252
CONDENSER
FAN NO. 2
SPEED
CONTR.
10M
LD11301
Programming as suggested assures the chiller control
points for the second fan in the fan staging sequence
and the inverter control points are matched for opti-
mum control of the fans at reduced ambient tempera-
tures. When the chiller and VFD fan control points are
programmed properly, the fans will operate as outlined
in Table 28 on page 174.
P1
P1
POTENTIOMETER SETTINGS
P1 P2
292 PSI 32 PSI
FIGURE 57 - POTENTIOMETER SETTINGS
LD11300a
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