JOHNSON CONTROLS
17
SECTION 2 - FIELD CONTROL MODIFICATIONS
FORM 160.79-PW2
ISSUE DATE: 01/31/2019
2
FIGURE 20 -
REMOTE LEAVING CHILLED LIQUID
TEMPERATURE SETPOINT WITH PWM SIGNAL
LD06833
The relay contacts should close for 1 to 11 seconds at
least once every 30 minutes to maintain the setpoint
to the desired value. If a 1 to 11 second closure is not
received within 30 minutes of the last closure, the
setpoint is defaulted to the Local setpoint value. A clo-
sure is only accepted at rates not to exceed once every
70 seconds. This input will only be accepted in
Digital
Remote Mode
. Calculate the setpoint for various pulse
widths as follows:
OFFSET(°F) = (PULSE WIDTH IN SECONDS)
(REMOTE RESET TEMP. RANGE)
10
SETPOINT(°F) = LOCAL SE OFFSET
For example, if the relay contacts close for 5 sec-
onds and the Remote Reset Temp Range setpoint is
programmed for 10°F, and the Local Leaving Chilled
Liquid Temperature setpoint is programmed for 40°F,
the setpoint would be set to 44°F as follows:
OFFSET (°F) = (5 – 1)(10)
10
= (4)(10)
10
= 40
10
= 4°F
SETPOINT (°F) = 40 + 4
= 44°F
EXTERNAL SIGNAL FOR REFRIGERATION
UNIT FAILURE
When the Safety Shutdown Contacts (see
) are not connected to an Energy Manage-
ment System they may be employed to energize a local
or remote safety alarm (by others). When the normally
open Safety Shutdown Contacts close, the alarm will
indicate shutdown of the unit. The cause of shutdown
will be one or more of the safety conditions listed
in
Unit Operations Manual (Forms 160.69‑O1 and
160.69‑O3).
FIGURE 21 -
EXTERNAL SIGNAL FOR
REFRIGERATION UNIT FAILURE (NOTE 6)
LD06834
CONFIGURED FOR MANUAL RESTART
AFTER POWER FAILURE
If the unit was shut down because of
Cycling Shutdown Contacts (see Fig‑
ure 7 page 10) the alarm will not be
energized, but the unit will have been
shut down. A closure of the safety alarm
contacts means that an operator must
manually reset and restart the unit.
When the Safety Shutdown contacts close, the
OptiView Control Center will display the follow-
ing message: SAFETY SHUTDOWN – MANUAL
RESTART, and cause of shutdown.
FIGURE 22 -
AUXILIARY SAFETY SHUTDOWN
INPUT
LD04399
