
FORM 150.66-NM1 (708)
141
JOHNSON CONTROLS
8
PROGRAMMING
Condenser fan control type must be programmed under
both the OPTIONS and PROGRAM keys when a VFD
is installed on the chiller. Under the OPTIONS key, FAN
CONTROL must be programmed for DISCHARGE
PRESSURE CONTROL only. This will assure the
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 240 PSIG
and the FAN DIFFERENTIAL OFF PRESSURE
must be programmed for 80 PSIG.
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 optimum
control of the fans at reduced ambient temperatures.
When the chiller and VFD fan control points are
programmed properly, the fans will operate as outlined
in Table 24.
FAN STAGE
ON
OFF
CONTACTOR
MICROBOARD
FAN #
SYS 1
SYS 2
SYS 1
SYS 2
SYS 1
SYS 2
1:
INVERTER
CONTROL
(1 FAN
VARIABLE
SPEED)
DISCHARGE
PRESSURE
> 145 PSIG
(FAN SPEED
VARIED WITH
PRESSURE
CHANGE FROM
145-170 PSIG)
DISCHARGE
PRESSURE
< 145 PSIG
7M
10M
TB7-3
TB10-3
1
2
2:
INVERTER
CONTROL
(1 FAN FULL
SPEED UNDER
INVERTER
CONTROL AND
2ND FAN FULL
SPEED UNDER
CONTACTOR
CONTROL)
DISCHARGE
PRESSURE
>
PROGRAMMED
FAN
CONTROL ON
PRESSURE
DISCHARGER
PRESSURE
< 170 PSIG
(PRESSURE IS
< FAN
CONTROL ON
PRESSURE
MINUS FAN
DIFFERENTIAL
PRESSURE
=170 PSIG)
7M
&
8M
10M
&
11M
TB7-3
&
TB7-10
TB10-3
&
TB10-10
1
&
3
2
&
4
TABLE 24 – INVERTER OPTION CONDENSER FAN CONTROL OPERATION
LOAD LIMITING
Load Limiting is a feature that prevents the unit from
loading beyond the desired value. 2 and 4 compressor
units can be load limited to 50%. This would allow only
1 compressor per system to run. 3 and 6 compressor units
can be load limited to 33% or 66%. The 66% limit would
allow up to 2 compressors per system to run, and the
33% limit would allow only 1 compressor per system
to run. Five-compressor units may be load limited to
40% (1 compressor per system runs) or 80% (up to 2
compressors per system) are permitted to run. No other
values of limiting are available.
There are two ways to load limit the unit. The fi rst is
through remote communication via an ISN.
A second way to load limit the unit is through closing
contacts connected to the Load Limit (CTB1 – Terminals
13 - 21) and PWM inputs (CTB1 – Terminals 13 - 20).
Stage 1 of load limiting involves closing the Load Limit
input. Stage 2 of load limiting involves closing both the
Load Limit and PWM inputs. The fi rst stage of limiting
is either 80 %, 66% or 50%, depending on the number
of compressors on the unit. The second stage of limiting
is either 40% or 33% and is only available on 3, 5 &
6 compressor units. Table 25 shows the load limiting
permitted for the various number of compressors.
Содержание YORK YCAL0041EC
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