Johnson Controls
5513350-JTG-1018
79
Table 44: Manufacturer Fault Detection & Diagnostics (FDD)
Manufacturer Fault
Description
Economizer - Damper Not Modulating
Economizer damper actuator is inoperable or not responding to commands.
Economizer - Not Econ When Available
Conditions are available for economizer operation but the unit does not use outside
air for cooling.
Economizer - Econ When Not Available
Conditions are not available for economizer operation but the unit uses outside air for
cooling.
Economizer - Excess Outside Air
Economizer damper is open greater than commanded position.
Ventilation
Minimum OA Damper Reset
Fixed Minimum
When the control is in the occupied mode and the fan out-
put energizes, the OA damper is positioned to the minimum
position setpoint (adjustable) unless another function com
-
mands it open or closed. When the control is in the unoc-
cupied mode, the minimum OA position is zero.
Supply Fan Speed
When the control is in the occupied mode, the fan output
energizes, and the output reaches 100%, the OA damper
position is the damper_min_pos_high_speed_fan setpoint.
When the VFD output reaches 50% (adjustable) or less,
the OA damper position is the damper_min_pos_low_
speed_fan setpoint.
When the VFD output is between 50–100% (adjustable),
the OA damper positions proportionally between damper_
min_pos_high_speed_fan setpoint and damper_min_pos_
low_speed_fan setpoint.
Note: Supply fan speed minimum OA damper reset is not
available when demand control ventilation (DCV) is en
-
abled.
Outside Airflow Measurement
This control sequence provides for the dynamic determi-
nation of the minimum damper position that meets the
ASHRAE building ventilation standards. If the outside air-
flow input is not reliable, then the damper is positioned
based upon the default minimum position.
When the fresh air intake value falls below the fresh air in
-
take setpoint, the OA damper position increases above its
minimum position until the fresh air intake value equals the
fresh air intake setpoint.
Controls (Continued)
Fault Detection and Diagnostics (FDD)
As required per 2016 California Title 24 and ASHRAE 90.1-
2016, the fault detection and diagnostics (FDD) system pro
-
.
Energy Recovery Wheel (ERW)
The energy recovery wheel (ERW) can run in both cooling
and heating modes. In cooling mode, if the conditions are
suitable for economizing, the ERW disables, and the by-
pass dampers fully open.
The ERW enables when the absolute value of the differ
-
ence between the return air and the outside air is greater
than the energy recovery setpoint. If the OA and RA humid-
ity values are reliable, then enthalpy is compared; other-
wise dry bulb temperature is compared.
When the ERW stops for extended periods, it energizes
briefly for cleaning and blocking protection.
Single Speed ERW
When enabled, the ERW runs at full speed and the ERW
bypass dampers fully close. When the exhaust air tem-
perature (EAT) drops below the energy recovery low limit
setpoint, the ERW bypass dampers fully open to bypass
the ERW.
Variable Speed ERW
When enabled, the ERW runs at full speed and the ERW
bypass dampers fully close. When the EAT drops below
the energy recovery low limit setpoint, the ERW slows to
maintain a minimum EAT to prevent freezing. If the mini-
mum speed does not maintain the temperature setpoint,
the bypass dampers fully open to bypass the ERW.
