195
JOHNSON CONTROLS
SECTION 8 – UNIT OPERATION
FORM 150.67-NM1
ISSUE DATE: 4/28/2017
8
TB3
TB1
TB2
TO PANEL 7M TO FAN #1 (EXISTING HARNESS)
TO MICROBOARD (P4)
151
150
152
150A
151A
152A
WHT
BLK
TB3
TB1
TB2
TB3
TB1
TB2
TO PANEL 7M TO FAN #1 (EXISTING HARNESS)
TO MICROBOARD (P4)
151
150
152
150A
151A
152A
WHT
BLK
LD11302a
FIGURE 53 - INVERTER WIRING
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 PRESSURE should be
programmed for 125 PSIG.
TABLE 26 - YCAL033 VFD LOW AMBIENT OPTION – CONDENSER FAN CONTROL OPERATION
FAN STAGE ON OFF
CONTACTOR
MICRO
BOARD
FAN #
SYS 1 SYS 1 SYS 1
1:
VFD CONTROL
(1 FAN
VARIABLE
SPEED)
FAN SPEED
IS A FUNCTION OF
DISCHARGE
PRESSURE.
WHEN THE LIQUID
LINE SOLENOID IS
ENERGIZED. SPEED
INCREASES WITH
PRESSURE
FAN WILL TURN
OFF OR TURN VERY
SLOWLY WHEN
PRESSURE DROPS
BELOW 260 PSIG.
7M TB7-3 1
2:
1 FAN VFD
CONTROL
2ND FAN
FULL SPEED
UNDER
CONTACTOR
CONTROL
425 PSIG,
BOTH FANS
WILL BE RUNNING
FULL SPEED
DISCHARGE
PRESSURE
< 260 PSIG
(PRESSURE IS
< FAN CONTROL ON
PRESSURE OF
425 PSIG MINUS FAN
DIFFERENTIAL
PRESSURE OF 125
PSIG = 300 PSIG)
7M
&
8M
TB7-3
&
TB7-10
3
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, assuring superheat and oil control is not compro-
mised. When the chiller and VFD fan control points are
programmed properly, the fans will operate as outlined
in Table 26.
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