98
JOHNSON CONTROLS
FORM 145.05-NOM2 (807)
Freeze (Fault / Alarm)
A non-averaging type freezestat T1 is provided to
protect hydronic coils from subfreezing temperatures.
The control is mounted on the entering face of the water
chiller coil. The switch is normally closed, and opens
on a decrease in temperature. The switch inputs are at
IN-13 – terminals 9 and 10 of the I/O Expansion Control
Board. The switch has a fi eld adjustable set point range
of 35.0° F to 45° F. If the switch opens for ten seconds,
the control initiates the following action:
•
Turns off the supply air blower and compres-
sors.
•
Sends a 100% analog output to the chilled water
valve.
•
Sends a 0% analog output to the outdoor air
economizer damper.
The control will register a
“Freeze Fault”
as long as the
switch is open. When the temperature switch closes, the
unit returns to normal operation. The control maintains
a running total of the number of times the freezestat
opens. Each time the freezestat opens the counter
increases by one. Every hour the control decreases
the fault count by one. The current condition of the
“Fault”
(ON - active / OFF – inactive) and the current
count can be viewed using the Keypad / Display. Use
the right arrow key > to scroll to
“Faults”
and press
the ENTER key. Press the right arrow key > to scroll
down to
“Freeze”
. The display will tell you Off or On
and # Trips. If the accumulated fault count reaches fi ve,
the control will declare a
“Freeze Alarm”
. The control
will then lockout the operation of the unit.
Service
Summary of Contents for YSCD
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