JOHNSON CONTROLS
113
FORM 150.62-NM6 (103)
EMS-PWM REMOTE TEMPERATURE RESET
EMS-PWM Remote Temperature Reset is a value that
resets the Chilled Liquid Setpoint based on a PWM
input (timed contact closure) to the microboard. This
PWM input would typically be sup plied by an Energy
Management System.
A contact closure on the PWM Temp Reset input at
CTB1 terminals 13 - 20, will reset the chilled liquid set-
point based on the length of time the contacts remain
closed. The maximum temperature reset is achieved
at a contact closure of 11 seconds. This is the longest
contact closure time allowed. One second is the shortest
time allowed and causes the Chilled Liquid Setpoint to
revert back to the Local programmed value. The reset
value is always added to the Chilled Liquid Setpoint,
meaning that this function never lowers the Chilled
Liquid Setpoint below the locally programmed value, it
can only reset to a higher value. The microboard must
be refreshed between 30 seconds and 30 minutes. Any
contact closure occurring sooner than 30 seconds will
be ignored. If more than 30 minutes elapse before the
next contact closure, the setpoint will revert back to the
locally programmed value. The new chilled liquid set-
point is calculated by the following equations:
setpoint = local chilled liquid setpoint + °reset
°reset = (Contact Closure - 1) x (*Max. Reset Value)
10
Example:
Local Chilled Liquid Setpoint = 45°F (7.22°C).
*Max Reset Value = 10°F (5.56°C)
Contact Closure Time = 6 Seconds.
(English)
(6 sec. - 1) (10°F/10) = 5°F Reset
So...the new chilled liquid setpoint = 45°F + 5°F= 50°F.
This can be viewed by pressing the Cooling Setpoints
key twice. The new value will be dis played as “REM
SETP = 50.0°F.”
(Metric)
(6 sec - 1) * (5.56°C/10) = 2.78°C
Reset Cooling Setpoint = 7.22°C + 2.78°C = 10.0°C
So...the new reset Cooling Setpoint = 7.22 °C + 2.78°C =
10°C. This can be viewed by pressing the Cooling Setpoints
key twice. The new value will be displayed as “REM SETP
= 10.0°C.”
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 under-
stand. 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 mi-
croboard. Figure 13 shows a diagram of the eld and
factory electrical connections.
If a 0 - 10VDC signal is available, it is applied to ter-
minals A+ and A-, and jumpers are applied to JU4
and JU2 on the reset board. This DC signal is condi-
tioned 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 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
setpoint = 45°F + 12°F = 57°F
(Metric)
°reset = 6VDC x 11. 11°C = 6.67°C reset
10
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 programming section under COOLING
SETPOINTS. Programmable values are from 2°F to 40°F (1.11°C to 22.22°C).
2
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