JOHNSON CONTROLS
169
SECTION 8 – UNIT OPERATION
FORM 150.67-NM2
ISSUE DATE: 01/31/2019
8
Configuration (Jumpers and Potentiometers)
Each VFD is pre-configured at the factory prior to ship-
ping and should be ready for operation when it arrives
onsite. A quick check of the settings is recommended.
The jumpers must be in the positions shown in the fol-
lowing Table.
VFD JUMPERS
J2 REMOVE —
J3 IN —
J4 REMOVE —
J5 IN —
J6 IN —
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 the following table. The pots do not have numerical
settings and are set according to the arrow positions
indicated. DO NOT change the potentiometer settings
unless they do not match the positioning of the potenti-
ometers shown in Figure 51 on page 169. P1 should
be full CW (292 PSIG) and P2 should be full CCW (32
PSIG). Modifying these settings may cause damage to
the chiller or control problems.
The P1 pot sets the setpoint which is the top end of the
control range. This setting is the discharge pressure at
which the fan will be operating at full speed. The P2
pot sets the range. This is the range of pressure where
the VSD modulates the fan speed from 0 RPM to full
speed. The range is subtracted from the setpoint to cal-
culate the 0 RPM pressure.
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 52
on page 170 and Figure 51 on page 169 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.
P1
P2
P1
P2
POTENTIOMETER SETTINGS
P1 P2
292 PSI 32 PSI
FIGURE 51 - POTENTIOMETER SETTINGS
LD11300A
YCAL0033 Programming
Condenser fan control type must be programmed un-
der both the OPTIONS and PROGRAM keys when an
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 the condenser fan control 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 should be programmed for 125 PSIG.
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