JOHNSON CONTROLS
140
FORM 150.66-NM2
ISSUE DATE: 09/25/2020
SECTION 8 - UNIT OPERATION
BAS/EMS TEMPERATURE RESET OPTION
The Remote Reset Option allows the Control Center
of the unit to reset the chilled liquid setpoint using a
0 - 10VDC input, a 4-20mA input, or a contact closure
input. The Remote Reset circuit board converts the
signals mentioned above into pulse width modulated
(PWM) signals which the microprocessor can understand.
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.”
The optional Remote Reset option would be used when
reset of the chilled liquid setpoint is required and a
PWM signal (timed contact closure) cannot be supplied
by an Energy Management System. The Remote Temp.
Reset Board will convert a voltage, current, or contact
signal that is available from an EMS to a PWM signal,
and every 80 seconds provide a PWM input to the
microboard. Fig. 26 shows a diagram of the field and
factory electrical connections.
If a
0 - 10 VDC
signal is available, it is applied to
terminals A+ and A-, and
jumpers are applied to
JU4 and JU2
on the reset board. This DC signal is
conditioned to a 1 - 11 second PWM output and supplied
to the PWM input on the microboard at CTB1 terminals
13 - 20. To calculate the reset chilled liquid setpoint for
values between 0 VDC and 10 VDC use the following
formula:
Setpoint = local Chilled liquid Se °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 = 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” 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 available,
it is applied to termi-
nals A+ and A- and
jumpers are applied to JU5 and
JU3
on the reset board. The mA signal is conditioned
to a 1 - 11 second PWM output. The PWM output is
then supplied to the PWM input on the microboard at
CTB1 terminals 13 - 20. To calculate the chilled liquid
setpoint for values between 4mA and 20 mA 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 = 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 V supply.
If the
Contact Closure input
is used, the connec tions
are made to terminals C and D and only
jumper JUI
must be in place
on the reset board. This input is used
when a
single
reset value is needed. When the contacts
are closed, the remote temperature reset board will con-
vert this contact closure to a PWM signal that is applied
to CTB1 terminals 13 - 20.
To set the PWM output, the contacts must be closed
on inputs C - D, and potentiometer R11 (located on the
front edge of the PC board) is adjusted to 10VDC as
measured at TP3 to terminal 10 on the circuit board. The
reset value will be the “Max EMS-PWM Remote Temp.
Reset” setpoint value pro grammed in the SETPOINTS
section under the Cooling Setpoints key.
The coil of any added relay used for
reset must be suppressed to prevent
possible component damage. Use
YORK PN 03100808000 suppres sor.
Summary of Contents for YCAL0012EC
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