York YCUL0020, Installation, Operation And Maintenance Manual

Page: 146 / 178

JOHNSON CONTROLS
146
Form 150.63-NM9
Issue date: 5/20/2021
SECTION 8 – UNIT OPERATION
BAS/EMS discharge air temperature reset using
a voltage or current signal
The Remote Reset Option allows the Control Center of
the unit to reset the discharge air temperature setpoint
using a 0 VDC to 10 VDC input, or a 4 mA to 20 mA
input connected to CTB1 terminals A- and A+. When-
ever a reset is called for, the change may be noted by
pressing the COOLING SETPOINTS key twice. The
new value will be displayed as “REM SETP = XXX
°F.”
If a 0 VDC to 10 VDC signal is supplied, it is applied
to terminals A+ and A-, and jumbeforeJP1 on the I/O
board must be inserted between pins 2 and 3. To cal-
culate the reset discharge air temperature setpoint for
values between 0 VDC and 10 VDC use the following
formula:
Setpoint = Local Discharge Air Temp Se °Reset
°Reset = (DC voltage signal) x (*Max Reset Value)
10
Example:
Local Discharge Air Temp Setpoint = 45°F (7.22°C)
*Max Reset Value = 20°F (11.11°C)
Input Signal = 6 VDC
(English)
°Reset = 6 VDC x 20°F = 12°F Reset
10
New Setpoint = 45°F + 12°F = 57°F
(Metric)
°Reset = 6 VDC 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” set-
point value described in the programming section under Cooling
Setpoints. Programmable values are from 2°F to 40°F (1.11°C to
11.11°C).
**Note: The Suction Pressure Setpoints are not remotely
resettable.
If a 4 mA to 20 mA signal is supplied, it is applied to
terminals A+ and A- and jumbeforeJP1 on the I/O
board must be installed between pin 1 and 2
. To cal-
culate the discharge air temperature setpoint for values
between 4 mA and 20 mA use the following formula:
Setpoint = Local Discharge Air Temp Se °Reset
°Reset = (mA signal - 4) x (*Max Reset Value)
16
Example:
Local Discharge Air Temp Setpoint = 45° (7.22°C)
*Max Reset Value = 10°F (5.56°C)
Input Signal = 12 mA
(English)
°Reset = 8 mA x 10°F = 5°F Reset
16
Setpoint = 45°F + 5°F = 50°F
(Metric)
°Reset = 8 mA x 5.56°C = 2.78°C Reset
16
Setpoint = 7.22°C + 2.78°C = 10.0°C
A 240-24 Volt Ratio Transformer (T3) is
used to derive nominal 12 volt output from
the 120 volt supply.