JOHNSON CONTROLS
165
SECTION 8 – UNIT OPERATION
FORM 150.72-ICOM7
ISSUE DATE: 10/22/2020
8
REMOTE 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 set point using a
0 to 10 VDC input, or a 4 mA to 20 mA input con-
nected to XTBC1 Terminals A- and A+. Whenever a
reset is called for, the change may be noted by pressing
the COOLING SET POINTS 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 jumper JP1 on the I/O
board must be inserted between pins 2 and 3. To calcu-
late the reset chilled liquid set point for values between
0 VDC and 10 VDC use the following formula:
Set Point = Local Chilled Liquid Set Point + °Reset
°Reset = (DC voltage signal) x (*Max Reset Value)
10
Example:
Local Chilled Liquid Set Point = 45°F (7.22°C)
*Max Reset Value = 20°F (11.11°C)
Input Signal = 6 VDC
(English)
°Reset = 6 VDC x 20°F
10
New Set Point = 45°F + 12°F = 57°F
(Metric)
°Reset = 6 VDC x 11.11°C
10
New Set Point = 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 “Remote Set Point Control” on page
124 under “Cooling Set Points”. Programmable values are from
2°F to 40°F (1.11°C to 11.11°C).
= 12°F Reset
= 6.67°C Reset
If a 4 mA to 20 mA 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 set point for values between 4 mA and 20
mA use the following formula:
Set Point = Local Chilled Liquid Set Point + °Reset
°Reset = (mA signal - 4) x (*Max Reset Value)
16
Example:
Local Chilled Liquid Set Point = 45°F (7.22°C)
*Max Reset Value = 10°F (5.56°C)
Input Signal = 12 mA
(English)
°Reset = 8 mA x 10°F
16
Set Point = 45°F + 5°F = 50°F
(Metric)
°Reset = 8 mA x 5.56°C
16
Set Point = 7.22°C + 2.78°C = 10.0°C
= 5°F Reset
= 2.78°C Reset
A 240 to 24 Volt Ratio Transformer (T3) is
used to derive nominal 12 V output from
the 120 V supply.
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