JOHNSON CONTROLS
134
FORM 150.27-NM1
ISSUE DATE: 09/30/2015
SECTION 8 – UNIT OPERATION
ALARM STATUS
System or unit shutdown is indicated by normally-open
alarm contacts opening whenever the unit shuts down
on a unit fault, locks out on a system fault, or experi-
ences a loss of power to the chiller electronics. System
1 alarm contacts are located at CTB2 – terminals 29
to 30. System 2 alarm contacts are located at CTB2 –
terminals 31 to 32. The alarm contacts will close when
conditions allow the unit to operate, or the fault is reset
during a loss of power, the contacts will remain open
until power is reapplied and no fault conditions exist.
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 supplied by an Energy
Management System.
A contact closure on the PWM Temp Reset input at
CTB1 terminals 13-20, will reset the Chilled Liquid
Setpoint 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 con-
tact 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
Setpoint is calculated by the following equation:
Setpoint = Local Chilled Liquid Se °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) x (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 COOL-
ING SETPOINTS key twice. The new value will be
displayed as “REM SETP = 10.0°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).
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 to 10VDC input, or a 4 to 20mA input connected to
CTB1 terminals A- and A+. Whenever a reset is called
for, the change may be noted by pressing the COOL-
ING SETPOINTS key twice. The new value will be
displayed as “REM SETP = XXX °F.” This reset value
is always added to the locally programmed Chilled
Liquid Setpoint, meaning this function never lowers
the Chilled Liquid Setpoint below the locally pro-
grammed value.
If a
0 to 10VDC
signal is supplied, it is applied to ter-
minals 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 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 = 6VDC
