JOHNSON CONTROLS
12
FORM 155.21-W2 (1209)
FIG. 19 –
REMOTE LEAVING CHILLED LIQUID
TEMPERATURE SETPOINT WITH PWM
SIGNAL
LD14447
REMOTE LEAVING CHILLED LIQUID
TEMPERATURE SETPOINT
(CONTROL SIGNAL; DIGITAL, PWM)
The pulse width modulation input is in the form of a
1 to 11 second contact closure that applies 115VAC
across I/O board terminals TB4-1 (115VAC) and TB4-
19 (input) for 1 – 11 seconds. A contact closure time
(pulse width) of 1 second produces a 0°F offset. An 11
second closure produces the maximum allowed offset
(10 to 20°F) above the local setpoint value. The relay
contacts should close for 1 to 11 seconds at least once
every 30 minutes to maintain the setpoint to the de‑
sired value. If the 1 to 11 second closure is not received
within 30 minutes of the last closure, the setpoint is
defaulted to the local setpoint value. The maximum
rate at which the OptiView control panel will accept a
remote PWM signal is one pulse each 60 seconds. The
OptiView control center must be configured appropri
‑
ately to accept the desired signal as follows:
• The appropriate signal source mode must be se
‑
lected. It is recommended that a qualified YORK/
Johnson Controls service technician accomplish this
in the local/service mode on the OptiView control
center. Digital mode must be selected when using
a 1- 11 pulse width modulated signal with contacts
rated 5mA @ 115VAC. Figure setpoint below;
OFFSET (°F) =
(PULSE WIDTH IN SECONDS) (REMOTE RESET TEMP. RANGE)
10
SETPOINT (°F) = LOCAL SE OFFSET
1
19
For example, if the relay contacts close for 5 seconds
and the Remote Reset Range setpoint is 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
TO ENERGY MANAGEMENT SYSTEM
(RELAY CLOSURE) 1 TO 11 SECOND
PULSE WIDTH MODULATED SIGNAL
FIG. 20 –
EXTERNAL SIGNAL FOR REFRIGERA-
TION UNIT FAILURE (NOTE 6)
EXTERNAL SIGNAL FOR REFRIGERATION UNIT
FAILURE
When the Safety Shutdown Contacts (see
Fig. 5) are not
connected to an Energy Management 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
following safety controls:
1. Solution or refrigerant pump overloads or thermal
switches tripped/open.
2. Low refrigerant temperature cut-out.
3. generator high pressure cut‑out.
4. generator high pressure cut‑out.
5. Steam / Hot water high temperature cut-out.
6. Steam supply pressure (Steam unit only) cut‑out at
35.0 PSIA.
7. Power failure.
8. Chilled water flow switch open.
9. Following a power failure, if the solution tempera‑
ture is less than 136°F when power is resored and
the unit did not complete its previous dilution cycle,
check for crystallization.
10. If, after a shutdown as described in item (1), while
the solution or refrigerant pump overloads or ther‑
mal switches are tripped, if the solution temperature
falls to less than 136°F before the switches re-close,
check for crystallization.
11. While the low refrigerant cut-out switch is tripped
or the refrigerant temperature sensor temperature
rises to 37°F (whichever device caused the shut
‑
down), if the solution temperature is less than
136°F, check for crystallization.
