117
JOHNSON CONTROLS
FORM 145.05-NOM1 (708)
• If supply fan operation is verified and the unit is
in normal operation and the airflow switch circuit
opens, the control waits three minutes ten seconds
and if the circuit is still open the control declares
a “Fan Failure Alarm” and locks out the unit.
Freeze (Fault / Alarm)
A non-averaging type freezestat T1 is provided to
protect hydronic coils from subfreezing temperatures. If
the unit has a water economizer, the control is mounted
on the entering face of the water economizer coil. If
the unit does not have an economizer coil, the control
will be mounted on the leaving face of the hydronic
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 field 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.
• Energizes the output to the condenser water
pump.
• Sends a 100% analog output to the water side
economizer valve.
• Sends a 0% analog output to the outdoor air
economizer damper.
• Sends a 50% analog output to the hydronic heat
valve.
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 five,
the control will declare a “Freeze Alarm”. The control
will then lockout the operation of the unit.
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