JOHNSON CONTROLS
120
FORM 150.66-NM2
ISSUE DATE: 09/25/2020
SECTION 7 - UNIT CONTROlS
This MUST be programmed correctly
to ensure proper chiller operation.
Depending on the option, the trip voltage for a
specific system or unit high current trip can be
programmed. On a single system chiller, either option
performs the same function. It also calibrates the current
readout under the OPER DATA key. The approximate
programmed value is calculated using the following
formulas:
SYSTEM TRIP VOLTS
For individual system high current trip programming
on chillers:
•
Add the sum of the compressor and fan RLA’s in the
system
• Multiply the sum by 1.25
• Divide by 225 A
• The resulting voltage is the value that should be
programmed
For example, if fan and compressor RLA’s total 100 A:
5V x 100 A x 1.25 = 625 VA = 2.8 V
225 A
225 A
The programmed value will be 2.8 V. A similar
calculation and programming will be necessary for the
other system in a 2-system chiller.
The microprocessor will not allow
programming the “FAN CONTROL
ON PRESSURE” minus the “FAN
CONTROL DIFFERENTIAL OFF
PRESSURE” below 160 psig. This
ensures discharge pressure does not
drop too low.
The Fan Differential Off Pressure is the programmed
differential pressure value that is used to stage the
condenser fans off, in relation to discharge pressure.
Refer to
TABLE 19 to
The microprocessor will not allow
programming the “FAN CONTROL
ON PRESSURE” minus the “FAN
CONTROL DIFFERENTIAL OFF
PRESSURE” below 160 psig. This
ensures discharge pressure does not
drop too low.
The TOTAL NUMBER OF COMPRESSORS is the total
quantity of compressors in the chiller, and determines the
stages of cooling available. This must be programmed
for “2”.
This MUST be programmed correctly
to ensure proper chiller operation.
A single system chiller MUST have a
jumper between terminals 13 17 on
terminal block CTB1. If the jumper
is not installed, the unit will act as a
2system chiller. The jumper is only
checked by the micro at unit powerup.
If the jumper is removed, power must
be removed and reapplied to register
the change in memory.
T O T A L N U M B E R O F
C O M P R E S S O R S = 2
S Y S X T R I P V O L T S
= X . X V O L T S
U N I T T R I P V O L T S
= X . X V O L T S
F A N D I F F E R E N T I A L O F F
P R E S S U R E = X X X P S I G
Summary of Contents for YCAL0012EC
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