York YCAL Series Installation Operation & Maintenance page 120

SECTION 7 - UNIT CONTROLS
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.
F A N D I F F E R E N T I A L
P R E S S U R E =
The Fan Differential Off Pressure is the programmed
differential pressure value that is used to stage the con-
denser fans off, in relation to discharge pressure. Refer
to Condenser Fan Control in the UNIT OPERATION
section and Tables 22, 23, and 24.
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.
T O T A L N U M B E R
C O M P R E S S O R S
The TOTAL NUMBER OF COMPRESSORS is the
total quantity of compressors in the chiller, and deter-
mines the stages of cooling available. Note in Table 16,
the chiller may have single or dual systems.
This MUST be programmed correctly
to ensure proper chiller operation.
A single system chiller MUST have a
jumper between terminals 13 and 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 microprocessor at unit
power­up. If the jumper is removed,
power must be removed and re­applied
to register the change in memory.
120
O F F
X X X P S I G
O F
= 6
This MUST be programmed correctly
to ensure proper chiller operation.
S Y S X T R I P
U N I T T R I P
= X . X
Depending on the option, the trip voltage for a
specific system or unit high current trip can be
programmed. It also calibrates the current read-
out 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:
5 V x 100 A
x 1.25 =
225 A
The programmed value will be 2.8V. A similar calcula-
tion and programming will be necessary for the other
system in a 2-system chiller.
FORM 150.66-NM3
ISSUE DATE: 09/25/2020
V O L T S
= X . X V O L T S
V O L T S
V O L T S
625 VA
= 2.8V
225 A
JOHNSON CONTROLS