JOHNSON CONTROLS
165
SECTION 8 – SERVICE
FORM 100.50-NOM6
ISSUE DATE: 8/07/2017
8
Economizer Minimum Position Alarm (40)
Prior to declaring this fault the Unit Controller checks
the outside air temperature and the economizer posi-
tion. If the outside air temperature is more than 20.0°
F warmer then the setpoint and the economizer is open
more than 20%, the Unit Controller will close the
economizer for 10 minutes and then check the supply
air temperature. If the SAT falls below the setpoint, the
control will declare an economizer minimum position
alarm. The Unit Controller will keep the economizer
closed until the end of the cooling cycle. It will then
return the economizer damper to its minimum position.
Space Temperature Trending Alarm (41)
This alarm will be generated based on the following
criteria:
•
The “
SPACE TEMP TRENDING ALARM TEMP
”
and the “
SPACE TEMPERATURE ALARM TIME
”
must be set.
•
The unit has been in a given mode of operation for
10 minutes.
•
The temperature is below or above the space tem-
perature setpoint and the trend continues to be
away from the space temperature setpoint and the
“
SPACE TEMP TRENDING ALARM TIME
” has
expired.
Duct Static Low Pressure Alarm (42)
This alarm is initiated on a VAV unit if after 35 seconds
of supply fan operation the duct static pressure is not
equal to or greater than 0.05" WC. When the alarm be-
comes active the unit stops all operation and locks out.
This can be the result of a faulty Duct Static Pressure
Transducer or in the transition from an unoccupied to
occupied mode if the VAV boxes are wide open.
To check the operation of the duct static transducer
measure the VDC input between terminal DP+ wire
337 at the P21 connector and terminal DP- wire 338 at
the P21 connector. Compare the voltage verses the duct
pressure the control indicates to
in this section of the manual. Also verify that 24VAC
is present between terminals “COM” and “EXC” at the
duct static transducer.
Hot Water Coil Freeze Alarm (43)
The alarm indicates the hydronic freeze stat switch has
opened. The 24VAC source originates at the terminal
FSP, wire 389. The input to the control originates at
terminal FSI, wire 388.