JOHNSON CONTROLS
135
SECTION 8 – UNIT OPERATION
FORM 150.27-NM1
ISSUE DATE: 09/30/2015
8
(English)
°Reset = 6VDC x 20 °F = 12 °F Reset
10
New Setpoint = 45 °F + 12 °F = 57 °F
(Metric)
°Reset = 6VDC x 11. 11 °C = 6.67 °C Reset
10
New Setpoint = 7.22 °C + 6.67 °C = 13.89 °C
* Max Reset Value is the “Max EMS-PWM Remote
Temp. Reset” setpoint value described in the “Program ming”
section under Cooling Setpoints.
Programmable values are from 2 °F to 40 °F (1.11 °C to
11.11 °C).
If a 4 to 20mA signal is supplied, it is applied to ter-
minals A+ and A- and jumper JP1 on the I/O board
must be installed between pin 1 and 2. To calculate the
Chilled Liquid Setpoint for values between 4mA and
20mA use the following formula:
Setpoint = Local Chilled Liquid Se °Reset
°Reset = (mA signal - 4) x (*Max Reset Value)
16
Example:
Local Chilled Liquid Setpoint = 45° (7.22 °C)
*Max Reset Value = 10 °F (5.56 °C)
Input Signal = 12mA
(English)
°Reset = 8mA x 10 °F = 5 °F Reset
16
Setpoint = 45 °F + 5 °F = 50 °F
(Metric)
°Reset = 8mA x 5.56 °C = 2.78 °C Reset
16
Setpoint = 7.22 °C + 2.78 °C = 10.0 °C
VDC PRESSURE SETTING GUIDELINES
When a Johnson Controls remote condenser type VDC
is used with a YCRL chiller, the VDC must be ordered
and installed with the “Head Pressure Control – High
Pressure” option which provides Johnson Controls
model P470 pressure controllers factory mounted in
the VDC control panel. Operating manuals for the
P470 controllers is included in the VDC control panel
to allow field setup of the fan staging.
The following pressure set points are recommended
for general use. If excessive fan cycling is noted the
final stage of cycling should be adjusted (deadband in-
creased). The dead band proposed in these guidelines
is set to 125 psi, which is the standard setting for John-
son Controls air cooled R410 units (YLAA, YCAL).
•
2 stage units (2 fan single wide, 4 fan double wide
VDC):
•
Stage 1, ON when any compressor is ON
•
Stage 2, ON at 385 psig, OFF at 260 psig
•
3 stage units (3 fan single wide, 6 fan double wide
VDC):
•
Stage 1, ON when any compressor is ON
•
Stage 2, ON at 385 psig, OFF at 260 psig
•
Stage 3, ON at 405 psig, OFF at 280 psig
•
4 stage units (4 fan single wide, 8 fan double wide
VDC):
•
Stage 1, ON when any compressor is ON
•
Stage 2, ON at 385 psig, OFF at 235 psig
•
Stage 3, ON at 405 psig, OFF at 280 psig
•
Stage 4, ON at 425 psig, OFF at 300 psig
