Specifications

JOHNSON CONTROLS
156
FORM 150.72-NM1 (908)
Unit Operation
BAS/EMS TEMPERATURE RESET USING
A VOLTAGE OR CURRENT SIGNAL
The Remote Reset Option allows the Control Center
of the unit to reset the chilled liquid setpoint using a
0 - 10VDC input, or a 4-20mA input connected to
XTBC1 terminals A- and A+. Whenever 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 - 10VDC signal is supplied, it is applied to
terminals A+ and A-, and jumper JP1 on the I/O board
must be inserted between pins 2 and 3. To calculate
the reset chilled liquid setpoint for values between 0VDC
and 10VDC use the following formula:
Setpoint = Local Chilled Liquid Setpoint + °Reset
°Reset = (DC voltage signal) x (*Max Reset Value)
10
Example:
Local Chilled Liquid Setpoint = 45 °F (7.22 °C)
*Max Reset Value = 20 °F (11.11 °C)
Input Signal = 6VDC
(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 4-20mA signal is supplied, it is applied to terminals
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 20 mA use
the following formula:
Setpoint = Local Chilled Liquid Setpoint + °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 = 12 mA
(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
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